Researchers have extracted DNA from a 50,000-year-old tooth belonging to an African antelope, setting a record for the oldest DNA ever retrieved from sub-Saharan Africa, a new study reports.

The finding suggests that DNA preservation in sub-Saharan Africa is possible for tens of thousands of years. In most cases, the region's hot climate breaks down the molecule and prevents researchers from understanding the evolution of numerous species, including ancient human ancestors and relatives.

While some temperate regions are known for preserving ancient human DNA — for instance, the Sima de los Huesos ("Pit of Bones") in Spain preserved DNA from a mysterious relative of modern humans that lived around 400,000 years ago — the sub-Saharan African climate is less forgiving. The oldest human DNA from sub-Saharan Africa is about 18,000 years old and was discovered in bones found in a rock shelter in Tanzania. And the oldest sub-Saharan animal DNA is just 9,300 years old, from an extinct antelope in South Africa.

In the new study, researchers tested whether DNA could be successfully extracted from ancient skeletons even older than that. By analyzing more than 300 teeth from animals that lived in the past 110,000 years, they discovered that small amounts of DNA could be identified even in remains from the Late Pleistocene, the latter part of the last ice age.

In a study published online May 27 in the journal Quaternary Science Reviews, researchers extracted DNA from dozens of Holocene bovid specimens younger than 11,700 years old and from four Late Pleistocene bovid specimens between 12,000 and 50,000 years old. Although many of the teeth didn't yield DNA, a handful did. The oldest DNA the researchers found came from a partial molar from an African antelope called a mountain reedbuck (Redunca fulvorufula) discovered in Boomplaas Cave in southern South Africa. The other old DNA samples came from three extinct long-horned buffalos (Syncerus antiquus) ‪—‬ two that died 21,000 years ago and one that died 12,000 years ago.

"The 50,000-year-old DNA is exciting," study first author Deon de Jager, a paleogenomics expert at the University of Copenhagen, told Live Science in an email. "But I am myself skeptical of it, for two reasons."

The reedbuck DNA is significantly older than the next-oldest DNA the researchers retrieved, from the long-horned buffalo, de Jager explained, and the reedbuck specimen was contaminated with some human DNA, which they were able to remove. These two issues mean the 50,000-year-old antelope DNA result is not ironclad. However, since the publication of the study, the researchers have also sequenced the genome of a 42,000-year-old wildebeest from Ethiopia, suggesting DNA lasts a lot longer in Africa's climate than experts once thought.

"There is of course a limit to DNA preservation in Africa, but what it is, is not clear," de Jager said. "There are certainly parts of Africa where DNA will be preserved even better than from the sites we have surveyed. Deep caves with stable, low temperatures will certainly be good candidates, but also high-elevation sites where temperatures have been very low for a long time."

The Late Pleistocene teeth that de Jager and colleagues analyzed produced very low amounts of DNA, which is thought to have a half-life of about 521 years, meaning half of the DNA in a specimen disappears every 521 years until none is left. But the amount the researchers found is still useful, de Jager said.

The DNA is sufficient for identifying evolutionary lineages, de Jager added. If they can gather enough data, researchers might be able to compare gene flow and interbreeding among species and populations.

Although these results suggest that DNA analysis is possible for understanding the past 40,000 to 50,000 years of animal and human evolution in South Africa, we may never be able to extract DNA from ancient human relatives like Homo naledi, which went extinct around 240,000 years ago, or Paranthropus robustus, which died out around 1 million years ago.

"I think the chances of obtaining DNA from Homo naledi are very, very low, unfortunately," de Jager said. "One would have to get very lucky with an incredibly well-preserved skull with the petrous bone still present, which is the best bone for obtaining ancient DNA. To get DNA from something in Africa nearly 1 million years old would probably be impossible, as the conditions in Africa are just too harsh."

How much do you know about Earth's frosty past? Find out with our last ice age quiz!

Around 100,000 years ago, an early Homo sapiens man was probably stabbed in the face with a sharp stone tool and later buried in a cave in what is now Israel, archaeologists have determined. The Stone Age cold case appears to be the earliest evidence of this kind of interpersonal violence, according to the research team.

In a study published June 30 in the journal Scientific Reports, the international team of researchers closely examined the skull and lower jaw of a person who was deliberately buried in Qafzeh cave in Israel during the Middle Paleolithic period.

At least 27 people were buried in Qafzeh cave between about 145,000 and 92,000 years ago, making them some of the earliest members of our species to be found outside Africa. Previous analysis of the skeletons, which were excavated between the 1930s and 1970s, revealed that two people had head injuries resulting from blunt trauma.

But the new analysis, which employed microscopic and micro-CT scanning techniques, revealed that Qafzeh 25, an adult male, had a cut mark across his lower left jaw that affected one of his bicuspids and part of his upper jaw. The jawbone showed signs of healing, suggesting that the man lived for a significant amount of time after being injured, the researchers wrote in the study.

Archaeologists had previously identified only a few cases of trauma caused by sharp weapons or projectiles in Middle Paleolithic skeletons. Although these injuries could have resulted from hunting accidents, the researchers wrote, they have generally been interpreted as evidence of interpersonal violence.

The cut mark on the jaw of Qafzeh 25 was found on the left side of his face, lending further support to the idea that the injury was not an accident.

It's not clear what kind of tool made the cut mark, but stone tools found at Qafzeh included flint scrapers and sharp points that could have been fashioned into spear tips.

"Forensic studies of modern human populations have reported that craniofacial injuries resulting from blows are more frequently observed on the left side of the skull, a distribution commonly attributed to the predominance of right-handed assailants in face-to-face confrontations," the researchers wrote.

If the researchers' interpretation of the cut mark is correct, it "would represent the earliest documented case of sharp force trauma in the archaeological record," they wrote.

Qafzeh cave is already well known within archaeology for its clear evidence that early humans buried their dead. The new discovery confirms that the earliest human groups left Africa with a complex culture.

"These results provide new data to the debate on the origin of complex behaviors such as interpersonal violence, the care of injured or sick individuals and funeral practices," study first author Ana Pantoja Pérez, a paleoanthropologist at Spain's National Research Center for Human Evolution, said in a statement.

See how much you know about early humans with our human evolution quiz!

Deep in a limestone cave on Turkey's Mediterranean coast, archaeologists have uncovered evidence that Neanderthals and the modern humans who moved in later left behind surprisingly similar traces of their daily lives — evidence that they hunted the same animals, crafted the same stone tools and collected the same type of seashells.

The findings, published Monday (July 6) in the journal PNAS, feed into some of the biggest questions in human evolution: How similar were the cultures of Neanderthals and Homo sapiens, given that we're so closely related? And did we share information with one another?

A series of archaeological finds over the past few decades, including the new paper's finding that the two had similar cultural practices, suggests that Neanderthals and H. sapiens behaved far more similarly in the Middle East than once assumed.

The new evidence comes from Üçağızlı II Cave (pronounced Ooch-ah-UHZ'-luh), on a stretch of coastline just north of Syria that served as a prehistoric corridor between the Levant (an area of land east of the Mediterranean) and Eurasia. Although the team found only teeth and a partial jawbone within the cave, they were able to distinguish between the remains of Neanderthals and H. sapiens by analyzing the internal structure of the fossilized teeth. Meanwhile, they dated the sediment at the site using optically stimulated luminescence, a technique that reveals how long ago buried mineral grains last saw sunlight.

The team found that the Neanderthals had lived within the cave between approximately 77,000 and 59,000 years ago, while H. sapiens stayed there between about 59,000 and 47,000 years ago. Despite the different time periods, the layers from both of these periods show "substantially uniform hunting-gathering strategies and lithic technology," showing how similar the Neanderthals and H. sapiens were in their hunting-gathering strategies and stone-tool use, the team wrote in the study.

What's more, Neanderthals and H. sapiens got raw materials, such as flint, from the same local sources and hunted the same prey: wild goats (Capra aegagrus), fallow deer (Dama mesopotamica), roe deer (Capreolus capreolus) and wild boar (Sus scrofa). Layer after layer also turned up 29 shells of a small marine snail, Columbella rustica, carried into the cave not for food but seemingly as ornaments. Some were pierced as if meant to be strung, and one shell dating to the Neanderthal occupation showed signs of deliberate heating that altered its color.

"Our findings indicate a deep level of cultural interaction," study co-author Naoki Morimoto, paleoanthropologist at Kyoto University, said in a statement. "These two distinct but closely related human groups were not just adapting to the same environment: they were probably sharing symbolic preferences."

That pattern breaks from findings at Mandrin Cave in France, where Neanderthals and modern humans are thought to have alternated occupation in distinct pulses from about 56,800 and 41,500 years ago, but did not leave evidence of a continuous culture. Instead, it echoes evidence from Tinshemet Cave in Israel, where researchers recently reported similar signs of shared behavior between the two groups tens of thousands of years earlier, from about 130,000 to 80,000 years ago.

Üçağızlı II Cave in Turkey and Tinshemet Cave in Israel suggest that even though there was a "biological" turnover as the caves went from being occupied by Neanderthal groups to modern humans, there weren't major cultural turnovers, too.

"Rather, we hypothesize that the two human species that coexisted in the region were in contact and shared cultural aspects," the researchers wrote in the study.

"A fascinating region"

Sites like these are forcing a rethink of how these two types of human were culturally related to each other, April Nowell, a Paleolithic archaeologist at the University of Victoria in Canada who was not involved in the new study, told Live Science in an email. "By demonstrating cultural continuity and elevated levels of interaction, sites such as Tinshemet and Üçağızlı II are changing what we thought we knew about Neandertals, Homo sapiens and other contemporary Homo groups … a fascinating region just got even more so!" she said.

But that cultural continuity only heightens the mystery of how modern humans and Neanderthals interacted, with Neanderthals eventually going extinct around 40,000 years ago. Two types of human can't occupy the same ecological niche indefinitely, Nowell noted, and some research into Neanderthal cognition suggests Neanderthals were less-flexible thinkers than modern humans, with more limited capacity for language and less of the kind of self-awareness and creativity that may have given H. sapiens an edge. (However, there is pushback against the idea that Neanderthals weren't as cognitively complex as H. sapiens.)

If the archaeological record at sites like Üçağızlı II shows this much overlap in behavior, Nowell said, the real differences between the two may be ones the fossil record simply hasn't revealed yet.

The authors noted that many big questions remain, including when and where these shared cultural practices took place and whether these cultural similarities happened because modern humans mated with Neanderthals.

Ongoing and future excavations at sites like Üçağızlı II Cave may help to answer these questions and build a "more comprehensive picture of human evolution and cultural development during the Late Pleistocene," the team wrote in the study.

How much do you know about our closest relatives? Find out with our Neanderthal quiz!

The diminutive, now-extinct humans known as the "hobbits" were scavengers who dined on dwarf elephants after Komodo dragons took the best cuts, archaeologists have discovered. The finding upends the assumption that Homo floresiensis, a human species that arrived on the Indonesian island of Flores at least 700,000 years ago, hunted big game.

First discovered in 2003, H. floresiensis has been nicknamed the hobbit because of its small size, averaging around 3 feet, 6 inches (106 centimeters) tall, along with its small brain, large teeth and big feet. But archaeologists also found stone tools, animal bones with cut marks, and charred bones that seemed to add up to sophisticated behavior common within our genus, Homo. The hobbits disappeared around 50,000 years ago as Homo sapiens began spreading around Southeast Asia.

But in a study published Friday (July 3) in the journal Science Advances, an international team of researchers questions whether the behavior of H. floresiensis was really as advanced as previously assumed.

The researchers looked at fossil bones of Stegodon florensis insularis, an extinct dwarf species of elephant relative discovered at Liang Bua cave, where bones from H. floresiensis and stone tools have also been found, to determine whether the cut marks were from hunting Stegodon meat or from scavenging the remains of the feasts of the only other carnivore on the island: the Komodo dragons (Varanus komodensis).

To distinguish the hobbit cut marks from Komodo dragon tooth marks, the researchers first conducted an experiment, feeding a goat carcass to a captive Komodo dragon at Zoo Atlanta. Then, they recovered the goat skeleton and painstakingly documented all of the marks, pits, notches and furrows the Komodo dragon's teeth made in the bones. The tooth marks were concentrated in areas with substantial amounts of goat flesh, the researchers wrote in the study, suggesting the Komodo dragon had a preference for meaty areas.

The researchers then investigated the ancient Stegodon bones for evidence of cut marks made by H. floresiensis' stone tools and tooth marks from Komodo dragons. They found 54 cut marks on the Stegodon bones and nearly twice as many Komodo dragon tooth marks. More importantly, they discovered that the Komodo dragon marks were focused on meaty areas, while the human cut marks were made primarily in areas without a lot of meat, suggesting H. floresiensis did not hunt and kill the Stegodon.

The overall patterns of cut marks and tooth marks suggest "a combination of mostly primary access by Komodo dragons and secondary access by H. floresiensis where both predators consumed Stegodon," the researchers wrote. And the hobbits likely ate this meat raw, according to the researchers, as they found no evidence on the Stegodon bones that they had been cooked. Nor did they find any evidence of burning on over 4,000 mouse bones from the site, suggesting the previous evidence of charring was actually natural manganese staining.

A lack of hunting and fire-making technology suggests that the hobbits were not as behaviorally sophisticated as previously thought and raises questions about their ancestry, the researchers said.

It's possible that the ancestor of H. floresiensis branched from the Homo genus before humans accomplished the control of fire and hunting, study first author E. Grace Veatch, a paleoanthropologist at the University of Tübingen in Germany, told Live Science in an email.

One hypothesis for the origin of the hobbits is island dwarfism, which occurs when a large species' average body size evolves to be smaller over generations due to the limited availability of natural resources. Another theory is that hobbits descended from an earlier Homo species that was already small-bodied.

"I think our study highlights the importance of considering behavior in these debates," Veatch said. "Our study suggests that H. floresiensis evolved from a hominin population that did not require these dietary strategies [of hunting and cooking], such as a form of early Homo."

But the new study has not entirely settled the debate about the hobbits' ancestry, because very little is known about the behavior of early hominins in Southeast Asia, such as Homo erectus on Java and other areas of Sunda or Sundaland, a landmass between the South China Sea and the Indian Ocean that has been exposed off and on over the past 2.6 million years.

If H. floresiensis really did branch off from H. erectus, that would suggest many evolutionary changes occurred.

"Taking place on an island that was cut off from contact with the Sunda mainland, this evolution from Homo erectus to Homo floresiensis may have involved not just profound anatomical transformations, such as reduced body size and brain volume, but also behavioural adaptations," Adam Brumm, an archaeologist at Griffith University in Australia who was not involved in the study, told Live Science in an email.

"Flores was clearly a wild card in the story of early human evolution, the sort of place where almost anything could have happened — including, potentially, the loss of deeply-rooted hominin behaviours, such as hunting and fire use," Brumm added.

Where H. floresiensis fits in with the rest of the Homo genus is still an open question, Veatch said. "Importantly, this study highlights the contribution of taphonomy [the study of what happens to organic remains after death] to speak to these larger questions about ancestry."

What do you know about early humans? Test your knowledge with our human origins quiz!

Nearly 70,000 years ago, modern humans created stunning rock art in an unexpected place: the tropical Indonesian island of Sulawesi. The finding, announced in January, made headlines for being the oldest known rock art in the world.

But the discovery's location also highlighted another surprising finding: that members of our species, Homo sapiens, were thriving in the tropics tens of thousands of years ago.

Researchers have long thought that early humans didn't live in tropical rainforests, as these places haven't yielded human fossils and are teeming with dangerous life, including venomous animals, poisonous plants and parasites that would deter early populations.

But that perspective has been changing over the past few decades. Sulawesi's ancient rock art is one of several clues that modern humans may have lived in tropical rainforests for hundreds of thousands of years. That would mean modern humans could have been living in these hot, wet regions since soon after the emergence of our species in Africa around 300,000 years ago.

Understanding how, when and where modern humans inhabited rainforests — and how that shaped our evolution — "may give us an insight into something about what it means to be uniquely human," Patrick Roberts, an archaeologist and anthropologist at the Max Planck Institute of Geoanthropology and author of the book "Jungle: How Tropical Forests Shaped World History" (Penguin, 2022), told Live Science.

From one origin story to many

Conventional wisdom held that modern humans emerged from one parent population in an East African savanna and did not encounter rainforests until around 12,000 years ago, after agriculture emerged to support survival in these climes. The lack of H. sapiens fossils from Africa's tropics appeared to support this view.

Then, in 2017, scientists identified the oldest modern-human fossils — except they weren't in East Africa, but rather in Jebel Irhoud, Morocco. The following year, Eleanor Scerri, an archaeological scientist at the Max Planck Institute of Geoanthropology in Germany, and her colleagues reviewed archaeological evidence, including the Jebel Irhoud fossils, and integrated it with genetic data from present-day populations. The evidence pointed toward H. sapiens originating from many subdivided populations across Africa.

These populations periodically met and exchanged genes and ideas, but they also spent long periods apart, adapting to different ecosystems and evolving diverse traits. In this new understanding, the earliest members of our species may have evolved not just in the grassy savanna but in tropical rainforests, too.

"One of the implications of the model is, if it's not one place and it's many places, then maybe it's not one ecosystem," Scerri told Live Science. "Maybe it's many ecosystems."

Because rainforests come with their own set of environmental pressures, people who lived there may have evolved traits to handle those challenges. When different early human populations came together, tropical rainforest dwellers would have contributed different gene variants than populations from open savannas. The ability to adapt to a variety of environments, including rainforests, may have come in handy later, when H. sapiens spread out of Africa and into tropical Southeast Asia, including places like Sulawesi.

But establishing what these traits were would first require evidence that humans lived in rainforests close to the dawn of our species.

Rainforests are terrible for fossil hunters

Unfortunately, the highly acidic soil in rainforests degrades organic material like bones. This makes evidence of ancient humans, such as fossils, or human activities, like bone arrows or potential woven fiber baskets, exceptionally rare in rainforests.

Even in the few instances this evidence is found, the conditions make it hard to date and contextualize it. Archaeologists often date early human fossils by measuring radioactive isotopes (versions of elements), such as carbon-14, in distinct, undisturbed layers of sediments — broken-down rocks and minerals that form via erosion and weathering. The more sediment layers there are, the longer the period of history that can be traced. But weather conditions in West and Central Africa's rainforests have left few long sediment sequences.

The lack of long sediment sequences also significantly reduces the odds of finding fossils at all, said Antonio Rosas, a paleobiologist at the National Museum of Natural Sciences in Spain who has been searching unsuccessfully for such fossils in Equatorial Guinean rainforests since 2014. "To be honest, I think I gave up the possibility of finding fossils properly," Rosas said.

Written in stone

As a result, many researchers studying early H. sapiens evolution have focused on a material that does preserve: stone.

In Africa, stone tools reveal humans were in coastal tropical forests in what is now Kenya roughly 78,000 years ago, the tropical rainforests of what is now Equatorial Guinea from around 45,000 years ago, and the rainforests of what is now the Democratic Republic of the Congo around 18,000 years ago.

Then, in 2025, researchers revealed that stone tools previously found in a tropical rainforest in the Ivory Coast in the 1980s were 150,000 years old. Because the area was also a tropical rainforest 150,000 years ago, this is evidence that our species inhabited rainforests "much earlier than previously thought," study first author Eslem Ben Arous, a geochronologist and archaeologist at the National Research Center on Human Evolution in Spain, told Live Science in an email.

The antiquity of these quartz tools — which were a mix of flakes and heavy-duty picks and choppers — show that early H. sapiens were capable of designing technology to survive in dense tropical forests. Dense forests weren't a barrier for early humans at that time, Ben Arous said.

Direct evidence

Although stone tools show ancient people were venturing into forests for food or living there part time, they don't prove humans lived there year-round. To do that, researchers still need fossils.

By analyzing the isotopes of elements found in human tooth enamel, researchers can reveal whether our distant relatives actually lived in rainforests. That's because closed, dense canopy rainforests have low levels of sunlight and high carbon dioxide, and the ratio of isotopes of elements in a person's teeth can reveal if they spent a lot of time in those conditions as a child.

Currently, zinc isotopes in two 46,000- to 63,000-year-old human teeth found in Tam Pà Ling cave in Laos are the oldest evidence of humans eating foods mainly from a tropical rainforest.

Similar evidence is currently lacking from African rainforests. But the ability to adapt to many different environments, including rainforests, and the capacity to develop highly specialized traits for such environments is "what's unique about our species," Roberts said.

Identifying adaptations

Early members of our species would have required certain adaptations to live in rainforests. So what were they?

Without preserved DNA or fossils, anthropologists guess by looking at contemporary populations living in the tropics. Many modern-day rainforest inhabitants are small, because it may help them cool off more easily, reduce their caloric needs, and make it easier to move in dense rainforests.

An analysis published in 2019 also found key differences in genes related to immunity and development in African rainforest hunter-gatherers compared with neighboring farmers. For example, the gene PITX1 — which codes for proteins crucial for limb development — is one of several genes that contributes to small stature and shows strong signs of positive selection in Gabonese hunger-gatherer populations.

There is evidence in multiple rainforest dwelling populations, including in those Gabon hunter-gatherers, of selection against specific pathogens.

Although early H. sapiens living in rainforests likely faced similar pressures, we don't have any evidence that similar adaptations evolved in these ancient members of our species.

Ancient DNA may be the key

But some scientists hope to someday find evidence of these adaptations in ancient DNA.

DNA preservation was historically considered impossible in hot and humid environments, but that assumption "turns out to be only partially true," Miklós Bálint, a functional environmental genomicist at the Senckenberg Biodiversity and Climate Research Centre in Germany, said in a statement.

Bálint and his colleagues recently reviewed ancient environmental DNA (aeDNA) recovered from tropical environments. They found 113 studies reported aeDNA in tropical and subtropical habitats between 1998 and 2025, including 1 million-year-old aeDNA extracted from a lake in Indonesia. This DNA came mainly from nearby plants, not from ancient humans. But because people leave "millions of DNA traces" in their environment during their lifetime, human DNA should also be present and retrievable, Bálint said in the statement.

"Obtaining DNA data will be a truly fundamental breakthrough in tropical forest research," Ben Arous said. For example, these genetic remnants peppered throughout the environment could reveal how humans changed the ecosystem, how they moved and interbred, and which diseases and parasites ancient people faced.

The new discoveries point to the need for more archaeological research in rainforest environments, Scerri said. Current efforts in Benin appear "really, really promising," Scerri said, and she and her team are also working on projects in Guinea, Ghana and Senegal, which are also yielding clues to ancient human habitation. "We're making some incredible finds," she said.

"There is enough evidence now to justify investigating areas that used to be well off the human origins map, considered to be very far from the main stage of human evolution," Scerri said.

The question now is how much further back in time people were living in rainforests and using their resources. "We consider ourselves to really be scratching the surface," Scerri said.

Human evolution quiz: What do you know about Homo sapiens?

Some of the last surviving Neanderthals displayed greater genetic diversity than scientists previously thought, a new study of ancient DNA reveals, challenging the idea that genetic decline was the main cause of their extinction.

Neanderthals were among the closest relatives of modern humans, with their lineages diverging around 500,000 years ago. Although Neanderthals once ranged across Eurasia, they are usually thought to have gone extinct about 40,000 years ago.

Much remains a mystery about why Neanderthals went extinct. Previous genetic analyses of DNA from Neanderthals in Siberia revealed that those groups lived in small, isolated communities with signs of frequent interbreeding between close relatives. This raised the possibility that Neanderthals might have died off due to genetic deterioration from inbreeding.

However, DNA from Neanderthals is rare, and high-quality genomes are especially uncommon; until the new study, only four were available, three of which came from Russia, at the edge of the Neanderthals' geographic range. As such, it was uncertain whether DNA analyses of just a few Neanderthals accurately reflected why the entire lineage went extinct.

In the new study, published Wednesday (June 24) in the journal Nature, scientists recovered genetic data from 27 more Neanderthals, including a new high-quality genome, one with enough DNA for scientists to analyze many times to ensure the accuracy of their results.

"Some people might think the retrieval of ancient DNA from Neanderthals is now conventional; the truth is that this is far from trivial," Carles Lalueza-Fox, director of the Natural Sciences Museum of Barcelona in Spain, who did not take part in this research, told Live Science. Adding 27 more Neanderthals "to our general knowledge is a remarkable achievement."

The new data comes from 10 archaeological sites in northwestern Europe, in present-day Belgium and France. Seven of these sites were located in the Meuse Basin in Belgium, an area with a high concentration of late Neanderthals — those who lived after about 70,000 years ago. One of these sites was the Goyet cave system in Belgium, which recent findings suggested may hold evidence of Neanderthal cannibalism.

The genetic analysis revealed the late Neanderthals of northwestern Europe separated from a common ancestor with other known Neanderthals about 54,000 years ago. The newly studied late Neanderthals were more closely related to one another than late Neanderthal groups in other parts of Europe.

The scientists discovered that unlike other Neanderthal groups, many of the Neanderthals they examined showed little evidence of inbreeding. In addition, the new high-quality Neanderthal genome did not show lower genetic diversity than earlier Neanderthals. This finding suggests that reduced genetic diversity may not have been the primary reason Neanderthals died off.

"I am very happy to dispel the misconception that all Neandertals went extinct because they were too inbred," Alba Bossoms Mesa, a doctoral researcher at the Max Planck Institute for Evolutionary Anthropology in Germany and first author of the study, told Live Science.

The study also revealed that the late Neanderthals of northwestern Europe that they analyzed were a large population of genetically interconnected groups, rather than the genetically isolated communities seen among Siberian Neanderthals.

"Neanderthals lived across vast regions of Eurasia over hundreds of thousands of years, so of course there is a lot of variation between them," Bossoms Mesa said. "It's not good to generalize about Neanderthals. We have to keep diversity in mind."

In addition, the newly analyzed late Neanderthals of northwestern Europe displayed a significant level of genetic diversity, dividing into at least four distinct groups, the researchers found. The splits between these groups appeared to originate during relatively warm spans of climate, perhaps reflecting times of population expansion during periods of favorable environmental conditions, the team noted.

Striking asymmetry

The late Neanderthals of northwestern Europe were contemporaries of modern humans (Homo sapiens) in Europe for up to 500 generations, the researchers said. Previous research has discovered Neanderthal DNA in modern-human genomes, revealing these lineages had mingled, with most modern-day humans outside Africa possessing some Neanderthal DNA. However, the new study found no evidence of recent modern-human DNA in these Neanderthals of Belgium and France, suggesting the two groups didn't mate there.

The new findings add to a striking asymmetry seen between Neanderthals and modern humans. "We have several examples of early modern humans who had a Neandertal ancestor only a few generations back," Bossoms Mesa said. "But in contrast, we do not yet have a single confirmed example of a Neanderthal individual with a recent modern human ancestor in their family tree."

There are several possible reasons for this asymmetry, Lalueza-Fox said. For instance, maybe there were genetic problems that prevented H. sapiens DNA from integrating with the Neanderthal gene pool. For instance, a 2025 study suggested that different versions of a gene tied to red blood cell function might have caused Neanderthal-human hybrid women to miscarry their fetuses.

However, "in my view, this conspicuous bias likely reflects a pattern of differential social acceptance among Neanderthals," he noted. "In brief, early modern humans were able to accept kids with Neanderthals but not the opposite, for whatever reason. This pattern, coupled with declining diversity in some Neanderthal populations, could explain their final extinction."

Future research can see if Neanderthals at other sites, such as the Iberian or Italian peninsulas, displayed similar levels of genetic diversity, Bossoms Mesa said. However, analyzing samples from these latter areas "is currently a bit more challenging, because ancient DNA preserves better in colder areas," she noted.

How much do you know about our closest relatives? Find out with our Neanderthal quiz!

For the first time, archaeologists have analyzed the genetic material of Homo naledi, a mysterious 300,000-year-old relative of modern humans discovered deep in a South African cave system. What they found is unique in human evolution studies: Every skeleton known from the species is female.

"I think it is fair to say that they surprised us," Lee Berger, a National Geographic explorer-in-residence, told Live Science in an email, but H. naledi "has always been an enigmatic discovery."

Since 2013, Berger has headed the Rising Star project, which discovered nearly two dozen skeletons of small-brained, two-legged creatures, which the research team named H. naledi, within a cave system in South Africa's Cradle of Humankind.

Research over the past decade has revealed that H. naledi was unusual for having a small brain and upper body, similar to earlier australopithecines like Lucy, but a face, hands and lower limbs that were more human-like. In 2023, the Rising Star team suggested H. naledi may have used fire in the cave, and in 2025, they advanced the controversial claim that H. naledi buried their dead — a complex behavior unexpected for a human relative with such a small brain.

But a new study of H. naledi teeth published Wednesday (June 24) in the journal Cell may bolster the team's interpretation of the Rising Star cave as a burial site.

An international team of experts studied 20 teeth from H. naledi skeletons using proteomic analysis, a minimally destructive technique that sequences genetic material from ancient proteins. Proteomics is a burgeoning field, especially because these proteins can last longer than DNA. The team focused on amelogenin genes (AMEL), which code for proteins in dental enamel and vary by sex. While the gene variant called AMELX is found in both males and females, another one, AMELY, is found only in biological males.

In analyzing the H. naledi teeth, the team found no AMELY proteins but plenty of AMELX ones, suggesting that all of the skeletons were from females. These included the nearly complete skeletons of Neo and DH1, the main representative of the species, both originally assumed to be male.

The result is surprising because there are no known ancient human cemeteries or collections of nonhuman primate skeletons that contain only females.

"The most likely reason for these robust results are, in my opinion, cultural selection after death for burial by sex and perhaps gender," Berger said. "There are many past human societies with sex-specific burial practices," study co-author John Hawks, a paleoanthropologist at the University of Wisconsin-Madison, said in a statement, but the H. naledi skeletons "are older than any known Neanderthal or modern human burial site, and it's remarkable to see that they may all be female."

"An already weird hominin"

The discovery that everything we know about H. naledi comes from female skeletons has surprised paleoanthropologists.

"The bottom line is this is a weird result from an already weird hominin," Elizabeth Sawchuk, curator of human evolution at the Cleveland Museum of Natural History, who was not involved in the study, told Live Science in an email. "The key thing to remember is that failure to detect evidence of AMELY does not mean there are no males in the sample — it just means that none were detected."

One possible reason for the lack of this gene in H. naledi skeletons is an AMELY gene deletion that is known to occur very rarely in some modern-human populations and that has been found in one Neanderthal male. If the AMELY gene doesn't exist in this H. naledi group, then the protein profiles of males would look identical to the profiles of females.

However, "it's very unlikely that this would be the case among even half of the 20 individuals we studied or for an entire population," study co-author Enrico Cappellini, a paleoproteomics professor at the University of Copenhagen in Denmark, said in the statement. "Either scenario, namely the absence of H. naledi males in the Rising Star cave system or a systematic deletion of their AMELY gene, is fascinating and would have deep implications for a better understanding of the biology and evolution of this species."

Studies of H. naledi, a species known from a single site, "continue to yield more questions than answers," Sawchuk said. "As the authors point out, this is a surprising result that requires more investigation."

Other hominins in South Africa

A second surprising result in the proteomic analysis was that H. naledi shares a gene variant with Paranthropus robustus, a human relative with a massive face and teeth that lived in South Africa around 1 million to 2 million years ago.

Proteomic analysis of four P. robustus skeletons in 2025 proved that limited genetic material could be recovered from ancient human relatives in Africa. The new study has revealed that some members of this species and H. naledi shared a gene variant related to collagen production, which is different from the genes found in modern humans, Neanderthals and Denisovans.

While H. naledi and P. robustus inhabited the same general geographic area, it is unclear if they lived there at the same time and overlapped or if they may have had an ancestor-descendant relationship.

"It is early days for sampling fossil hominins with ancient proteins, and until we build a better, bigger sample, we just don't know" what the shared genetic variant means, Berger said.

Building a larger database of ancient proteins from other human relatives that evolved in Africa, such as Australopithecus africanus and Homo erectus, may clarify where H. naledi fits into the picture of human evolution.

"Key data are missing from H. erectus and A. africanus that would help put this evidence into context," Sawchuk said. "For now, this is another curious finding that bears further investigation."

What does sex change?

In 2015, Berger and colleagues named the new hominin H. naledi and described what they presumed to be male and female variants of the species based on the skeletons' sizes. In many groups of human relatives and in modern humans, males are physically larger than females, on average. This assumption led the researchers to classify the presumed male individual DH1, discovered in the Dinaledi chamber of the cave, as the main representative of the new species.

But a 2024 study was the first to question the assumption that the H. naledi skeletons came from two sexes. In that study, researchers found variation in the teeth of H. naledi that was "so low that the possibility that one sex is represented by few or no individuals in the sample cannot be excluded," they wrote.

"Our study helps resolve the long-standing mystery of why Homo naledi lacked significant variation," study first author Palesa Madupe, a researcher at the Max Planck Institute for Evolutionary Anthropology in Germany, said in the statement. "It's probably because they could have all belonged to one sex."

If the proteomic sex analysis is correct and H. naledi does not have AMELY deletion issues, it means everything we know about the species comes from females. But this doesn't mean interpretations of the species are wrong.

"The only thing that has changed is that we have never seen a male!" Berger said. "When and if we do, we will have to extend the description to include male sex characters and the likely extension of certain aspects of variation."

The researchers hope their study paves the way for more proteomic analyses of human relatives in the future.

The new analysis proves that protein analysis of fossils from the Pleistocene (2.58 million years ago to 11,700 years ago) can be done in a minimally destructive way, Madupe said. "This means potentially opening the door to a whole new way of sustainably investigating the differences between sexes in groups of extinct hominins and other animals without causing visible damage to these priceless fossils."

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Some people from Oceania harbor thousands of genetic variants inherited from the Denisovans ‪—‬ a mysterious group of extinct humans ‪—‬ that are still active in their immune systems today, a new study finds.

The findings, published June 11 in the journal Science, come from the largest-ever map of Denisovan-inherited DNA ever created. The discovery shows that Denisovan DNA "is not just a remnant of ancient liaisons; it continues to influence our biology today," study co-author Serena Tucci, an assistant professor of anthropology and head of the Human Evolutionary Genomics Laboratory at Yale University, said in a statement.

Experiments revealed 3,127 variants inherited from Denisovans that still function in the immune systems of modern-day people; some of these variants switch genes that turn the immune response on or off, according to the new research.

However, because many of the immune system genes identified also affect other bodily functions, it is unclear exactly how these genes benefited survival, study first author Patrick Reilly, an evolutionary genomics researcher at Yale, told Live Science.

Denisovan DNA is active in humans today

Previous research has already found that some modern-day people in Oceania ‪—‬ a region that includes New Guinea, the Solomon Islands and Fiji ‪—‬ have some Denisovan DNA. For example, people from Papua New Guinea are known to carry up to 5% Denisovan DNA in their genomes thanks to prehistoric trysts with the enigmatic group of humans who lived in Asia and disappeared around 30,000 years ago. This is among the highest proportion in the world, with modern-day East Asians typically carrying only around 0.1% Denisovan DNA.

Previous research has also shown that modern-day Tibetans carry a Denisovan version of the EPAS1 gene that supports their adaptation to living at high altitudes. People living in the highlands and lowlands of Papua New Guinea have different Denisovan gene variants depending on their local environments.

Yet Oceanians are vastly underrepresented in genomic databases. Sequencing the genomes of Oceanians can give a glimpse into the lives of the Denisovans and is essential for closing gaps in health disparities in Pacific Islanders as a whole, Reilly said.

To fill this gap, Tucci and her team sequenced the genomes of 177 Oceanians from 12 populations and compared them to 1,284 previously published genomes from populations worldwide. Then, they compared these segments to the known Denisovan genome and three Neanderthal genomes.

Combined, the team built a catalog containing three times more Denisovan genetic sequences inherited from Denisovans than were previously identified, over 70% of which were unique to Oceanians.

Natural selection increased the frequency of some of these variants in people from Near Oceania, which includes New Guinea, the Bismarck Archipelago and the Solomon Islands in the Pacific Ocean, including genes linked to bone development, metabolism and fertility.

The team also ran experiments to assess whether any of the Densiovan DNA was changing how genes behaved in these populations, Reilly said.

This revealed that Denisovan genetic variants can switch various immune system genes on or off, although the exact immune functions that were targeted varied among the Oceanic populations studied.

Early migrants to Oceania at least 42,000 years ago benefited from Denisovan genes when they entered their new environment and encountered new disease-causing pathogens, Reilly said.

"This is consistent with multiple independent instances of local adaptation in response to novel immune environments and pathogens during human dispersal into the Pacific," the authors wrote in the study.

Although the researchers don't know exactly why natural selection acted on these genes, the findings highlight the major role pathogens played in shaping the way humans and our extinct relatives evolved, Reilly said.

The research is an "outstanding effort to try to understand the biological implications" of the enduring Denisovan genetic variants, Mathilde André, an evolutionary geneticist at the Pasteur Institute in France who was not involved in the study, told Live Science in an email.

The tripling of known Denisovan-inherited genetic sequences, most of which are unique to Oceanians, highlights the need to sequence the genomes from previously unrepresented populations to capture the diversity of Denisovan DNA, André said.

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Indigenous Andeans in Peru may be able to digest potatoes and other starches more easily than anyone in the world, a new study finds.

Scientists discovered that Indigenous Andeans have more copies of the gene for saliva-based starch digestion enzymes — called amylase — than any other population worldwide. Natural selection drove the surge in amylase genes following the local domestication of potatoes around 10,000 years ago, according to the study published May 5 in the journal Nature Communications.

Amylase in humans' saliva breaks complex starch down into simple sugars, making the starch easier to digest. Populations worldwide differ in the number of gene copies that encode for amylase, but more copies means more amylase production and presumably, improved starch digestion.

On average, people around the world have seven copies of the amylase gene, but Indigenous Andeans in Peru possess an average of 10 copies. People with a higher number of amylase genes had a 1.24% higher chance of surviving and reproducing than those with fewer copies, the researchers wrote in the study.

While that number seems small, this is an "insanely high" adaptive advantage that would have compounded over each successive generation, study co-author Omer Gokcumen, a professor of biological sciences at the University of Buffalo, told Live Science.

Being able to digest amylase effectively was more than just passing gas when eating potatoes, Gokcumen said. The strong survival and reproductive advantage suggests either a substantial number of babies did not survive because the pregnancies were not successful, or people with more gene copies have more babies, he said. "It's actually a life or death kind of situation."

Variation in starch digestion

Beginning around 12,000 years ago, the ancient people living in the Andes had developed a slew of new adaptations, including the ability to live at high altitudes and digest new foods.

Previous analysis of the genomes of Peruvians of Indigenous South American ancestry revealed signs of selection for an intestinal starch digestion enzyme. That adaptation was likely the result of Indigenous Andean populations having domesticated potatoes as early as 10,000 years ago.

In 2024, Gokcumen and his team identified variation in the structure of salivary amylase genes across global populations. But the cause of that variation was unclear.

To figure out what caused the difference, in the new study, Gokcumen and his team created a map of salivary amylase gene copy numbers using genome data from 3,723 individuals from 85 global populations. They found that Peruvian Andeans and Akimel O'odham people in southern Arizona and northern Mexico had the highest average number of salivary amylase genes out of the populations they studied.

The researchers found that, beginning around 10,000 years ago, Indigenous Andean individuals with 10 or more copies of the salivary amylase gene had a 1.24% higher chance of surviving and reproducing than those with fewer copies — evidence that natural selection caused the elevated copy number in the Indigenous Andeans in their sample.

The Akimel O'odham samples also showed high copy numbers, but the researchers could not perform tests looking for signs of natural selection in this population as too few Akimel O'odham individuals were included in their sample.

The functional advantage of having more salivary amylase copies is unknown. Gokcumen said it could have something to do with the microbiome, metabolism and immune system. For instance, people with more copies of the gene may get more calories from cooked potatoes. He and his team are now running experiments to clarify these potential relationships, he said.

This is an "exciting and important study," Charles Lee, a human genomics expert at The Jackson Laboratory for Genomic Medicine in Connecticut who was not involved in the new study, told Live Science in an email.

The high copy numbers in the Akimel O'odham samples suggests that "different Indigenous American groups may have developed high amylase copy numbers in different ways, depending on their diets," Lee said.

Salivary amylase gene copy number variation is unlikely to be the only example of adaptive variation in gene structure, Lee added. "It is simply one of the best examples we currently have of how complex copy number variation can intersect with diet, culture and human evolution," he said.

Do you know where pumpkins and blueberries come from? Find out with our fruits and vegetables quiz!

Whether using family records, DNA tests or genealogy websites, many people can trace their family histories back generations. The world-record holder for the longest family tree is Chinese philosopher Confucius (551 to 479 B.C.), whose family tree extends more than 80 generations from his ancestors in the eighth century B.C. to his living descendants. That's almost 3,000 years.

But our species has been around for 300,000 years, based on scientific dates of the oldest known fossils. So how many generations do we go back as a species?

To find out, you need to know how long modern humans (Homo sapiens) have existed and the length of a generation, according to Matthew Hahn, a population geneticist at Indiana University Bloomington. The number of human generations that have lived would be equal to the time since H. sapiens emerged as a species divided by the length of a generation, also called the generation interval.

The generation interval is typically defined as the average age at which humans have children, Hahn said. It tends to be longer for men than for women because men can have children later in life, Hahn explained.

There are many estimates of our species' generation interval, each of which produces a different answer to the question of how many human generations have come before us.

For example, a 2003 study of Icelanders published in the American Journal of Human Genetics based generation interval estimates on the country's extensive records from churches and other sources. Using these records, researchers at the company deCODE Genetics created a genealogical database of the country's entire population. They found that the average generation interval in Iceland over the past 300 years was 30.3 years.

A 2005 study used data about the average age at which European women had children between 1960 and 2000 and estimated the generation intervals for men to arrive at an average generation interval of 29.1 years.

But those are estimates of the generation interval in the recent past. A study led by Hahn and published in the journal Science Advances in 2023 estimated the generation interval over the past 250,000 years. Hahn's study put together data from two others. A 2017 study of Icelanders, also led by deCODE Genetics and published in the journal Nature, found that as parents age, the blend of mutations that arise in their children changes. Using this data, Hahn and colleagues built a model of the mix of new mutations that you would expect to find in a group of people according to the generation interval at the time.

"If you know the types of mutations that individuals leave to their children according to their age, if you have a collection of mutations, you can try to estimate how old the mixture of individuals was," Hahn said.

A 2020 study in the journal PLOS Biology estimated when millions of mutations found in humans today first arose. Hahn and colleagues grouped the mutations from the 2020 paper according to when they arose and then determined the blend of new mutations that popped up during each time period. With that information, they could estimate the generation interval for each time span. While the generation interval varied over the course of an estimated 250,000 years, it was an estimated 26.9 years, on average. Using that generation interval, there would have been an estimated 11,152 generations of humans over 300,000 years, Hahn said.

Moisès Coll Macià, an evolutionary biologist and population geneticist who works as a postdoctoral researcher at the Institute of Evolutionary Biology in Barcelona, Spain, told Live Science that while a generation interval of 26.9 years is "not unimaginable," he prefers to give a range of possible generation intervals.

In Coll Macià's view, the lower bound would be the generation interval for one of our closest living relatives, chimpanzees (Pan troglodytes). Because humans and chimps share a common ancestor that lived during the Miocene epoch (23 million to 5 million years ago), you would expect that past human generations would have had a generation interval somewhere between that of contemporary humans and that of contemporary chimps, Coll Macià said. Chimpanzees have an estimated generation time of about 24.6 years, according to a 2012 paper in the journal PNAS.

As for the upper bound in modern humans, Coll Macià suggested 26 to 30 years. That's based on a 2016 PNAS study that analyzed fragments of Neanderthal DNA found in ancient and contemporary human genomes to estimate the human generation interval across the past 45,000 years.

Based on Coll Macià's upper-bound generation interval of about 30 years, there have been at least 10,000 generations of humans. Based on the lower-bound generation interval of 24.6 years, there have been at most 12,195 generations. These numbers attest that the human family tree is pretty tall, however you look at it.

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Around 60,000 years ago in Siberia, a Neanderthal opened their mouth so that a rotten tooth could be drilled — and the case is the oldest evidence of an intentional dental treatment to date, a new study finds.

A lower molar tooth belonging to a Neanderthal adult was originally unearthed in 2016, but it was not clear what had caused the deep hole in its surface. Now, experimental evidence indicates the hole was made with a small stone drill used to clean out bits of severely rotten tooth tissue, according to a study published Wednesday (May 13) in the journal PLOS One.

This intricate procedure shows Neanderthals — our closest human relatives who lived from around 400,000 to 40,000 years ago — had the brains to recognize this painful tooth cavity could be treated and possessed the fine motor skills to successfully execute the procedure.

"The fact that this invasive treatment took place and the person survived lends me to believe that this is another example of the really very sophisticated Neanderthal understanding of human biology and when you need to intervene," study co-author John W. Olsen, a professor emeritus of anthropology at the University of Arizona, told Live Science.

It's unclear whether this was self-treatment or dentistry performed by another individual. Even so, "it suggests that the roots of invasive medicine and surgery do not belong exclusively to Homo sapiens, but are part of a broader legacy shared with our closest relatives," Gregorio Oxilia, an associate professor of human anatomy at the Free Mediterranean University in Italy who was not involved in the research, told Live Science in an email.

The oldest evidence of our own species, Homo sapiens, treating tooth decay dates to roughly 14,000 years ago in what is now Italy. By pushing back the date of intentional dentistry by roughly 45,000 years, this new finding "fundamentally reshapes our understanding of the evolution of human healthcare," said Oxilia, who was the first author on the study detailing the 14,000-year-old finding.

Prehistoric healthcare

There are now multiple known cases of Neanderthal healthcare. For example, different sites in Spain show that Neanderthals seem to have cared for a child with Down syndrome and ate medicinal plants.

However, in part because their generally low-carbohydrate diets kept the rates of tooth decay low, evidence of dental interventions in Neanderthals has been limited.

So, to determine whether the unusual hole in the roughly 59,000-year-old Neanderthal molar found in Chagyrskaya Cave was deliberately human-made, the researchers inspected the tooth and ran experiments using three modern human teeth.

Microscopic analyses of the Neanderthal molar revealed two patches of deep demineralization, indicative of severe tooth decay. One area of tooth decay was located where the tooth would have met the gumline. Here, the researchers identified straight grooves characteristic of tooth picking.

The other decayed patch overlapped with the 0.17 inch long, 0.11 inch wide and 0.10 inch deep (4.2 mm long, 2.8 mm wide and 2.6 mm deep) cavity on the tooth's surface. There were tiny markings along the top edge of this hole.

The team then ran experiments on three modern human teeth to see which tools and motions were required to replicate these markings. This revealed the grooves could be made by the twisting motion of small stone tools made from locally available jasper. Multiple examples of tools with long, thin, pointed tips that could have served this purpose have previously been found in Chagyrskaya Cave.

Evidence of chew marks overlaying the grooves around the cavity indicates this individual "not only survived the operation," Olsen said, "but that they lived for some significant period of time, allowing their normal chewing activities to begin to erase the evidence of the original drilling."

While scientists cannot be certain the hole was made using a stone dental drill, the very localized markings make this conclusion more likely than other possible explanations, such as the hole being the result of damage after the individual died, said Marina Lozano Ruiz, a bioarchaeologist who researches Neanderthal teeth at the University of Rovira i Virgili in Catalonia, who was not involved in the study.

The case is "exceptional precisely because it shows that they were able to react to an uncommon pathology with a highly targeted and technically complex response," Oxilia said.

Rebecca Wragg Sykes, an archaeologist at the University of Cambridge and author of "Kindred: Neanderthal Life, Love, Death and Art" (Bloomsbury Sigma, 2020), thinks the procedure was likely self-treatment. "Digging into this rotten tooth probably didn't need anyone to help," Sykes, who was not involved in the study, told Live Science in an email.

Although group members may have provided emotional support during the painful procedure, "we've learned from other primates that they can actually survive really serious conditions without any help from their group," she said.

Editor's note: This story was updated at 9:33 a.m. ET on May 14 to update Gregorio Oxilia's title to associate professor of human anatomy.

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In a first, researchers have sequenced genetic material from 400,000-year-old Homo erectus fossils — and the results reveal deep genetic links to both modern humans and the enigmatic Denisovans.

H. erectus was the earliest human ancestor to travel outside Africa and successfully spread into Europe, Asia and Oceania beginning 1.8 million years ago. With a relatively large brain and the ability to craft complex stone tools, H. erectus was the longest-lasting human ancestor until it disappeared around 108,000 years ago. But paleoanthropologists have long wondered if H. erectus overlapped and interbred with Homo sapiens, which evolved around 300,000 years ago in Africa.

In a new study published Wednesday (May 13) in the journal Nature, researchers detailed their analysis of dental enamel from six H. erectus skeletons discovered in three locations in China, all dating to about 400,000 years ago. The researchers extracted 11 different proteins from the enamel and identified hundreds of positions of amino acids, the building blocks of the proteins.

Two of those amino acid variants surprised the researchers — one was present in all six H. erectus individuals but not in any other human lineage, while the other was present in all H. erectus samples as well as in Denisovans, a group of archaic humans who lived in Asia and went extinct around 30,000 years ago. This amino acid variant was then passed from Denisovans to some H. sapiens groups through interbreeding tens of thousands of years ago.

The results are the first to show "deep genetic links" between these H. erectus individuals and present-day modern humans, the researchers wrote in a statement. The results are also a step forward for the relatively new technique called paleoproteomics, which allows scientists to sequence genetic material that lasts longer than DNA does.

"I don't believe that any previous DNA or proteomics have been done before" on H. erectus, study first author Qiaomei Fu, director of the Ancient DNA Laboratory at the Institute of Vertebrate Paleontology and Paleoanthropology, part of the Chinese Academy of Sciences, in Beijing, told Live Science in an email. But "how they evolved into modern humans and are related to the Denisovans, we really need to get DNA to understand that," she said.

DNA has a shorter shelf life than proteins do, and so far, researchers haven't found any H. erectus DNA that can be sequenced. However, Denisovan DNA has been sequenced.

The muddle in the middle

The Middle Pleistocene era (also called the Chibanian age) spanned from 774,000 to 129,000 years ago. During this era, a number of ancient human groups overlapped in Africa, Europe and Asia, including H. erectus, H. sapiens, Neanderthals and Denisovans, presenting paleoanthropologists with the difficult task of figuring out how they were all related — a confusion they call a "muddle."

"Scientists used to call this 'the muddle in the Middle Pleistocene,'" John Hawks, a paleoanthropologist at the University of Wisconsin-Madison who was not involved in the study, told Live Science in an email, "and now we know that muddling is just mixing." The new study of 400,000-year-old enamel proteins shows that mixing of different evolutionary branches was important to our evolution, "even earlier than DNA evidence can show us," Hawks said.

But what exactly the new results mean for the evolution of H. erectus — and the possibility that it interbred with modern H. sapiens in Eurasia — is still murky. "I think this raises the question of whether we know what Homo erectus even is," Hawks said.

Paleoanthropologists often define an ancient human species based on a group's physical features, such as the size and shape of their bones and teeth ‪—‬ a method called the "morphological species concept." But that way of determining species has been complicated by the rise in genomic analysis over the past two decades, which has revealed interbreeding among groups such as Neanderthals, Denisovans and modern humans, proving that there is some biological overlap among these groups.

But whereas the genetic information shared among groups around 50,000 years ago in Europe and Asia is relatively clear-cut thanks to DNA and genomic analysis, the newly revealed amino acid variations in 400,000-year-old fossils from China are just the first step in clarifying the "muddle in the Middle Pleistocene."

"What I'm concluding is that probably paleoanthropologists of the past were too willing to glom these Middle Pleistocene fossils from China into Homo erectus," Hawks said. "Many of these fossils are probably Denisovan relatives, or possibly they came from other groups we've been calling 'erectus' just because we don't really understand them."

The bottom line, according to Hawks, is that the new study is a great piece of work. "It's tough to look at data like these and not be impressed with the uncertainty of boundaries and the mixing between them in these past people," he said.

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Over the past two decades, some studies have suggested that human brains are shrinking. But there is also evidence that IQ scores have risen over the past century.

But is it possible for us to get smarter as our brains shrink? Live Science contacted experts to find out.

First, it's important to note that a bigger brain size does not necessarily mean higher intelligence, said Jeremy DeSilva, an anthropology professor at Dartmouth College. Brain size "is only weakly related to measures of intelligence in humans. Albert Einstein's brain, for instance, was quite small, and he was Einstein!" he told Live Science in an email.

In Einstein's case, it appears that extraordinary folding patterns in several of his brain regions may help account for his genius. While there is some debate, studies suggest that there is little or no relationship between our intelligence and brain size in humans.

Have human brains shrunk?

Not all scientists agree on whether human brains have gotten smaller. However, many experts we spoke with said there is evidence for shrinkage over time.

"My research indicates that human brain size declined during the [entire span of the] Holocene by about 10% of its volume or about 150 ml on average," Maciej Henneberg, a professor emeritus of anthropological and comparative anatomy at Adelaide University in Australia, told Live Science in an email. The Holocene is an epoch that followed the last ice age, and spans from 11,700 years ago to the present day. In his research, Henneberg looked at the brain size by analyzing skulls from all over the world. In many cases, he analyzed the skeletons personally.

It's important to remember that Homo sapiens emerged around 300,000 years ago, so a brain shrinkage starting around 11,700 years ago would be a relatively recent development.

Other scientists have reported similar findings. "Our lab thinks that the data currently available show a clear, global trend toward a decrease in brain size in more recent times," said DeSilva, whose research looked at more than 5,000 skulls from people who lived in Europe, Asia, Africa and Australia. Many of the skulls date to the Holocene.

Jeff Stibel, who holds a doctorate in brain science and has published a number of papers on the topic of brain shrinkage, said the "Holocene warming period has coincided with more than a 10% reduction in brain size in modern humans." Stibel took part in DeSilva's research, and then gathered more data by analyzing the brain size of roughly 800 additional skulls from around the world.

However, some scientists disagree. Research by Brian Villmoare, an associate professor of anthropology at the University of Nevada, Las Vegas, and his team found no evidence that human brains are shrinking. "I see no evidence that, once we acquired our modern form, that our brains have changed in any meaningful way," Villmoare said in an email.

Some say more nuance needs to be considered. "Brain size in some human populations decreased over the last 15000 years," John Hawks, an anthropology professor at the University of Wisconsin-Madison, told Live Science in an email. "But there are some complexities."

Hawks noted that datasets of brain size tend to overrepresent men of European ancestry, making it difficult to determine whether there is a global trend among diverse populations.

"Brain size did rebound toward larger sizes during the last 150 years in industrializing countries," Hawks said. "This was likely mostly attributable to nutrition and correlated with body size, but whether body size accounts for the entire effect is not clear from the limited data."

Why are human brains getting smaller?

If our brains have shrunk, then why? Scientists have proposed a few ideas.

One has to do with the introduction of farming.

"During the Holocene, humans gradually introduced food production [such as agriculture and animal husbandry] that allowed them to live in larger communities," Henneberg said. "The brute physical strength required for hunting big game and protecting families against strong predators became less necessary while a smaller body size required less food, so it was favoured by natural selection."

In fact, it's not just our brains; our bodies have also shrunk. "At the end of the Ice Age, male body height was about 1.75 m [5.74 feet], whereas in mid-Holocene agricultural communities it was 1.65 m [5.41 feet]," Henneberg said. "Body mass has declined even more since we see thinner (less robust) human bones." Heights have rebounded recently in some parts of the world, and Hawks said that our brain sizes may be rebounding also.

The warming that occurred after the end of the last ice age also may be a factor. Stibel said two biological principles, known as Bergmann's rule and Allen's rule, state that "bodies and organs tend to become leaner in warmer climates to increase surface area and dissipate heat."

Another possible explanation is that human intelligence itself has changed as we have taken on more specialized jobs and share more information with each other, meaning we don't have to know everything, just a subset of knowledge to keep society going.

DeSilva said his team proposed that a "population increase, the subsequent specialization of people into specific roles in society and the growth of collective intelligence may have contributed to individual brain size decrease as modeled in some eusocial insects like ants and wasps." For instance, "I'm a decent enough anthropologist and anatomist, but you wouldn't want me fixing your car or investing your retirement savings on Wall Street."

Stibel agrees that this is a significant factor. "Some ant species that develop complex social systems see similar reductions in individual brain size as the colony carries more of the cognitive load," he said. "We appear to have done something remarkably similar with culture and technology.

"What our research suggests is that we've undergone a fundamental shift in how cognition works," Stibel added. "Rather than relying solely on individual brainpower, we've become extraordinarily dependent on cultural and technological networks."

Stibel noted that large brains can be a burden, consuming more energy which requires people to eat more food to survive. "Large brains are metabolically expensive, consuming roughly 20% of our resting energy and producing significant heat." During times when food is scarce, such as during an Ice Age, this can result in people with larger brains being more likely to die of starvation.

This doesn't mean humans are smarter or dumber than they were; it just shows our intelligence is different.

"We've likely traded some raw computational capacity for the ability to leverage collective intelligence," Stibel said. "Whether that's a gain or a loss depends entirely on how you define intelligence. And, of course, how stable the cultural and technological systems we now depend on turn out to be in the long run."

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The risk of malaria influenced where prehistoric people lived in sub-Saharan Africa, a new study suggests.

The research is the first to link early human habitation with the deadly disease and contrasts with early assumptions that prehistoric people migrated to different regions mainly for agricultural reasons.

In the study, researchers analyzed existing models of climate and environmental data that indicate where malaria was likely prevalent, and compared it with maps of early human settlements. They found that prehistoric humans seem to have avoided regions where malaria was endemic long before the introduction of farming in sub-Saharan Africa between about 3000 and 1000 B.C.

"For a long time, it was thought that infectious diseases only really became a problem with the advent of farming, and this was particularly true of malaria," study co-author Eleanor Scerri, an archaeological scientist at the Max Panck Institute of Geoanthropology in Germany, told Live Science in an email.

But the study by Scerri and her colleagues, published April 22 in the journal Science Advances, suggests that humans have avoided settling in areas with a high risk of malaria for more than 70,000 years.

"Our work shows that we can no longer ignore diseases in the deep human past," she said. "They don't just have a small effect, they have — in the case of malaria, at least — transformative impacts that have helped to shape who humans are today."

Malaria risks

The study authors used data from earlier studies to reconstruct the climate of sub-Saharan Africa over the past 74,000 years in intervals of between 1,000 and 2,000 years.

Then, they calculated a "malaria stability index" for each area at every step, based on modern epidemiological data and the likelihood that an area contained habitats for the Anopheles genus of mosquito. The bites of female Anopheles mosquitoes transmit the parasite Plasmodium falciparum to humans, which causes malaria.

By comparing this index to maps of early human settlements, the authors showed that prehistoric hunter-gatherers in sub-Saharan Africa had actively avoided high-risk malaria hotspots. The researchers said that this behavior, in turn, helped determine human population structures by at least 13,000 years ago — several thousand years before the introduction of farming.

"The key message from our paper is that malaria was already a bit of a problem before agriculture," study co-author Andrea Manica, an evolutionary ecologist at the University of Cambridge, told Live Science. But "it likely became even worse after people became sedentary and settled at high density as a consequence of food production."

The study suggests that Central West Africa was hardest hit, he added, and the region remains a malaria hotspot today.

"Archaeology in Central West Africa is limited, but a number of findings agree with a view that populations in this area were highly fragmented," Manica said.

Malaria hotspots

The study is the first to suggest that the locations of prehistoric human settlements were influenced by the risk of disease, rather than just changes in the climate — although both rainier and warmer weather would have encouraged populations of disease-carrying Anopheles mosquitoes.

"The role of disease in the deep human past, particularly in the earliest, African phases of our species' prehistory has not been well investigated because we lack ancient DNA from those time periods," Scerri said.

But the new study showed how the lack of evidence could be overcome. "We have developed a pipeline that is capable of exploring a number of vector-borne diseases," Scerri said. "It's an exciting breakthrough and we hope it will open up a new field of inquiry."

"We have shown that it is possible to track a disease back in time and assess its potential impact on past inhabitation," Manica added. "The next phase is to start exploring other diseases besides Plasmodium falciparum to see their role."

Simon Underdown, a biological anthropologist at Oxford Brookes University in the U.K., who was not involved in the new study, said he agreed with the study's conclusions.

"Disease has always been with us, and it actually shaped what humans could do, where humans could move," he told Live Science.

See how much you know about early humans with our human evolution quiz!

One idea given for the mysterious disappearance of Neanderthals around 40,000 years ago is a difference in brain power compared with early modern humans (Homo sapiens), who invaded their territory in Eurasia and outcompeted them. But a new study of brain variation reveals that Neanderthals and humans were much more alike than previously assumed.

Neanderthal skulls are quite obviously different in shape from those of early modern humans. While Neanderthals had longer, lower skulls with heavier brow ridges and larger nasal openings, modern humans have more globular skulls with smaller facial features. The inside of the skull, called the endocranium, also looks different in Neanderthals versus modern humans.

"These shape differences have long been used to suggest Neanderthals differed cognitively from modern humans," first author Tom Schoenemann, an anthropologist at Indiana University Bloomington, and colleagues wrote in a study published Monday (April 27) in the journal PNAS.

Because of the anatomical differences in the skulls, many experts have assumed that Neanderthals couldn't talk as well as humans, had poor planning skills, and had limited short-term memory. But, problematically, these differences "were not put into the context of modern human populational variation in brain anatomy, which is known to be substantial," the researchers wrote.

To better understand variation in brain anatomy, the researchers compared two large MRI datasets of the brains of living people: 100 ethnic Han Chinese and 100 Americans with European ancestry. In nearly 70% of the brain regions the researchers assessed, they found that the volume differences between the group of Chinese brains and American brains were larger than those previously found between Neanderthals and early modern humans.

"This evidence does not support the idea of Neanderthals having significantly different brains and cognitive abilities compared to anatomically modern humans that existed at the time," Schoenemann told Live Science in an email.

If modern human population differences are not evolutionarily significant, which is what experts assume, then similar brain differences between Neanderthals and early modern humans would also not be considered evolutionarily significant, the researchers wrote.

The researchers noted that even small differences in behavior and brain size can potentially have significant evolutionary consequences. One of the largest differences between Neanderthal and H. sapiens brains was found to be correlated with attention and inhibition, suggesting Neanderthals may have had a slightly lower executive functioning ability. However, "the correlations between brain anatomy and cognition are very weak," Schoenemann said, and "even if the differences in brain anatomy are correct, the implied cognitive differences would be very small."

Since Neanderthals disappeared relatively quickly after modern humans arrived, "it is not clear that such small differences could actually have meaningfully contributed to their replacement," the researchers wrote. Given that human brains differ between living populations today to a greater degree than Neanderthal and early modern human brains differed some 40,000 years ago, the researchers don't think Neanderthals died out because they lacked the intelligence to adapt.

The new study "strongly points to demography and genetic swamping — possibly as a result of some kinds of cultural differences — and not to innate differences in cognitive ability as the most likely cause of Neanderthal replacement," the researchers wrote. This idea — in which the genes of a minority species are overwhelmed by those of the majority species — echoes recent research that has modeled the integration of H. sapiens into Neanderthal populations, which could have led to the latter's disappearance within as little as 10,000 years.

More research along these lines may be warranted, the researchers concluded, since they only compared the brains of Chinese and American people.

"It is entirely possible that even larger differences exist among modern human populations, further calling into question the evolutionary significance of the estimated Neanderthal differences in brain anatomy with contemporary anatomically modern H. sapiens," they wrote.

Editor's note: This story was updated at 4:36 p.m. EDT to include quotes from study first author Tom Schoenemann.

How much do you know about our closest relatives? Find out with our Neanderthal quiz!

Humans migrated to South America in three distinct waves over the course of thousands of years, a new large-scale analysis of Indigenous Americans' DNA reveals. The investigation also found that genes related to fertility, metabolism and the immune response helped people adapt to their unique environment in the "final frontier" of human migration, the researchers said.

In a study published Wednesday (April 22) in the journal Nature, an international team of scientists detailed findings from the Indigenous American Genomic Diversity Project, which analyzed 128 genomes from people living in Argentina, Bolivia, Brazil, Colombia, Ecuador, Mexico, Paraguay and Peru — an investigation that included 45 populations and 28 language families. The researchers' goal was to better understand how and when people arrived on the continent and the factors that shaped these populations' genetics.

"Until now, only two Amazonian Indigenous populations had been genetically characterized, and due to the particularity of their environment and their isolation, they were not very representative," study first author Marcos Araújo Castro e Silva, a researcher at the Spanish National Research Council's Institute of Evolutionary Biology (IBE) and Pompeu Fabra University in Spain, said in a translated statement. The research team worked in collaboration with Indigenous communities to develop the study and integrate the findings into Indigenous history, study co-author Tábita Hünemeier, head of the Human Population Genomics Lab at IBE, said in the statement.

An analysis of the 128 new genomes plus 71 previously published Indigenous genomes revealed two new findings and contributed additional data that confirmed two previous discoveries.

The researchers found that South America was populated in at least three waves, one of which was previously unknown. Their genetic data suggested that the earliest wave of people flowed into South America more than 9,000 years ago, followed by a distinct genetic lineage — shared today by the Quechua in Peru — that spread through Central America and into South America around 9,000 years ago.

But the genomes also revealed "a previously unrecognized third dispersal into South America," the researchers wrote in the study, that "probably occurred at least 1,300 years ago" from Mesoamerican-related groups. Although that timeframe roughly matches up with the collapse of Mesoamerican cities like Teotihuacan, which declined between A.D. 650 and 750, the genetic data does not point to a single event, Hünemeier told Live Science in an email.

"What we see is a more gradual and complex process, probably involving increasing connectivity and gene flow between Mesoamerica, the Caribbean and South America over time," Hünemeier said.

The genetic analysis also revealed traces of an ancient Asian "ghost lineage" that contributed genes to both Indigenous Americans and early Australasians, who lived in the subregion of Oceania including present-day Australia, New Zealand and the Pacific Islands. This genetic signal, which the researchers call Ypykuéra (meaning "ancestor" in the Indigenous Tupi language of Brazil), has been present at low-but-consistent levels in Indigenous people for more than 10,000 years, they noted in the study. Although the genetic signal of Ypykuéra has been found in modern people, no fossil evidence of the group has been discovered yet.

"Overall, both findings reinforce the idea that the peopling of the Americas was more dynamic and complex than previously thought," Hünemeier said, including "contributions from ancestral populations that are not yet represented in the archaeological or fossil record."

The Indigenous American Genomic Diversity Project, which nearly tripled the number of Indigenous genomes that scientists have sequenced, also revealed that the Americas' Indigenous population was less genetically diverse than other continental human groups but that it also had more genetic diversity than previously thought, including genes important for surviving in the novel environments of the Americas, such as the Amazon rainforest and the Andes.

"Current genetic diversity is only a fraction of the original, as [European] colonization decimated Indigenous populations by 90%," Hünemeier said in the statement. The combination of population collapse, fragmentation and isolation ‪—‬ along with epidemics, enslavement and warfare ‪—‬ caused major evolutionary bottlenecks, which reduced Indigenous peoples' genetic diversity. "Even so, we observe genetic continuity of more than 9,000 years in some regions," Hünemeier said.

Some of the genes that persisted in Indigenous populations were those associated with immune function, energy metabolism, fertility, fetal growth and malaria protection, the researchers wrote, revealing that diverse biological processes were shaped by natural selection in Indigenous American populations. Some of these genes were found to be shared with modern Australasian populations, suggesting several ancient Ypykuéra traits were positively selected to help Indigenous Americans thrive in a new environment.

"Genetic information from Indigenous American populations is essential because these groups have been historically underrepresented in genomic research, leaving major gaps in our understanding of human diversity, evolution and health," study co-author Carlos Eduardo Amorim, an anthropologist at Arizona State University, said in a statement. "Our findings provide the most comprehensive view of Indigenous American genomic diversity and evolutionary history to date."

How much do you know about the first people to reach the Americas? Find out with our First Americans quiz!

Neanderthal toddlers grew faster than their modern human counterparts, likely as an adaptation to living in a cold, harsh environment, new research suggests.

The discovery, which was made using the bones of a young Neanderthal discovered in Amud Cave in northern Israel in the 1990s, suggests that Neanderthals and modern humans (Homo sapiens) followed different evolutionary paths after they split from a common ancestor around 600,000 years ago, the researchers reported April 15 in the journal Current Biology.

The Neanderthal child's partial skeleton, called Amud 7, had been placed in a niche in the cave wall with a red deer (Cervus elaphus) jaw on top of it, possibly as a burial offering. Based on stone tools and the shape of the bones, archaeologists determined that the Amud Cave skeletons were Neanderthals who lived sometime between 51,000 and 56,000 years ago.

The Amud 7 skeleton was found in more than 100 pieces, which included fragments of the child's arms, legs, chest and skull, all of which displayed distinctively Neanderthal anatomical features even at the child's young age. However, because Neanderthal infant skeletons are rarely found, the actual age at death of Amud 7 has been difficult for researchers to pin down.

Archaeologists typically estimate an ancient child's age based on the growth and eruption of teeth and on the size and completeness of various bones. The growth curves for the bones and teeth of modern human babies are well documented, but Amud 7 has revealed that at least one of the Neanderthals' growth stages was much faster than modern humans'.

When the researchers compared the tooth development of Amud 7 with that of modern humans, they found that the Neanderthal's lower front teeth yielded an age estimate of about 6 months. But Amud 7's bones were more in line with those of a 14-month-old modern human. This discrepancy is likely related to differing growth stages, the researchers wrote in the study.

While newborn Neanderthals were comparable with modern human newborns in terms of tooth formation, tooth eruption and the lengths of the arm and leg bones, they had significantly larger skulls. In the second growth stage — infants, toddlers and young children, or about 1 to 6 years old — Neanderthals' bodies grew significantly faster than their teeth, while modern human babies' teeth and bodies grew more proportionately. Then, in later childhood, Neanderthals' body growth and tooth development evened out and more closely matched modern human children's trajectories, the researchers found.

"The results of this study suggest that the growth trajectory of young Neandertal infants may have differed from that of H. sapiens," the researchers wrote in the study. Specifically, Neanderthal babies' bodies developed more rapidly than modern humans' did in the first years of life but then evened out during later childhood. "This suggests an evolutionary strategy emphasizing accelerated development in the early years of life, likely advantageous in the harsh environments Neandertals inhabited," the researchers wrote.

Although this new analysis of the Amud 7 skeleton reveals important information about Neanderthal children's growth and development, the researchers cautioned that more data is needed from other non-adult Neanderthal skeletons. They noted that a larger sample size may shed light on whether this pattern was widespread or a specific ecological adaptation.

How much do you know about our closest relatives? Test your knowledge with our Neanderthal quiz!

Using ancient-DNA analysis, researchers have identified the presence of Streptococcus pyogenes, or group A strep, in a 700-year-old mummy from Bolivia, confirming that strep infections were present in the Americas prior to European exploration. The strain of strep discovered in the mummy is similar to modern ones that can cause strep throat and scarlet fever.

This is the first time group A strep has been identified in archaeological remains, the researchers said.

"We weren't looking for this pathogen specifically," Frank Maixner, director of the Eurac Research Institute for Mummy Studies in Italy and co-author of a study published April 13 in the journal Nature Communications, said in a statement. "When conducting genetic analysis of mummies, we approach the work with an open mind, analyzing not only human genetic material but also the DNA of the numerous microorganisms present in human remains."

Maixner and colleagues had been studying naturally mummified remains found in "chullpas," a type of ancient funeral tower, across the Andean Plateau in Bolivia. These people were buried in the Late Intermediate Period (1000 to 1450), after the collapse of a pre-Inca civilization known as Tiwanaku but before the rise of the Inca Empire.

When analyzing one particular mummy ‪—‬ a young adult male with a modified skull who lived sometime between 1283 and 1383 ‪—‬ the researchers found DNA from several different bacteria, including S. pyogenes and Clostridium botulinum, which can cause botulism.

"The detection of Streptococcus pyogenes was particularly significant," the researchers wrote in the study. "Despite its presence in modern outbreaks, this pathogen has not yet been detected in ancient times."

Group A strep is found globally today and is responsible for a spectrum of diseases, from mild conditions like strep throat to life-threatening infections like necrotizing fasciitis. The bacterium also causes scarlet fever, an illness that was historically one of the leading causes of childhood mortality prior to the development of antibiotics in the 1940s.

Despite the worldwide ubiquity of strep for centuries, information about the evolution of the bacterium has come only from modern strains, leaving unanswered questions about whether it was present in the Americas prior to European colonization.

In the new study, however, the researchers were able to isolate a near-complete genome of S. pyogenes from one tooth of the Bolivian mummy. At 700 years old, the genome is the earliest confirmed occurrence of this bacterium in the Americas, the researchers wrote.

DNA analysis also revealed that the ancient Bolivian strep strain diverged from all other S. pyogenes lineages around 10,000 years ago. This time frame may have coincided with humans' first foray into the Andes, as they encountered previously unknown animals that may have carried the pathogen, the researchers noted in the study.

It's not yet clear, though, which diseases caused by group A strep were present in pre-Hispanic Bolivia. The genome that the researchers identified is most similar to modern strains that are "throat specialists," or the strains that cause strep throat and scarlet fever rather than skin conditions like impetigo and "flesh-eating disease." These strains of strep also increase in prevalence in cooler months, which align with the climate of the Bolivian highlands, which were cold and dry.

The young adult whose skeleton was positive for strep DNA lived in a society with increasing population density and high rates of migration, and the researchers found from his bones that his nutritional status was likely below average. All of this evidence "could impact immune function and susceptibility to such ancient infections or potential outbreaks in the past," they wrote, but they can't confirm exactly how the man died.

Evidence from the new Bolivian strain of strep is consistent with an American origin for the pathogen, the researchers wrote. But because this is the first time group A strep has been identified in ancient remains, the researchers noted that additional work is sorely needed, including a broader dataset of ancient and modern S. pyogenes genomes from Europe, Africa, Asia and the Americas. Amassing that information could help experts unravel the evolutionary history of strep and the impact it had on the lives and deaths of ancient people.

First Americans quiz: How much do you know about the first people to reach the Americas?

Over the past 10,000 years, natural selection has contributed to the evolution of nearly 500 genes in the DNA of West Eurasians, affecting their looks and susceptibility to different illnesses, a new study finds.

Natural selection in this group led to an increased frequency of light skin tone, red hair, and resistance to HIV and leprosy (also called Hansen's disease), and it decreased the frequency of male-pattern baldness and rheumatoid arthritis susceptibility, the new study of 16,000 genomes reveals. This discovery contradicts the long-standing view that recent human evolution was limited.

"Human evolution didn't slow down; we were just missing the signal," study first author Ali Akbari, a staff scientist at Harvard University, told Live Science in an email.

Evolutionary change can occur through a variety of mechanisms, including mutation; natural selection, in which traits that are advantageous to survival are passed to offspring; gene flow, in which genetic material is mixed between populations; and genetic drift, in which the frequency of a gene in a population changes due to random chance.

In a study published Wednesday (April 15) in the journal Nature, Akbari and colleagues developed a new statistical method to identify natural selection over an 18,000-year period in thousands of ancient and modern genomes from people living in West Eurasia, an area encompassing Europe and parts of western Asia, like Turkey.

"Previous work, based on the scars that natural selection leaves in present-day genomes, led to the view that directional selection was rare," Akbari said. But with large datasets like the one that the researchers amassed and methods that can separate the signal of natural selection from other evolutionary processes, "we can now detect small, consistent changes over time," he explained.

The researchers found evidence of natural selection in 479 gene variants in the West Eurasian genome dataset, 60% of which correspond with known traits in present-day people. Some of the gene variants that were strongly positively selected for are involved in expressing traits such as light skin tone, red hair, resistance to HIV and leprosy infections, and the B blood type. They also discovered genes related to a lower chance of male-pattern baldness and a lower risk of rheumatoid arthritis.

The results suggest that all of these variants were useful in the evolution of modern West Eurasian people — but the DNA does not help to explain exactly why these traits were useful. The increase in the frequency of light skin pigmentation probably reflects selection for increased synthesis of vitamin D in regions of low sunlight, the researchers wrote in the study. But it's harder to explain the rise in redheads. It is possible that red hair itself was not beneficial but rather that the genes for the trait are also associated with a more important adaptation.

Some traits were positively or negatively selected at different times, the researchers found. For several millennia, genes for tuberculosis susceptibility increased in frequency and then decreased around 3,500 years ago. Similarly, genes for susceptibility for multiple sclerosis increased until about 2,000 years ago and then decreased in frequency.

"This likely reflects changes in environment or selective pressures over time; for example, the introduction of new pathogens," Akbari said.

The researchers have made their data and methods — called AGES (Ancient Genome Selection) — freely available so that other scientists can expand on this work. Akbari said the research team now plans to explore other groups outside West Eurasia to better understand how the global human population evolved. They have already posted a preprint of a study investigating East Eurasia, which looked at people with East Asian ancestry; this research found similar patterns, Akbari said.

"What is likely to differ across regions is not whether selection occurred, but how local environments and cultural changes shaped it, including factors like diet, pathogens, and climate," Akbari said. "Extending this approach more broadly will help us understand how different historical pressures influenced human biology in different settings."

How much do you know about human evolution? Test your knowledge with our human evolution quiz!

Archaeologists in Israel have unearthed 10 "extremely rare" prehistoric stone hand axes that were crafted to deliberately include geological features, including fossils and geodes, a new study finds.

The hand axes were probably made by Homo erectus between 500,000 and 200,000 years ago, likely because our human ancestors thought these objects were imbued with potency and cosmic significance, the study researchers suggested, although others argue further evidence would benefit the study.

The discovery, reported March 17 in the journal Tel Aviv, is the largest concentration of fossil and geode-bearing stone tools found to date: All previous finds were singular stone tools scattered across continents and time periods.

Local resident and study co-author Muataz Shalata discovered several ordinary hand axes in the Sakhnin Valley, Israel, between 2024 and 2025. Following his discovery, Shalata notified Ran Barkai, a professor of archaeology at Tel-Aviv University.

A dedicated survey in 2025 revealed more than 200 hand axes at Sakhnin Valley, including 10 that include fossils, geodes or other geological features, such as hollows that looked like mini-caves and a concretion forming a round ripple-like feature.

These tools are "unique because until now such items were singularly found, only one extraordinary piece here and there," Barkai, the study's first author, told Live Science in an email."

The discovery contributes to a debate regarding whether early humans recognized or consciously noted geological features and fossils, or whether their occurrence in stone tools was merely accidental. However, the new discovery of multiple tools with these features in the same area suggests it was a deliberate act, the researchers said in the study.

Incorporating these fossil-carrying rocks into tools created "true obstacles towards the stone worker and user," Barkai said, because they made the tools more brittle and difficult to shape. Yet, despite these disadvantages, Homo erectus incorporated these features into their hand axes, which suggests it was done deliberately, he said.

Imbued with potency and cosmological significance

The researchers speculate that early humans were drawn to these unusual features and possibly believed they had metaphysical importance. This, the researchers argue, is a behavioral trait seen across cultures and time and even in other primates, suggesting that curiosity about extraordinary objects is an ancient trait. In this case, the researchers "cautiously suggest" that early humans saw these fossils "as traces of a primordial time and place," and ascribed to them a special potency, they wrote in the study.

Once these rocks were crafted into tools, they were mainly used to butcher large animals, including elephants and their extinct relatives, species that were central to early human survival.

This link between elephants and hand axes is supported by the fact that replicas of stone hand axes were sometimes also made from broken elephant bones, suggesting a deeper relationship between humans, elephants and hand axes, according to the study.

When elephant populations began to decline in the Levant (an area in the Eastern Mediterranean) at this time, it likely created a period of great stress, Barkai said. He stated that previous studies have shown that early humans deliberately placed their hand ax production sites along elephant migration routes close to water sources. The researchers called this the "holy triad of elephants, stone and water," suggesting a deep connection between humans and elephants.

The researchers speculated that early humans saw stone not just as a natural resource to be utilized but also as a way to connect with the cosmos. For example, the study found that Homo erectus deliberately shaped a stone ball from a geode — a painstaking process that would have served no practical purpose, suggesting these early hominins likely saw a value beyond the practical in these features.

"Early humans were more and more desperate for the potency of the cosmos to come to their assistance," Barkai said. "I believe that humans were not just manipulating 'natural resources' by using stone tools, but were doing this while paying respect to these entities … thus the stone tools were always conceived as mediators between humans and the cosmos."

Other researchers note that while the findings are significant, more evidence is needed to further support the symbolic inferences. Sarah Wurz, a professor of archaeology at the University of the Witwatersrand in South Africa who was not involved with the study, told Live Science in an email that "these extraordinary hand axe finds are noteworthy and provide new evidence of the perceptive abilities of past humans." However, she added that "further inferential scaffolding [evidence] would strengthen the interpretation of symbolic behavior."

Barkai plans to conduct more excavations that will provide greater insights into these tools and their uses.

"The artifacts that have been retrieved by now are from the surface only," Barkai said. "We plan to conduct excavations at the site in the future, and will surely run these kinds of analyses on items recovered from pristine archaeological context, as we did in the past with very good results."

Imagine a creature nearly twice the size of a modern African elephant (which can weigh up to 6,000kg [13,000 lbs]). This was Elephas (Paleoxodon) recki, a prehistoric titan that roamed the landscape of what is now Tanzania nearly two million years ago. Now, imagine a group of our ancestors standing over its carcass, then butchering it and eating it.

For decades, archaeologists have debated when the hominin ancestors of humans first started eating megafauna — animals weighing more than 1,000kg [2,200 pounds].

In a new study, our team of archaeologists studying the evolution of the earliest humans in Africa has identified one of the earliest cases of elephant butchery.

This was at Olduvai Gorge in Tanzania, a site famous for containing some of the oldest and best preserved remains of our human ancestors. Dating back to 1.80 million years ago, this discovery at the site known as EAK reveals that our ancestors were engaging with megafauna substantially earlier than previously thought (about 1.5 million years ago was the previous estimate at Olduvai), and in a more sophisticated way.

This finding suggests that hominins (most likely, Homo erectus) may have been living in large social groups at this period, probably because their brains were developing and demanding higher-calorie diets rich in fatty acids.

"Smoking guns"

Part of the reason our ancient diet has been debated is that it is not easy to find evidence of how much animal food early humans were eating and how they were acquiring it.

In traditional archaeology, the "smoking gun" for butchery (cutting up carcasses) is a cut mark left on a bone by a stone tool. However, when dealing with big animals like elephants, these marks are difficult to find. An elephant's skin is several centimeters thick, and its muscle mass is so vast that a butcher's tool might never touch the bone. Furthermore, millions of years of burial can weather the bone surface, erasing any subtle traces. And if a bone is deposited in an abrasive sediment, trampling by other animals may generate marks on bones that look like cut marks.

At the EAK site, we found the partial skeleton of a single Elephas recki individual in the same place as Oldowan stone tools. But to prove that this wasn't just a natural death or the work of scavengers, we couldn't rely on bone marks. Instead, we turned to a new kind of detective work: spatial taphonomy. This is the study of how stone artefacts and bones occur spatially on the same site. We also turned to more direct evidence: bones from those fossilized elephants that had been splintered while they were fresh ("green breaks").

The geometry of a carcass

To solve this 1.8-million-year-old mystery, we analyzed the way the bones were scattered across the site. Every agent that interacts with a carcass — whether it’s a pride of lions, a group of hyenas, or a band of humans — leaves a unique "spatial fingerprint". Lions and hyenas tend to drag bones away, scattering them in predictable patterns based on their weight and the amount of attached meat. Natural deaths, like an elephant dying in a swamp, result in a different, more localised skeletal "collapse".

By using advanced spatial statistics, and later comparing the EAK site to several modern elephant carcasses that we studied in Botswana (not yet published), we found that the spatial configuration at EAK was unique. The clustering of the bones and the density of the stone tools among them did not match the "random" or "scavenger-driven" models. Instead, it reflected a focused, high-intensity processing event. The spatial signature was a match for hominin butchery, which has also been documented at Olduvai sites that are half a million years younger.

This was confirmed by the presence of green-broken long bones not just at EAK, but in several locations in the landscape where other elephant and hippopotamus carcasses were butchered. Today, only humans can break elephant long bone shafts; not even spotted hyenas, which have very powerful jaws, can do it.

Glimpses of this behavior can be detected at other sites too. For example, a cut-marked bone fragment of a large animal (probably a hippopotamus) was documented at El-Kherba (Algeria) dated to 1.78 million years ago.

This intensive and repeated discovery of multiple elephant and hippopotamus carcasses butchered at different landscape locations indicates that humans were butchering the remains of large animals, whether hunted or scavenged.

Why does an elephant meal matter?

This discovery isn't just about a prehistoric menu; it's about the evolution of the human brain and social structure. There is a long-standing theory in paleoanthropology called the "expensive tissue hypothesis". It suggests that as our ancestors’ brains grew larger, they required a massive increase in high-quality calories, specifically fat and protein. Large mammals like elephants are essentially giant "packages" of these calories. Processing even a single elephant provides a caloric windfall that could sustain a group for weeks.

Butchering an elephant is a monumental task, however. It requires sharp stone tools and, most importantly, social cooperation. Our ancestors had to work together to defend the carcass from predators like saber-toothed cats and giant hyenas, while others worked to extract the meat and marrow.

This suggests that even 1.8 million years ago, our ancestors already possessed a level of social organization and environmental awareness that was truly "human".

The discovery also has another dimension. Humans at that time, like modern carnivores, consumed animals whose size was related to their own group size. Small prides of lions eat wildebeests; larger prides eat buffalo and in some places even juvenile elephants. The evidence that those early humans were exploiting large animals comes in parallel with evidence that they were living in much larger sites than before, probably reflecting bigger group sizes.

Why early humans started living in large groups at that time remains to be explained, but this indicates that they certainly needed more food.

A shift in the ecosystem

The EAK site also tells us about the environment. By analyzing the tiny fossils of plants and microscopic animals found in the same soil layers, we reconstructed a landscape that was transitioning from a lush, wooded lake margin to a more open, grassy savanna. Our ancestors were already eating smaller game. There is evidence that two million years ago, they were hunting small and medium-sized animals (like gazelles and waterbucks). A little earlier, they began using technology (stone tools) to bypass their biological limitations.

The evidence from Olduvai Gorge shows that our ancestors were remarkably adaptable, capable of thriving in changing climates by developing new behaviours.

As we look at the spatial layout of these ancient remains, we aren't just looking at the bones of an extinct elephant. We are looking at the traces of a pivotal moment in our own history — when a small group of hominins looked at a giant and saw not just a threat, but a key to their survival.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Editor's note: This story was updated at 12:49 p.m. ET on April 13 to change hominids to hominins in the strapline. Hominins are a group that includes humans and our most closely related relatives.

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Our species, Homo sapiens, is the most geographically diverse of all primate species, permanently living on every continent except Antarctica. We have achieved this through our unprecedented ability to develop adaptations that increase the odds of surviving and producing in different environments.

Highly localized adaptations, like those that enable people to survive at high altitude, arise when there's a sustained environmental pressure driving the need to produce new biological solutions, Herman Pontzer, a professor of evolutionary anthropology and global health at Duke University, previously told Live Science.

In his new book, "Adaptable: How Your Unique Body Really Works and Why Our Biology Unites Us" (Penguin Random House, 2025), Pontzer explores the science of this human adaptability and diversity, and why it's essential to get these facts straight. In this extract, Pontzer looks at how our throats changed to enable speech, and how different populations have adapted to survive in environments where breathing is tricky.

The sophistication and control of the heart and lungs can make the system seem like a jewel of evolutionary perfection. But evolution is a tinkerer, a junkyard mechanic solving problems with the materials at hand. Trade-offs and limitations are inevitable. Just ask Jimi Hendrix.

Hendrix was a guitarist of otherworldly talent who revolutionized rock music in the 1960s. He was also an avid participant in the recreational chemistry of the era, indulging heavily in a range of legal and illicit pharmaceuticals. On September 18, 1970, in a hotel in London, after taking roughly eighteen times the recommended dose of sleeping pills after an evening of drinking, Hendrix died. But while the drugs were certainly responsible for his death, it wasn’t the chemicals per se that killed him. Instead, having passed out and vomited from the massive overdose, Hendrix fell victim to a much more common killer. He choked.

Humans are uniquely vulnerable to choking. More than five thousand die that way each year in the U.S. alone. Other species don't have this problem, which is fundamentally a plumbing issue. Your larynx (also called a voice box) is the doorway to your lungs. It's a stiff cartilage cylinder that can be closed off at the top by two fleshy lips called vocal folds and a flapping lid called an epiglottis. The human larynx sits in a precarious position, low in the throat, practically begging to be clogged with every bite of food or gulp of water. Why would evolution favor such a dangerous position for the larynx, threatening our breathing and access to oxygen, when every other animal (including our ape relatives) has theirs sensibly tucked up high and out of the way, behind their nose?

It turns out the dumb position of our larynx is the result of evolutionary tinkering to our breathing system to produce language. The sound of your voice is produced by squeezing air through your larynx with the vocal folds pushed together. This is similar to the way a trumpet player makes a ptbtptpbptptp! noise by pushing air through their pursed lips (what I'd call a raspberry and my children insist is a fart sound). The puff puff puff of air that escapes becomes pressure waves that travel through the air, which our ears register as sound. Higher or lower notes are achieved by pulling the vocal folds tighter or relaxing them. (Testosterone thickens the vocal folds, which is why men tend to have lower voices.)

You form that sound into vowels by manipulating the shapes of your mouth and throat, and cut it into consonants with your teeth, tongue, and lips. The low position of the larynx makes this possible. If it's higher up, at the same level with the nostrils as we see in other apes, you could make noise, but the ability to shape that sound into words would be severely limited. That's why it's nearly impossible to get a dog, chimpanzee, or other mammal to form speech-like words. They can still communicate, of course, with a bark or a grunt, but the rich sonic landscape of human language is out of reach.

Our ancestors were so social, so cooperative, that the evolutionary benefits of better communication outweighed the increased risk of choking to death. Choking is the price we pay for the ability to speak.

Other adaptations to our breathing and circulatory systems come at a cost as well. When we travel into the mountains, we're faced with the challenge of extracting enough oxygen from the high-altitude air. The evolved solution is to produce more red blood cells. When the liver and kidneys sense low oxygen concentrations in the blood, they produce the hormone EPO [erythropoietin], which stimulates the bone marrow to crank out more red blood cells. (That's why some endurance athletes cheat with EPO injections — it gives them extra red blood cells and oxygen-carrying capacity.) It's a good solution, but it increases the ratio of cells to water in the blood, making it slightly thicker. That, in turn, can cause altitude sickness, which typically involves headaches and nausea, but can progress to dangerous and even fatal fluid buildup in the lungs and brain.

Native populations in the Andes, the highest mountain range in South America, live with elevated red blood cell counts their entire lives. They have larger lungs and rib cages as well, through what appears to be a combination of genetic adaptations for increased air exchange and the environmental pressures of growing up at high altitude. But while a number of genetic adaptations to altitude have been identified in Andean groups, they still struggle with altitude sickness. Approximately 15 percent of adults experience chronic mountain sickness. The physiological solution to low oxygen levels carries a steep price for many.

Intriguingly, altitude sickness isn't as much of an issue for native high-altitude communities in the Himalayan Mountains of Asia. Himalayan and Andean populations are descended from different lowland groups thousands of miles and thousands of years apart. Their movements into the mountains were completely independent, and the adaptations they evolved solved the same set of challenges, but in different ways.

Himalayan populations carry a particular allele [version] of a gene called EPAS1 that's involved in the production of red blood cells. This Himalayan allele has the effect of keeping EPO levels and red blood cell numbers low, allowing people to live with the chronic stresses of altitude without developing mountain sickness. This solution comes with its own downsides, as it also means their ability to carry oxygen is limited, but other adaptations in their vessels and breathing rate maintain oxygen delivery throughout the body.

Even more remarkable than the Himalayan EPAS1 allele is the story of how they got it. As our ancestors spread out across Africa and then Eurasia over the past two hundred thousand years or so, they encountered other closely related humanlike species, like Neanderthals in the Near East and Europe. And, like humans everywhere throughout history, some of our ancestors weren't particularly picky, and slept with them.

Our species were so genetically similar that these couplings produced fertile children, hybrids of our species and others. (Some would argue that we should consider Neanderthals and other groups human because of this ability to interbreed — a semantic argument that's fun to have over drinks with an anthropologist.) We can find the genetic evidence of these affairs scattered around our genome today, fragments of DNA from other species that allow retail genetics companies to calculate how much Neanderthal DNA you carry, for example. I'm a bit less than 2 percent Neanderthal, genomically speaking.

Most of these fragments don't have any impact on how our bodies function — they're just mementos from our ancestor's wild affairs, like misspelled tattoos from some Paleolithic spring break, and a reminder that humans will sleep with just about anything. Using the distinction we discussed in the last chapter, these alleles would be considered neutral.

The Himalayan EPAS1 allele is a clear exception. That allele appears to have entered the human gene pool through a Paleolithic tryst with a group called the Denisovans, somewhere in Asia, roughly fifty thousand years ago. For tens of thousands of years it was just there in the mix, a neutral allele that had no strong effect on survival or reproduction. But around nine thousand years ago, as some of those populations started pushing farther and farther up into the mountains, that allele proved to be advantageous. Those with the Denisovan variant for EPAS1 were free from altitude sickness, and better able to thrive and raise families in the high mountains. It went from neutral to local and became the predominant allele in Himalayan populations, the adaptive EPAS1 allele we see in virtually everyone native to the Himalayas today.

Another remarkable case of local cardiovascular adaptation was discovered just recently, in a population known as the Sama (also called the Bajau). The Sama live on houseboats in the ocean around the Philippines, Indonesia and Malaysia, spending nearly all of their lives at sea. Theirs is a hunter-gatherer lifestyle, but in the ocean: they spearfish and collect food in the depths, sometimes more than two hundred feet below the surface, swimming or using weights to hold themselves down as they walk the seafloor. Like many Indigenous groups, their lifestyle is rapidly changing, but traditionally they could spend four or five hours per day underwater, foraging. It's a lifestyle they appear to have maintained for thousands of years.

Life spent partially underwater poses similar oxygen-delivery challenges as life in the mountains. One evolutionarily ancient response to diving, common among mammals, is to contract the spleen, an organ the shape of a child's slipper tucked up high in the left side of your abdomen, beside your stomach. The spleen is a monitoring station for the immune system, a spongelike organ that checks the blood for bacteria and other nasties. Since it's normally full of blood, it's essentially a reserve tank of red blood cells. When you dive into cold water, the spleen contracts, ejecting its payload of red blood cells to help oxygenate the rest of your body. If you train breath-holding, your spleen will grow to do this job more effectively. High-mountain groups, like those in the Himalayas, have larger spleens than lowlanders, apparently from a combination of genetic adaptation and a life spent at altitude.

Natural selection has favored an allele of the PDE10A gene that increases spleen size in the Sama, with nearly double the average volume for those carrying two copies of the allele compared to those with none. Other diving-response genes appear to be under selection in this population as well. Environment still matters — all that breath-holding also helps them increase the size of their spleens. But it's a clear case of genetic adaptation, with natural selection responding to a consistent, strong, and localized challenge in the Sama population.

Excerpted from Adaptable: How Your Unique Body Really Works and Why Our Biology Unites Us (Penguin Random House, 2025)

For 60 years, the earliest known human species has also been one of the most mysterious. Homo habilis was added to our family tree in 1964. But it's long been unclear exactly what the ancient species, which lived between about 2.4 million and 1.65 million years ago, looked like.

That's because, until recently, only three very incomplete fossilized skeletons had been unearthed.

Then in January, researchers described a fourth, more complete skeleton — and it revealed that H. habilis had an anatomy very unlike our own. The discovery has some researchers asking a big question: Is the earliest known human ancestor not human after all?

"As we have discovered more fossils, we've stretched the definition of the Homo genus," Bernard Wood, a paleoanthropologist at the George Washington University in Washington, D.C., told Live Science. "Maybe this time we just stretched it too far."

Obviously our species, Homo sapiens, belongs in the Homo genus. We also know that our closest living relatives, the chimpanzees and bonobos, don't. This means that the human genus evolved at some point after our evolutionary lineage, which includes humans and our closest extinct relatives, split away from the chimpanzee line, an event that occurred more than 5 million years ago. So, when exactly did the human genus evolve?

One approach would be to argue that it dates to the split with the chimpanzee lineage. But the first creatures that appeared after the split don't look much like we do. They include species, like Australopithecus afarensis, that had long, ape-like arms and relatively small brains.. This species existed in Africa between about 3.9 million and 2.9 million years ago, and includes the famous Lucy skeleton. Very few researchers consider Lucy to be human.

Most anthropologists, however, have historically considered H. habilis a member of the Homo genus.

Few skeletons

The first, very incomplete Homo habilis skeleton was discovered in Tanzania in the 1960s. The 1.75 million-year-old specimen included fragments of the skull, from which it was possible to estimate that they came from an individual whose brain had been roughly 45% the size of the average living person's. This may sound small, but that was substantially bigger than the average australopithecine's brain, which was about 35% the size of ours. Because of this evidence, the skeleton was placed in our Homo genus, and given the name Homo habilis, meaning handy or skillful human, it was a decision that most researchers have accepted.

But the H. habilis skeleton described in 2026 complicates things. This skeleton is 2 million years old, and was found in Kenya, about 500 miles (800 kilometers) north of where the first H. habilis remains were unearthed. Just like the first skeleton, the Kenyan skeleton is far from complete. But the bones that survived give us our best ever look at H. habilis's arms, said study co-author Carrie Mongle, a paleoanthropologist at Stony Brook University in New York. The problem is that those arms aren't like ours. Instead, they are long and ape-like, similar to the arms of our australopithecine relatives like Lucy.

"They are very much australopith-like," Ian Tattersall, a paleoanthropologist at the American Museum of Natural History in New York City, told Live Science. In an article published earlier this year, Tattersall argued that these ape-like arms are a clear indication that H. habilis wasn't a member of the human genus.

He isn't the first to make this suggestion. Wood and his colleague, Mark Collard, an archaeologist at Simon Fraser University in Canada, argued in 1999 that H. habilis wasn't a member of the human genus. By then, the second and third H. habilis skeletons had been discovered, and although extremely incomplete, they hinted that the species had limb proportions unlike ours — something that the fourth skeleton confirms.

Wood and Collard suggested transferring the species to the same genus as Lucy, which would mean renaming Homo habilis to Australopithecus habilis. Tattersall doesn't think that's a good solution, because the species had human-like brain size and teeth. He thinks habilis should be put in its own genus, although he hasn't yet come up with a name.

A different approach

Other researchers, meanwhile, suspect that Wood and Tattersall are both wrong.

They think there is no need to rename H. habilis despite its arms. "Those ape-like limb proportions don't necessarily tell us all that much," Carol Ward, an anthropologist at the University of Missouri, told Live Science. This is because of the way most evolutionary scientists operate when they are defining species and genera.

We know that our very earliest ancestors, living just after the split with the chimpanzee line, spent plenty of time climbing trees, where long, ape-like arms would have been useful. Gradually, they adapted to spend more time walking on the ground before ultimately evolving into humans.

These bipedal ancestors probably no longer needed long, ape-like arms. But crucially, Ward said, long arms were almost certainly not a hindrance to survival either. Under those circumstances, even the first species in the Homo genus might have retained the long arms of their ancestors, because there was no strong evolutionary pressure to shorten them. Why arms eventually shrank is still not entirely clear, although some researchers think shorter arms may have brought some subtle advantages while running and using tools. This suggests there was weak evolutionary pressure for shorter arms, meaning they shrank, but at a relatively slow rate.

There's a broader point here. "We want to think there was this big change with Homo, that we're different from everything else that came before," Ward said. "But this H. habilis skeleton supports the idea that maybe there was a more gradual transition from australopiths to Homo."

This idea highlights an awkward problem that scientists are still grappling with.

Evolution is so complicated that it's surprisingly difficult to divide living things into clear groups, such as species, which is one reason why there are now dozens of different ways to define species, and a heated debate on which one is the best. It turns out that genera are just as difficult to define, which means there isn't actually any agreement on what a genus is, Wood said.

In other words, researchers will probably continue to debate whether or not H. habilis is in the human genus, for the simple reason that they still can't fully agree what a genus actually is.

Human origins quiz: How well do you know the story of humanity?

Before Neanderthals went extinct, they experienced a major upheaval that resulted in just one of their genetic lineages surviving in Europe and then expanding across the continent, a new study shows.

The findings, published March 23 in the journal PNAS, may shed light on what ultimately doomed the Neanderthals.

Neanderthals were among the closest relatives of modern humans (Homo sapiens), with their lineages diverging around 500,000 years ago. Although Neanderthals once ranged across Eurasia, they are generally thought to have gone extinct about 40,000 years ago.

DNA recovered from Neanderthal fossils can shed light not just on their extinction but on their history in general. In the new study, researchers examined DNA from mitochondria in cells, which help generate energy for the body, and get passed down from mothers to offspring.

The scientists gathered 10 mitochondrial DNA sequences from Neanderthals excavated from six archaeological sites in Belgium, France, Germany and Serbia. They analyzed them alongside 49 Neanderthal mitochondrial DNA sequences released in previous research.

The team found that in Europe, where Neanderthals ultimately died out, several mitochondrial DNA lineages existed until about 65,000 years ago. After this point, these groups were replaced by a single Neanderthal mitochondrial genetic lineage originating from southwestern France. These "Late Neanderthals" proceeded to disperse across Europe.

"This tells us there was this major disruption in Neanderthal history," study senior author Cosimo Posth, a paleogeneticist at the University of Tübingen in Germany, told Live Science. "There was really a genetic transformation."

Posth noted that about 75,000 years ago, glaciers came to dominate Europe.

"We don't think our findings suggest that Neanderthals were migrating to the Mediterranean," he said. "We think Neanderthal groups in northern Europe perished, while a Neanderthal group that was already in southwestern France survived this climate change and then went on to expand across a broader region. Neanderthals had experienced multiple glaciations before, but the last one proved harsh on their survival."

The study also found that "there was a kind of genetic impoverishment among the Late Neanderthals," Posth said. "Since they appeared to emerge from this single group, their genetic diversity overall was reduced drastically compared to what came before — they were all extremely similar on a genetic level across Europe, from Spain to the Caucasus to northern Europe."

This low genetic diversity ‪—‬ which grew most pronounced about 42,000 years ago, shortly before Neanderthals generally died out ‪—‬ "might have played a role in their extinction," Posth noted. "We don't think there was a single reason the Neanderthals went extinct, but this lack of genetic diversity would have made them more predisposed to not really survive climatic changes and other disruptions."

Likewise, Neanderthal groups in the Altai Mountains of Siberia were more closely related to each other than to European Neanderthals, and these Siberian Neanderthals also had low genetic diversity and lived in small, isolated groups, another March 23 study published in the journal PNAS found.

Despite this low genetic diversity, the Late Neanderthals in Europe appeared quite diverse across sites in terms of their artifacts and art. "So after the Neanderthals re-expanded across Europe, we think that Late Neanderthal groups were not highly connected with each other," Posth said. "This would have led to more inbred groups, explaining the low genetic diversity, but also more cultural and archaeological diversity, since these groups were isolated and so would have developed more specialized cultures."

"We've seen evidence that Neanderthal populations replaced each other, and this paper really creates a ground story as to why that might be — because Neanderthals went extinct in places all the time, and then other Neanderthal groups went in and recolonized the same places," Fernando Villanea, a population geneticist at the University of Colorado Boulder who was not involved in the study, told Live Science.

Future research could seek to test these findings by analyzing DNA from Neanderthal cell nuclei instead of their mitochondria, Posth said. However, this will be a major challenge, as DNA from nuclei is several hundred times less abundant than DNA from mitochondria in cells.

Neanderthal quiz: How much do you know about our closest relatives?

Two Neanderthals present at the same cave site 10 millennia apart were distant relatives, a tiny 110,000-year-old bone fragment from the Altai Mountains in Siberia reveals. The fragment has also produced the fourth full genome of a Neanderthal to date, shedding light on how small and isolated Neanderthals were long before they disappeared around 40,000 years ago.

Researchers found the bone fragment in Denisova Cave, which both Neanderthals and Denisovans lived in off and on for nearly 300,000 years. In a study published Monday (March 23) in the journal PNAS, the researchers compared the genome of the 110,000-year-old Neanderthal male (called D17) with three other complete Neanderthal genomes to better understand Neanderthals' population structure.

The researchers compared the genome of D17 with the genome of a female Neanderthal (called D5) dated to 120,000 years ago from the same cave. They found that, while D5 was not a direct ancestor of D17, the two Neanderthals belonged to closely related lineages connected by a common ancestor. This distant biological relationship suggests Neanderthals had a long-term presence in the Altai region, the researchers said.

"But it is likely that Denisova Cave was part of a broader landscape used repeatedly by these Neanderthal populations over time, rather than a site occupied by a single, continuous group," study first author Diyendo Massilani, a genetics professor at the Yale School of Medicine, told Live Science in an email.

The study results also revealed that Neanderthals in the Altai region lived in very small and highly isolated populations of 50 or fewer people, as shown by stronger genetic markers of inbreeding. Specifically, researchers found that the individuals they analyzed had large sections of identical DNA, an indication that their parents were very closely related — as close as first cousins, for example.

The new research complements previous studies that showed Neanderthals lived in smaller and more isolated groups than our own species did. A 2022 study indicated that one Altai Neanderthal community numbered around 20 individuals, while another study provided evidence of a group being isolated for roughly 50,000 years. Many researchers have pointed to inbreeding and isolation as causes for Neanderthals' disappearance around 40,000 years ago. But the latest results suggest that Neanderthals also survived for long periods under extreme conditions of isolation and small population size.

Massiliani and colleagues also discovered that Altai Neanderthals were very different from later European Neanderthals. In their genetic analysis, the researchers found that Altai Neanderthal D17 was more closely related to D5 than either of them was to Neanderthals in Europe or to later populations in the Altai region. This suggests that Neanderthal populations from eastern and western Eurasia became genetically different from one another in a relatively short time frame and within a fairly small geographic area.

"Even though the individuals from which we have genomes were separated for only about 50,000 years on average, they reached levels of difference similar to what we see today between some of the most distinct human populations, like people from Central Africa and Papua New Guinea that separated about 300,000 years ago," Massilani said.

Likely because they were small and isolated, Neanderthal populations became genetically distinct from one another much more quickly, Massilani said. This may have been because in small, isolated groups, a process called genetic drift can cause random genetic changes to become more common over time.

"We already knew that Neanderthals were not a single, homogeneous population spread across Eurasia, but a patchwork of groups shaped by complex demographic processes, including divergence, migration, local extinctions and replacements," he said. "What is striking in our results is just how differentiated these populations could become."

The high amount of genetic separation and differences between groups may have limited Neanderthals' ability to adapt to environmental changes, Massilani said.

The study provides new details about how Neanderthal populations were structured, one expert said.

"To have two sequenced Neanderthals in such a close geographic place does bring new and more fine-grained insight" into their population, Léo Planche, a population geneticist at Paris-Saclay University's Interdisciplinary Laboratory for Digital Sciences who was not involved in the study, told Live Science in an email. "We start to have enough Neanderthal genomes to actually have some claim about their population structure. Populations are groups of individuals, so the more data the better."

Editor's note: This article was updated on March 27, 2026 to note that the vast majority of Neanderthals went extinct 40,000 years ago, not 34,000 years ago as was previously stated.

Neanderthal quiz: How much do you know about our closest relatives?

The discovery of an enigmatic ape's 18 million year-old fossils in Egypt hints that the ancestors of all living apes, a group that includes humans, may have originated in northeast Africa or Arabia, a new study finds.

Scientists have long assumed that modern apes originated in East Africa, but the newfound fossils, which belong to a new genus and species, suggest they emerged farther north.

"Discovering a fossil ape in this region is both significant and somewhat surprising," study first author Shorouq Al-Ashqar, a paleontologist at Mansoura University in Egypt, told Live Science in an email. "But it also highlights how incomplete our picture has been."

Previous research has established that apes first appeared at least 25 million years ago. They soon flourished, diversifying into dozens of species and spreading across Africa, Europe and Asia.

But relatively few of these ancient apes were on the evolutionary line leading to modern apes ‪—‬ a group that includes humans and other great apes, along with gibbons and siamangs. Moreover, the apes that were on our ancestral line seem to have been confined largely to East Africa. As such, this region has long appeared to be a good place to search for the origins of modern apes.

However, after finding the fossilized remains of an ape that lived in what is now northern Egypt between 17 million and 18 million years ago, Al-Ashqar and her colleagues challenge this idea in a study published March 26 in the journal Science.

The remains, discovered in 2023 and 2024, are very incomplete ‪—‬ just a few fragments of lower jawbone and some worn teeth. But Al-Ashqar and her colleagues established that the remains didn't belong to any known ape species. The researchers have assigned the fossils to a new genus and species named Masripithecus moghraensis; the genus name translates to "Egypt monkey or trickster" in Arabic and Greek, while the species name refers to "Wadi Moghra," where it was found.

The find is important, said Sergio Almécija, a biological anthropologist at the Miquel Crusafont Catalan Institute of Paleontology in Spain who was not involved in the study. "Any new fossil ape discovery is precious because of their scarcity, especially when it comes from a region where their presence has previously gone unnoticed," he told Live Science in an email.

To determine where M. moghraensis fits in the ape evolutionary tree, Al-Ashqar and her colleagues looked at the age and anatomy of a range of ape fossils, as well as evolutionary information in the DNA of living apes.

The analysis placed M. moghraensis on the ancestral line of living apes, just before the split between the great-ape group and the gibbon-siamang, or "lesser ape," group. This implies that M. moghraensis was very closely related to the last common ancestor of all living apes. That, in turn, suggests this common ancestor must have lived in roughly the same place as M. moghraensis.

"The highest odds are [that it lived] in the northern part of the Afro-Arabian landmass," study co-author Erik Seiffert, an evolutionary biologist at the University of Southern California in Los Angeles, told Live Science in an email.

However, not everyone agrees with this interpretation. Almécija describes it as "a bit far-fetched." He would like to see far more complete fossils of M. moghraensis before any attempt to update mainstream scientific ideas about the last common ancestor of living apes.

But Al-Ashqar said the jaw and teeth are among the most useful skeletal parts for working out the evolutionary history of apes. "In mammalian palaeontology, dental anatomy is a cornerstone for interpreting diet and evolutionary history," she said.

Moreover, the idea that modern apes originated in North Africa and Arabia about 17 million years ago fits to some extent with known evidence, according to David Alba, a paleontologist at the Miquel Crusafont Catalan Institute of Paleontology who wasn't involved in the analysis.

For instance, today's nonhuman great apes are found in Africa and Southeast Asia, and fossils show great apes once lived in West Asia, too. Given this information, and the fact that today's lesser apes are found in South and Southeast Asia, "modern hominoids [apes] must have gone through northeastern Afro-Arabia," Alba told Live Science in an email, although this doesn't necessarily mean they originated there.

The exact evolutionary significance of M. moghraensis remains unclear, but its discovery hints that there are more ape fossils yet to be found in and around Egypt. "Further work there could significantly refine our understanding of early ape evolution," Al-Ashqar said.

Human origins quiz: How well do you know the story of humanity?

Humans have evolved the ability to live anywhere on Earth, thanks to gradual changes to our biology and our knack for developing new technologies, like clothes and shelter. This adaptability is often touted as being unique to our species, Homo sapiens.

In his new book, "Adaptable: How Your Unique Body Really Works and Why Our Biology Unites Us" (Penguin Random House, 2025), Herman Pontzer, a professor of evolutionary anthropology and global health at Duke University, explores how local environments work in tandem with genetics to produce the full spectrum of diversity we see in people today.

The book journeys through the human body and focuses just as much on what connects us as it does on the conditions required for differences to arise. Pontzer weaves in his work with contemporary hunter-gatherer populations, like the Hadza in Tanzania, to explore the lifestyles of pre-farming cultures and how the stark departure from these ways of life for many people today is making us sick.

"Adaptable" is a finalist for the PEN/E.O. Wilson Literary Science Writing Award, which celebrates excellence in nonfiction in the physical or biological sciences. The winner will be announced March 31 at the Literary Awards Ceremony and will receive a $10,000 cash prize.

Live Science spoke with Pontzer about his book and why understanding why and how diversity occurs is essential for questioning and challenging scientific misinformation.

Sophie Berdugo: Why did you decide to write the book now?

Herman Pontzer: In having conversations about "Burn" [Pontzer's book on the science of the metabolism (Penguin, 2022)], it became very clear to me that when you move outside of the ivory tower and start having these conversations more broadly, that there's just a lot of misunderstanding and misinformation about just how the body works in general. It's not just our metabolism. The metabolism is one of those blackbox things that we love to blame everything on and people don't really understand what it means or how it works.

SB: What is your favorite fact about the human body that you feel is completely underappreciated?

HP: I mean, where to start? Your kidneys. Kidneys are the forgotten essential workers of the body. And I could start anywhere, but let's start there ‪—‬ because if I say brains or hearts, people go, "Yeah, those are important; we know that."

Your kidneys, man: 180 liters [47.5 gallons] of water a day [are] filtered through your kidneys. All of the detox stuff that you think you're doing with the supplements you're taking, they're [your kidneys are] doing it for free and better. Somehow our bodies have learned to regulate water in a way that's different from the other apes, because we evolved in a dry environment. So, it's the interplay of water balance across our whole systems.

Spleens ‪—‬ let's do another unappreciated organ. Most people don't even know what their spleen does, I think. But among others, it's an immune function organ. Your spleen is this reservoir for red blood cells. And so, whether you're at altitude and you need a little bit more oxygen, your spleen gets bigger to be this bigger red blood cell reservoir for that.

There's this fascinating population called the Sama in the Philippines. They spend their lives on boats and in the ocean, and they forage underwater. And so there's been local adaptations, local evolution to give them bigger spleens [to have more blood oxygen when holding their breath for long periods under water when diving for food]. The alleles, the gene variants, that give them bigger spleens have become more common, and now people there have bigger spleens, on average, than everybody else.

Literally everywhere you look in the body, there's a story that I bet you haven't heard of.

SB: That case of the spleen being enlarged in this population in the Philippines is a great example of a local adaptation. Could you explain how these local adaptations occur?

HP: To talk about those local adaptations becomes a little bit tricky because they do happen, right? Certain populations do have a trait that gets more common there, or bigger or smaller, whatever it is. Natural selection can shape a trait in a population, but it's actually pretty rare because the conditions have to be just right.

So how do we do it? Local adaptation is just like any other kind of evolutionary adaptation. The reason a certain trait becomes common in a place is because it helps individuals there survive and reproduce. And that could be anything from being the right body shape and size to having a bigger spleen that helps you forage underwater. Anything that helps you survive and reproduce could end up as a local adaptation.

But the important thing here for why we see these localized events happening — and what makes them different from things that affect our whole species — is that it really has to be localized to a specific environment. It can't be that if the same trait is good everywhere, then that trait's going to spread because there's so much interbreeding, gene flow as we call it, that eventually if it's a good trait everywhere, it'll get everywhere.

So it has to be just good there. There has to be something about that trait that makes it really helpful right there but not other places. And that has to persist for generations and generations so that there's enough time for selection, because natural selection acts very slowly over generations. So it has to be good for survival and reproduction, has to be very localized and persistent for generations and generations.

Very few selection pressures meet all those criteria. Skin color is a good example of one that does ‪—‬ the best skin color to have in terms of ultraviolet light production. The darker your skin, the more protected you are against ultraviolet light damage versus having lighter skin if you need to be able to make more vitamin D, because that's the trade-off.

Those conditions have been around since the sun and the Earth have been where they are. There's always been more ultraviolet light at the equator and less towards the poles, and so that gradient has been really consistent. And then we see, surprisingly, a really consistent gradient in local populations' skin tone, how much melanin they make and, therefore, how dark their skin is.

[Then there are] things like high-altitude adaptations. The Himalayas have been thousands of meters tall since forever basically, for our purposes. And so humans living there have always had that selection pressure to be able to handle high altitude. And so you see altitude adaptations there. That's the kind of stories we see with local adaptation.

Where we get into trouble is when people talk about local adaptations with things like heart disease. There's been the argument in the '90s that Black Americans might be more likely to have heart disease because there's some localized set of alleles that affects their heart function that makes them more likely to develop hypertension and heart disease. Well, that doesn't make a lot of sense, because the selection pressures on the heart have been kind of the same for our whole species forever.

Same with all these ridiculous and really dangerous things about IQ evolution in different populations. Having a smart brain has been selected for — it's been a good idea — for our whole species since forever. And so any traits that make us have smarter brains are going to be selected for equally everywhere. Gene flow is going to push them all around.

SB: So hypothetically, if I was born with the same genetics but in the Philippines, like your earlier example, instead of the U.K., would the environment override the genetic hand I've been dealt?

HP: The way I try to talk about genetics in my classes and in the book is, your genetics — the hand you're dealt — kind of gives you a universe of possibilities where you could end up. Now, it's not unlimited. There's nothing that you could ever do to me that would have made me 8 feet [2.4 meters] tall, right? My parents could have given me all the best nutrition. I was never going to be 8 feet tall, or even 7 feet [2.1 m] tall, for that matter. So there are limits.

So I don't think of it as overriding. I think whether nature or nurture is what you see emerging more, it's almost always nurture. The environment usually has a much, much larger effect. But they really work together.

SB: What role does epigenetics play in shaping how you develop over developmental time, rather than evolutionary time?

HP: It's a wonderful example of nature and nurture working together because epigenetics is the environmental effects on your body that actually sort of change the way that your genes act for the rest of your life. An environmental experience, a stress, can affect the body in a way that it actually affects the genome, which affects your DNA so that a particular gene might be turned off or actually amplified. It can have different effects for the rest of your life.

But what's really interesting about epigenetics is this possibility that those changes might persist across generations. And so we know this is true in mice, that the epigenetic effects on the genome that we see within a lifetime are somehow transmitted to the offspring and they will have those same epigenetic effects. So the environment experienced by mom as she's growing up could actually affect her offspring when they're born and for their lives.

We have some interesting hints that it's also happening in humans. It's a really exciting space to watch in biology. I don't think we have the full answer yet for humans; it's just so hard to do the work because you're talking about studies that take decades, basically. But it's an exciting new frontier in the sort of nature-nurture interface.

SB: Would you mind explaining what evolutionary mismatches are, and why they're important?

HP: Our species evolved as hunter-gatherers. And so that environment's been the norm for humans for millions of years actually, even before we were Homo sapiens. Being a hunter-gatherer looks different depending on where you are in the world and what time frame we're talking about, but it always involves a lot of physical activity. It always involves foods that you're getting from the wild environment around you. It generally involves a fair amount of pathogens and stuff — the world's dirty out there in the wild. And so they're the kind of environments that our bodies are evolved to be best at because that's what shaped us.

Our environments today are so different from that, and that's the mismatch. The environment that I'm living in right now —‬ my house is climate controlled; I've got thousands of calories of food in the refrigerator; if I don't want to walk around too much today, I don't have to. I've got all sorts of antibacterial soaps and antibiotics if I need them.

Our environments have shifted so much that we're well outside the kind of micro-adjustments our bodies are used to making over a lifetime. And so our physiologies respond in ways that can be bad ‪—‬ so, heart disease, allergies, all sorts of modern ailments that we know didn't used to be common but are common now because of that mismatch.

SB: You mentioned how you see the human body as an anthropologist. You talk throughout the book about the Hadza and other contemporary hunter-gatherer populations. What can we learn about local adaptations from these populations?

HP: We are an incredibly diverse species. Our ability to adapt to our different environments and the cultural adaptations we see, the biological — that's our superpower. That's why there's 9 billion of us and not 9 billion of some other primate. We are as successful as we are because of this adaptability, this flexibility. And what that means is that if we only look to our own population, if I only did this book pulling what we could understand from my fellow Americans, it would be an impoverished book. There would be less to say, and we'd learn less about our bodies and ourselves because we wouldn't have the full extent of human diversity to pull from and learn from.

SB: Your book covers a lot of ground. What do you hope readers take away from it?

HP: More than anything, I hope it gives them the tool set to engage because they're going to put that book down, and the next day they're going to read the paper or be online, and they're going to see some new study about the brain or about diet or they're going to hear some headline about vaccines. And I want people to have a tool set to digest that, make sense of it, and ask the right questions about how we interpret all of this and move forward.

SB: What are those key questions that you hope readers will start to ask?

HP: First of all, to understand that diversity is multilayered. And so, just because I know the color of your skin, it doesn't mean I know anything else about you. I can understand something about that and why people's skin might be darker or lighter and understand that that's a separate question completely from hearts and heart health, or intelligence or anything, really. All these systems develop independently. So, when we think about diversity, we need to move away from the categories that we're taught and [away from] putting everybody in a bucket, and understand this is multilayered. It's true for yourself; it's true for everybody else.

Science has done a lot of work in the past couple hundred years, at least, on the human body to develop some really important consensus ideas around health. We know what kinds of diets keep us healthy. We know that vaccines keep us healthy. We can understand these things and move forward, comfortable in that knowledge. So the debates, for example, around vaccination, I think, are hurtful because we actually have been debating vaccines for 300 years at least, and the evidence is really clear that they're one of the biggest public health victories ever.

So both the kind of concrete details like that, but also the kind of mental tool kit to how we understand diversity. I think those are two different things to walk away with.

Editor's note: This interview has been condensed and edited for clarity.

Humans are the only species with a chin — a feature absent from even our closest relatives. Indeed, it's such a unique anatomical quirk that it's one of the main traits anthropologists use to identify Homo sapiens remains in the fossil record.

Yet, for such a defining feature, we know surprisingly little about its evolutionary purpose. So why are we the only species with a chin?

This question is hard to answer because experts haven't agreed on a single definition of a chin. While some researchers have argued that animals like elephants and manatees have chin-like protrusions, they’re not the same T-shaped structures that protrude beyond our own bottom teeth. As a result, some scientists have moved away from thinking of the chin as a single trait, instead referring to it as the collective result of interactions between many different parts of our head and jaw.

"So much about the chin is complicated," said Scott A. Williams, an evolutionary morphologist at New York University. "It cannot be quantified by a single metric but is rather composed of a constellation of morphological features."

A better understanding of the chin's function, in turn, could help scientists craft a definition. Experts have proposed several possible purposes for the chin.

Some have suggested that as we evolved smaller teeth, the chin appeared to reinforce our lower jaw and keep our teeth from breaking as we chewed. Others believe the chin may be linked to yet another unique human trait — our capacity for speech — with the chin providing an anchor point for our tongue muscles. And still others say the variation in how pronounced our chins are offers a hint that it could be linked to sexual selection.

Noreen von Cramon-Taubadel, an evolutionary morphologist at the University at Buffalo in New York, set out to winnow that list by determining whether the chin could have evolved by random chance or if evolution has been acting upon it directly.

To do so, von Cramon-Taubadel and her team studied dozens of traits linked to head and mandible size, including nine traits associated with the chin. Then, using an evolutionary tree of 15 hominoids — a group that includes humans, their fossil ancestors, gorillas, chimpanzees, orangutans and gibbons — they looked at whether those traits have changed more or less over time compared to random chance. Either result would suggest a role for natural selection in the evolution of the lower jaw.

Compared with other species, "the human cranium is more different from our ancestors' than we would expect given how much time has passed," she said. However, only three of the nine chin-specific traits appeared to be under direct selection.

Together, the team's results, published in the journal PLOS One, suggest the chin may be what's known as a spandrel — a term borrowed from architecture to describe a feature that is a side effect of something else. Coined by evolutionary biologists Stephen Jay Gould and Richard Lewontin in 1979, the concept of a spandrel was introduced to argue against the view that every feature must serve a specific, evolved purpose.

"Instead, it appears that structurally, we have to have a chin, but not because the chin evolved to have a particular function," von Cramon-Taubadel told Live Science. "More and more studies are showing that things that we used to think were terribly important in terms of differences between humans and other apes actually could evolve just by random drift and gene flow."

Von Cramon-Taubadel said the group's findings appear to be more strongly influenced by known major landmarks in human evolution, including when we started walking upright and growing larger brains.

Despite these takeaways, von Cramon-Taubadel and Williams agree that the question is far from settled. It's unknown, for example, when traits like speech first appeared, so it's difficult to link them to chin evolution. While Williams accepts that the chin may not have evolved for a specific purpose, that doesn't make it arbitrary.

"It is still one of the defining features of our lineage that is present in some form in every human living on the planet today," he said.

Human skeleton quiz: What do you know about the bones in your body?

Humans first developed complex and information-dense writing around 3000 B.C., when the Sumerians of southern Mesopotamia (modern-day Iraq) invented cuneiform scripts. But new research suggests the precursors to writing can be found on sculptures and tools made by Paleolithic hunter-gatherers in Central Europe tens of thousands of years earlier.

When modern humans (Homo sapiens) first arrived in Europe around 55,000 years ago, they brought with them a sophisticated tool culture that included projectile points and drilling implements. Humans began decorating cave walls with geometric shapes, hand stencils and representations of animals, and they adorned their tools and sculptures with geometric signs whose meaning has baffled archaeologists for decades.

In a study published Feb. 23 in the journal PNAS, linguist Christian Bentz of Saarland University in Germany and archaeologist Ewa Dutkiewicz of the Museum of Prehistory and Early History in Berlin statistically analyzed more than 3,000 mysterious markings on 260 ancient objects and determined that they constitute "sign sequences" that encoded Paleolithic people's thoughts.

"Our research is helping us uncover the unique statistical properties — or statistical fingerprint — of these sign systems, which are an early predecessor to writing," Bentz said in a statement.

The researchers cataloged intentional symbols — lines, points, crosses, stars, grids and zigzags — carved into a variety of tools and figurines, most of which were discovered in previous archaeological excavations in cave sites in the Swabian Jura, a mountain range in southern Germany. Then, they used computational techniques to look at the statistical properties of the signs, discovering that the Paleolithic sequences were comparable to proto-cuneiform in their potential to encode information.

Bentz's research deals with frequency trends and measurable aspects of signs. (In linguistics, a sign is a physical representation of a concept or meaning.) By statistically investigating two series of signs — in this case, the Paleolithic system and proto-cuneiform — Bentz compared the sign systems to discover similarities and differences.

"Our analyses demonstrate that these sign sequences have nothing to do with the writing systems of today," Bentz said. "The signs on the archaeological objects are frequently repeated – cross, cross, cross, line, line, line. This type of repetition is not a feature found in spoken language."

The Paleolithic hunter-gatherers instead developed a system of symbols comparable to early proto-cuneiform, a system created tens of thousands of years later. "In terms of complexity, the sign sequences are comparable," Bentz said.

But while cuneiform evolved rapidly in Mesopotamia over the course of a millennium, the Paleolithic sign system the researchers discovered stayed consistent for nearly 10,000 years.

"The human ability to encode information in signs and symbols was developed over many thousands of years," Bentz said. "Writing is only one specific form in a long series of sign systems."

The statistical analysis did not reveal what the carved signs meant, although the researchers did discover that figurines had a higher "information density" than tools did.

This is not the first research to propose that the origin of human writing systems dates to the Paleolithic. In a 2023 study, researchers investigated dots and lines in 20,000-year-old cave paintings of animals and concluded that they constituted an early calendar. And paleoanthropologist Genevieve von Petzinger has argued that three dozen symbols found in caves throughout the world show humans developed an early form of writing at least 40,000 years ago.

The new study includes "two excellent approaches for at least trying to confirm that these marks were meaningful beyond being decorative doodles," von Petzinger, who was not involved in the study, told Scientific American. "The more we can learn about the selection of 'writing' surfaces and choices about specific images and signs, the more we will be able to learn about this period."

The researchers continue to look for objects with intentionally made signs to add to their understanding of early human communication.

"Countless tools and sculptures from the Paleolithic, or the Old Stone Age, bear intentional sign sequences," Dutkiewicz said in the statement. "There are many sign sequences to be found on artefacts. We've only just scratched the surface."

Stone Age quiz: What do you know about the Paleolithic, Mesolithic and Neolithic?

When Neanderthals and modern humans first got together, they preferred pairings between Neanderthal men and human women, a new study of ancient and modern genomes suggests. The finding helps to explain why modern humans (Homo sapiens) have a relatively low level of Neanderthal genes and why those genes are found in some populations today and not in others.

Ever since the first modern-human and Neanderthal genomes were sequenced over 20 years ago, scientists have puzzled over "Neanderthal deserts," or places in the modern-human genome where Neanderthal genes are rare. The two groups interbred during a few periods after their ancestors split around 600,000 years ago. The result is that most non-African people on the planet today carry an average of 2% Neanderthal DNA, while some African groups have up to 1.5%, which was inherited from H. sapiens who mixed with Neanderthals in Eurasia and then moved to Africa.

But what has stymied experts is that the genes we inherited from Neanderthals are found only in tiny patches on our X chromosome, even though those genes appear in greater numbers across our other chromosomes. There are regions on the X chromosome — the sex chromosome that every human has at least one copy of — where no living humans have any Neanderthal ancestry.

"For years, we just assumed these deserts existed because certain Neanderthal genes were biologically 'toxic' to humans — as tends to be the case when species diverge — so we thought the genes may have caused health problems and were likely purged by natural selection," Alexander Platt, a population geneticist at the University of Pennsylvania, said in a statement.

But in a study published Thursday (Feb. 26) in the journal Science, Platt and colleagues concluded that the most plausible explanation for these "Neanderthal deserts" is actually mate preference, an evolutionary mechanism that is a major part of sexual selection. Biologists commonly illustrate the evolutionary result of mate preference with the large, colorful tail of the male peacock. Early humans and Neanderthals likely chose their mates for specific reasons as well.

DNA deep dive

The researchers analyzed the genomes of 73 women from three modern-day African populations that have no Neanderthal ancestry, including the !Xoo, Ju|'hoansi and Khoisan, and compared them with the genomes of a few Neanderthals. First, they looked at the Neanderthals' X chromosomes and found significantly higher amounts of modern-human ancestry there than on the other Neanderthal chromosomes. This result revealed that the lack of Neanderthal genes in the human X chromosome is not the result of incompatibility, which would have suggested Neanderthal genes caused modern humans problems and were eliminated through natural selection.

Rather, the surprisingly high amount of modern human DNA chunks found in Neanderthals can be explained by mate preference, the researchers concluded. Because females carry two X chromosomes and males carry only one, a preference for mating between female H. sapiens and male Neanderthals would mean fewer Neanderthal X chromosomes would enter the human gene pool, producing the pattern the researchers identified in the genomes.

But the reasons for the mate preference — and the direction of it — remain elusive.

"I have no idea whose preference is being expressed here," Platt told Live Science in an email.

Previous research into the Neanderthal Y chromosome — one of the two sex chromosomes of male individuals — indicates there was interbreeding between male H. sapiens and female Neanderthals. But it is apparent from the new study that, in effect, male Neanderthals and female H. sapiens liked each other more than female Neanderthals and male H. sapiens did.

"We simply don't have a genetic signature to discern beyond that at the moment," Platt said.

The researchers did not rule out more complicated evolutionary scenarios that might have combined natural selection, sex biases, mate preference and sex-specific migration to contribute to the "Neanderthal deserts" in the human genome.

Questions about the structure of Neanderthal and modern-human societies are also important to answer for a fuller understanding of mate choice in the past, as anthropologists and evolutionary biologists who have studied the phenomenon show that mate choice is partially learned.

The research team plans to "look at the evolution of the social structures and gender roles within Neanderthals," which "could conceivably shed some light on the picture," Platt said. "But I think we're a long way from knowing this."

Neanderthal quiz: How much do you know about our closest relatives?

Three Homo erectus skulls previously unearthed in China are almost 1.8 million years old, around 600,000 years older than originally thought, a new study finds.

This revelation has made the Yunxian skulls from Hubei province the oldest evidence of our early human relatives, known as hominins, in East Asia, according to research published Wednesday (Feb. 18) in the journal Science Advances.

Study co-author Christopher Bae, a professor of anthropology at the University of Hawaii at Manoa, told Live Science in an email that he felt "absolute surprise" when he first saw the results of the analysis. This more ancient age may force experts to rethink the date that H. erectus first emerged, which is believed to have occurred around 2 million years ago in Africa.

"What this means is that we need to consider pushing the origin of Homo erectus back" to around 2.6 million years ago, Bae said in an email.

H. erectus has long been considered the first human relative to leave Africa, with 1.78 million to 1.85 million-year-old fossils found at the Dmanisi site in Georgia being the earliest evidence of humans in Asia. But stone tools discovered at two sites in China dated to 2.1 million and 2.43 million years ago have complicated that picture, since they predate experts' theory of when H. erectus originated.

The exact date of the three Yunxian skulls, which were found between 1989 and 2022, has long been debated, but they were previously considered to be around 1 million years old based on the age of animal teeth found close by, although one study dated them to around 1.1 million years ago using electron spin resonance and uranium-series dating. So when the opportunity arose to try a new dating technique at the site, Bae and his colleagues thought it was a good chance to revisit the debate.

Their team used a technique called cosmogenic nuclide burial dating to determine the age of the quartz found in the sediment layers where the skulls were found. This dating technique measures the half-life of two chemical variants — Aluminum-26 and Beryllium-10 — to determine how much time has passed since the quartz was exposed to cosmic rays.

This dating method revealed the hominin fossils were approximately 1.77 million years old, which is about 600,000 years older than the oldest age proposed for the site previously, Bae said.

Because the new date is younger than the stone tools discovered elsewhere in China, there is still a large time gap of around 600,000 years between the earliest fossil evidence and the earliest tool evidence, he added.

But since this date is close in time to the Dmanisi fossils in Georgia, the results suggest that H. erectus moved across Asia relatively quickly, Bae said. The size and shape of the Yunxian skulls, however, shows that these hominins had larger brains than those found in Dmanisi, despite being a relatively similar age. "This points to important variation in the early hominins outside of Africa," Karen Baab, a professor of anatomy at Midwestern University in Arizona who was not involved in the new study, told Live Science in an email.

Chris Stringer, a paleoanthropologist at the National History Museum in London who was not involved in the new study, told Live Science in an email that "it would indeed be remarkable" if the Yunxian skulls were nearly 1.8 million years old, but "placing Yunxian at such a great age would put it completely out of sync with the rest of the fossil record."

According to previous work by Stringer and his colleagues, the Yunxian fossils may belong to a group that gave rise to the Denisovans, which their model suggests emerged around 1.2 million years ago.

The new date for the Yunxian fossils, if correct, may also require experts to reconsider the origin of the ancestor to our own species, Homo sapiens, Stringer said. "I would suggest that further work on the dating of the site is certainly needed!"

Human origins quiz: How well do you know the story of humanity?

The mysterious disappearance of our Neanderthal cousins may have been related to preeclampsia, a life-threatening complication of pregnancy and/or the postpartum period, doctors propose in a new study. But experts in paleoanthropology are not convinced.

In a paper published Jan. 30 in the Journal of Reproductive Immunology, an international team of neonatologists and OB-GYNs argued that preeclampsia and eclampsia — a related disorder that involves one or more seizures during pregnancy or the postpartum period — have "never been seriously considered in hypotheses concerning Neanderthal reproductive biology and their eventual extinction."

These conditions are not fully understood by medical experts, but they appear to be related to an evolutionary quirk of the human placenta — which, given the number of genes we share with our extinct relatives, also may have affected the Neanderthal placenta. (However, the researchers did not investigate any such genes in the new study.)

Preeclampsia in human species

Preeclampsia involves dangerously elevated blood pressure and can put strain on the pregnant person's heart and other organs, including the kidneys and liver. The condition affects up to 8% of pregnancies today, and it can also occur during the postpartum period. It can also progress to eclampsia, which involves seizures and, sometimes, brain damage. If not treated, both conditions can be life-threatening for the pregnant person and the fetus.

Research into preeclampsia has shown that abnormal, shallow implantation of the placenta in the uterus may be one possible cause of the condition. The exceptional metabolic demands of babies of large-brained human species were likely responsible for the deep implantation of the placenta to ensure sufficient maternal-fetal nutrient transfer, the researchers wrote.

An inadequately placed placenta's efforts to acquire adequate nutrients for the fetus can lead to a rise in maternal blood pressure, particularly in the third trimester, when the fetus's brain is rapidly developing, according to this hypothesis. This can lead to preeclampsia, eclampsia and fetal growth restriction, all of which complicate pregnancy and threaten the survival of mothers and babies.

Given this insight into preeclampsia, the study authors wrote that the condition "may have constituted an additional, underappreciated selective pressure on Neanderthals, contributing to their extinction." They hypothesized that Neanderthals "may have lacked a key protective mechanism" against preeclampsia that some of the study authors previously suggested modern humans have. This idea, however, is still speculative and such a mechanism has yet to be found.

If Neanderthals lacked a "maternal safety mechanism" to avoid preeclampsia, this may have led to reproductive loss and maternal mortality, thus hastening their extinction as a group, the team proposed.

Anthropologists respond

But experts in Neanderthal archaeology and genetics are not convinced, particularly since the new study does not provide any evidence that Neanderthals dealt with preeclampsia.

"The 'preeclampsia doomed Neanderthals' framing goes well beyond the available evidence," Patrick Eppenberger, co-head of the Evolutionary Pathophysiology and Mummy Studies Group at the Institute of Evolutionary Medicine in Zurich who was not involved in the study, told Live Science in an email.

While Eppenberger agreed that preeclampsia is uniquely human and linked to the evolution of the human placenta, he said that "what is much harder to support is the claim that it was more frequent or more lethal in Neanderthals than in early Homo sapiens or that it played a primary role in their disappearance, especially given Neanderthals' long persistence" over more than 300,000 years.

In his own research, Eppenberger discovered that a red blood cell gene variant between Neanderthals and modern humans may have caused some hybrid babies to fail to survive, which could have hastened their extinction.

"Why Neanderthals went extinct is a question that has captured the imagination of the public and researchers," April Nowell, a Paleolithic archaeologist at the University of Victoria in Canada who was not involved in the study, told Live Science in an email, and "everyone is looking for a smoking gun."

But the reasons for Neanderthals' disappearance are complicated. "I have long argued that differential survivorship of the littlest Neanderthals is key to understanding the Neanderthal story, but I am not particularly persuaded by this study," Nowell said.

If the researchers are correct that H. sapiens evolved a mechanism to mitigate preeclampsia, Nowell said, the condition could have contributed to Neanderthals' extinction. But given the widespread evidence of gene sharing among groups of humans, "to my mind, it is equally possible that Neanderthals, Denisovans and Homo sapiens shared this mitigating mechanism," Nowell said.

"I think the paper is an interesting evolutionary-medicine thought experiment," Eppenberger said. Although there is no direct evidence currently that Neanderthals had higher rates of preeclampsia or eclampsia than modern humans do, Eppenberger said, there may be ways to test the researchers' theory, including investigating genes involved in maternal-fetal immune interactions and in the regulation of placental and fetal growth. But we might not get a clear answer.

"Genetics can provide clues about plausibility and population differences, but it likely won't 'confirm' preeclampsia in Neanderthals the way clinical data would," Eppenberger said.

The study authors did not respond to a request for comment by the time of publication.

Neanderthal quiz: How much do you know about our closest relatives?

"Ghost lineages" may sound paranormal, but the term is rooted in real science that genetic studies have revealed only relatively recently.

So what is a ghost lineage?

A ghost lineage is an extinct population that has left no fossils but whose traces can still be detected in the genomes of many living things, including humans and other primates. University of Wisconsin-Madison palaeoanthropologist John Hawks defines them as "ancient groups that became extinct, but not before contributing some of their own genes to other populations that survived."

In animals generally, not just in humans, finding ghost lineages has "mostly been by accident," Love Dalén, an evolutionary geneticist at Stockholm University who studies extinct animals, told Live Science. "Our goals have been to study the evolution of mammoths, bovids and lemmings, and finding these ghost lineages was quite unexpected."

In their analyses of ancient DNA recovered from the frozen fossils of key ice age animals that are now extinct — including mammoths, Pleistocene yaks and certain types of lemmings — Dalén and colleagues have detected several ancient populations that were revealed only by genetics.

These ghost lineages indicate that genetic diversity — the range of inherited traits within a population — was greater during the last ice age than it is now. "This is definitely a pattern we see in Arctic species that are alive today," Dalén said. "Nearly all of them had much higher genetic diversity in the past, and to me this illustrates how important past climate change has been in shaping present-day biodiversity."

But ghost lineages are too important to leave to chance findings. "It becomes more and more clear that we need to use an ancient DNA approach to fully quantify past changes in biodiversity," Dalén said.

Human "ghosts"

Genetic ghosts in human evolution are especially interesting to scientists because they reveal a much more complex story of human evolution than many experts supposed.

The ghost lineages detected in the genomes of modern humans and our extinct relatives have revolutionized the study of millions of years of human evolution.

Most scientists once thought human evolution had progressed at a steady pace through known stages, culminating in the emergence of Homo sapiens in Africa about 300,000 years ago and its eventual replacement of all other forms of humans, with some limited interbreeding.

But genetic analyses over the past two decades have revealed traces of several human ghost lineages in the ancestry of people today and in the ancient DNA recovered from fossils. These human ghost lineages are echoes of archaic groups that existed for hundreds of thousands or even millions of years but that left no known fossils.

"Our discipline has gone from a simplified, straightforward linear model of evolution to a 'bushier' model in describing the last 7 million years," Michael Petraglia, a paleoanthropologist at Griffith University in Australia, told Live Science in an email.

The human evolutionary "tree" grew ever larger and less well defined — turning into a "braided stream" of ancient groups — as more ghost lineages were identified, he said, and it is still growing.

When newfound fossils match "ghost genetics," lineages become "de-ghosted," and de-ghosting human ghost lineages is an important area of research. "With the application of DNA, it has become clear that gaps in our evolution existed, suggesting the presence of ghost populations for which the fossil record was not clearly present," Petraglia said.

"Superarchaic" ancestors

Scientists have seen traces of human ghost lineages in the genomes of some modern-day human populations in parts of West Africa, Asia and Oceania, and Petraglia said paleoanthropological research has focused on a group of "superarchaic" hominins known only from their genes.

This ancient human ghost lineage separated from our own family tree of modern humans, Neanderthals and Denisovans between about 2 million and 1.8 million years ago — roughly when Homo erectus was the dominant species in Africa.

There are no fossils from the superarchaic ghost lineage, so scientists have only inferred its existence from the presence of ghost genes in their analyses of Neanderthal, Denisovan and H. sapiens genomes.

But the picture is complicated because of the confusion created by interbreeding. "Genetic work suggests that the ancestors of Denisovans, Neanderthals and Homo sapiens met and interbred a number of times," Petraglia said. "This has set off debate as to finding the last common ancestor and understanding the line of descendants."

There is genetic evidence that the Denisovans interbred with the superarchaic lineage in at least two distinct interbreeding events, resulting in a relatively high number of "ghost" genes from the superarchaic human lineage in the genomes of Denisovans and those of modern humans with Denisovan ancestry.

"These are exciting times in human evolutionary studies, and there is growing support that hominin evolution was much more complex than imagined before, including multiple interbreeding events that make us what we are today," Petraglia said.

Human evolution quiz: What do you know about Homo sapiens?

A group of people living in the far southern reaches of Greece's Peloponnesian Peninsula have been genetically isolated for over a millennium and can trace their roots back to the Bronze Age, an analysis of their DNA reveals.

A new genetic study shows that this group, known as the Deep Maniot Greeks, are paternally descended from ancient Greeks and Byzantine-era Romans. Long-term genetic isolation and strict patriarchal clans likely contributed to the unique genetics of the Deep Maniot Greeks over the past 1,400 years, according to the study authors.

The Mani Peninsula is the middle of three peninsulas that extend south from mainland Greece. In ancient times, the area was part of the Laconia region, which was dominated by the city-state Sparta in the seventh century B.C. Much of the Greek Peloponnese region experienced demographic upheaval as Slavic peoples invaded in the sixth century A.D. However, the Mani Peninsula was spared, and the Deep Maniots who lived in the far southern part of the peninsula became geographically and culturally isolated from the rest of Greece.

In a study published Wednesday (Feb. 4) in the journal Communications Biology, researchers analyzed the DNA of more than 100 living Deep Maniots and discovered that they represent a "genetic island" due to long-standing isolation.

"Our results show that historical isolation left a clear genetic signature," study lead author Leonidas-Romanos Davranoglou, a zoologist at the Oxford University Museum of Natural History, said in a statement. "Deep Maniots preserve a snapshot of the genetic landscape of southern Greece before the demographic upheavals of the early Middle Ages."

During Europe's Migration Period (circa A.D. 300 to 700), which is sometimes called the "Barbarian Invasions," various groups of people — including Germanic tribes, the Visigoths, the Huns and early Slavs — moved throughout the continent. This resulted in numerous waves of migration, only some of which were historically documented. Ancient DNA research has begun to tease out these Migration Period population waves.

But these Migration Period movements did not seem to affect the Deep Maniots, according to historical, linguistic and archaeological evidence. So Davranoglou and colleagues turned to DNA analysis of modern Maniots to investigate why.

The researchers looked at genetic markers on the Y chromosomes (which are passed down from father to son) of 102 people with Deep Maniot ancestry on their paternal side, as well as mitochondrial DNA (passed down from mother to child) sequence data from 50 people with maternal Deep Maniot ancestry.

The DNA analysis revealed that Deep Maniots have an extremely high frequency of a rare paternal lineage that originated in the Caucasus region around 28,000 years ago, the researchers wrote in the study. And when compared with the DNA of present-day mainland Greeks, the DNA of Deep Maniots lacked evidence of common lineages that came from Germanic and Slavic peoples during the Migration Period.

Taken together, these results suggest that genetic drift (a reduction in genetic variation due to a small population size) played an important role in shaping the paternal lineage of Deep Maniots, the researchers wrote, forming a kind of "genetic island." This island of paternal ancestry is rooted in the ancient Balkans and West Asia and is strongly linked to Bronze Age, Iron Age and Roman-period Greek-speaking populations, they noted.

Analysis of the maternal Deep Maniot lineages through mitochondrial DNA revealed a more complex genetic picture, however. The researchers identified 30 distinct maternal lineages in their population sample of 50 Deep Maniots. Most of those lineages have connections to Bronze Age and Iron Age people from Western Eurasia, but several appear to be Deep Maniot-specific, showing no close matches to other present-day European populations.

"These patterns are consistent with a strongly patriarchal society, in which male lineages remained locally rooted, while a small number of women from outside communities were integrated," study co-author Alexandros Heraclides, an epidemiologist at European University Cyprus, said in the statement.

Both the paternal and maternal DNA markers also show evidence of a founder effect, which happens when a new population is established by a very small subset of a larger population. The new population includes only the genes of its small number of founders and, over time, becomes distinct from the larger population.

The genes of present-day Deep Maniots reveal that there was a founder effect among their paternal ancestors around A.D. 380 to 670. As a result, over 50% of Maniot men today descend from a single male ancestor from the seventh century. There was also a founder effect among their maternal ancestors around 540 to 866, the team found, suggesting the number of both maternal and paternal lineages shrank around the same time.

The DNA study suggests that the Deep Maniot population "represents a snapshot of the genetic landscape of the Greek-speaking world prior to the demographic turmoil of the Migration Period," the researchers wrote.

"Many oral traditions of shared descent, some dating back hundreds of years, are now verified through genetics," study co-author and independent researcher Athanasios Kofinakos said in the statement.

Neanderthals purposefully collected and positioned horned and antlered animal skulls in a cave in what is now Spain, suggesting that these extinct human relatives had complex cultural practices over 43,000 years ago, a new study finds.

Des-Cubierta cave in central Iberia was initially discovered in 2009. In 2023, researchers announced the unusual discovery of an assortment of 35 large mammal skulls inside the cave. Most jaw bones were missing, but all skulls came from horned or antlered species like steppe bison and aurochs. Over 1,400 stone tools were uncovered in the same level, all in the Mousterian style typical of Neanderthals.

"At first glance, the deposit appears chaotic," study first author Lucía Villaescusa Fernández, a doctoral researcher in archaeology at the University of Alcalá in Spain, told Live Science in an email. "What initially looked like a disorganised accumulation of materials turned out to preserve a clear record of both geological processes and human activity," she said.

The cave experienced many rockfalls in the millennia following its use, so Villaescusa Fernández and her team teased the role of these disturbances apart from the Neanderthal activity. This confirmed the Neanderthals were collecting animal skulls over a long period of time in particularly cold periods between 135,000 and 43,000 years ago, according to a study published Jan. 3 in the journal Archaeological and Anthropological Sciences.

"This distinction is essential in archaeology because understanding past human behaviour requires first identifying which parts of the archaeological record were created by people and which were shaped by nature," Villaescusa Fernández said.

To fill this gap, Villaescusa Fernández and her colleagues carefully mapped the location of all the archaeological remains. They then compared the rockfall debris distribution with that of the animal bones and stone tools. It became clear that the bones had been purposefully positioned within the cave. "These materials had different origins and were not introduced into the cave by the same processes," Villaescusa Fernández said.

Although the timescale cannot be directly measured, and the precise duration of the practice remains uncertain, the team also found the animal skulls had been placed in specific areas of the cave repeatedly over a prolonged period of time. This suggests that this practice may have been maintained over generations and was not directly tied to economic or subsistence needs, Villaescusa Fernández said.

Exactly why Neanderthals collected the skulls is unclear, but the selection, treatment and placement of horned animal skulls in a cave they did not live in "highlights their capacity for cultural practices that are not directly related to survival," Villaescusa Fernández said. "This has important implications for how we understand Neanderthal societies, particularly in terms of cultural transmission and shared traditions," she added.

"Too often, discussions of Neanderthal symbolism rely on fragile evidence or optimistic interpretations," Ludovic Slimak, an archaeologist at the University of Toulouse in France and author of the book "The Naked Neanderthal" (Penguin, 2024) who was not involved in the study, told Live Science by email. "Here, the authors take a more grounded approach, testing whether the spatial organization of the remains could be explained by natural processes alone," he said.

Slimak said that the findings of this study add new evidence to the debate over Neanderthal symbolism. "Rather than asking whether Neanderthals were 'symbolic like us,' we should ask what kinds of meaningful behaviors they developed on their own terms. This site suggests that Neanderthal worlds of meaning existed, but they may have been structured very differently from those of Homo sapiens," he said.

Neanderthal quiz: How much do you know about our closest relatives?

Archaeologists in Greece have discovered 430,000-year-old handheld wooden tools, the oldest surviving examples of their kind in the world, a new study finds. The two tools, found on the Peloponnese peninsula in southern Greece, were created by an unidentified hominin species that predates modern humans.

"The objects represent the oldest hand-held wooden tools ever found, pushing back evidence of this type of tool use by at least 40,000 years," the researchers wrote in a statement.

One of the wooden tools, which was found in the site of Marathousa, is 31.9 inches (81 centimeters) long and is splintered and frayed at one end, which suggests that it was likely used as a digging stick. "The tool has a morphology and size comparable to digging sticks," the team wrote in the study, which was published Jan. 26 in the journal PNAS.

The other wooden tool is 2.2 inches (5.7 cm) long and has been completely debarked, with rounding and pitting at one end. It's not clear what it was used for, but it's possible that it may have been used to help craft stone tools, the researchers wrote.

The artifacts appear to have become buried in wet soil, the researchers wrote in the study. This allowed the wooden tools, and other organic remains, to be preserved in a low-oxygen environment.

The scientists also excavated the remains of animals and plants from the site, which enabled them to reconstruct what the landscape would have looked like around the time the tools were made.

"The fauna comprises both terrestrial and semiaquatic mammals, as well as freshwater mollusks, turtles, and birds indicating a rich lakeshore environment," the team wrote in the paper. The finds also include the remains of elephants, hippopotamuses, deer and wild boar.

At the time the wooden tools were used, the climate in Europe was experiencing "an extremely cold glacial period," but this lakeshore environment would have been a place of relative comfort, study first author Annemieke Milks, an archaeologist at the University of Reading in the U.K., told Live Science in an email.

Early humans

The tools date to around 430,000 years ago — around 130,000 years before Homo sapiens existed — and it's not clear which hominin made them. "There aren't human remains from [Marathousa] and for this period there is a bit of ambiguity at the moment about hominin species. It could have been Homo heidelbergensis, or possibly very early Neanderthals," Milks said.

Tools made of stone and bones have previously been identified at the site, and the new discovery of wooden tools means that early humans were using a variety of materials, Milks noted. For instance, the oldest known wooden structure in the world, which was found in Zambia, is even older and from 476,000 years ago.

We "understand that these hominins had an understanding of these different materials and their properties, and used different tools presumably for different tasks," Milks said. "I think it really helps us understand how humans in the deep past were making use of so many different materials and resources in their surroundings."

Study co-author Katerina Harvati, a paleoanthropology professor at the University of Tübingen in Germany, told Live Science in an email that these "tools provide a rare glimpse into a component of their technology that we know very little about, that which was based on [perishable] plant derived materials rather than stones." They "highlight the behavioral adaptability and flexibility of the Marathousa hominins," she added.

Excavations at the site were carried out between 2013 to 2019. The digging stick was found in 2015, and the wooden tools whose purpose is uncertain was discovered in 2018.

Archaeologists have found that early humans in what is now China were using sophisticated stone tools as far back as 160,000 years ago.

"This discovery challenges the perception that stone tool technology in Asia lagged behind Europe and Africa during this period," the research team wrote in a statement about the discovery.

At the site of Xigou, discovered in 2017 in Henan province in central China, the archaeological team found the remains of more than 2,600 stone tools and determined that some of them were "hafted," or attached to a piece of wood or other form of stick.

"The identification of the hafted tools provides the earliest evidence for composite tools in Eastern Asia, to our knowledge," the team wrote in a study published Tuesday (Jan. 27) in the journal Nature Communications.

Researchers already knew of extremely early tool use in East Asia, with the oldest known wooden tools there dating to 300,000 years ago. However, the new findings, which were excavated between 2019 and 2021, are the earliest known tools consisting of two materials, as is evidenced by the hafted artifacts.

Hafting "is a new technological innovation whereby the stone tool is inserted or bound to a handle or a shaft," Michael Petraglia, director of the Australian Research Centre for Human Evolution at Griffith University and a co-author of the paper, told Live Science in an email. "This improved tool performance by allowing the user to increase leverage and providing more force for actions such as boring."

It appears that the tools were used to process plant materials. "Microscopic analysis on the edges of the stone tools indicate boring actions, used against plant material, likely wood or reeds," Petraglia said.

Their toolmaking techniques "appear to be well established and involve several intermediate steps, showing evidence of planning and foresight," the team said in a statement.

Ben Marwick, an archaeology professor at the University of Washington and a co-author of the paper, said it is not clear which early human species made the tools.

"The exact identity of the makers of these tools is not clear, because during this time there were probably multiple hominin species living in the region," Marwick told Live Science in an email. "So it could be, for example, the Denisovans, H. longi, H. juluensis or H. sapiens that made these tools. Hopefully future work will recover fossil remains or DNA that will shed more light onto this interesting question."

It is noteworthy that many of the artifacts are small — less than 2 inches (50 millimeters) — but were made with complex techniques, Marwick noted. "These come from a period when previous archaeological research has mostly found large artefacts produced using simple flaking methods," he said. "So our finds suggest that complex tool production strategies appear earlier than previously understood."

The newly discovered tools date to between 160,000 and 72,000 years ago. At this time, people in the region lived as hunter-gatherers, but the details of their lifestyles are unclear.

"While the lack of mammal bones and other evidence makes it difficult to deduce how they lived, at least, their stone tools indicate a high degree of behavioral flexibility and successful adaptation to the local climate and resources," Shi-Xia Yang, a paleoanthropologist at the Chinese Academy of Sciences who is a co-author of the paper, told Live Science in an email.

Stone tools in East Asia

The discovery of the sophisticated stone tools from this region and time period dispute a long-held assumption about early toolmaking, the study authors noted.

"The broader relevance of the finds are that they challenge the entrenched bias that East Asian hominins only produced 'conservative' tools," Marwick said. "The bias was deeply entrenched, dominating archaeology for over half a century through the concept of the Movius Line.

"Proposed in the 1940s, this 'line' suggested a geographical divide between the 'advanced' Acheulean handaxe cultures of Africa and Western Eurasia and the 'conservative' chopper-chopping tool cultures of East Asia," he continued. "This created a narrative of East Asia as a cultural backwater, where hominins were thought to be evolutionarily stagnant."

John Shea, an anthropology professor at Stony Brook University who was not involved with the research, praised the paper but noted that the idea that East Asia was a cultural backwater was never accurate. He noted that, in his own stone tool experiments, the small, complex and sharp stone tools that were being constructed more often in Europe could be dangerous to work with. "Trust me on this, for I have the scars to back it up," he said.

Any "hominins with a lick of common sense almost certainly minimized the amount of time they spent pounding out razor-sharp flakes," Shea said. "In this respect, [Southeast] Asian hominins were doing what one would expect them to do. … The "idea that 'simple tools equals simple minds' is archaeological mythology."

Anne Ford, an associate professor of archaeology at the University of Otago in New Zealand, praised the research.

"This is really an excellent discovery and highlights our need to move away from older descriptions of Asian technologies as simple core-flake industries," Ford told Live Science in an email. She noted that hafting is an "important technological step and has implications for assessing the cognitive ability of hominins in China during this time period."

A triangular artifact crafted from elephant bone was used by archaic human relatives to sharpen hand axes around 480,000 years ago in what is now the U.K., a new analysis reveals.

The item — which measures about 4.3 by 2.3 inches (10.9 by 5.8 centimeters) — represents the oldest known elephant bone tool ever found in Europe, according to the study, which was published Wednesday (Jan. 21) in the journal Science Advances, and demonstrates human relatives' high level of resourcefulness and ability to adapt to new environments as they settled in northern climates.

While evidence suggests that early human relatives used elephant bones and tusks throughout the Paleolithic period for a wide range of purposes, it's "very rare" to find an elephant-bone tool of this age or older anywhere in the world, said study co-author Silvia Bello, a paleoanthropologist at the Natural History Museum in London.

The "unexpected" find of one of the world's oldest elephant bone tools indicates a relatively advanced level of technological development, thus highlighting the innovation, resourcefulness and craftsmanship of archaic human relatives almost half a million years ago, the researchers said in the study.

While the researchers are unsure which group of human relatives used the elephant tool, given the age of the tool and the location where it was found, two candidates are early Neanderthals or Homo heidelbergensis, Bello told Live Science in an email.

The tool "provides an extraordinary glimpse into the ingenuity of the early human ancestors who made it," Bello said.

The fossilized bone artifact was originally uncovered in the early 1990s during excavations at the archaeological site of Boxgrove in southern England. This internationally renowned site has yielded many finds that have shed light on Paleolithic life around half a million years ago. These include various bone and stone tools, numerous animal remains displaying signs of butchery, and even the oldest human remains ever found in Britain.

The significance of the bone artifact was not immediately apparent. But a recent analysis of the artifact conducted by Bello and her co-author Simon Parfitt, an archaeologist at the Institute of Archaeology at University College London, revealed that the artifact represents an elephant bone fragment deliberately shaped into a "retoucher" tool.

Retouchers were used to shape and resharpen the edges of hand axes. The elephant bone retoucher would have contributed to the production of the "finely worked" hand axes that were thought to have been used primarily as cutting tools and are typical of Boxgrove, according to the study.

"The elephant bone tool shows signs of being shaped and used to knap and re-sharpen lithic tools while the bone was still fresh, suggesting that these humans knew that elephant bone was a great material for this," Bello said.

The find represents the only documented case of elephant bone being used to make a retoucher, according to the researchers. Knapping tools made from organic materials such as bone, antler and wood were essential pieces of equipment for early humans but are rarely preserved in the archaeological record.

Furthermore, prehistoric elephant bone remains are "exceptionally rare" at Boxgrove, suggesting that archaic humans in the area came across this resource infrequently, the study authors noted. Nonetheless, it appears that the creators of the tool recognized the usefulness of the material.

"This remarkable discovery showcases the resourcefulness of our ancient relatives," Parfitt told Live Science in an email. "They possessed not only a deep knowledge of the local materials around them, but also a sophisticated understanding of how to craft highly refined stone tools."

"Elephant bone would have been a rare but highly useful resource, and it's likely this was a tool of considerable value," he said in a statement.

Human evolution quiz: What do you know about Homo sapiens?

Fragments of a 2.6 million-year-old fossil jaw discovered in northeastern Ethiopia are transforming the picture of early human evolution in Africa. The jaw, from a bipedal hominin — an extinct relative of humans — shows that its kind journeyed far north, to a region where other hominins were already living.

The ancient jaw belongs to the genus Paranthropus and was found more than 620 miles (1,000 kilometers) farther north than any other fossil of its kind.

"Until now, not a single fossil of Paranthropus had been identified" in the Afar region of Ethiopia, researchers wrote in a study published Wednesday (Jan. 21) in the journal Nature. "Hundreds of fossils representing over a dozen species" of hominins had been found in the Afar, study lead author Zeresenay Alemseged, a paleoanthropologist at the University of Chicago, said in a statement, "so the apparent absence of Paranthropus was conspicuous and puzzling to paleoanthropologists, many of whom had concluded the genus simply never ventured that far north."

The genus Paranthropus contains three species distantly related to humans: P. robustus, P. boisei and P. aethiopicus, collectively known as the "robusts." These species walked upright beginning around 2.7 million years ago, but they are unique in having massive teeth and jaws, which earned one fossil skull the nickname "Nutcracker Man." Paranthropus fossils were previously found in locations from southern Ethiopia to southern Africa and have been dated to between 2.8 million and 1.4 million years ago.

Jaw-dropping find

In January 2019, paleoanthropologists discovered a partial lower jaw, designated MLP-3000, at the site of Mille-Logya in the Afar region of northeast Ethiopia. Dated to about 2.6 million years ago, the jaw came from an older individual whose teeth and bone structure resembled those of members of the Paranthropus genus. While one species — P. aethiopicus — has been found in southern Ethiopia, the new MLP-3000 jaw was discovered much farther north than any previous fossil from this genus.

"The discovery of Paranthropus in the Afar provides critical new information," the researchers wrote, suggesting that "the genus could exploit diverse habitats and regions from north Ethiopia to South Africa as Australopithecus and Homo did." This means that Paranthropus likely had a much more flexible diet than the "Nutcracker Man" moniker suggests, enabling these hominins to disperse and adapt to a wide range of environmental conditions.

The newfound Paranthropus fossil at Mille-Logya adds a third genus to the variety of hominins present in the Afar region between 2.8 million and 2.5 million years ago, including Australopithecus and early Homo. It is not yet clear, though, whether the species would have encountered one another directly.

"Discoveries like this really trigger interesting questions in terms of reviewing, revising, and then coming up with new hypotheses as to what the key differences were between the main hominin groups," Alemseged said.

Carol Ward, a biological anthropologist at the University of Missouri who was not involved in the study, wrote in an accompanying perspective that, given the diversity of hominin species present, "the revelation that Paranthropus inhabited the Afar between 3 million and 2.4 million years ago is particularly exciting."

Although all humans on the planet today are one species, hominin diversity lasted millions of years, until our extinct cousins the Neanderthals and Denisovans disappeared more than 30,000 years ago, Ward noted.

"Researchers can no longer accept that humans evolved from a single lineage of species marching towards modernity in isolation from others," she wrote.

Human origins quiz: How well do you know the story of humanity?

Scientists have identified the world's oldest known rock art — a hand stencil created at least 67,800 years ago in Indonesia.

This artwork, nestled in a cave in southeast Sulawesi, is also the earliest archaeological evidence of modern humans (Homo sapiens) living on the islands between the Asian and Australian continental shelves, according to a study published Wednesday (Jan. 21) in the journal Nature. The hand stencil is surrounded by younger rock art, including another hand stencil.

This discovery could fill a major gap in scientists' understanding of the journey the ancestors of Indigenous Australians took before reaching the continent at least 60,000 years ago. "It is very likely that the people who made these paintings in Sulawesi were part of the broader population that would later spread through the region and ultimately reach Australia," study first author Adhi Agus Oktaviana, an archaeologist at the National Research and Innovation Agency in Indonesia, said in a statement.

Although the rock art's original meaning is unknown, the hand stencils hint that the artists belonged to a relatively large group with its own cultural identity, study co-author Maxime Aubert, an archaeologist and geochemist at Griffith University in Australia, told Live Science. The hand stencils could have been made to signify group membership, Aubert said. "If you know about that cave and you know about this rock art, you're part of that group, you're part of that culture," he said.

Prehistoric art

Prehistoric rock art — or art on a rock face like a cave wall or a rock shelter — has been discovered all around the world, from 12,000-year-old engravings in Saudi Arabia to 4,000-year-old paintings along the U.S.-Mexico border. The oldest dated rock art previously identified — a roughly 66,700-year-old hand stencil in Spain — was believed to have been made by Neanderthals, as current evidence suggests modern humans didn't reach Europe until 54,000 years ago. But the dating technique used for that discovery is debated.

However, humans have been creating art for even longer than these examples. The oldest known drawing is a 73,000-year-old hashtag on a stone from South Africa, and a 540,000-year-old shell with zigzag carvings from Indonesia may have been crafted by Homo erectus.

Sulawesi also has a longstanding artistic legacy, with a depiction of a human interacting with a warty pig dating to 51,200 years ago. As part of a broader project documenting the prehistoric artwork on Sulawesi, Aubert and his team inspected 11 designs found in eight caves: seven hand stencils, two human figures and two geometric patterns.

All these prehistoric works had lumps of calcium carbonate — called "cave popcorn" — growing over them. Because the cave popcorn must have developed after the artwork was created, dating these growths provides a minimum age for the underlying image. In a handful of instances, maximum ages could also be obtained as the pigment overlaid one of these mineral deposits.

During the project, the researchers dated one hand stencil, measuring 5.5 by 3.9 inches (14 by 10 centimeters), to at least 67,800 years ago, making it 1,100 years more ancient than the rock art linked to Neanderthals in Spain. The image has faded considerably, but the remains of the fingers and palm are still faintly visible. The fingers had been purposefully narrowed — an artistic technique only found in Sulawesi.

About 4.4 inches (11 cm) to the left of this artwork is a hand stencil created using darker pigment that dates to no older than 32,800 years ago. This shows that prehistoric humans used this cave as their canvas over a period of at least 35,000 years.

Although other human species once called Sulawesi home, the researchers believe H. sapiens created these artworks, because the narrowed fingers are technically complex to produce and modern humans are known to have lived in the region at the time.

The stencils may have been created by the individuals spraying pigment over their hands with their mouths. This opens up the possibility for DNA to be extracted from the artwork. "We could have the genetic signature of the people doing this," Aubert said. "That would be amazing."

The identification of the oldest rock art in Sulawesi is an important discovery because it adds another data point on the journey humans took to spread across Island Southeast Asia and Australia. As a critical point on the journey to Australia, this discovery supports the suggestion that modern humans reached Australia by sailing a northern route from present-day Borneo to Sulawesi and then through to western Papua (the western half of the island of New Guinea) or the Indonesian island of Misool, the authors wrote in the study.

"This is a stunning discovery," Chris Clarkson, a professor of archaeology also at Griffith University who was not involved in the new research, told Live Science in an email.

He agreed with the conclusion that ancient modern humans are the most likely artists of the hand stencils because the dates align perfectly with when H. sapiens arrived in the region.

"What amazes me most is that these artworks sit directly on a migration route into Australia," he said. What's more, it shows that the first people to populate Australia had rich cultural lives. "The first people to cross Island Southeast Asia and reach Australia weren't just surviving, they were creating art, crossing oceans, and carrying complex symbolic traditions," Clarkson said.

Human evolution quiz: What do you know about Homo sapiens?

Our species, Homo sapiens, has been evolving for more than 300,000 years, but the story of human origins starts much earlier. Since evolving from the common ancestor that we share with our closest living relatives, chimpanzees and bonobos, there have been many different species along the human lineage — known as hominins.

Scientists who study human origins and evolution, called paleoanthropologists, sometimes find new hominin fossils that give us a glimpse into our evolutionary history. And advances in the analysis of ancient proteins are helping to identify which species a fossil belongs to, and whether they were male or female. We now know there were large periods of time when multiple hominin species shared the landscape, and that sometimes they mated.

How much do you know about the origins and evolution of our closest evolutionary relatives? Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button. Good luck!

More science quizzes

• Human evolution quiz: What do you know about Homo sapiens?
• Neanderthal quiz: How much do you know about our closest relatives?
• Primates quiz: Go ape and test your knowledge on our closest relatives

Paleoanthropologists have announced the world's most complete skeleton of Homo habilis, a human ancestor that lived more than 2 million years ago in northern Kenya. The collection of fossil bones has revealed unusually strong arms that distinguished H. habilis from later species.

The bones were initially found in 2012 by a team of researchers led by Meave Leakey, of the Turkana Basin Institute, and were subsequently announced in 2015 at a research conference. Now, the complete analysis of the remains has been described in a paper published Tuesday (Jan. 13) in the journal The Anatomical Record.

The skeleton, designated KNM-ER 64061, was found in geological layers dated to between 2.02 million and 2.06 million years ago. A complete set of lower teeth clearly identified the skeleton as H. habilis. The skeleton included the collarbones; pieces of the shoulder blades; all of the upper and lower arm bones; and fragments of a vertebra, a rib, an upper leg bone, and the pelvis, making it the most complete H. habilis skeleton ever recovered, as well as one of the oldest, the researchers noted in the study. (The oldest H. habilis skeleton on record is from Ethiopia and dates to 2.33 million years ago.)

"There are only three other very fragmentary and incomplete partial skeletons known for this important species," study lead author Fred Grine, a paleoanthropologist at Stony Brook University in New York, said in a statement. The find is significant because it represents both the most complete and the oldest partial skeleton of early Homo, the researchers wrote in the study.

H. habilis was a transitional species, in that it's the first named species to kick-start our genus after evolving from australopithecines — the lineage that includes the celebrity fossil skeleton "Lucy" — but was distinct from our much better understood ancestor Homo erectus, which spread around the world. Fossils from H. habilis are therefore key to understanding the adaptations of our early hominin ancestors. Hominins include modern humans and our extinct relatives.

A close analysis of the KNM-ER 64061 fossils revealed that the arm bones of H. habilis were similar to those of other early Homo specimens and to those of some australopithecines. For example, H. habilis had a longer forearm than did the later H. erectus and had heavy, thick arm bones more similar to those of australopithecines.

Based on the length of the humerus (the upper arm bone), the researchers determined that KNM-ER 64061 was a young adult who was about 5 feet, 3 inches (160 centimeters) tall. From the leg bone fragment, they estimated that the individual weighed only about 67.7 pounds (30.7 kilograms). These anatomical traits suggest that H. habilis retained upper-limb proportions similar to australopithecines' and was shorter and weighed less than H. erectus.

But those traits don't necessarily mean H. habilis could swing through the trees, according to the researchers. "The relatively long forearm of H. habilis may have enabled a greater degree of arboreal locomotion in this species than in H. erectus, but whether arboreality was indeed practiced by H. habilis must remain a matter of speculation," they wrote in the study.

"Homo habilis limbs have been coming more and more into focus," study co-author Ashley Hammond, a paleoanthropologist at the Catalan Institute of Paleontology Miquel Crusafont, said in the statement, and the new skeleton "confirms that the arms were fairly long and strong. What remains elusive is the lower limb build and proportions."

Only a few fragments of KNM-ER 64061's pelvis were recovered, but they suggest that this H. habilis individual may have walked more like H. erectus than like earlier australopithecines, the researchers noted in the study.

"Going forward, we need lower limb fossils of Homo habilis, which may further change our perspective on this key species," Hammond said in the statement.

The discovery of a surprisingly complete H. habilis skeleton may also help paleoanthropologists sort out the abundance of hominin groups that lived in eastern Africa between 2.2 million and 1.8 million years ago.

Researchers have found that up to four hominin species — Paranthropus boisei, H. habilis, Homo rudolfensis and probably H. erectus — lived in the same place around the same time. And because H. erectus appeared nearly 500,000 years before H. habilis disappeared from the fossil record, it is currently unclear whether H. habilis was the ancestor to H. erectus or a related species.

Human evolution quiz: What do you know about Homo sapiens?

Early, ancestral members of the human lineage may have left Africa earlier than widely thought, a new study of fossil teeth suggests.

Modern humans, Homo sapiens, are the only living member of the human lineage, Homo, which is thought to have arisen in Africa about 2 million to 3 million years ago and first left that continent a few hundred thousand years ago. But many other extinct human species previously roamed Earth, such as Homo habilis, suspected to be among the first stone-tool makers, and Homo erectus, the first to regularly keep the tools it made.

Scientists investigated fossils excavated from the medieval hilltop town of Dmanisi in the Republic of Georgia. Archaeological excavations there about 35 years ago unexpectedly revealed that Dmanisi is one of the oldest-known sites for ancient human species outside Africa, with the five skulls recovered from there dating to approximately 1.8 million years ago.

The fossils of Dmanisi have drawn intense debate because of the unusual level of variation they display. Many researchers have suggested these specimens all belong to H. erectus, with the anatomical diversity seen between the specimens resulting from factors such as natural differences between the sexes. Other scientists have argued that the Dmanisi fossils represent two distinct human species. One, dubbed Homo georgicus, seemed more closely related to predecessors of humans known as australopiths, while the other, Homo caucasi, appeared more similar to early human species.

Resolving this controversy might reveal whether H. erectus was the first human species to leave Africa, or if others preceded it, study co-author Victor Nery, a historian and archaeologist at the University of São Paulo in Brazil, told Live Science.

Previous analyses of the Dmanisi fossils mostly focused on the skulls. In the new study, published Dec. 3 in the journal PLOS One, researchers instead concentrated on similarities and differences among the teeth.

The scientists analyzed 24 teeth from three individuals at Dmanisi. They compared them not only with each other, but also 559 teeth from other species, including australopiths, early humans such as H. habilis and H. erectus, and modern humans.

The teeth appeared to split into two groups, one closer to australopiths, and the other more similar to early humans, the researchers found. The differences between these groups was especially evident in teeth from the upper jaw.

These dental discoveries suggest "there were likely more than one species that occurred in the Dmanisi region," study co-author Mark Hubbe, head and professor of anthropology at the University of Tennessee, Knoxville, told Live Science.

The scientists noted the dissimilarities between these two groups of teeth was akin to the levels of differences seen between the sexes in chimps and gorillas. That raises the possibility that these represent the teeth from both sexes in one species. However, the researchers argued the Dmanisi fossils did not come from just one human species, since the more australopith-like group had relatively large third molars, in contrast to the trend in humans of smaller third molars when compared to their relatives.

"I agree with the authors that Dmanisi probably has more than one lineage represented," Chris Stringer, a paleoanthropologist at the Natural History Museum in London who did not take part in this study, told Live Science. The large but small-brained "skull looks much more primitive than the others — at least [H.] habilis-like, if not australopithecine. The others might still represent a very primitive form of [H.] erectus, which has been the mainstream view so far."

If one accepts the new study's conclusions that there were two species present at Dmanisi at the same time, then the biggest implication is that "there was an earlier, and more 'primitive' species that migrated out of Africa than generally thought, which is quite interesting," Karen Baab, a paleoanthropologist at Midwestern University in Glendale, Arizona, who did not participate in this work, told Live Science.

If human species did leave Africa before H. erectus, these early humans "could have given rise to remote descendants like [H.] luzonensis, [H.] floresiensis and Meganthropus," Stringer added. (Fossils of Meganthropus, an extinct primate, were first found in Indonesia in the 1940s, and scientists have long argued whether it was an ape, an australopith, or a member of an early human species.)

Still, Baab cautioned that these new findings do not conclusively prove there was more than one species at Dmanisi. For instance, she noted the new study's analysis of teeth from the lower jaw suggested these fossils might belong just to H. erectus, and not two species.

Although the new study argues that the simplest explanation for its results is that multiple species existed at Dmanisi, the simplest explanation might actually be "to propose a single, albeit highly variable species, where some individuals retain more ancestral features and others are more derived in the direction of later Homo erectus," Baab said.

Human evolution quiz: What do you know about Homo sapiens?

The discovery of a never-before-seen bump on the leg bone of a 7 million-year-old fossil ape shows it walked upright on two legs while it was on the ground, a new study finds.

Only members of the human lineage have this lump, called the femoral tubercle. That makes the species, Sahelanthropus tchadensis, the earliest known hominin, according to the study, published Jan. 2 in the journal Science Advances. (Hominins are the group of species, including humans, that existed after the split from chimpanzees and bonobos. Walking upright on two legs is a defining characteristic of hominins.)

"That [bump] really sold it to us," study lead author Scott A. Williams, an associate professor of paleoanthropology at New York University, told Live Science. "That really convinced me that, OK, we think it's a biped, and therefore, we think it's a member of the hominin lineage."

The reanalysis of S. tchadensis' femur also confirmed two more human-like anatomical features. First, the bone twisted inward, placing the knees closer together than the hips, as in modern humans. Second, there was a distinct lump on the side of the fossil where the largest glute muscle attaches, which isn't found in living nonhuman apes.

S. tchadesis' curved arm bones suggest that, like modern-day chimps and bonobos, the species was adapted to climbing trees. But its hips and knees functioned like those of hominins which suggests the ape frequently walked bipedally while on the ground.

"I think it must have been on the ground a significant amount of the time in order to evolve bipedalism," Williams said.

A hotly debated fossil

Discovered in modern-day Chad, S. tchadensis was first described in 2002 and remains highly controversial. The authors of that study claimed the fossil ape was the earliest known hominin based on the position of the opening in the skull where the spinal cord attaches, called the foramen magnum. The opening was in the middle of the skull, which suggests the ape stood upright like humans do, but others argued that positioning didn't prove S. tchadensis walked on two feet.

Twenty years later, two forearm bones, or ulnae, and a femur fragment belonging to S. tchadensis were revealed. The authors argued that the femur belonged to an ape that walked on two legs. But other scientists disagreed with this assessment, stating that the thigh bone shape did not indicate frequent bipedality.

Williams said he was on the fence about S. tchadensis being bipedal — and, therefore, a hominin — because it is "really old." The ape lived around the time scientists believe the last common ancestor of humans and chimpanzees lived, approximately 6 million to 7 million years ago. Rather than being a hominin, S. tchadensis may have been an ancient ape more closely related to chimps and bonobos than to humans, he explained.

Because he was interested in the answer either way, Williams and his team inspected the 3D scans of limb bones. They looked at various hallmark features on the femur and compared them to the thigh bones of all living and extinct ape species for which these bones exist.

This analysis revealed that the size and shape of S. tchadensis' ulna and femur resembled those of modern-day chimps and bonobos. "We were getting a very great-ape signal," Williams said.

But there were key differences that convinced the team that this ape was bipedal. Their analyses confirmed the presence of an inwardly twisted femur shaft and the attachment for the largest glute muscle, both linked to a hominin way of moving.

Critically, however, they spotted something no one had previously noticed: a tiny bump on the top front of the femur. "It's a very subtle little bump that I actually didn't identify initially by looking at the fossil but by rubbing my thumb along it and bumping into it," Williams said. The team then verified that the original S. tchadensis fossil also had this lump.

"It's beyond convincing," Jeremy DeSilva, a biological anthropologist at Dartmouth College who was not involved in the research, told Live Science. "I immediately pulled this [the femur 3D scan] out and said, 'Wait, how did I not see this?' And sure as day, some of the key anatomies that they point out in this paper, I can see in this fossil," he said. "I'm kind of kicking myself. I wish I had seen these things."

This research makes the question of what the last common ancestor between humans and chimpanzees looked like "even more puzzling and fascinating," DeSilva said.

If S. tchadensis was a hominin, it could suggest, as Williams believes, that this ancestor was more chimpanzee-like than human-like. However, DeSilva said S. tchadensis could potentially be a bipedal ape not on the human lineage.

"So the question we now have as a field that we have to contend with is," he said, "can you be bipedal and not be a hominin? Is that possible?"

Human evolution quiz: What do you know about Homo sapiens?

The discovery of 773,000-year-old fossils in a cave in Morocco is transforming the geography of human origins by placing the start of the modern-human lineage squarely in northwestern Africa, according to a new study.

In the research, published Wednesday (Jan. 7) in the journal Nature, a team of Moroccan and French researchers detailed their analysis of a handful of bones they think represent the last common ancestor of modern humans (Homo sapiens), Neanderthals and Denisovans.

The researchers discovered the fossils in a cave called Grotte à Hominidés (Cave of Hominids) at the site of Thomas Quarry I in Casablanca, Morocco. The bones consist of three partial lower jaws, several vertebrae and numerous individual teeth, all of which share some characteristics of Homo erectus but also have traits distinct from this human ancestor.

Additionally, there were numerous stone tools at the site, and one leg bone suggests that hyenas might have dined on the hominins. By testing the magnetic properties of 180 samples of sediment from around the fossils, the researchers found that the sequence spanned the Matuyama-Brunhes magnetic-field reversal, a geological event that occurred 773,000 years ago.

The new discovery fills a major gap in the African hominin fossil record between 1 million and 600,000 years ago, study co-author Jean-Jacques Hublin, a paleoanthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, told Live Science in an email. Genetic evidence has suggested that, during this time span, the last common ancestor of modern humans, Neanderthals and Denisovans was living in Africa.

Hublin and colleagues think the Thomas Quarry fossils are the best candidates yet for the "root" of the ancestral tree that led to our species and our archaic cousins.

While the early chapters of the story of human evolution took place in eastern and southern Africa, the last million years of our evolution are complicated by our ancestors' tendency to wander throughout Africa and Eurasia.

After H. erectus evolved in Africa around 2 million years ago, some groups spread eastward, reaching as far as Oceania. But others stayed put, evolved further and spread north into Europe around 800,000 years ago, where the groups from Spain are known as Homo antecessor and are the most likely direct ancestor of Neanderthals.

The newly analyzed Moroccan fossils are from roughly the same time period as H. antecessor and share some of their distinctive traits, which "may reflect intermittent connections across the Strait of Gibraltar that deserve further investigation," Hublin said. The Thomas Quarry fossils, however, are distinct from both H. erectus and H. antecessor.

"This supports a deep African origin for Homo sapiens and argues against Eurasian origin scenarios," Hublin said.

More work on the exceptionally rich fossil record of North Africa is needed to expand an understanding of human origins that is based largely on eastern and southern Africa, Hublin said, particularly since the clearest early evidence of H. sapiens comes from the 300,000-year-old site of Jebel Irhoud in Morocco.

A focus on this geographic area may also reveal new clues about the split between our species and our Neanderthal and Denisovan cousins.

"While we cannot claim that the emergence of the lineage leading to Homo sapiens occurred exclusively in North Africa," Hublin said, "the [new] Moroccan fossils strongly suggest that populations close to the divergence between the Homo sapiens lineage and those leading to Neanderthals and Denisovans were present there at that time."

John Hawks, a biological anthropologist at the University of Wisconsin-Madison who was not involved in the study, agreed with the researchers' conclusions.

"It's clear from the new study that these fossils don't fit easily into the variation of Homo erectus in some ways," Hawks told Live Science. "It's likely that they're close to the common ancestor that gave rise to Neanderthals, Denisovans and modern people."

But it's unclear what the Thomas Quarry fossils should be called. "In my way of thinking, they might be the earliest fossils that we should really call Homo sapiens," Hawks said.

Hublin is hesitant to classify the fossils as a particular species or population, particularly because there are only a handful of fragmentary remains from Thomas Quarry. "Palaeoproteomic analyses are planned and could potentially help to elucidate the relationships between the European and North African fossils," Hublin said.

Human evolution quiz: What do you know about Homo sapiens?

The group had traveled for thousands of miles, crossing Africa and the Middle East until finally reaching the dimly lit forests of the new continent. They were long-vanished members of our modern human tribe, and among the first Homo sapiens to enter Europe.

There, these people would likely have encountered their distant cousins: Neanderthals.

These small bands of modern-human relatives had hooded brows, large heads and squat bodies, and they had spent epochs acclimating to Europe's colder climate. At several points across millennia, these two forms of humanity would meet, mingle and mate.

Tens of thousands of years later, these ancient encounters have left traces in the genetic code of billions of humans alive today. The lingering genes affect us in ways large and small, from our appearance to our risk of disease.

"In some places in our genome, we're more Neanderthal than we are human," Joshua Akey, a professor of integrative genomics at Princeton University, told Live Science.

These were our closest human relatives, and this is their legacy.

The first encounter

By 75,000 years ago, but possibly up to 250,000 years ago, the ancestors of most modern Eurasians first ventured out of Africa and into Eurasia. Here, modern humans came face-to-face with Neanderthals, who last shared a common ancestor with modern humans hundreds of thousands of years earlier and had been living in these continents ever since. On multiple occasions over the millennia, the groups interbred.

Related: Could Neanderthals talk?

At first, modern humans inherited whole chromosomes from Neanderthals, Sriram Sankararaman, a professor of computer science, human genetics and computational medicine at UCLA, told Live Science. However, from generation to generation, via a process known as genetic recombination, these stretches of DNA were broken up and shuffled around.

Neanderthal DNA was generally "deleterious" to modern humans, meaning it was rapidly weeded out of modern humans' DNA through evolution. This resulted in "deserts of Neanderthal DNA," or large regions of the modern human genome lacking it, Sankararaman said. For instance, scientists think the Y chromosome in males doesn't contain any Neanderthal genes. It may be that genes on the Neanderthal Y were incompatible with other human genes or they may have been randomly lost via a process known as genetic drift.

In people who inherited Neanderthal DNA, the X-chromosome also contains a lot less Neanderthal ancestry than other, non-sex chromosomes carry. This is probably because any harmful or nonfunctional mutations on the X chromosome will be expressed in males, because they lack a matching, functional copy of the gene to compensate. That likely created strong evolutionary pressure to remove such harmful Neanderthal genes from the modern human X, Emilia Huerta-Sanchez, an associate professor of ecology, evolution, and organismal biology at Brown University, told Live Science.

But some Neanderthal DNA helped modern humans survive and reproduce, and thus it has lingered in our genomes. Nowadays, Neanderthal DNA occupies, on average, 2% of the genomes of people outside Africa. However, the frequency of Neanderthal DNA that codes for beneficial traits may be as high as 80% in some regions of the genome, Akey said.

Our physical appearance

For many people, the legacy of Neanderthals is apparent in a highly visible feature: skin color.

A Neanderthal gene variant on chromosome 9 that influences skin color is carried by 70% of Europeans today. Another Neanderthal gene variant, found in most East Asians, regulates keratinocytes, which protect the skin against ultraviolet radiation via a dark pigment called melanin.

Neanderthal gene variants are also associated with a greater risk of sunburn in modern humans. Likewise, around 66% of Europeans carry a Neanderthal allele linked to a heightened risk of childhood sunburn and poor tanning ability.

Neanderthals had spent millennia at higher latitudes with less direct sun exposure, which is needed for vitamin D production. Therefore, changes to hair and skin biology may have allowed modern humans to quickly capitalize on lower levels of sunlight while still producing enough vitamin D to be healthy, John Capra, an evolutionary geneticist at Vanderbilt University, told Live Science.

"One of the cool things about interbreeding is that instead of waiting for new beneficial mutations to arise, which is a really slow process, you introduce a ton of genetic variation at once," essentially fast-tracking evolution, Huerta-Sanchez said.

Related: What's the difference between Neanderthals and Homo sapiens?

In addition, our ancestors had to adapt to colder Eurasian weather. To do so, they may have acquired Neanderthal genes that affected face shape. In a 2023 study, scientists discovered that modern humans inherited tall-nose genes from Neanderthals. A taller nose may have allowed more cold air to be heated to body temperature in the nose before reaching the lungs, suggested Kaustubh Adhikari, co-senior study author and a statistical geneticist at University College London.

The clock that makes our cells tick

Neanderthal DNA also may have helped H. sapiens adjust to the bigger differences in day and night length at northern latitudes.

Lingering Neanderthal genes affect our circadian clock, which regulates internal processes such as body temperature and metabolism. For instance, some early risers can thank Neanderthals for their circadian clock genes, Capra and colleagues found.

This may have helped our ancestors adapt to shorter winter days farther from the equator, Capra said.

"It seems like it's not that being a morning person is what matters," Capra said. "It's that that's a signal of how essentially flexible your clock is and how able it is to adapt to the variation in light-dark cycles with seasons," he said.

Our internal defenses

Many of the strongly retained Neanderthal genes are tied to immune function.

By the time H. sapiens arrived in Europe, Neanderthals had already spent hundreds of thousands of years fighting infections specific to Eurasia. By mating with Neanderthals, modern humans got an instant infusion of those infection-fighting genes.

"Those pieces of Neanderthal DNA, especially the immune ones, that were already adapted against pathogens that Neanderthals had been living with for a long time started to rise in frequency under natural selection in modern human populations," David Enard, an assistant professor of ecology and evolutionary biology at the University of Arizona, told Live Science.

While many of the ancestral pathogens that sickened ancient humans are lost to time, some of the Neanderthal genes that helped fight them off still work against modern pathogens. For example, a 2018 study by Enard and a colleague revealed that modern humans inherited Neanderthal DNA that helped them combat RNA viruses, a group that today includes the flu (influenza), HIV and hepatitis C.

Related: 10 unexpected ways Neanderthal DNA affects our health

The darker side of Neanderthal DNA

Some of the Neanderthal genes that once helped our ancestors may be harmful in the modern world.

For the most part, Neanderthal genes are not strongly expressed in the brain, which hints that they were strongly selected against during evolution. Neanderthal genes have been linked to mood disorders such as depression and to brain signaling pathways that make people more likely to become addicted to nicotine.

And even the immune boost from Neanderthals may have a downside. In 2016, scientists discovered that Neanderthal genes that prime the immune system to fight pathogens may also predispose people to allergic diseases. In addition, Neanderthal genes have been tied to a higher risk of developing autoimmune diseases, such as Graves' disease, caused by an overactive thyroid; and rheumatoid arthritis, which inflames the joints and even "Viking disease," in which one or more fingers become bent or frozen.

One Neanderthal gene variant may have made us more likely to have a severe case of COVID-19. That variant, found on chromosome 3, is found in half of South Asians and one-sixth of Europeans. But even there, the picture is complicated, as other Neanderthal genes, carried by up to half of people in Eurasia and the Americas, are associated with a reduced risk of severe COVID-19.

"Unfortunately, there are no diseases we can really say, or even traits in general, we can say, 'Oh, you can blame your Neanderthal DNA for that,'" Capra said.

That's especially true for some of the biggest health ailments, such as heart disease and cancer, where dozens or hundreds of genes, along with myriad environmental factors, affect your risk of disease.

What lies ahead

So how long will the traces of these long-lost humans linger in our genomes? Over hundreds of thousands of years, some of these Neanderthal fragments will gradually be eliminated from our genomes. Others will become firmly embedded, Akey said.

In the meantime, there's still much more to learn about how Neanderthals left their mark on us.

"Being able to leverage new genomic technology like CRISPR and gene editing is going to play an important role in understanding the actual underlying biology of how Neanderthal sequences contribute to human traits and diseases," Akey said.

Deciphering what these genes actually do could aid the development of treatments for certain conditions, he said.

And the gene flow wasn't one-way; scientists are also trying to determine how modern-human DNA may have influenced Neanderthals and are applying artificial intelligence (AI) methods to ancient genomes to create a more detailed picture of what our long-lost cousins were like.

Figuring out the role of Neanderthal DNA in our genomes does more than help us understand our health. These bits of DNA can provide clues as to what makes us unique, Sankararaman said.

"Neanderthal DNA entered our genomes at an important time in our history," Sankararaman said, when our ancestors were moving into new environments.

"By looking at the fate of these bits of DNA," he said, "we can hope to understand what were the functionally important regions in our genome over this period of time."

Editor's Note: This story was originally published in March 2024.

Neanderthals have fascinated scientists since they were first discovered in the 19th century. Their long heads and low brow ridges initially convinced experts that Neanderthals were some kind of evolutionary wrong turn that ended up in European caves.

It took more than a century for researchers to prove that Neanderthals were actually quite intelligent and that they interbred with modern humans (Homo sapiens). The number of discoveries related to Neanderthals' biology and culture has skyrocketed in recent years — and 2025 was a noteworthy year. While we learned that Neanderthals had biological features that were strikingly different from modern humans', this year's discoveries also showed that some aspects of their behavior and culture were similar to ours.

Here are 10 major Neanderthal findings from 2025 — and what they teach us about our own evolution.

1. Neanderthals were the first to make fire.

The hottest — but also somewhat controversial — Neanderthal discovery of the year was that the first humans to make and control fire were Neanderthals living in England more than 400,000 years ago.

In December, researchers announced that they had found reddened clay and heat-shattered flint hand axes at an archaeological site in Suffolk. But the smoking gun was the discovery of tiny flakes of pyrite, a mineral that produces sparks when struck against flint.

Experts have debated for decades whether early human ancestors deliberately made fire or whether they opportunistically used wildfires that sprang up. The combination of flakes of pyrite and charred soil and tools points to Neanderthals' purposeful creation of fire.

The discovery, however, does not tell us whether Neanderthals invented this technology or they learned it from even earlier ancestors, such as Homo erectus. Regardless, the fire evidence shows that Neanderthals were smart enough to figure out how to survive in cold and dark European climates.

2. Neanderthals cannibalized women and children.

Around 45,000 years ago — very close to when Neanderthals disappeared forever — six members of a Neanderthal group were cannibalized, according to a study published in November. Their remains were discovered in the Goyet cave system in Belgium with butchery marks similar to those on animal bones.

This isn't the first time archaeologists have found evidence of cannibalism in Neanderthals. But it is the best evidence experts have to suggest one group — probably Neanderthals but possibly modern humans — deliberately targeted the women and children of another group, perhaps as a way to eliminate the group's reproductive potential.

3. A Neanderthal left the world's oldest fingerprint.

A curious-looking rock found in Spain contains the world's oldest known fingerprint, and it was probably made by a Neanderthal using ocher 43,000 years ago, researchers announced in May.

The team investigating the rock, which is the size of a large potato, thinks that it has face-like features and that the red dot may be a nose. If they're correct, it would mean Neanderthals were creating symbolic art, which could settle a decades-long debate in paleoanthropology.

Not all experts agree that the rock is an early version of Mr. Potato Head, but they do think the fingerprint and its characteristic whorl pattern represent a clear example of Neanderthals' use of red ocher pigment.

4. Neanderthals may have used "crayons."

Scientists in Crimea found three pointy chunks of red and yellow ocher that Neanderthals may have used as early "crayons" 100,000 years ago, according to research published in November.

The hunks of mineral appear to have been repeatedly sharpened, which suggested to the researchers that the ocher was used for culturally meaningful purposes rather than in practical tasks, such as tanning hides.

Although ocher has been found at other Neanderthal sites, not all experts are convinced of the crayon interpretation. Instead, they suggest Neanderthals may have scraped powder from the ocher chunks for another purpose, such as to leave a fingerprint.

5. Neanderthals were low-energy.

In July, researchers discovered that a key Neanderthal gene variant that is still found in some humans today could be detrimental to athletic performance because it limits the body's ability to produce energy during intense exercise.

Researchers found that the Neanderthal version of an enzyme called AMPD1 was different from the one in most modern humans. The Neanderthal enzyme variant allowed adenosine monophosphate (AMP) to build up in their muscles rather than being quickly removed. This AMP buildup is problematic because it makes it harder to produce adenosine triphosphate (ATP), a molecule that the body uses to store energy.

Modern humans who carry the Neanderthal variant of the gene have a lower probability of achieving elite athletic status, the researchers found. But while the Neanderthal variant may have affected their muscle metabolism slightly, it may not have contributed to their extinction.

6. Neanderthals were more susceptible to lead poisoning compared with humans.

In a study published in October, researchers examined 51 teeth from H. sapiens, Neanderthals and other ancestors for evidence of lead exposure. Lead occurs naturally in our environment, but it is known to be toxic at high levels, causing damage to the brain and other organs. Researchers discovered that human ancestors were affected by episodic lead exposure for nearly 2 million years — and that human brains may have evolved some protection against lead poisoning.

Humans living today have a unique version of a gene called NOVA1 that is important for brain development and language skills. The gene also appears to confer greater resistance to lead than other versions of the gene do, such as the one in our Neanderthal cousins.

Therefore, researchers propose, the modern-human version of NOVA1 may have given us a slight advantage over Neanderthals and may have contributed to the demise of the Neanderthals.

7. Neanderthals had a "fat factory" in Germany.

Neanderthals primarily ate meat (and maggots), which put them at risk of developing protein poisoning, a lethal condition that results from eating too much protein and too few fats and carbohydrates.

But in July, researchers announced their discovery of a "fat factory" that Neanderthals may have used to stave off this condition 125,000 years ago. Their survey of nearly 200 animal bones revealed that Neanderthals smashed the bones to get at the marrow inside, which they boiled to extract the fat.

Fat is high in calories, and Neanderthals may have saved it to eat during food shortages. This innovative food-collection method is similar to what some ancient modern-human foraging groups did, suggesting that, in at least one way, Neanderthals were similar to us.

8. Neanderthals lacked a key DNA-synthesizing gene.

In August, researchers investigating the enzyme adenylosuccinate lyase (ADSL) found that the version in Neanderthals was more active than the one in humans. ADSL helps synthesize purine, which is one of the fundamental building blocks of DNA, and an ADSL deficiency is known to result in intellectual disability in modern humans. So researchers modified mice to have a modern-human-like ADSL gene and found that they were better at completing a task to get water.

But even though ADSL deficiency can cause intellectual and behavioral problems in modern-day people, it's not yet clear whether the Neanderthal variant impaired them.

9. Our cousins suffered a population bottleneck.

Even before Neanderthals disappeared forever, their numbers were dwindling because of a population bottleneck, according to research published in February.

Scientists looked at the tiny inner-ear bones of Neanderthals from various time periods and noticed that, around 110,000 years ago, there was an abrupt decline in the diversity of bone shapes. This decline suggests a bottleneck event, when a species undergoes a sudden reduction in variation due to factors such as genocide or climate change.

While the ear bones alone didn't cause the Neanderthals' downfall, the bottleneck may have been the beginning of the end.

10. Neanderthals' blood may have doomed them.

Biologically, Neanderthals had distinct blood variants that separated them from modern humans — and two of those variants we learned about this year may have hastened our ancient cousins' extinction.

In January, researchers discovered that Neanderthals had a rare blood type that may have been fatal to their offspring when they mated with Denisovans or early H. sapiens.

Neanderthals carried a variation of the blood antigen Rh, which gives the positive and negative signs to blood types. Before modern medical interventions, if someone who was Rh-negative was pregnant with a fetus that was Rh-positive, it caused a miscarriage or stillbirth. The researchers found that, if a Neanderthal female mated with a H. sapiens or Denisovan male, there would have been a high risk of anemia, brain damage and infant death. And that might have spelled the end of the line for Neanderthals.

Another study published in October suggested that a fatal red blood cell incompatibility between Neanderthals and humans also contributed to our ancient cousins' extinction. Researchers focused on the PIEZO1 gene that affects oxygen transportation in red blood cells. Neanderthals' version of this gene essentially let their blood cells trap oxygen efficiently, while the modern-human version more efficiently released oxygen to tissues. When maternal oxygen isn't passed on to the fetus, it can restrict the growth of the fetus or lead to miscarriage. So, if a hybrid Neanderthal-human mother mated with a modern-human father or with a hybrid Neanderthal-human father, their offspring would be more likely to die than the offspring of non-hybrids.

Although Neanderthals' extinction likely did not hinge on any one specific gene variant, the new research into red blood cells and maternal-fetal incompatibility is providing key insight into the demise of our archaic cousins around 35,000 years ago.

Neanderthal quiz: How much do you know about our closest relatives?

Scientists have reconstructed the head of an ancient human relative from 1.5 million year-old fossilized bones and teeth. But the face staring back is complicating scientists' understanding of early human evolution and dispersal, according to a new study.

The rebuilt fossil skull, called DAN5, shares traits with Homo erectus, the first early human relatives to have modern body proportions and to disperse from Africa. But the skull also has some features associated with the earlier species Homo habilis. The findings suggest a complex evolutionary path from early human ancestors to H. erectus, researchers reported Dec. 16 in the journal Nature Communications.

DAN5 was discovered in the Gona study region of northern Ethiopia and was first reported in a 2020 study published in the journal Science Advances. The fossils are between 1.5 million and 1.6 million years old and were thought to belong to a small H. erectus female based on the shape and size of the skull.

"We already knew that the DAN5 fossil had a small brain, but this new reconstruction shows that the face is also more primitive than classic African Homo erectus of the same antiquity," study co-author Karen Baab, a paleontologist at Midwestern University in Arizona, said in a statement. This could mean that the population from the Gona region might have "retained the anatomy of the population that originally migrated out of Africa approximately 300,000 years earlier," she said.

To reconstruct DAN5's face, the researchers used micro-computerized tomographic (CT) scans of 10 fossils — five fragments of facial bones and five teeth — to build a 3D model. The process was like "a very complicated 3D puzzle, and one where you do not know the exact outcome in advance," Baab said. "Fortunately, we do know how faces fit together in general, so we were not starting from scratch."

The shape of DAN5's braincase was similar to that of H. erectus. But some of the facial features such as large molars and a flat and narrow nose were more similar to features in the older human ancestor H. habilis.

A similar mix of old and new traits was previously observed in 1.8 million-year-old H. erectus fossils from Dmanisi in the Republic of Georgia, which led some scientists to believe that the species evolved in Eurasia from an earlier Homo population. Older H. erectus fossils dating back 1.8 million years have also been found in Africa. But DAN5 is the first African fossil to have the same mixture of attributes as the Dmanisi hominins, which could support the hypothesis that H. erectus evolved primarily in Africa like other hominins before it. Further complicating the picture, though, is the fact that the DAN5 fossils are younger than those from Dmanisi, suggesting the mixture of old and new traits persisted in Africa for at least 300,000 years.

In future work, the team plans to compare the DAN5 fossils to 1 million-year-old human fossils from Europe, including some that have been identified as H. erectus and as Homo antecessor — a later human relative that lived 1.2 million to 0.8 million years ago — to better understand variability in face shape in the early Homo genus. The team also plans to investigate whether DAN5 might be a product of interbreeding between multiple Homo species.

"We're going to need several more fossils dated between one to two million years ago to sort this out," study co-author Michael Rogers, an anthropologist at Southern Connecticut State University, said in the statement.

Human evolution quiz: What do you know about Homo sapiens?

Our understanding of how our species evolved has improved dramatically since we first began analyzing ancient DNA. This year, researchers made impressive discoveries across 3 million years of human evolution, most of which relied on DNA, genomic or proteomic analyses.

Here are 10 major findings about human ancestors and our close ancient relatives that scientists announced in 2025.

1. Two new species of human relatives were discovered in Ethiopia.

A handful of teeth found at the Ledi-Geraru site in Ethiopia suggest that diverse species of human relatives unlike any seen before were roaming the area 2.6 million years ago.

In August, researchers announced the discovery of 13 teeth. Ten are estimated to be 2.63 million years old and don't belong to either Australopithecus afarensis or Australopithecus garhi, the two australopithecine species known from the area. Because the teeth don't have any especially unique features and aren't in a skull, the newfound species they may come from does not have an official name. Researchers are calling it the Ledi-Geraru Australopithecus.

In the same study, the researchers found two teeth that are 2.59 million years old and one that is 2.78 million years old. All of them seem to belong to the genus Homo, which would make them some of the earliest remains of our own genus.

The dental discoveries mean that at least three archaic human relatives were living in this region of Ethiopia around 2.5 million years ago.

2. Imported stone tools show our relatives were much smarter than we thought.

Hundreds of stone tools discovered in Kenya revealed that our ancient relatives had a high degree of forward planning 600,000 years earlier than experts previously thought.

In an August study, researchers looked at more than 400 stone tools from the site of Nyayanga dated to 3 million to 2.6 million years ago. The tools were likely not made by our genus. While the tools were fairly basic — flakes chipped off of a larger stone — the stones used to make them came from locations more than 6 miles (9.7 kilometers) away.

The fact that hominins were transporting stones from far away to make tools suggests an excellent ability to plan ahead, long before our genus Homo arose.

3. Earliest evidence of Homo erectus found in Georgia

In July, researchers announced the discovery of a 1.8 million-year-old jawbone from Homo erectus at the site of Orozmani in the Republic of Georgia. In 2022, the paleoanthropologists had found a single tooth that they thought was from H. erectus, and the jawbone discovered this year clinched the identification.

H. erectus was our direct ancestor and evolved around 2 million years ago in Africa. It was also the first human ancestor to leave Africa, and eventually ended up in parts of Europe, Asia and Oceania.

To date, the earliest evidence of H. erectus outside Africa comes from Orozmani and a second site in Georgia called Dmanisi, suggesting human ancestors settled in the Caucasus region shortly after leaving Africa.

4. A mystery human reached Indonesia 1.5 million years ago.

Stone tools discovered on the Indonesian island of Sulawesi this year suggest that either H. erectus or an unknown human relative reached Oceania nearly 1.5 million years ago. This matches up well with previous evidence that H. erectus arrived on the island of Java around 1.6 million years ago.

But because no ancient skeletal remains have been found on Sulawesi yet, researchers are unsure if the toolmaker was indeed H. erectus. Another candidate could be H. floresiensis, the diminutive "hobbit" species, which has been found on the neighboring island of Flores. Some researchers think the hobbits originally came from Sulawesi.

Additional excavation on Sulawesi may eventually clarify which species called the island home.

5. Humans arrived in Australia 60,000 years ago.

Genetic research published in November showed that Homo sapiens reached Australia 60,000 years ago, likely via two different routes through the Western Pacific. This finding appears to settle a long-standing debate about humans' arrival on the continent — a feat that required expert knowledge of watercraft and sailing.

The new DNA evidence supports archaeological evidence, including stone tools and pigments on cave walls, of a "long chronology" in which the first arrivals showed up around 60,000 to 65,000 years ago.

But not everyone is convinced. In a July study, researchers used the fact that some Indigenous Australians have Neanderthal DNA to suggest that Australia wasn't populated until about 50,000 years ago — an idea known as the "short chronology."

More research into the origins of the earliest Australians is forthcoming.

6. Drought may have doomed the "hobbits."

By 50,000 years ago, H. floresiensis seems to have disappeared from Flores. In December, researchers published a study suggesting that drought may have fueled their demise.

While studying the rainfall on Flores, scientists discovered that it declined considerably between about 76,000 and 61,000 years ago and that the population of an elephant relative called Stegodon, which the hobbits hunted, disappeared around 50,000 years ago.

The researchers think decreased rainfall led to the reduction in the Stegodon population, which made life more difficult for the hobbits. And if modern humans also reached Flores — perhaps part of the wave of people who eventually settled Australia — the pressure of competition from another species may have wiped out H. floresiensis.

7. Denisovans got a face.

Our extinct relatives the Denisovans were first discovered in 2010 based on DNA extracted from a tiny finger bone. But until this year, no one knew what a Denisovan skull looked like.

Researchers debated for years what species the thick jawbone, recovered off the coast of Taiwan in 2000, came from, with some suggesting H. erectus and others suggesting H. sapiens. But using paleoproteomic analysis, researchers announced in May that the jawbone was from a male Denisovan.

Ancient proteins also revealed in June that a skull discovered in China in 1933, called the "Dragon Man," is from a Denisovan, finally putting a face to the name. But while Dragon Man has now been slotted into the story of human evolution, it is not yet clear whether the group should be considered a separate species, Homo longi.

And in September, researchers reconstructed a 1 million-year-old squashed skull from China and suggested that it may have been a Denisovan ancestor rather than H. erectus.

These three discoveries are pointing paleoanthropologists to clues about the origins and spread of the mysterious Denisovans — a task that will surely continue in the coming years.

8. Denisovan DNA helped Native Americans survive.

Researchers announced in August that some people with Indigenous American ancestry carry Denisovan genes, likely passed on through Neanderthals who mated with modern humans.

In looking at a protein-coding gene called MUC19, scientists discovered that 1 in 3 Mexicans alive today has a version of the gene similar to Denisovans' and that it likely "hitched a ride" from Neanderthals. Essentially, Neanderthals got the gene from mating with Denisovans and then passed it along when they mated with humans. This is the first time scientists have found a Denisovan gene in humans that came via Neanderthals.

Exactly what the Denisovan variant of the MUC19 gene does is currently unclear, but the researchers think it must have been beneficial to the earliest Americans for it to be preserved in the human genome.

9. Interbreeding was rampant among our archaic relatives.

The story of human evolution has gotten wonderfully messy since the genomic revolution. DNA and protein analyses have revealed new groups like the Denisovans, as well as the mating of Neanderthals, modern humans and Denisovans. But this year brought a few surprise pairings as well.

In August, researchers announced that a handful of 300,000-year-old teeth suggested humans and H. erectus may have interbred in China. The teeth had an unusual combination of ancient features, like thick molar roots, and modern features, like small wisdom teeth, that could mean two different species were sharing their genes.

Researchers announced in March that Neanderthals, modern humans and a mysterious third lineage lived alongside one another in caves in what is now Israel around 130,000 years ago. The Homo groups may have mixed and mingled for 50,000 years, potentially sharing cultural practices in addition to genetic material.

And in November, a DNA study of humans' arrival in Australia suggested that, along the way, these early human pioneers likely interbred with one or more archaic human groups, such as H. longi, Homo luzonensis or H. floresiensis.

Although we can see genetic differences among these groups using 21st-century technology, perhaps our earliest ancestors simply saw Neanderthals, Denisovans and others as fellow humans.

10. Most Europeans had a dark complexion until 3,000 years ago.

In a study published in July, scientists found that the genes for lighter skin, lighter hair and lighter eyes emerged among Europeans only about 14,000 years ago and that, until 3,000 years ago, most Europeans had dark skin, hair and eyes.

The researchers determined this from 348 samples of ancient DNA from archaeological sites spread throughout Western Europe and Asia. The first humans to reach Europe around 50,000 years ago carried genes for dark complexions. Once lighter traits emerged, they appeared only sporadically in the genetic data until fairly recently. By about 1000 B.C., those lighter traits became widespread in Europe.

Whether lighter skin, hair and eyes had any sort of evolutionary advantage for early Europeans is still unclear, though.

Human evolution quiz: What do you know about Homo sapiens?

From a distance, it might have looked like a small child was wending her way through the waving grass along a vast lake. But a closer look would have revealed a strange, in-between creature — a big-eyed imp with a small head and an apelike face who walked upright like a human.

She may have looked warily over her shoulder as she walked, on alert for saber-toothed cats or hyenas. She may have used her strong arms to climb the shrubby trees nearby, searching for fruit, eggs, or insects to eat. Or perhaps she simply rested on the shores of the croc-infested waters, gulping down water on a hot day.

She likely had no idea it was her last day on Earth.

Roughly 3.2 million years later, her skeleton was unearthed by paleoanthropologist Donald Johanson and his team on the International Afar Research Expedition.

The stunningly complete fossil was nicknamed "Lucy." And her remarkable species, Australopithecus afarensis, may have been our direct ancestor. Our discoveries about Lucy have transformed our understanding of humanity's tangled family tree.

Fifty years later, we know so much more about her species. In fact, anthropologists have learned so much about Lucy and her kind that we can now paint a picture of how she lived and died.

Her last day may have been filled with companionship, but it also entailed a relentless search for food. And it was likely dominated by the ever-present fear of predators.

"I suspect that the last day in her life was filled with danger," Johanson told Live Science.

Finding Lucy

The modern story of Lucy began on Nov. 24, 1974, in Hadar, Ethiopia. Johanson and then-graduate student Tom Gray stumbled upon a bone poking out of a gully. Following two weeks of careful excavation, their team recovered dozens of fossilized bones. Together, these bones made up 40% of the skeleton of a human ancestor, making it the most complete skeleton of an archaic human species that had ever been found.

Pamela Alderman, another member of the expedition, suggested the team nickname the skeleton Lucy, after the Beatles song "Lucy in the Sky with Diamonds."

"And it just became iconic," Johanson said, "a moniker that everybody knew."

Lucy’s discovery transformed the study of ancient human relatives.

"I was in high school when she was found," John Kappelman, a paleoanthropologist at the University of Texas at Austin, told Live Science. "It really did reset the way paleoanthropology worked."

Lucy's skeleton, along with subsequent discoveries of other fossils of her species, have given anthropologists a wealth of information about what is essentially the halfway point in human evolution. At 3.2 million years old, Lucy and her kind lived equidistant in time from our ape ancestors and contemporary humans.

"She's our touchstone," Jeremy DeSilva, a paleoanthropologist at Dartmouth College, told Live Science. "Everything sort of comes back to her as the reference point, and she deserves it."

"A lot like us"

One thing is fairly certain: Though there were some obvious differences, Lucy looked and acted a lot like us.

"If we saw her coming out of a grocery store today, we would recognize her as upright walking and some kind of human," Johanson said.

Although her strong arms and the shape of her finger bones suggest Lucy could climb trees, her pelvis and knees were clearly adapted to walking on two feet.

The size of Lucy's thigh bone also revealed that she was only about 42 inches (1.1 meters) tall and 60 to 65 pounds (27 to 30 kilograms) — about the size of a 6- or 7-year-old child today. And the eruption of her wisdom teeth showed that, although she was in her early teens when she died, she was a fully mature young adult.

"Australopithecus in general was maturing fast," DeSilva said, "and it makes sense if you're on a landscape full of predators." In species that are frequently prey, individuals that mature faster are more likely to pass on their genes. But australopithecines were unique—while their teeth and bodies matured quickly, their brains grew more slowly, telling us that they relied quite a bit on learning for survival, DeSilva said.

Her discovery also settled a debate that was raging in the early 1970s: Did our big brains evolve before we learned to walk upright? Lucy's head, which was not much bigger than a chimp's, showed the answer was no. Our ancestors became bipedal long before they evolved large brains.

Lucy's clan

Because her skeleton was found on its own, Lucy's "social life" is a little murkier than other parts of her daily life. But many researchers think she lived in a mixed-sex group of about 15 to 20 males and females, not unlike modern-day chimpanzees do.

And although there's no direct evidence, Lucy's skeletal maturity suggests she could have had a baby. Bringing that relatively large-headed newborn through her relatively narrow pelvis would have been challenging, which means she may have had the help of a primitive "midwife."

If Lucy had a baby, she also likely had a partner. Other A. afarensis fossils, such as those of Kadanuumuu, show male australopithecines were only slightly larger than females, which, in primates, usually corresponds to more monogamous pairings.

Lucy and her kind would have spent a significant amount of their time avoiding becoming another animal's lunch. "These small creatures would have been nice hors d'oeuvres for a sabertooth or a large cat or hyena," Johanson said.

Perhaps because of that omnipresent danger, the group likely relied on each other.

"I think they had each other's backs and helped each other out," DeSilva said, "especially when they were in dangerous situations."

A healed bone fracture seen in Kadanuumuu provides evidence that these primates cared for one another. Around 3.6 million years ago, this male australopithecine broke his lower leg. By the time he died, though, the break was fully healed.

"On that landscape with that many predators, no doctors, no hospitals, no casts, no crutches, how in the world do you survive if not for social assistance?" DeSilva said. "It's really strong evidence that they didn't leave each other for dead."

Lucy's last day

Lucy probably started her last day much like any other, waking up from the treetop nest made of branches and leaves where she slept, along with her group, before setting off to find food.

It's not clear whether she would have been alone or in a group when she left to forage; if she did have a baby, she may have carried it.

But there's no doubt that she would have spent a significant part of her day looking for food. She most likely ate a few staples, such as grasses, roots and insects, chemical elements in her tooth enamel showed. She may have happened upon the eggs of birds or turtles and promptly gobbled them up as tasty, protein-rich treats. And if she was lucky enough to come across a carcass of a large mammal, such as an antelope, that hadn't been picked clean, she and her troop mates may have pulled the flesh from the bone, using large rocks.

"They can't afford to be picky eaters as these slow bipeds in a dangerous environment," DeSilva said. "They're eating everything they can get their hands on."

However, there's no evidence that Lucy’s species used fire to cook any of their food.

Death at the water's edge

In the past 50 years, we've created a picture of Lucy's last moments. It's not clear exactly why she was by the lake; maybe she was thirsty, or perhaps it was a great spot to look for food.

But there are two main theories for how she died.

"Perhaps she was down there at the water and — bam! — a crocodile comes out," Johanson said. "Crocodiles are incredibly fast, and it's a dangerous place if you're a little creature" like Lucy.

Johanson found one carnivore tooth mark on Lucy's pelvis, and it had not healed, meaning it occurred around the time of her death. Although the animal that made the mark has not been conclusively identified, "we know that australopithecines were preyed upon because there are a number of examples," Johanson said.

In 2016, Kappelman and his colleagues put forward an alternate ending for Lucy: a catastrophic fall from a tree.

Based on high-resolution CT scans and 3D reconstructions of Lucy's skeleton, Kappelman identified fractures in her right shoulder, ribs and knees that were unlike the typical fracturing that occurs in fossils crushed under the weight of dirt and rocks for millions of years.

"Something traumatic happened here during life," Kappelman said.

The kinds of fractures Lucy suffered are consistent with a fall from a considerable height, perhaps from a tall tree in which she was foraging for food.

"She hit on her feet and then her hands, which meant she was conscious when she hit the ground," Kappelman said. "I don't think she survived very long."

It's not clear whether she was alone when she died. But even if she was with others of her kind, they likely wouldn't have done much with her body.

There's no evidence that A. afarensis "bodies were treated any differently than any other animal," DeSilva said. "Maybe there was some curiosity around it, and then they carried on."

Primate researchers have documented other species' curiosity about inanimate bodies. For example, chimpanzees often care for the body for a few hours or days after death, sometimes guarding the body.

Lucy's group may have done the same for her until her body was naturally buried, which would have happened quite rapidly, perhaps by a flood or mudslide.

In the end, though, "we know very little about how any of these creatures died," Johanson said.

Lucy lives on

Thanks to Johanson's 1974 discovery of Lucy — as well as other important findings, like the "First Family" and the footprints at Laetoli in Tanzania — we now know quite a lot about A. afarensis.

"It was a highly successful species that was comfortable in lots of different habitats," Johanson said; A. afarensis fossils have been found in Kenya in addition to Ethiopia and Tanzania. "From an evolutionary perspective, her species was highly adaptable," he said.

Lucy has had a broad impact on the field of anthropology.

"The discovery of Lucy really hit the start button for looking in older and older sediments in Africa," Kappelman said. As a result, we have found numerous ancient hominin species and now have 50 years' worth of fossil evidence that human evolution was messy and complex.

Lucy was the only human ancestor discovered at Hadar. But a couple dozen miles away at Woranso-Mille, a paleontological site in Ethiopia, Yohannes Haile-Selassie, director of the Institute of Human Origins at Arizona State University, and his colleagues have found evidence of a strange land inhabited by multiple humanlike species between 3.8 million and 3.3 million years ago. For instance, Lucy's kind coexisted alongside another ancient relative, A. anamensis.

Would they have been friends, enemies, competitors or something in between? Right now, anthropologists still have little idea what this landscape teeming with ancient hominins would have looked like.

But perhaps 50 years from now, we'll have a better picture of how Lucy's kind interacted with these other ancient hominins. Even then, Lucy will likely remain one of the most famous fossils of all time.

"I like to think all fossils are pretty special," DeSilva said, "but there's nothing like Lucy."

Editor's note: This article was originally published in November, 2024 as part of a special package written for the 50th anniversary of the discovery of a 3.2 million-year-old A. afarensis fossil (AL 288-1), nicknamed "Lucy."