Homo erectus, an ancestor to modern humans, arose at least 1.8 million years ago. Around that time in the fossil record, archaeologists see big shifts in brain size and body size in ancient hominins.
Credit: Thomas Roche | Wikimedia Commons
Homo erectus, or "upright man," was an ancient ancestor of modern humans that lived between 2 million and 100,000 years ago. Compared to modern Homo sapiens, which evolved just 200,000 years ago, the ancient man had a long reign.H. erectus is the first human ancestor to have similar limb and torso proportions to those seen in modern humans, without the adaptations needed to swing from the branches, suggesting it had adapted to walking on two feet in a more open, grassland environment.
Homo erectus was taller than earlier human ancestors. For instance, one of the most complete fossil skeletons ever found, a 1.5-million-year-old specimen of an adolescent male known as Turkana Boy, was 5 feet 3 inches (1.6 meters) tall. The iconic, 3.2-million-year-old Australopithecus skeleton dubbed Lucy, in comparison, was just 3 feet 7 inches (1.1 meters) tall at death. The species also had more variation in height — with more tall and short individuals — than more primitive humans.
Notably, H. erectus also had much larger brains than its precursors. Those bigger brains and bodies required more food and energy to survive. Wear on the teeth of H. erectus fossils suggest the ancient man ate a fairly diverse diet, and most scientists believe the species ate more animal protein compared to older human species.
Homo erectus' larger brain may explain why it displays so many distinctly human behaviors. For instance, ancient tools reveal the human ancestor was butchering animals by at least 1.75 million years ago, and may have harnessed fire to cook food as early as 1.9 million years ago. The species' increased smarts may have also enabled it to expand into so many different environments.
Homo erectus likely first evolved from an earlier human ancestor, known as Homo habilis, somewhere in East Africa, but spread out from there. Fossils dating from about 1.8 million years ago until about 100,000 years ago have been found in Southeast Asia, Europe, the Caucasus, India and China.
H. erectus would eventually give rise to a host of other early humans, such as Homo heidelbergensis and Homo floresiensis, though scientists still don't agree on whether the species is a direct human ancestor to Homo sapiens. Anthropologists also disagree on whether all the Homo erectus fossils found around the world represent one species, or several slightly different ones (some anthropologists consider Turkana Boy, for instance, to be a slightly different species dubbed Homo ergaster).
The first Homo erectus fossil was a 1-million-year-old skull discovered by Dutch surgeon Eugene Dubois in Indonesia in 1891. Other notable fossils include the 1.77-million-year-old skull of an elderly man, discovered in Dmanisi, Georgia. The man had lost all his teeth and much of his jaw had deteriorated long before death, leading researchers to believe that other members of the group must have cared for him, one of the first examples of such compassionate social behavior in a human ancestor.
Other H. erectus fossils have been found in Olduvai Gorge, Tanzania, where anthropologists have discovered primate and early human ancestor fossils going back almost 25 million years.