14,000-year-old ivory tools found in Alaska hint at how Clovis ancestors first arrived in the New World

Ancient tools found in Alaska may shed light on how humans first arrived in the Americas, a new study finds.

The artifacts, which include items linked with crafting stone tools and ocher, a red mineral often used in ceremonies, are about 600 years older than similar artifacts from the Clovis people who lived farther south, in New Mexico and elsewhere.

The similarities suggest that the people who used the Alaskan artifacts are the ancestors of the Clovis, which in turn hints that the ancestors of the Clovis may have marched across the land bridge that once connected Asia with the Americas, and not along a coastal route as recently argued.

Based on stone artifacts up to 13,400 years old, for most of the 20th century archaeologists suggested that ancestors of the prehistoric culture dubbed the Clovis were among the first to migrate from Asia to the Americas. Researchers have discovered Clovis artifacts — such as distinctive, pointy stone tools — across the Great Plains and the Rocky Mountains. (But research over the past few decades has revealed that the Clovis were far from the first people to reach the Americas.)

It remains uncertain how the predecessors of the Clovis made their way to the New World. It was long thought that they reached North America via the Bering Land Bridge, which emerged as sea levels dropped during the last ice age (2.6 million to 11,700 years ago). These migrants could have wended their way across this expanse of land and then south through an ice-free corridor to give rise to the Clovis.

However, other work raises the question of whether the corridor through what is now Canada was actually ice-free when the ancestors of the Clovis might have been able to cross it. Therefore, a competing idea proposes that they migrated to the New World through other routes, such as in watercraft along the coast of Asia, the Bering Land Bridge and the Americas.

Alaska archaeology

To investigate this mystery, scientists analyzed findings from the Tanana Valley in central Alaska. For more than four decades, excavations there have uncovered artifacts from early Alaskan hunters of woolly mammoths and other "megafauna," or giant beasts.

The researchers focused on recent discoveries from the Holzman site in the middle Tanana Valley, where they found evidence of stone and mammoth ivory tool manufacturing dating to about 14,000 years ago, such as a nearly complete mammoth tusk, which could have been raw material for ivory production, and a hammerstone for crafting stone tools. This makes this pre-Clovis area one of the earliest known human sites in the Americas.

"What's exceptional [about this site] is its remarkable preservation," study co-author Kathryn Krasinski, an archaeologist at Adelphi University in New York, told Live Science. "The lower components tend to be frozen much of the year, so we have also recovered ancient plant DNA and even a strand of 13,600-year-old bison hair. This type of organic material preservation is quite rare."

The Tanana Valley was located between the Bering Land Bridge and the ice-free corridor, the scientists noted, and the ivory tools and the process of manufacturing them at the Holzman site are similar to those used for Clovis artifacts found farther south.

"People lived and thrived in interior Alaska around 1,000 years before the appearance of Clovis technology further south," study co-author Brian Wygal, an archaeologist at Adelphi University, told Live Science. "We argue that the growing evidence from interior Alaska confirms an inland route through an ice-free corridor as the most likely scenario for the initial arrival of people in midcontinental North America."

In other words, the ancestors of the Clovis may have first wandered across the Bering Land Bridge from Asia to Alaska, and then migrated further south down an ice-free corridor to give rise to the Clovis.

The evidence from Holzman and other sites in that area of Alaska is consistent with "migration to the continental United States by an interior route," Todd Surovell, a professor of anthropology at the University of Wyoming who did not participate in the study, told Live Science. "The evidence for ivory working provides a nice cultural tie to the Clovis tradition further south."

Difficult to know

However, Jack Ives, a professor emeritus of anthropology at the University of Alberta who did not take part in this research, cautioned that the people of ancient northeast Asia where migrants to the Americas likely came from shared many features, such as symbolic use of ocher in burials, and similar stone artifacts. This raises the question of whether the ivory artifacts seen at Holzman and elsewhere are directly tied to the Clovis or whether "they were part of a broader suite of ideas for various populations entering the Western Hemisphere," Ives told Live Science.

Ives also noted that scientists often pose the inland and coastal scenarios of migration into the Americas as competing ideas "with either one or the other telling the entire story." However, a better way to go about it, he said, "is to realize that if we would like to have a comprehensive picture of this early time frame, we need to understand what is going on in both the early period coastal and [ice-free] corridor worlds." Geneticists often suggest the peopling of the New World involved successive episodes of small founding lineages, so both the inland and coastal scenarios might have played a part, Ives added.

Wygal and his colleagues aim to continue excavations in the Tanana Valley to learn more about how the first Alaskans interacted with woolly mammoths and other aspects of their environment, he said. Future research should also investigate "the ice-free corridor itself," Surovell said. "There has been considerable research on coastal areas, but the ice-free corridor by contrast has been largely neglected."

The scientists detailed their findings in the Feb. 15 issue of the journal Quaternary International.

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