The usual story is that they traveled south through a gap between two glaciers. But a new study suggests humans couldn’t have survived the trek.
By Nathan Collins
Peace River, Canada. (Photo: Wikimedia Commons)
How did the first human beings spread throughout North America? It’s a controversial issue, but a common theory is that once they made it over a land bridge from Asia to Alaska, humans traveled south through a recently opened gap in the ice sheets that at the time covered the continent. But according to a new study, people couldn’t have survived that journey—as it turns out, there probably wasn’t anything to eat.
According to the traditional story, the first people to settle North America arrived around 13,000 years ago near present-day Clovis, New Mexico, having crossed the Bering Land Bridge from Asia and traversed a recently opened, 1,000-mile-long corridor between the Laurentide and Cordilleran ice sheets that covered much of the continent.
Well, that story is almost certainly wrong. For one thing, DNA and archaeological evidence from a number of sites in the United States and Canada demonstrate that humans not only inhabited North America at least 15,000 years ago, but were by that point pretty much spread throughout the continent.
It’s most likely the first people to arrive in the present-day U.S. came via the Pacific Coast.
But it’s a different aspect of the story that University of Copenhagen researchers Mikkel Pederson and Eske Willerslev take issue with. “Whether the ice-free corridor could have been used for a Clovis-age migration depends on when it became biologically viable,” Pederson, Willerslev, and their colleagues write in Nature. In other words, it depends on whether there was enough to eat along the way from Alaska to the heart of North America.
To see how much food might have been available, the team took core samples from lake beds in the Peace River basin, right in the middle of the path the ice corridor once took. The researchers searched those for fossils, pollen, and other biological materials. Those findings would establish both what food sources were available and, using radiocarbon dating, when those sources first arrived. The team’s analysis suggests that the region was largely lacking in plant life prior to about 12,600 years ago, after which vegetation expanded and began to support bison, jackrabbits, and voles.
“From our findings, it follows that an ice-free corridor was unavailable to those groups who appear to have arrived in the Americas south of the continental ice sheets” prior to about 15,000 years ago, the team writes. Although the results do not preclude the possibility that people did at some point travel through the corridor, it’s most likely the first people to arrive in the present-day U.S. came via the Pacific Coast, the authors argue.