A present-day view south of the area where the retreating ice sheets created an ice-free corridor in the United States more than 13,000 years ago, according to researchers. Photo by Mikkel Winther Pedersen
Researchers are once again questioning their own theories about the migration of the first Americans. Evidence of the first Americans has been found at sites that date back 15,500 years in the United States and 14,000 years in South America. Researchers have long assumed that these populations traveled through an ice-free corridor that stretched from present-day Alaska to Montana. But a study published in Nature on Wednesday casts doubt on the theory. Based on DNA tests of plants and animal life, researchers believe the corridor only became habitable 12,600 years ago -- well after the first people were living in the America.s The team behind the study includes Eske Willerslev, the director of the Center for GeoGenetics at the University of Copenhagen. Through DNA studies, he has shown that present-day Native Americans are related to people that have been found at older sites, such as one in Montana that is 12,600 years old. "The bottom line is that even though the physical corridor was open by 13,000 years ago, it was several hundred years before it was possible to use it," Willerslev said in a press release. "That means that the first people entering what is now the US, Central and South America must have taken a different route." A different team of researchers, however, believes the corridor was open at least 13,000 years ago. If that date is accepted, it might account for some, but not all, of the older sites. The first Americans who reached the older sites could have gotten there by traveling along the Pacific Coast, according to Peter Heintzman, the lead author the second study. His team's research was based on DNA tests of bison remains that were found in the ice-free corridor. "The opening of the corridor provided new opportunities for migration and the exchange of ideas between people living north and south of the ice sheets," Heintzman said in a press release. The study, which was published in the Proceedings of the National Academy of Sciences in June, acknowledges that the first Americans were already living south of the ice sheets before the corridor was fully "open" for travel. Read More on the Story:
Plant and animal DNA suggests first Americans took the coastal route (Nature 8/10)
How Did People Migrate to the Americas? Bison DNA Helps Chart the Way (The New York Times 8/11)
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