Scientists have long believed that the first people to reach the Americas crossed via a temporary ancient land bridge between Siberia and Alaska nearly 15,000 years ago. According to conventional wisdom, the travelers had to wait until two large ice sheets that covered present-day Canada began to recede, creating an “ice-free corridor” that enabled them to move south.
But in a study published Wednesday in the journal Nature, an international team of researchers present findings that incorporate ancient DNA extracted from an important pinch-point within this corridor to investigate how its ecosystem evolved as the glaciers began to melt.
The team created a detailed picture showing when and how flora and fauna emerged, and the once ice-covered landscape became a practical passageway. And while people may have crossed this corridor after roughly 12,600 years ago, the team concludes it would have been impassable before that point in time since it lacked necessary resources such as wood for fuel and tools and game animals to hunt.
“The ice-free corridor was long considered the principal entry route for the first Americans. Our results reveal that it simply opened up too late for that to have been possible,” said Mikkel Winther Pedersen, study co-author and PhD student at the Center for GeoGenetics, University of Copenhagen.
If their theory is accurate, then the first Americans — who were present south of the ice sheets long before 12,600 years ago — must have made the journey south via an alternate route. The authors believe that they probably migrated along the Pacific coast.
The identity of these people is still widely disputed, but archaeologists agree that early inhabitants of the modern-day continental United States included the so-called “Clovis” culture, which initially appeared in the archaeological record roughly 13,000 years ago.
The study argues that the corridor would have been impassable at that time.
“That means that the first people entering what is now the U.S., Central and South America must have taken a different route. Whether you believe these people were Clovis, or someone else, they simply could not have come through the corridor as long claimed,” Eske Willerslev, who led the research, said.
The team believes the corridor was about 932 miles wide, and emerged east of the Rocky Mountains 13,000 years ago in modern-day western Canada, as two great ice sheets — the Cordilleran and Laurentide — retreated.
The first evidence of the Clovis people, who are believed to be the first group to disperse across the Americas, was found at about the same time.
The team gathered evidence such as pollen, macrofossils, radiocarbon dates and DNA taken from lake sediment cores. Upon recovering the DNA, the group used a process called “shotgun sequencing.”
“Instead of looking for specific pieces of DNA from individual species, we basically sequenced everything in there, from bacteria to animals,” Willerslev said. “It’s amazing what you can get out of this. We found evidence of fish, eagles, mammals and plants. It shows how effective this approach can be to reconstruct past environments.”
Photo: Mikkel Winther Pedersen
- EU Merger Concerns
- Cracking on Stand, Ex-Kane Aide Says He Lied to Protect Self & AG