Ever older remains of early migrants rewrite the story of the first North Americans

New artifacts uncovered from an archeological site in western Idaho support the idea that the first Americans arrived in North America well before the end of the last ice age opened a path for them. 

The new finds, dated to roughly 16,000 years ago, and the location in which they were found, both tend to lend support to the theory that the first people in North America island-hopped down the west coast, and bypassed the glaciers that would have covered any interior route.

• Research paper in the journal Science 

Dr. Loren Davis, a professor of anthropology at Oregon State University, led the excavation at a site called Cooper's Ferry, which is located at the Lower Salmon river canyon in western Idaho. Davis had worked there as a PhD student back in the 90s, and returned in 2009 to excavate the lower layers. That's when he found the oldest artifacts he'd seen at the site, including hunting weapons, cutting tools, animal bones and evidence of a fire pit.

Using carbon dating, the research team found many of the artifacts from the lowest layers of the site are between 15,000 and 16,000 years old. This suggests that people had lived in North America much earlier than previously thought. 

The new dates also discredit the ice-free corridor theory of how the early Americans' moved past Canada to the United States, after they crossed the Bering Land Bridge. An ice-free corridor was thought to have opened by about 13,000 years ago, but Davis' research clearly shows that these migrants had arrived in Idaho before that time. 

The simple explanation, according to Davis, is that they didn't use the corridor, and took the coastal route to the United States. He thinks the theory is very strong, given how easy it is to get to the Cooper's Ferry site from the coast. 

"All they had to was make a left turn once they're south of the ice to get to the Columbia River, and go along the river to get to Cooper's Ferry site."