Archaeological discoveries in western Idaho indicate that humans were in that part of the US nearly 16,500 years ago – more than a thousand years earlier than previously thought.
The findings expand the timing of human settlement in the Americas to a period predating the appearance of an ice-free corridor linking Siberia and North America, researchers say, and support the notion that the first Americans landed upon the shores of the Pacific coast.
Researchers from Oregon State University have unearthed stone tools and other artefacts from the Cooper’s Ferry site on the Salmon River, a tributary of the Columbia River.
“Early peoples moving south along the Pacific coast would have encountered the Columbia River as the first place below the glaciers where they could easily walk and paddle into North America,” says Loren Davis, lead author of a paper in the journal Science.
Davis and colleagues are working two dig areas and have uncovered several hundred artefacts, as well as evidence of a fire hearth, a food processing station and other pits created as part of domestic activities at the site.
They recently had a number of animal bone fragments radiocarbon dated at Oxford University in the UK, and the results show many artefacts from the lowest layers are associated with dates in the range of 15,000 to 16,000 years old.
“Prior to getting these radiocarbon ages, the oldest things we’d found dated mostly in the 13,000-year range, and the earliest evidence of people in the Americas had been dated to just before 14,000 years old in a handful of other sites,” Davis says.
“When I first saw that the lower archaeological layer contained radiocarbon ages older than 14,000 years, I was stunned but sceptical and needed to see those numbers repeated over and over just to be sure they’re right.
“So we ran more radiocarbon dates, and the lower layer consistently dated between 14,000-16,000 years old.”
This challenges the long-held Clovis First theory that people first crossed into North America from Siberia and travelled down through an opening in the ice sheet near the present-day Dakotas.
The ice-free corridor is hypothesised to have opened around 14,800 years ago, Davis says, well after the date of the oldest artefacts found at Cooper’s Ferry.
“Now we have good evidence that people were in Idaho before that corridor opened,” he adds.
The oldest artefacts at Cooper’s Ferry are similar in form to some found in northeastern Asia, so Davis is collaborating with Japanese researchers to do make further comparisons with items from Japan and Russia.