The butchered remains of an extinct horse were found at a site of human occupation potentially dating back more than 16,000 years – a date which suggests they most likely arrived in a trans-Pacific migration.
The dating of charcoal and bone samples from the site’s oldest layers linked with human occupation have been radiocarbon dated to between 16,560 and 15,280 years ago – some 1000 years before melting ice created a corridor through what is now the western United States.
It is the widely held view that the first humans crossed into North America via this land bridge, but the findings of research led by Loren Davis, of Oregon State University, makes a seas migration the more likely scenario for the arrival of these earliest North Americans.
The site investigated by Davis and his colleagues appears to have been used for food processing, with the fragmented remains of an extinct horse and a hearth with charcoal-speckled sediments. The study team, who reported their findings in the journal Science, also found the site littered with stone tools, including spearheads.
The artifacts unearthed from the archeological dig at the Cooper’s Ferry site in western Idaho amount to the earliest evidence of people in North America.
The findings add weight to the hypothesis that initial human migration to the Americas followed a Pacific coastal route rather than through the opening of an inland ice-free corridor, said Davis, a professor of anthropology.
“The Cooper’s Ferry site is located along the Salmon River, which is a tributary of the larger Columbia River basin. 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 in to North America,” Davis said.
“Essentially, the Columbia River corridor was the first off-ramp of a Pacific coast migration route.
Davis first began studying Cooper’s Ferry as an archaeologist for the BLM in the 1990s.
After joining the Oregon State faculty, he partnered with the BLM to establish a summer archaeological field school there, bringing undergraduate and graduate students from Oregon State and elsewhere for eight weeks each summer from 2009 to 2018 to help with the research.
The site includes two dig areas. The published findings are about artifacts found in what is known as area A.
In the lower part of that area, researchers uncovered several hundred artifacts, including stone tools; charcoal; fire-cracked rock; and bone fragments likely from medium-to large-bodied animals, Davis said. They also found evidence of a fire hearth, a food processing station and other pits created as part of domestic activities at the site.
Over the last two summers, the team of students and researchers reached the lower layers of the site, which, as expected, contained some of the oldest artifacts uncovered, said Davis, who was lead author on the study.
He worked with a team of researchers at Oxford University that was able to successfully radiocarbon date several animal bone fragments.
The results showed many artifacts 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 said.
“When I first saw that the lower archaeological layer contained radiocarbon ages older than 14,000 years, I was stunned but skeptical 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 to 16,000 years old.”
Davis’s team also found tooth fragments from an extinct form of horse known to have lived in North America at the end of the last glacial period. These tooth fragments, along with the radiocarbon dating, show that Cooper’s Ferry is the oldest radiocarbon-dated site in North America that includes artifacts associated with the bones of extinct animals, Davis said.
Around the animal bone fragments there were many stone tools, and nearby was evidence of a hearth or fire pit. It is possible someone had butchered the horse, David told media.
The dates from the oldest artifacts challenge the long-held “Clovis First” theory of early migration to the Americas, which suggested that people crossed from Siberia into North America and traveled down through an opening in the ice sheet near the present-day Dakotas. The ice-free corridor is hypothesized to have opened as early as 14,800 years ago, well after the date of the oldest artifacts found at Cooper’s Ferry, Davis said.
“Now we have good evidence that people were in Idaho before that corridor opened,” he said. “This evidence leads us to conclude that early peoples moved south of continental ice sheets along the Pacific coast.”
The oldest artifacts uncovered at Cooper’s Ferry also are very similar in form to older artifacts found in northeastern Asia, and particularly, Japan, Davis said.
He is now collaborating with Japanese researchers to do further comparisons of artifacts from Japan, Russia and Cooper’s Ferry. He is also awaiting carbon-dating information from artifacts from a second dig location at the Cooper’s Ferry site.
“We have 10 years’ worth of excavated artifacts and samples to analyze,” Davis said. “We anticipate we’ll make other exciting discoveries as we continue to study the artifacts and samples from our excavations.”
Co-authors of the paper include David Sisson, an archaeologist with the BLM; David Madsen of the University of Texas at Austin; Lorena Becerra Valdivia and Thomas Higham of the Oxford University radiocarbon accelerator unit; and other researchers in the US, Japan and Canada. The research was funded in part by the Keystone Archaeological Research Fund and the Bernice Peltier Huber Charitable Trust.