© Loren DavisLasers help record the precise position of each artifact on the site.
Evidence from the Cooper's Ferry archaeological site in Western Idaho shows that
people lived in the Columbia River Basin around 16,000 years ago. That's well before a corridor between ice sheets opened up, clearing an inland route south from the Bering land bridge. That suggests that people migrated south along the Pacific coast.
Stone tools from the site suggest a possible connection between these first Americans and Northeast Asian hunter-gatherers from the same period.Route closed due to iceA piece of charcoal unearthed in the lowest layer of sediment that contains artifacts is between 15,945 and 15,335 years old, according to radiocarbon dating. More charcoal, from the remains of an ancient hearth pit, dated to between 14,075 and 15,195 years old. A few other pieces of bone and charcoal returned radiocarbon dates in the 14,000- to 15,500-year-old range. In higher, more recent layers, archaeologists found bone and charcoal as recent as 8,000 years old, with a range of dates in between.
This makes clear that people had been using the Cooper's Ferry site for a very long time, but it's hard to say whether they stuck around or just kept coming back. "Because we did not excavate the entire site, it is difficult to know if people occupied the site continuously starting at 16,000 years ago," Oregon State University archaeologist Loren Davis told Ars. "I expect that this site was used on a seasonal basis, perhaps as a base camp for hunting, gathering, and fishing activities."
Either way, the local
Nimiipuu (Nez Perce) people know the site as the location of an ancient village called
Nipéhe. "We worked with archaeologists and student interns from the Nez Perce Tribe who visited to get tours of the excavation and to participate in excavations at the site," said Davis.
Davis and his colleagues used a statistical model to calculate how old the very oldest layers of artifacts at the site should be. "The Bayesian model makes predictions about the age of the lower portion of [the excavated layers] based on the chronological trend of known radiocarbon ages in the upper and middle third," Davis explained. According to the model, the very oldest artifacts at
Nipéhe are probably between 16,560 and 15,280 years old.
That's about 2,000 to 1,500 years before the great continent-spanning ice sheets of the Pleistocene began to break up. That break-up opened an ice-free corridor southward from the Bering land bridge between the towering sides of the Cordilleran and Laurentian ice sheets. According to computer simulations, that corridor was closed and buried under several kilometers of ice until at least 14,800 years ago, and possibly even later. And that has some important implications for when, and how, people first set foot in the Americas.
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