Stone tools, animal bones, and fire-cracked rock are among the hundreds of artifacts found at Cooper's Ferry in western Idaho, some of which date back to a time 16,000 years ago – making them among the oldest artifacts found in the Americas, say researchers writing in Science.
The booty adds to a growing body of evidence that the first migrants to the Americas reached the New World via a Pacific coastal route and not, as had long been assumed, through the Bering Strait.
The location of the site is important – Cooper's Ferry sits on the junction between Rock Creek and the Lower Salmon River, which is a tributary of the larger Columbia River basin. The Columbia River could have served as the first point of entry into North America, said lead author Loren Davis, a professor of anthropology at Oregon State University.
"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," Davis said in a statement. "Essentially, the Columbia River corridor was the first off-ramp of a Pacific coast migration route."
In addition to the treasure trove of artifacts (the stone tools, charcoal, fire-cracked rock, and bone fragments of medium-to-large-bodied animals), archaeologists unearthed evidence of a fire hearth, a food processing station, and various other pits built for domestic tasks.
In the last couple of years, the team reached the lower layers of the site, which has some of the oldest remains not just of the site but of the entirety of the Americas.
"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," said Davis. "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 14,000-16,000 years old."
The Bering Strait hypothesis postulates that the first migrants arrived in America circa 13,000 years ago after warmer temps melted the region's glaciers, opening up an inland corridor and allowing humans from Russia's northeastern tip to head east to Alaska. However, the hypothesis has had a bit of a battering of late.
Various discoveries, from 14,500-year-old human footprints in Monte Verde to equally ancient mastodon bones (butchered by human hands) in Florida and 16,000-year (plus) tools in Texas, have undermined the theory and instead suggest the Americas were settled following various waves of migration, at least one of which would have occurred before the Bering Strait glaciers melted.
With the indoor corridor firmly shut (or, at the very least, blocked by a lot of ice), early travelers would have had to have found another path to the continents. The leading hypothesis is that the Americas' first residents arrived there by boat and journeyed by way of the Pacific Ocean, using the islands around the northern section of the Ring of Fire as their route. The location of Cooper's Ferry and its proximity to the Columbia River supports this argument.
Furthermore, say researchers, the oldest artifacts found there show a remarkable resemblance to the types of artifacts found in northeastern Asia – and Japan, especially. Davis is now collaborating with Japanese researchers to compare the artifacts found in Cooper's Ferry with those in Japan and Russia.