Excavation site at Cooper’s Ferry in 2018

Dating back to 16,000 years, items from a dig site in Idaho point to the first settlers arriving by a Pacific coastal route rather than by an ice-free land bridge from Siberia.

Charcoal and animal bones found alongside tools and other artifacts at a dig site in Cooper’s Ferry in western Idaho date back 15,000 to 16,000 years—the oldest radiocarbon-dated record of humans in North America, according to a study published today (August 29) in Science. The discovery supports the idea that the first people who lived on the continent didn’t come by a land bridge from Siberia given that the ice-free route wouldn’t open for another roughly 1,000 years. Instead, the authors write in their report, their finding “supports the hypothesis that initial human migration into the Americas occurred via a Pacific coastal route.”

Although it’s not along the coast, Cooper’s Ferry is reachable by the Columbia River and its tributaries. “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,” says coauthor Loren Davis of Oregon State University in a press release. “Essentially, the Columbia River corridor was the first off-ramp of a Pacific coast migration route.”

Other experts are not convinced that the artifacts represent a migration from Asia. The radiocarbon dates may not be linked to human occupation and the analysis of the site requires more work to determine when people lived there, archeologist Ben Potter of the University of Alaska Fairbanks who was not involved with the study tells Nature. Dave Meltzer of Southern Methodist University who was also not involved with the work says the carbon dating is “rock solid,” though he isn’t ready to accept that the tools found at Cooper’s Ferry are from humans who migrated from Asia, reports Nature.

Before it was known as Cooper’s Ferry, the Nez Perce Tribe, or the Niimíipuu, knew it as Nipéhe. “Our stories already tell us how long we’ve been here. . . . This [study] only reaffirms that,” Nakia Williamson, the tribe’s director of cultural resources, tells Science. Nez Perce archeologists and interns participated in the excavations. “This is not just something that happened 16,000 years ago. It’s something that is still important to us today,” he says.