Ancient people apparently followed rivers more than 500 kilometers inland to Cooper's Ferry in western Idaho.

LOREN DAVIS

First people in the Americas came by sea, ancient tools unearthed by Idaho river suggest

About 16,000 years ago, on the banks of a river in western Idaho, people kindled fires, shaped stone blades and spearpoints, and butchered large mammals. All were routine activities in prehistory, but their legacy today is anything but. The charcoal and bone left at that ancient site, now called Cooper’s Ferry, are some 16,000 years old—the oldest radiocarbon-dated record of human presence in North America, according to work reported this week in Science.

The findings do more than add a few centuries to the timeline of people in the Americas. They also shore up a new picture of how humans first arrived, by showing that people lived at Cooper’s Ferry more than 1 millennium before melting glaciers opened an ice-free corridor through Canada about 14,800 years ago. That implies the first people in the Americas must have come by sea, moving rapidly down the Pacific coast and up rivers. The dates from Cooper’s Ferry “fit really nicely with the [coastal] model that we’re increasingly getting a consensus on from genetics and archaeology,” says Jennifer Raff, a geneticist at the University of Kansas in Lawrence who studies the peopling of the Americas.

The Clovis people, big game hunters who made characteristic stone tools dated to about 13,000 years ago, were once thought to have been the first to reach the Americas, presumably through the ice-free corridor. But a handful of earlier sites have persuaded many researchers that the coastal route is more likely. Archaeologists have questioned the signs of occupation at some putative pre-Clovis sites, but the stone tools and dating at Cooper’s Ferry pass the test with flying colors, says David Meltzer, an archaeologist at Southern Methodist University in Dallas, Texas. “It’s pre-Clovis. I’m convinced.”

Over 10 years of excavations, the Cooper’s Ferry team uncovered dozens of stone spear points, blades, and multipurpose tools called bifaces, as well as hundreds of pieces of debris from their manufacture. Although the site is near the Salmon River, most of the ancient bones belonged to mammals, including extinct horses. The team also found a hearth and pits dug by the site’s ancient residents, containing stone artifacts and animal bones.

Radiocarbon dates on the charcoal and bone are as old as 15,500 years. In North America, few tree ring records can precisely calibrate such early radiocarbon dates, but a state-of-the-art probabilistic model placed the start of the occupation at between 16,560 and 15,280 years. “I may not think it goes back to 16,000 years ago, but I surely can believe it goes back 15,000 years,” says Michael Waters, an archaeologist at Texas A&M University in College Station.

A 6-centimeter blade is among the oldest at an Idaho site.

L. DAVIS ET AL., SCIENCE, VOL. 365, 891 (2019)

The only rival to Cooper’s Ferry as the oldest site in North America is the Gault site in Texas. Researchers dated that site to about 16,000 years ago by optical luminescence, a method with larger error bars than radiocarbon dating.

It’s easy to see how seafaring people might have reached Cooper’s Ferry, says Loren Davis, an archaeologist at Oregon State University in Corvallis who led the excavations. Although the site is more than 500 kilometers from the coast, the Salmon, Snake, and Columbia rivers link it to the sea. “As people come down the coast, the first left-hand turn to get south of the ice comes up the Columbia River Basin,” Davis says. “It’s the first off-ramp.”

The area is now federal land but was long occupied by the Nez Perce Tribe, or the Niimíipuu. They know Cooper’s Ferry as Nipéhe, an ancient village founded by a young couple after a flood destroyed their previous home, says Nakia Williamson, the tribe’s director of cultural resources. “Our stories already tell us how long we’ve been here. … This [study] only reaffirms that,” Williamson says. He hopes the excavations—in which Nez Perce archaeologists and interns participated—will help others recognize the deep ties the Nez Perce have to their ancestral lands. “This is not just something that happened 16,000 years ago. It’s something that is still important to us today,” he says.

Cooper’s Ferry may also offer a glimpse of the tools carried by the first arrivals to the Americas. Many of the spearpoints found there belong to the western stemmed point tradition, smaller—about the size of a pinkie—and lighter than the hefty Clovis points. Such tools have been found at early sites from British Columbia to Peru, and as far inland as Texas. Similar points are known from Japan from about 16,000 to 13,000 years ago, Davis says. He and others argue that western stemmed points are emerging as the best markers of the first people to arrive in the Americas, and that they carried the tradition with them from Asia.

But Meltzer isn’t convinced the western stemmed tradition conclusively predates Clovis or represents a coastal connection around the Pacific Rim. There are plenty of sites in Siberia in Russia without the technology, he says, and the complete points at Cooper’s Ferry are almost the same age as Clovis. (The site’s oldest tools are blades, bifaces, and fragments of points, fashioned with the same methods used to make western stemmed points.) Just as archaeology puts one debate about stone tools in the Americas to rest, it could be gearing up for the next one.

*Correction 29 August, 3:15 p.m.: An earlier version of this story misstated that Michael Waters excavated the Gault site in Texas. He excavated the nearby Debra L. Friedkin site.