Stone tools may place some of the first Americans in Idaho 16,500 years ago

America’s first settlers may have coasted in. Northeast Asians traveled down North America’s Pacific coast and then eastward into the continent more than 1,500 years before an inland, ice-free corridor opened up, researchers say.

That conclusion, reported in the Aug. 30 Science, rests on discoveries at a site in western Idaho called Cooper’s Ferry. Stone tools excavated there point to repeated human visits between around 16,560 and 15,280 years ago, says a team led by archaeologist Loren Davis of Oregon State University in Corvallis.

Those tools look much like stone artifacts that were made around that time in what’s now Japan, Davis’ group says. Asian toolmakers could have reached Idaho only by first heading down the Pacific coast, the researchers contend, possibly by combining canoe travel with walking. 

How North America’s first settlers arrived, and when, is a hotly debated topic. And the Idaho finds show no signs of cooling that conflict. One long-standing idea is that melting of massive ice sheets cleared a path from what’s now Alaska into the heart of North America by around 14,800 years ago. That possibly enabled people to reach Florida and South America a few hundred years later (SN: 8/8/18).

But some scientists have argued that colonizers from Asia arrived earlier, primarily traveling by canoe down the coast before moving inland. Evidence from Texas places people there roughly 15,000 years ago (SN: 10/24/18). And previous research has found evidence that an ice-free path along Alaska’s coast formed by around 17,000 years ago (SN: 5/30/18).

The Idaho tools lack the signature grooved bases of points made by well-known Clovis hunters, who arrived in the Americas around 13,250 years ago (SN: 4/14/17). Clovis people were once thought to be North America’s first inhabitants, but Cooper’s Ferry joins a growing number of pre-Clovis sites.

New findings at the Idaho site are intriguing, but “much more work needs to be done to establish the nature and age of the occupations,” says archaeologist Ben Potter of the University of Alaska Fairbanks. Potter favors an ice-free corridor as the original entryway for humans into North America.

A minority of Cooper’s Ferry artifacts may date to as early as around 15,000 years ago, but sediment at the site dating to 16,000 years ago or more shows no direct links to stone tools or any other signs of human activity, Potter says. Dates of animal bones and burned wood bits from one sediment layer range over more than 4,000 years, raising questions about the extent to which geologic forces have rearranged the site’s sediment layers over time, he contends.

Even if people arrived at Cooper’s Ferry as early as 16,000 years ago, “it doesn’t refute the idea that the ice-free corridor was a potential migration route well before the Clovis occupation,” says archaeologist Vance Holliday of the University of Arizona in Tucson.