By about 13,000 years ago, the Ice Age had finally begun to wane. As the glaciers that once blanketed the westward flank of what’s now Canada receded, a thin, iceless corridor appeared between two towering walls of ice—clearing, at long last, an accessible path from modern-day Alaska to the rest of the Americas.

But when—or even, if—humans utilized this newly exposed strip of land in their southbound migration, the footprints they left probably weren’t the continent’s first: Another group of early people almost certainly beat these terrestrial migrants to the punch.

Reporting today in the journal Science, an international team of archaeologists has uncovered a cache of artifacts from Idaho that suggest humans had already settled the Pacific Northwest 16,000 years ago, long before rising temperatures had time to expose the continent’s ice-free footpath. The findings lend support to the idea that the continent’s inaugural human inhabitants were migrants from across the Pacific who first entered the New World not by land—but by sea.

“This is really exciting work...that presents some of the oldest evidence of a human presence in North America,” says Alia Lesnek, a geologist at the University of New Hampshire who studies early coastal migrations, but was not involved in the study. The dates associated with the site’s artifacts, she adds, “basically preclude the idea that people first traveled here [through] the ice-free corridor.”