Stone tools and other artefacts from the Cooper's Ferry site on the Salmon River in western Idaho, about 600 kilometres east-southeast of Seattle, support the hypothesis that initial human migration to the Americas followed a Pacific coastal route rather than an inland ice-free corridor.
     The site includes two dig areas. In the lower part of Area A, researchers uncovered several hundred artefacts, including stone tools, charcoal, fire-cracked rock, and animal bone fragments. They also found evidence of a fire hearth, a food processing station, and other pits created as part of domestic activities at the site. Radiocarbon dating shows many artefacts from the lowest layers are 15,000 to 16,000 years old - at least a thousand years before before the ice-free corridor opened.
     The oldest artefacts are also very similar in form to older artefacts found in northeastern Asia, particularly Japan.
     Other finds include tooth fragments from an extinct form of horse known to have lived in North America at the end of the last glacial period, making Cooper's Ferry the oldest radiocarbon-dated site in North America that includes artefacts associated with the bones of extinct animals.

Edited from Phys.Org (29 August 2019)