Pioneers from Northern Japan in Idaho 16,000 Years Ago? A Critical Evaluation of the Evidence from Cooper’s Ferry

ABSTRACT Davis et al. (2019) recently presented the results of excavations at the Cooper’s Ferry site, located beside the Salmon River in Idaho. They claim that initial occupation of this site dates from ∼16,000 calendar years ago, that the first inhabitants came from northern Japan, and that this site conclusively demonstrates that “humans initially migrated into the Americas along the Pacific coast.” Here, we critically examine the chronological, geoarchaeological, and artifactual evidence for the claimed antiquity of the Cooper’s Ferry site and show that this evidence remains inconclusive. We also show that the coastal migration theory proposed by Davis et al. is incompatible with emerging paleogenomic evidence. We conclude that the oldest demonstrated occupation of Cooper’s Ferry dates to ∼11,500 calendar years ago, although ambiguous evidence might (but probably does not) indicate an earlier episode of occupation at ∼14,600–14,100 calendar years ago.