INITIAL HUMAN COLONIZATION OF THE AMERICAS, REDUX

Abstract

ABSTRACTThe study of the peopling of the Americas has been transformed in the past decade by astonishing progress in paleogenomic research. Ancient genomes now show that Native American ancestors were formed in Siberia or the Amur region by admixture of ca. 15–30% Ancient North Eurasian genes with those of East Asians. The Anzick infant, buried with Clovis bifaces at 12,900 cal BP, belonged to a group that was ancestral to later Native Central and South Americans. Fishtail points, derived from Clovis, mark the arrival and rapid expansion of Clovis-descended Paleoindians across South America, also evident in the sharp increase of radiocarbon dates, continent-wide, at 13,000–12,500 cal BP. In both North and South America, extinction of most genera of megafauna was virtually simultaneous with Paleoindian expansion. Human hunting must have been involved, perhaps in concert with other indirect impacts. Contrary to the alternative bolide impact theory, there is no evidence of a dramatic human population decline after 12,800 cal BP. Ancient genomes show that divergent lithic traditions after 13,000 cal BP need not be attributed to a separate Pacific Rim migration stream. Several recent finds raise the possibility that pre-Clovis people might have reached the Americas before 20,000 cal BP, but these precursors must have either failed to thrive, or were ultimately replaced by proto-Clovis or Clovis people. Consilient paleogenomic and archaeological data indicate that initial colonization by Paleoindian ancestors of living Native Americans occurred after 14,500 cal BP.