Current evidence allows multiple models for the peopling of the Americas

Abstract

Some recent academic and popular literature implies that the problem of the colonization of the Americas has been largely resolved in favor of one specific model: a Pacific coastal migration, dependent on high marine productivity, from the Bering Strait to South America, thousands of years before Clovis, the earliest widespread cultural manifestation south of the glacial ice. Speculations on maritime adaptations and typological links (stemmed points) across thousands of kilometers have also been advanced. A review of the current genetic, archeological, and paleoecological evidence indicates that ancestral Native American population expansion occurred after 16,000 years ago, consistent with the archeological record, particularly with the earliest securely dated sites after ~15,000 years ago. These data are largely consistent with either an inland (ice-free corridor) or Pacific coastal routes (or both), but neither can be rejected at present. Systematic archeological and paleoecological investigations, informed by geomorphology, are required to test each hypothesis.

Fig. 1. Northwest North America with archeological sites older than 10,000 calibrated years before the present (Supplementary Materials) and proposed colonization routes: IFC and NPC.

Glacial ice extent (white) from (48), and archeological site and geological sample locations summarized in (12, 78). Laurentide Ice Sheet limits (dotted lines) from (55). ka, thousand years; IFC, ice-free corridor; NPC, North Pacific coast.

Fig. 2. Sea-level curves by region and periods above modern sea level (in thousands of calibrated years before the present) (that is, pre-Clovis occupations would be potentially accessible if they are extant), adapted from data in (38, 79).

Fig. 3. Chronology of the central IFC.

OSL and IRSL dates indicate minima ages of deglaciation and pro-glacial lake drainage (55), and calibrated ¹⁴C dates indicate minima dates for fauna and vegetation (, , , , –82). Demic expansion estimates of Native American ancestors from (13). All dates are shown with 1 SD.