Beringia and the Settlement of the Western Hemisphere

Previously, we addressed the problem of what variable(s) limited widespread human settlement of the Americas before ~15 ka. We concluded that while non-modern human taxa (e. g., Neanderthals) probably did not inhabit high-latitude environments (due to cold climate and/ or low plant and animal productivity) and thus could not disperse in the Western Hemispherevia Beringia, modern humans likely were denied access to mid-latitude North America >15 ka by coastal and interior ice sheets. Here we reexamine the problem with respect to modern humans in light of a revised chronology for glaciers and sea level, new research in paleo-genomics, and some new archaeological discoveries. During 35–30 ka, a lineage with west Eurasian roots occupied the Great Arctic Plain and may have expanded into eastern arctic Beringia and mid-latitude North America via an ice-free corridor. An East Asian lineage associated with microblade technology occupied the Lena Basin during the LGM and expanded onto the Great Arctic Plain >15 ka, possibly as early as the GI 2 interstadial (24–23 ka). Their immediate descendants probably occupied the southern Bering Land Bridge and Northwest Pacific coast >15 ka and dispersed widely in the Western Hemisphere during GI 1 (14.5–12.9 ka), primarily if not exclusively via a coastal route. The coalesced Laurentide and Cordilleran ice sheets blocked interior access to mid-latitude America until 13.8 ± 0.5 ka (and possibly later due to the length and narrow width of the ice-free corridor >13 ka).