Figure 4. Maps depicting each phase of our three-step colonization model for the peopling of the Americas.

(A) Divergence, then gradual population expansion of the Amerind ancestors from their East Central Asian gene pool (blue arrow). (B) Proto-Amerind occupation of Beringia with little to no population growth for ≈20,000 years. (C) Rapid colonization of the New World by a founder group migrating southward through the ice free, inland corridor between the eastern Laurentide and western Cordilleran Ice Sheets (green arrow) and/or along the Pacific coast (red arrow). In (B), the exposed seafloor is shown at its greatest extent during the last glacial maximum at ≈20–18 kya [25]. In (A) and (C), the exposed seafloor is depicted at ≈40 kya and ≈16 kya, when prehistoric sea levels were comparable [24], [25]. Because of the earth's curvature, the km scale (which is based on the straight line distance at the equator) provides only an approximation of the same distance between two points on these maps. In addition, a scaled-down version of Beringia today (60% reduction of A–C) is presented in the lower left corner. This smaller map highlights the Bering Strait that has geographically separated the New World from Asia since ≈11–10 kya.