EARLY LATE-PLEISTOCENE MEGADROUGHTS IN AFRICA AND THEIR ECOLOGICAL CONSEQUENCES FOR HOMO SAPIENS
These drought episodes and their termination ~90ka provide a context for understanding both an hypothesized human population bottleneck suggested by molecular genetic evidence to have occurred in the Late-Middle or Early-Late Pleistocene in Africa, and the subsequent rebound of human populations and their expansion out of Africa. Archaeological data shows that whereas occupation sites in both North and South Africa are common during the megadrought period, in tropical Africa such sites are rare and restricted to high elevations. Furthermore, archaeological sites become much more common in the immediate aftermath of the worst episodes of megadrought after 90ka. The combined data suggests a most probable period for expansion of anatomically modern humans out of Africa occurring between ~90-75ka.