Assimilation and modern human origins in the African peripheries

Abstract

The vast majority of pertinent genetic and human palaeontological evidence indicates that an early transition from archaic to modern humans occurs in Africa. Interestingly, the earliest well dated modern human fossils all derive from eastern Africa: Omo Kibish KHS (104 ka to 196 ka) and Herto (154 ka to 160 ka), both in Ethiopia (ka = thousand years ago). This suggests that modern humans may have originated in, and ultimately radiated out of, eastern Africa into the ‘peripheral’ regions of Africa, defined here as northern Africa and southern Africa, as well as into Eurasia. Evidence of the earliest presence of purported modern humans from both African ‘peripheral’ regions is assessed in this study. These include the Klasies River Mouth (KRM) sample from southern Africa and the Aterian-associated remains from North Africa, particularly the fragmentary subadult maxilla from Mugharet el ‘Aliya (High cave) near Tangier, Morocco. Both samples are maximally dated to ~130 ka and thus are significantly younger than the earliest eastern African modern humans. The KRM sample exhibits a significant amount of size and morphological variation, the latter reflecting a mosaic of archaic/modern anatomy. We interpret this morphological pattern as reflecting an admixed sample. The northern African evidence is less clear, but the morphology of the Tangier maxilla demonstrates archaic elements in the Aterian population, and this may well reflect the same pattern of admixture. We conclude that the evidence from the African ‘peripheries’ is consistent with admixture and that this broadly supports the assimilation model of modern human origins.