Reply to Hublin and Klein: Locating a geographic point of dispersion in Africa for contemporary humans

Abstract

Hublin et al. (1) are correct to emphasize the importance of concordance among multiple disciplines, including paleoanthropology, as researchers reconstruct human evolutionary history. We would like to discriminate between two possible models relevant to the letter written by Hublin et al. (1). First, if these researchers are proposing that anatomically and behaviorally modern humans originated in North Africa and then migrated south throughout sub-Saharan Africa, we would expect to see the opposite cline of genetic diversity observed by Henn et al. (2) under a serial founder model. We included seven new North African samples in our analysis of the geographic patterns of diversity. These are the first genomic data to span the breadth of North Africa. Our North African samples are, without exception, the least diverse within Africa, and additional analysis suggests that contemporary North Africans derive the majority of their ancestry from “back-to-Africa” migrations. Putting aside our North African data, Fst and linkage disequilibrium patterns based on sub-Saharan samples show that western and eastern African populations are less diverse than those in southern Africa. We find this pattern especially striking because southern Africa is the region with the fewest population samples and the genetic diversity there is likely still substantially undersampled. Alternatively, if Hublin et al. (1) are proposing that North Africa was a stepping-stone for the “out-of-Africa” migration(s), we believe our model is consistent with an origin in southern Africa but an exit out of North Africa.