Genetic data shows that the highest genetic diversity can be found among Africans, especially East Africans. The common interpretation is African, possibly East African, origin of Anatomically Modern Homo Sapiens (AMHS), but I always wonder if we can find the greatest genetic diversity in East Africa, because of recent gene flow between African and Eurasian populations. Many genetic research projects have demonstrated that East African was cross-road between Africa and Eurasia and both males and females were involved in bidirectional gene flow between two areas (see here and here). Here are three relatively recent articles that demonstrated that AMHS could have evolved in East Africa first.
Omo I and II discovered from Kibish, Ethiopia, between 1967 and 1974 exhibit morphological features of AMHS with some archaic features and they could be “the earliest well-dated anatomically modern human yet described.” McDougall and colleagues obtained the 40Ar/39Ar date of 198 ± 14 kyr from tuff lay just below the level that the fossils were found.
White and colleagues recently found other fossils of early AMHS from Middle Awash, Ethiopia. Like Omo I and II, they have morphological features of AMHS, but also robust archaic features, and they believe that these hominids are “the probable immediate ancestors of anatomically modern humans.” Using the 40Ar/39Ar dating method, the fossils and artifacts were dated between 16,000 and 154,000. Interestingly, the skulls show cut marks and they are interpreted as evidence of cultural modification or defleshing after the death of these individuals.
Setting the debate on whether there was gene flow between AMHS and archaic homo sapiens aside, I believe that based on current genetic and paleoanthropological data, we cannot answer whether East Africans exhibit the greatest genetic diversity because of recent gene flow or the place of human origin. In the future, maybe, human geneticists can address this question by looking at genetic markers that evolved different rates, and paleoanthropologists can securely date the fossils and artifacts from other parts of Africa.