Thursday, February 18, 2016

The earliest Modern Humans to leave Africa mostly died out?

There's a new study out with some very intriguing genetic implications that have been somewhat implied in the past which is that there was (or were) a much earlier dispersal(s) out of Africa by Anatomically Modern Humans (Homo Sapien Sapiens):

"It has been shown that Neanderthals contributed genetically to modern humans outside Africa 47,000–65,000 years ago. Here we analyse the genomes of a Neanderthal and a Denisovan from the Altai Mountains in Siberia together with the sequences of chromosome 21 of two Neanderthals from Spain and Croatia. We find that a population that diverged early from other modern humans in Africa contributed genetically to the ancestors of Neanderthals from the Altai Mountains roughly 100,000 years ago. By contrast, we do not detect such a genetic contribution in the Denisovan or the two European Neanderthals. We conclude that in addition to later interbreeding events, the ancestors of Neanderthals from the Altai Mountains and early modern humans met and interbred, possibly in the Near East, many thousands of years earlier than previously thought."

But one important detail pointed out by this study that is escaping some people aware of it is the following:

"However, it is clear that the source of the gene flow is a population equally related to present-day Africans and non-Africans (Extended Data Fig. 3). We conclude that the introgressing population diverged from other modern human populations before or shortly after the split between the ancestors of San and other Africans (Fig. 3a), which occurred approximately 200,000 years ago."

What they've found is that the hypothetical Homo Sapien Sapien population responsible for this admixture into those Neanderthals diverged from the ancestors of all Modern Humans (San & Yoruba included) well over 150,000 years ago so these people were not ancestral to modern Out-of-Africa/Eurasian populations to the exclusion of African populations like Yorubas and they probably did mostly die out whilst current Out-of-Africa populations seem like they're descended from later migrations out of Africa.

There have long been theories about Eastern Non-Africans like Australo-Melanesians tracing some of their ancestry to people who may have left Africa before the OoA migration (or migrations) mostly responsible for modern OoA populations, I do wonder if there is any truth to that.

Reference List:

1 comment:

  1. Very intriguing. For some time now I have been reading various journal articles and have noticed an uptick of evidence in favor of a multiple dispersal OOA beginning around MIS-5. However, part of me see's the more extreme interpretation of these findings, that perhaps there were significant populations of homo sapiens in Asia prior to their appearance and predominance in Africa, as very captivating since I've never been fully persuaded the modern human form came out of Africa after a long period of incubation there.

    Not saying this shows homo sapiens didn't evolve in Africa first, but there have been plenty of archaeologists who say that there's plenty of fossils in the near east/levant that are in the blurry classification zone between homo sapiens and homo heidelbergensis.

    The plot thickens once again.