Let me enter the following points which might be very relevant to the finding that in North Africa: "the Neandertal's genetic signal is higher in populations with a local, pre-Neolithic North African ancestry".
First of all, this is unexpected if Neandertal admixture took place in the Near East; if that were the case, then Near Eastern back-migrants would be more Neandertal-like than aboriginal Homo sapiens that had not participated in the Out-of-Africa event.
Second, I have followed up on John Hawks' suggestion that UP Europeans were more Neandertal-admixed than current Europeans, and using Oetzi's genome, discovered that potentially this is true. This is also unexpected if admixture with Neandertals took place in the Near East.
A link between aboriginal North Africans and UP Europeans of course exists: relationships between the Mechta-Afalou and Cro-Magnoids have long been recognized in physical anthropology.
An even more remote link involves Jebel Irhoud 1, the first modern human whose skull we possess from North Africa. Not only were the associated industries Mousterian (same as European Neandertals), but the skull itself was originally considered to be an African Neandertal, before it was reclassified as a member of H. sapiens.
I will update this entry after reading the paper with any further observations.
PLoS ONE 7(10): e47765. doi:10.1371/journal.pone.0047765
North African Populations Carry the Signature of Admixture with Neandertals
Federico Sánchez-Quinto et al.
One of the main findings derived from the analysis of the Neandertal genome was the evidence for admixture between Neandertals and non-African modern humans. An alternative scenario is that the ancestral population of non-Africans was closer to Neandertals than to Africans because of ancient population substructure. Thus, the study of North African populations is crucial for testing both hypotheses. We analyzed a total of 780,000 SNPs in 125 individuals representing seven different North African locations and searched for their ancestral/derived state in comparison to different human populations and Neandertals. We found that North African populations have a significant excess of derived alleles shared with Neandertals, when compared to sub-Saharan Africans. This excess is similar to that found in non-African humans, a fact that can be interpreted as a sign of Neandertal admixture. Furthermore, the Neandertal's genetic signal is higher in populations with a local, pre-Neolithic North African ancestry. Therefore, the detected ancient admixture is not due to recent Near Eastern or European migrations. Sub-Saharan populations are the only ones not affected by the admixture event with Neandertals.
Link
From what I understand, the North African element that contains Neanderthal ancestry dates back to the back to Africa movement of Near Eastern humans 12,000 years ago. This is prior to the Neolithic farmer/pastoral movements, and in the Mesolithic.
ReplyDeleteIt is unlikely those Mesolithic North Africans had much in common with the humans that lived in North Africa 40,000 years ago.
Note that this is all based on the inbred Tunisian sample. Other North Africans carry 'expected' levels of Neanderthal admixture, relative to their West Eurasian and African admixture proportions.
ReplyDeleteQuestion:
ReplyDeleteCould this correspond with the M1/U6 back migration into North Africa? This demographic movement is strongly supported by the archaeological evidence, with the Dabban Industry of Cyrenaica seemingly derived from the early Ahmarian from the Levant. New dates from Hauh Fteah in Libya show the initial Dabban post-dating a hiatus around 40 ka BP; so, a few thousand years after the development of the Ahmarian in the Levant, which in turns develops from the Emiran Initial Upper Palaeolithic.
Or am I totally off base and this more likely the result of a later event?
The age of U6 is 37ky, so this seems like a very good suggestion.
ReplyDeletehttp://download.cell.com/AJHG/mmcs/journals/0002-9297/PIIS0002929712001462.mmc1.pdf
M1 at 24ky appears younger.
Given the relatively long ages of U subclades in Europe and North Africa, and the overrepresentation of U in ancient DNA from Europe, I'd say it's a pretty good hypothesis that some of the earliest post-UP modern humans in both regions may have belonged to it.
"Note that this is all based on the inbred Tunisian sample".
ReplyDeleteIs it possible that the Neanderthal admixture entered North Africa through that region? It is after all reasonably close to Southern Italy, and haven't Otzi and Sardinians elevated levels of Neanderthal?