August 13, 2015

Rethinking the dispersal of Homo sapiens out of Africa


An excellent review which -among its other graces- demolishes the view that mtDNA haplogroup L3 provides a terminus post quem of 70 thousand years for the Out-of-Africa expansion, a question I've discussed in this blog before.

I think the evidence is overwhelming at this point that there were modern humans outside Africa before 100,000 years ago. The argument that they were a  failed expansion is shoddy and is based, as far as I can tell on things like the age of L3, the assumption that Y-chromosome haplogroup E is native to Africa and not derived from back-to-Africa migrants, the assumption that Out-of-Africa coincided with the Upper Paleolithic cultural efflorescence (disproven by the earlier dating of Neandertal admixture), or the failed hypothesis of a coastal route Out of Africa 60 thousand years ago that seems to be repeated in inverse proportion to the evidence for it. The halving of the human autosomal mutation rate relative to what was inferred before has certainly not helped either.

Evolutionary Anthropology: Issues, News, and Reviews Volume 24, Issue 4, pages 149–164, July/August 2015

Rethinking the dispersal of Homo sapiens out of Africa

Huw S. Groucutt, Michael D. Petraglia, Geoff Bailey, Eleanor M. L. Scerri, Ash Parton, Laine Clark-Balzan, Richard P. Jennings, Laura Lewis, James Blinkhorn, Nick A. Drake, Paul S. Breeze, Robyn H. Inglis, Maud H. Devès, Matthew Meredith-Williams, Nicole Boivin, Mark G. Thomas andAylwyn Scally

Current fossil, genetic, and archeological data indicate that Homo sapiens originated in Africa in the late Middle Pleistocene. By the end of the Late Pleistocene, our species was distributed across every continent except Antarctica, setting the foundations for the subsequent demographic and cultural changes of the Holocene. The intervening processes remain intensely debated and a key theme in hominin evolutionary studies. We review archeological, fossil, environmental, and genetic data to evaluate the current state of knowledge on the dispersal of Homo sapiens out of Africa. The emerging picture of the dispersal process suggests dynamic behavioral variability, complex interactions between populations, and an intricate genetic and cultural legacy. This evolutionary and historical complexity challenges simple narratives and suggests that hybrid models and the testing of explicit hypotheses are required to understand the expansion of Homo sapiens into Eurasia.

Link and here

8 comments:

terryt said...

"the failed hypothesis of a coastal route Out of Africa 60 thousand years ago that seems to be repeated in inverse proportion to the evidence for it".

Yet I still see it mentioned rather often. A great paper, thanks for posting.

Grogard said...
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pequerobles said...

Could model C explain the presence of L3 in Western Iberia ?

Is this a remanant of the 1st out of africa migration into europe ?

Always struck me as very strange the incidence of L3 in Iberia was much higher in the west than the east, including places like Galicia that were never under Muslim rule or experienced the atlantic slave trade

arch said...

"...the assumption that Y-chromosome haplogroup E is native to Africa and not derived from back-to-Africa migrants"

Speculated NON-L3 populations have no legacy in any modern populations, so whether they existed or COULD be inferred to have existed, they did not prosper and have no legacy into modern non-african human populations.

you have let me disagree with you before, and I appreciate that fact, however I will have to once again point out that too much of modern genetics has gone over to those with a specific agenda they want to prove/include/piggyback and that this is no way to either reach or establish valid conclusions.

I personally believe I see why you are attached to a opinion advocating for Y-Hg E as a back migration into Africa - which is due to that fact that Hg E accounts for at least a simple majority of modern Greek paternal line ancestries.

While its certainly possible that modern europid or caucasoid populations that are often paternally some variety of Y-Hg 'E' such as Greeks, greek-ancestry southern Italians, Askenazi Jewish populations, Albanians etc.. COULD in fact be responsible for back migrations into Northern Africa, as you suggest, I strongly doubt that this is the most logical conclusion and I cant fathom a basis for asserting it as factual and scientifically established.

I think that its extremely likely that Hg E- were we expending resources on actually collecting useful data on PLENTIFUL ancient remains instead of Neandertal-apalooza whimsy claims- would likely be shown to not have been a significant element of early greek populations prior to the establishment of med. sea trade routes and their dominance of said routes.

I think what likely happened is what we generally know happened,
which is that the early Greeks saw dollar signs (actually Obol signs), not very differently from many other modern western societies, and as their culture and language became a defacto lingua franca across the Mediterranean, their cities became destinations, attractions and trade hubs with large immigrant communities, which only accelerated once levantine populations settled in vast numbers during the Roman purges from their homelands of asia minor and modern Israel and Syria. I think a vast portion, if not the majority of Hg E in Greece originates from Levantine populations, not from aboriginal Greek populations.

Overtime, the Greek gene pool became reflective of these large volume of migrants who began to control and dominate the globalized mercantile society that emerged out of what was formerly a tribal kinship society, that no longer favored its native sons but favored those with the most money and the largest trade contacts.

I strongly suspect the Greek Y-Hg E population came to dominance in much the same manner that a once Gothic populated Crimea is today close to 100% devoid of biological descendants of actual Gothic populations. The truly sad part is, if a fraction of scientific inquiry were diverted to useful purposes, this is something so basic and so easy to establish that it requires no hypothesis or debates of opinion.. It could easily be proven either way factually with fairly minimal expense.

I suspect that the 'simple' work on ancient remains recovered from within early Greek population remains has likely actually been done in some case or another and possibly not published if it does not comport with what you seem to be hinting at as your hypothesis.

If I had to go out on a limb, I think its quite possible that Y-Hg E could have been present in most levantine and med. rim populations, but I think most likely given the large scale levantine, semitic and asia minor migration into the Greek mainland population centers, this is most probably how the preponderance of Y-Hg E came to be present among modern Greek populations, a legacy of traders and migrants who adopted Greek language customs and trade opportunities, not of athenians or spartans.

German Dziebel said...

The review is in fact pretty bad as none of their fossil, genetic and archaeological "evidence" is integrated into a single datapoint. What we need at this stage of the evolution of our understanding of human origins is ancient DNA from taxonomically well defined skulls found in association with specific tool traditions. We don't have a shred of data of this nature to support human origins in Africa and human dispersal outside of Africa. What we are offered instead are speculations and simulations.

Molecular evidence from modern populations (such as the mtDNA "phylogeny") has never been reconciled with cultural and linguistic patterns found in modern human populations (e.g., highest linguistic diversity way outside of Africa) and hence should be treated as provisional and potentially subject to rethinking. The need for such a rethinking is especially burning considering that no African-specific mtDNA lineages have ever been found in the earliest human remains outside of Africa (e.g., Oase or Ust-Ishim).

The authors also continue to persist in showing an anti-Amerindian bias ("The lower rate is more consistent
with inferences for the timing of recent events such as the divergence of Native American and East Asian populations.") That those "events" are indeed "recent" has to be proven and not assumed.

Grogard said...
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cosasdehombres said...

Are you alive, man? Have you got any info about this: http://www.pnas.org/content/early/2015/09/02/1509851112
"The secret of the Basques is discovered", so they say but I can´t read it.

QFG said...

Has out-of-Africa proponent, Prof. Geoffrey Rose, addressed these issues?