A Libyan ‘Out of Africa’ route for ancient humans.

Is suggested in this recent article, kindly pointed out by Mr Mathilda a couple of days ago. Finally, I manage to pry my kids off the damn computer to post it.

The widely held belief that the Nile valley was the most likely route out of sub-Saharan Africa for early modern humans 120,000 year ago is challenged in a paper published this week in the Proceedings of the National Academy of Sciences. A team led by the University of Bristol shows that wetter conditions reached a lot further north than previously thought, providing a wet ‘corridor’ through Libya for early human migrations. The results also help explain inconsistencies between archaeological finds.

While it is widely accepted that modern humans originated in sub-Saharan Africa 150-200 thousand years ago, their route of dispersal across the hyper-arid Sahara remains controversial. The Sahara covers most of North Africa and to cross it on foot would be a serious undertaking, even today with the most advanced equipment.

Well-documented evidence shows there was increased rainfall across the southern part of the Sahara during the last interglacial period (130-170 thousand years ago). The Bristol University team, with collaborators from the universities of Southampton, Oxford, Hull and Tripoli (Libya), investigated whether these wetter conditions had reached a lot further north than previously thought.

Anne Osborne, lead author on the paper said: “Space-born radar images showed fossil river channels crossing the Sahara in Libya, flowing north from the central Saharan watershed all the way to the Mediterranean. Using geochemical analyses, we demonstrate that these channels were active during the last interglacial period. This provides an important water course across this otherwise arid region.” The critical ‘central Saharan watershed’ is a range of volcanic mountains formerly considered to be the limit of this wetter region.

The researchers measured the isotopic composition of snail shells taken from two sites in the fossil river channels and from the shells of planktonic microfossils in the Mediterranean. Despite being hundreds of kilometres from the volcanic rocks in the mountains of the Saharan watershed, these shells had a distinctly volcanic ‘signature’, very different from the other rocks surrounding the sites. Water flowing from these volcanic mountains is the only possible source of this signature.

Dr Derek Vance, senior author on the paper, added: “The study shows, for the first time, that monsoon rains fed rivers that extended from the Saharan watershed, across the northern Sahara, to the Mediterranean Sea. These corridors rivalled the Nile Valley as potential routes for early modern human migrations to the Mediterranean shores.”

The similarities between Middle Stone Age artefacts in places like Chad and the Sudan, with those of Libya, strongly support this theory. “We now need to focus archaeological fieldwork around the large drainage channels and palaeo-lakes to test these ideas” said Nick Barton, a contributor to the project from the University of Oxford.

Link

The widely held belief that it was the Nile? Generally I see the Gate of Tears pushed as the exit point, whenever I bang on about the Nile being the most likely exit route everyone ignores me. What really interested me is the 120,000 date. Very interesting. I think the 120k date is quite possible. I think the dates from the mt DNA and Y DNA don’t show any signs of accuracy. When I compared a couple they didn’t match the population expansions I knew of at all (in North Africa).

I’d like to point out that the Nile flows through the Sudan, then up into North Africa. Personally I think this theory is a bit weak, I’m still going with the Nile. I support 120k as a reasonable exit date, there was never any good evidence modern humans became extinct in the Levant when it’s climate changed.

4 responses to “A Libyan ‘Out of Africa’ route for ancient humans.

  1. … whenever I bang on about the Nile being the most likely exit route everyone ignores me.

    Well, I think you may be right in fact (not sure but at least as a valid possibility). But I know the feeling.

    There’s too much faith in TRMCA estimates these days – and honestly, I trust C14 much more. The evidence for either model is not conclusive anyhow.

    Admittedly it’s hard to explain how people had much better chances of survival in South Asia than in the West (West Asia and North Africa), as the genetic evidence clearly suggests, specially with Toba supercaldera throwing all those thick layes of ashes on the subcontinent specifically. But the fact is that there are cultures in India that show continuity before and after Toba (and have African affinities, apparently). The other weak point of an old OOA via the Nile is the lack of direct evidence in form of well dated H. sapiens remains between the Skuhl and Aterian early epysodes and the well estabilished fossils beginning c. 50,000 BP. It would be really nice to find some “modern” skulls in India or elsewhere in Asia with solid old datations: that would really settle the issue in favor of an old OOA pretty much.

  2. “Generally I see the Gate of Tears pushed as the exit point”. I’m sure this was proposed by someone (I think it was Spencer Wells) who came up with the extremely unlikely scenario of a coastal migration along the Arabian, Makran and Indian coastline, with boats what’s more! This proposal was used to explain the crossing of Wallace’s Line to Australia so soon after an apparent emergence from Africa.

    “I think the dates from the mt DNA and Y DNA don’t show any signs of accuracy”. There’s no problem even if they’re accurate. The first emmigrants didn’t necessarily have those haplogroups. Besides, if there was interbreeding we would expect genes in general to travel faster than Y-chromosome or mtDNA. After all in a mixing population the grandson of an incoming Y-chromosome has a good chance of finishing up having a resident Y-chromosome. likewise for mtDNA and incoming women mixing with locals. On the other hand any beneficial genes, technology or culture introduced could easily outpace the haplogroups in just a few generations. Of course beneficial resident genes, technology and culture would remain.

    I believe this explains the partially modern-looking Neanderthals in Central Asia and the apparently totally modern-looking humans in India pre the origin of modern out of Africa haplogroups.

  3. Many people think that there are Neanderthal genes present among present day Europeans and alittle in West Asians. I’ve heard about 5% are Neanderthal genes. I am not sure if there is any truth to it, as some websites post false or later discredited information. Do any of you? And if so supply a link to the article.

    I don’t know much about genetics, but there are theories that Homo-Sapien-Sapiens diversed “Out-Of-Africa” and differnt times, numbers, and with different routes.
    I believe that Australoids were first right. This is supported by the genetic variety among all Africans alone, and the rest of the world. Also I’ve heard the ancestors of Arabs were the last to leave Africa and the fact that Asians are very genetically distant to Europeans, despite the skin-color. Europeans are more related to Africans than anyother groups, which makes aeverything confusing.

  4. Europeans are more closely related to Asian, but are Africans closest relatives.

    Europeans are about twice as closely related to Asians as Africans. There’s an FST chart on my blog somewhere with the distances between races on it (done by Cavalli Sforza, a man who claims to support the ‘no such thing as race’ party, oddly).

    I’ve got several DNA multiple loci studies that support a modest level of introgression with archaics. One suggests five percent Neanderthal in European, one shows three waves of exits from Africa, and one says that there has to have been low levels of archaic introgression or none of the numbers make sense. Give me a bit and I’ll post the links. Here.

    I’ve got an entry called the out of Africa deception, which has a list of DNA studies on single genes that directly disagree with the OOA theory.

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