September 12, 2013

Rivers across the Sahara

PLoS ONE 8(9): e74834. doi:10.1371/journal.pone.0074834

Were Rivers Flowing across the Sahara During the Last Interglacial? Implications for Human Migration through Africa

Tom J. Coulthard et al.

Human migration north through Africa is contentious. This paper uses a novel palaeohydrological and hydraulic modelling approach to test the hypothesis that under wetter climates c.100,000 years ago major river systems ran north across the Sahara to the Mediterranean, creating viable migration routes. We confirm that three of these now buried palaeo river systems could have been active at the key time of human migration across the Sahara. Unexpectedly, it is the most western of these three rivers, the Irharhar river, that represents the most likely route for human migration. The Irharhar river flows directly south to north, uniquely linking the mountain areas experiencing monsoon climates at these times to temperate Mediterranean environments where food and resources would have been abundant. The findings have major implications for our understanding of how humans migrated north through Africa, for the first time providing a quantitative perspective on the probabilities that these routes were viable for human habitation at these times.

Link

7 comments:

Chak said...

It could have been one of the out-of-Africa routes (northern), also a backward migration corridor for e.g. R1b1c and T from Egypt to the paleo-lake Megachad.

Also see the Sahara Megalakes Project
http://www.kcl.ac.uk/sspp/departments/geography/people/academic/drake/Research/The-Sahara-Megalakes-Project/The-corridor-across-the-Sahara-and-the-out-of-Africa-hypothesis.aspx

terryt said...

"It could have been one of the out-of-Africa routes"

My guess is theat it was THE out-of-Africa route. Perhaps finally the Great Southern Coastal Migration Theory has taken its final nose-dive and crashed completely. Forget the Bab el Mandeb and groups of humans sailing (or paddling) blithely past coastal cliffs and through vast mangrove swamps all the way to Australia.

"Unexpectedly, it is the most western of these three rivers, the Irharhar river, that represents the most likely route for human migration".

It has long seemed to me that there is more Y-DNA B/E and mt-DNA L3 action in Central/West Africa than in East Africa, especially in eastern Ethiopia.

terryt said...

Sorry for the double post but thaks for the link Chak. For me this sums up the situation:

"Though potential ‘Out of Africa’ routes which avoid the Sahara Desert have been proposed, notably the Red Sea coast and the Nile Valley, the results presented here suggest that the Sahara could well have been a less effective barrier than has previously been thought. This view is supported by the lithic evidence. Stone tools from Achulean, Mousterian, Aterian, Epipalaeolithic and Neolithic have been found in the Fezzan (Mattingly et al., 2003; Reynolds 2006) suggesting that the region was periodically inhabited by hominids during both glacial and interglacial periods".

Annie Mouse said...

Interesting paper. Shame we cannot see the Nile also for reference.

Firstly it does not look to me like stone age folk were travelling up/down the river Irharhar. There are very few settlements reasonably near it. There is what appears to be a well worn path ~125 km to the west of the river though.

Clearly however there were a lot of folk trying to live in Tunis and Algeria, but NOT many in northern coastal Libya. Odd, as I would have expected a dense sprinkling of settlements all along the coast from Egypt. Is this a sea level issue? The bare areas do seem to be more low lying and what few settlements there are appear to be on outcrops.

So this leads me to ask where these folk living in NorthWest Africa 100kya came from? And who were they? Are we looking at African Homo sapiens who have travelled up the West Coast? Or neanderthals down from Europe? or is the main pathway west from Egypt lying underwater, just off the Libyan coast.

Today these folk are genetic Southern Europeans, with significant flow DOWN the west coast of Africa. I am favouring the third (soggy) explanation.

Annie Mouse said...

Interesting paper. Shame we cannot see the Nile also for reference.

Firstly it does not look to me like stone age folk were travelling up/down the river Irharhar. There are very few settlements reasonably near it. There is what appears to be a well worn path ~125 km to the west of the river though.

Clearly however there were a lot of folk trying to live in Tunis and Algeria, but NOT many in northern coastal Libya. Odd, as I would have expected a dense sprinkling of settlements all along the coast from Egypt. Is this a sea level issue? The bare areas do seem to be more low lying and what few settlements there are appear to be on outcrops.

So this leads me to ask where these folk living in NorthWest Africa 100kya came from? And who were they? Are we looking at African Homo sapiens who have travelled up the West Coast? Or neanderthals down from Europe? or is the main pathway west from Egypt lying underwater, just off the Libyan coast.

Today these folk are genetic Southern Europeans, with significant flow DOWN the west coast of Africa. I am favouring the third explanation.

eurologist said...

I am sure that the entire region must have played a role in an exceptional population expansion, and with it, uniparental marker diversification (such as BT vs. A1b1, CT vs. B, perhaps DE off CT; L3 vs. the other Ls, L3 subgroups).

Still, expansion along the Nile route is much faster - so the first ooA people who went via the northern Sinai would be expected from there, in agreement with the Nubian clusters.

On the flip side, the DE vs. CF and M vs. N splits are strongly pointing to two ooA expansions.

terryt said...

"On the flip side, the DE vs. CF and M vs. N splits are strongly pointing to two ooA expansions".

Perhaps, but not necessarily so. The population that spread through the Sahara may have consisted mainly of Y-DNA BT and mt-DNA L3. Of that population just Y-DNAs D (probably in the form of DE which developed into E in Africa and D beyond) along with mt-DNAs M and N were able to move beyond Africa through a similar ecosystem to the Middle East. From where they spread more widely through other regions with a similar ecosystem.