A western riverine route for human migration to North Africa in the Abbassia Pluvial

Interesting study on paleo-rivers of the Sahara providing insight for a likely route for Homo sapiens to cross the Sahara towards NW Africa.

Tom J. Coulthard et al., Were Rivers Flowing across the Sahara During the Last Interglacial? Implications for Human Migration through Africa. PLoS ONE 2013. Open access → LINK [doi:10.1371/journal.pone.0074834]

Abstract


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.

Figure 2. Simulated probability of surface water during the last interglacial. This figure details Archaeological sites, and an annual probability that a location has surface water. The archaeological data are derived from a number of sources (including [42], [66], [67], [68]. The findspots are characterised by Aterian and Middle Stone Age artefacts such as bifacial foliates and stemmed Aterian points and/or typical ‘Mousterian’ points, side scrapers and Levallois technology. Most are represented by surface scatters but where stratified examples exist these can be shown by dating (OSL and U-series techniques) and geomorphological setting to belong within MIS 5e [41], [42].

As discussed in other occasions, it seems likely that some genetic remnants of those early migrations are still visible in at least some NW Africans.

See also:

• North African autosomal genetics through the prism of ADMIXTURE.
• Major upheaval of human Y-DNA phylogeny: we are all ‘A’ now (on some very ancient lineages shared by West and North Africans).

 

Middle Paleolithic industries of African affinity of the Thar Desert go back to c. 96 Ka ago

Again Team Petraglia revealing fascinating evidence on the Middle Paleolithic dispersal of Homo sapiens, and one that fits well the genetic data (speculative “molecular clock” excluded), as well as with the climatic data.

James Blinkhorn et al., Middle Palaeolithic occupation in the Thar Desert during the Upper Pleistocene: the signature of a modern human exit out of Africa? Quaternary Science Reviews, 2013. Pay per view → LINK [doi:10.1016/j.quascirev.2013.06.012]

Abstract

The Thar Desert marks the transition from the Saharo-Arabian deserts to the Oriental biogeographical zone and is therefore an important location in understanding hominin occupation and dispersal during the Upper Pleistocene. Here, we report the discovery of stratified Middle Palaeolithic assemblages at Katoati in the north-eastern Thar Desert, dating to Marine Isotope Stages (MIS) 5 and the MIS 4–3 boundary, during periods of enhanced humidity. Hominins procured cobbles from gravels at the site as evidenced by early stages of stone tool reduction, with a component of more formalised point production. The MIS 5c assemblages at Katoati represent the earliest securely dated Middle Palaeolithic occupation of South Asia. Distinctive artefacts identified in both MIS 5 and MIS 4–3 boundary horizons match technological entities observed in Middle Palaeolithic assemblages in South Asia, Arabia and Middle Stone Age sites in the Sahara. The evidence from Katoati is consistent with arguments for the dispersal of Homo sapiens populations from Africa across southern Asia using Middle Palaeolithic technologies.

Possibly the most strikingly unmistakable evidence for a Homo sapiens affiliation of these findings is the Aterian-like tanged point, which is almost identical to another one found previously in Jwalapuram:

Fig. 4. 1) Tanged point from Jwalapuram 22 (adapted from Haslam et al., 2012); 2 & 3) Tanged point from Katoati.

Not just Aterian: the, visually less obvious, Nubian technology is also present:

Two Levallois cores from S4 and one from S8 exhibit a mixture of distal divergent and lateral preparation of the flaking surface to produce a distale medial ridge resulting in the removal of prepared points (Fig. 3). These reduction schemes are consistent with descriptions of Nubian Levallois technologies (Rose et al., 2011; Usik et al., 2013).

…

A single flake from S4 presents a combination of distal divergent and lateral removals on the dorsal surface and a prior removal of a pre-determined pointed flake,indicative of the use of Nubian Levallois strategies (Fig. 3).

Table 2. I added at bottom (red) median OSL ages from table 1.

Zhirendong jaw

In synthesis: groups of unmistakably Homo sapiens with obvious African techno-cultural heritage were already within the modern boundaries of the Indian Federation around 96,000 years ago (CI: 109-83 Ka). This totally debunks Mellars’ and Mishra’s recent claims, the usual “molecular clock” nonsense (that so many people seems willing to believe at face value), and widens significantly the earliest plausible dates for the colonization of Asia (beyond Arabia-Palestine-Persian Gulf) making findings like Zhirendong jaw (the oldest non-Palestinian H. sapiens remains out of Africa, dated to c. 100,000 BP) much more credible.

Until today I was very much in doubt about accepting dates of c. 100,000 years ago for the Asian colonization but since right now I am adopting this model as the most likely one. In other words: it seems clear that the people already settled in Arabia and the Persian Gulf “oasis” did not wait for climatic pressure at the end of the Abbassia Pluvial to send them out in search of new lands: they did it when the pluvial period was still holding the arid gates of Asia open for them.

All the evidence adds up well now. 

_______________________________________

Note: the full paper was available at Academia.edu at the time of writing this:  HERE and HERE.

 

African MSA

As I mentioned recently, I am collaborating in a joint series of articles in Spanish language which try to explore the expansion of Homo sapiens from the double viewpoint of archaeology and population genetics. The series, hosted by Noticias de Prehistoria – Prehistoria al Día, began this past Thursday with David Sánchez’ article on the African MSA, earliest fossils of H. sapiens and other early African cultures like the Lupemban and Aterian. In the next week I plan to explore the genetic aspects, in line with what has been published in this blog and its predecessor Leherensuge.

But so far let’s try to synthesize the most important aspects of David’s entry at his blog. First and foremost is this map, which I believe is of great interest because of its synthetic informative value:

Legend translation: · Fossil remains of Homo sapiens (195-90 Ka BP) · Aterian sites (170*-40 Ka BP) · Nubian complex [MSA] sites (115-37 Ka BP) · Lupemban sites (230-130 Ka BP) · Undetermined MSA · South African [MSA] sites (165-59 Ka BP) · Some early MSA sites [* personally I am a bit skeptic about the oldest Aterian dates but well…]

It’s possible that it’s not totally complete (feel free to add to our unavoidably limited knowledge) but it does gather in a quick view most of the African Middle Paleolithic (MSA, Aterian and Lupemban). The site of Katanda which has a special interest because of the harpoons, the earliest known ever, was absent in the version first uploaded but this has been corrected now.

This synthetic map, together with the extensive bibliography (in several languages) that David links at the bottom of his article are, I believe, an interesting reference for all those interested in the origins of Homo sapiens and its first prehistory in the African continent.

Paleolithic mattresses

Most readers are probably at least somewhat familiar with the many, often impressive and revealing, South African sites but, besides the already mentioned Katanda harpoons, what really impressed me a lot was the finding in Sibudu, Northern Mozambique, near Lake Malawi, of fragments of ancient fossilized mattresses made up of vegetation that has bug-repealing properties (→ news article at El Mundo[es]). Apparently the owners, some 73,000 years ago, burnt them now and then in order to destroy parasites. Since c. 58,000 BP the number of mattresses, fires and ashes grew, surely indicating greater population densities, at least locally. 

The ancient inhabitants of that area of Mozambique are also known to have milled and processed, some 100,000 years ago, a diverse array of plants, including sorghum, “African potato” (medicinal), wine palm, false banana, pigeon peas, etc.

 

North African autosomal genetics (again)

Two weeks ago I performed almost the same exercise here at this blog but now a paper with academic seal of proficiency has been published at PLoS Genetics:

Brenna M. Henn et al., Genomic Ancestry of North Africans Supports Back-to-Africa Migrations. PLoS Genetics 2012. Open access.

The basic results are very very similar if not outright identical to what I achieved. And that is because the sampling strategy was also very similar. If anything Henn and colleagues used a broader sample of Tropical African populations.

From Fig. 1 (click to expand)

The choice of North African populations is exactly the same as mine (actually the samples I used are from a previous paper by Brenna Henn, who is making a great job in exploring African genetics, and must be the same as in this paper) exception made that I included 10 HGDP Mozabites also. The choice of West Eurasian populations is different but does not seem to produce any relevant difference in the result. The main differences are in the choice of Tropical African samples, which does produces some differences.

Tunisian Berbers’ endogamy

But first of all let’s explain what happens with the weird Tunisia sample:

… the Tunisian Berber population displayed an excess of pairs of individuals sharing 200–1200 cM IBD. This bimodal distribution indicates that many 1st and 2nd cousin genetic equivalent pairs were present in this sample, even though donors declared themselves to be unrelated during the sampling process. Analysis of long runs of homozygosity (ROH) indicate that the Tunisian population averaged almost twice as much of their genome is in ROH than other North African populations, 230 Kb versus 120 Kb respectively (Figure S3). The pattern of ROH and pairwise IBD in the Tunisian Berbers is likely the result of endogamy due to geographic isolation or cultural marriage preferences.

That’s why they perform so weirdly, relating always to themselves almost before any other affinity. This fact makes them a poor and mostly uninformative population. 

Different sampling strategy, somewhat different results

As I say, the main difference between my sample strategy and Henn’s (and the result produced) is in Tropical Africa: I used Ethiopians, Mandenka and Fulani; Henn used also Fulani and then also West and East Africans but different ones. I found apparent Mandinka (West African) admixture in NW Africa (and almost no East African/Ethiopian one), Henn found apparent Luhya (East African) admixture instead (and almost no West African one).

I don’t know yet how these two apparent different findings may conciliate but the difference of findings is in itself interesting, outlining the strategy of future research. 

Something that is quite obvious as Henn uses such a broad Tropical African sample is that many of the components discerned are just one for each Tropical African population. This is interesting, underlining the immense genetic diversity of Africa, but not very informative in regard to North Africans. 

That (and the fact that I went down to K=11 – and even K=12 but this one was uninformative) is probably the reason why I, with a smaller peripheral sample, could detect what I believe that is a very old layer of North African specificity. 

So the sampling strategy (both sample choice and number of individuals in each sample), as well as the K-depth reached can affect the results of these analysis of the population genetic structure. There is almost always a different approach that can produce complementary information as result. 

Back to Africa but when?

But overall the results are very similar: the bulk of North African genetic affinity is with West Eurasia and not so much Africa as such. That is the most obvious result and indicates that the Out-of-Africa migration had an important backflow which affected several parts of Africa but very specially the North. 

Nothing unexpected, at least for me. But it really hits a blow to those who, quite lightly, associate Y-DNA and overall ancestry: if there is Y-DNA and mtDNA contradiction, as is the case in North Africa, where most of the patrilineages are African but most of the matrilineages are of Eurasian origin, in most cases the mtDNA is right and the Y-DNA is nothing but a varnish. 

The main exceptions seem to be areas of sustained male inflow across generations, notably some parts of Latin America. But this kind of sustained industrialized migration pattern is unlikely to have ever existed in prehistory or even pre-Modern history anywhere. 

Anyhow, interestingly, the authors make an interesting exercise to find out estimate times of Eurasian arrival. The result is forewarned with reasonable precautions:

Since this model neglects migration, we expect our results to form a lower bound on the population divergence time, as similar levels of population divergence would require a longer separation in the presence of migration.

So at least this old:

Fig. 3 (edited to correct a color typo) – click to expand

Although these divergence time estimates may not be precise, as they do not adequately model ancient migration, they do suggest that the population divergence between the ancestral Maghrebi population and neighboring Mediterranean populations occurred at least 12,000 ya and indeed more likely predated even the Last Glacial Maximum.

It is interesting anyhow that the Fst distance to Europe are lower than to Arabia and that the window for a possible migration from Europe can well fit with the Oranian genesis c. 22,000 years ago, which I am pretty sure that is related with Iberian Gravetto-Solutrean: Oranian was back in the day called Iberomaurusian for a reason and, regardless of revisionisms, the Oranian dates for the West are quite older than those of the East – never mind that at least 25% of North African mtDNA (and maybe 10% of Y-DNA) is of European (and most likely Iberian) derivation and that European affinity remains apparent, distinct and important (specially in Algeria and North Morocco) even after North African specific components have become obvious and dominant.

So the old theory of migration from Iberia c. 22,000 years ago (maybe with some backmigration northwards as well) is not any colonial construct but something most probable, as indicate both archaeological and genetic data very consistently.

Less clear is whether there was a previous West Eurasian flow c. 40,000 years ago with the Dabban industries (so far only known in Libya, although unmistakably “Aurignacoid” in character). Genetically the main support for this first Eurasian backflow is mtDNA U6 (derived from Eurasian U), whose origin is probably in Morocco, where most of the basal diversity accumulates (and then around it, in Canary Islands and Iberia). 

It is not impossible that the lineage might have arrived, still as undefined U*, via Europe, however the structure of the autosomal DNA, as illustrated in this study or in my exercise from December, evidences that the North African specific components (excepted the “Aterian” one) are most akin to West Eurasia (by much). So there was probably a first migration from West Asia c. 40 Ka. ago and then an Iberian layer overlapped. 

This paper also suggests more recent migrations from Tropical Africa, although I am unsure if I can take their timeline conclusions at face value, specially regarding the East African component, that I imagine quite older (they suggest, table 1, just 25 generations ago, what I find most hard to believe for such a notable impact).

I would personally conclude that the North African genetic composition appears to be made up of:

1. A deep, quite diluted, ‘Aterian’ layer
2. A dominant North African specific layer of mostly West Eurasian roots
3. An Iberian or European layer (Oranian)
4. Maybe an East African (Capsian) layer (needs clarification but agrees with Y-DNA)
5. Maybe a lesser Arab layer and also maybe some recent Tropical African input

 

Homo sapiens child’s remains found in Morocco (108 Ka BP)

Artistic recreation of Bouchra (right)

The quite complete remnants of a child of our species, Homo sapiens, have been found in the site known as Smugglers’ Cave (Dar es Soltan, Morocco) in Aterian context. The child has been nicknamed Bouchra, meaning Good News in Arabic.

No paper or image of the infant’s skeleton are known, as the research is financed by the sensationalist media National Geographic, which aims to keep the exclusive. 

There are several older known members of our species in Africa (from Mozambique to Morocco) and Palestine but this one seems to be the first one dead at such a young age: approximately 8 years old. The remains have been dated to c. 108 Ka ago.

Sources: Philly.com[en] and Mundo Neandertal[es].