Wednesday, January 14, 2009

Unwinding the Convoluted Character of the Emergence of Imazighen Groups

The sequence of events involved in the genesis of the diversity that we see today in Imazighen groups is something that not only generates a considerable degree of interest, but also one that continues to challenge even the experts who've spent a good deal of their time in unwinding the archaeological, cultural and biological developments that accompanied the development of the Imazighen.

Amongst the Imazighen, perhaps the tawny-hued coastal northwestern groups draw in the most curiousity, in terms of their seemingly asymmetric sourcing of their gene pool—comprising of Y DNA, predominantly made up of autochthonous African markers, and mtDNA, in most cases made up of largely "Eurasian"-tagged markers—and the question of when they attained their apparent tawny or "light-skin" epidermal phenotype, in a continent dominated largely by 'dark skin' [of varying degrees] autochthonous groups. All sorts of rounds of rationalizing and speculation have taken place over the years, in efforts to explain what appears to be an anomaly of some sort to some, from tying contemporary Imazighens to the so-called Mecthoid (or supposed "Cro-Magnoid") types of the EpiPaleolithic and Neolithic era to being outright descendents of the likes of Vandals, Arabs or "Near Easterners", as opposed to being descendents of autochthonous Africans with genetic influence from groups that spent their evolutionary history outside of mainland Africa. None of these of course, have born out to be based on facts consistent with evidence. To take the "Mechtoid" example for instance, attempts had been taken by Eurocentric scholars to suggest that these were the ancestors of contemporary coastal northwest African Imazighen populations, by arguing for their supposed "caucasoid" cranio-facial phenotype, the supposed morphological link with the European Cro-Magnon specimens, and by typifying them as "Mediterranean caucasiod" types [See: Mechta and Afalou: Do they and the so-called "Mechtoids" constitute a type with the "Cro-Magnon"? and Mechta-Afalou and the so-called Mechtoids: Continued!]

At least one study states this: 

the most ancient, i.e. those from Taforalt in Morocco, Afalou-bou-Rhummel in Algeria and Singa in the Sudan, cannot be considered as being either Negro or San, whereas the later Jebel Sahaba sample (c. 12000 B.P.), the Wadi Halfa (c. 11950 - 6400 B.P.) and the Mechta-el-Arbi individuals (c. 8500 B.P.) and the Jebel Moya sample (c. 2950 - 2350 B.P.) are not significantly removed from the Negro populations. - Santiago Genov├ęs

Bearing in mind those ages provided in that extract above, it should be noted that from DNA analysis, it has been implied that the Imazighen ("Berbers") ancestor emerged ca. 8.2 kya or so [Arredi et al. 2004] in northeast Africa; given this, the northwest African samples here [the Taforalt, Afalou-bou-Rhummel, and the Mechta-el-Arbi] are all too old to be associated with the contemporary Imazighen. The age given to the Mechta-el-Arbi specimens is the only one that comes close to any age associated with contemporary Imazighen speakers; but even here, it is questionable, given that Imazighen expansion in northwest Africa is dated even more recently than the upper end 8 kya time frame—that expansion dates to ca. 2.3 kya or so. The point is, although some find it tempting to associate the contemporary Imazighen with these EpiPaleolithic and Neolithic era northwest African specimens, available data suggest otherwise.

Speaking of DNA, skin pigmentation analysis suggest that "west Eurasian" contribution likely explains the coastal northwest African 'outlier' skin tones; granted, it is quite highly likely that coastal northwest African Imazighen would have still undergone *some* level of skin tone lightening, even if they weren't influenced by "west Eurasians", as they moved to the sub-tropical areas, especially in the Atlas mountain areas. This skin lightening event though, would have likely produced—at most—the level of skin tones seen in the likes of the San "Bushmen" and the KhoiSans. The UV radiation levels in the supra-tropical and sub-tropical regions of Africa are simply not as acute as those found in the even more northerly latitudes of Europe, Asia and elsewhere. Recalling on Norton et al (clickable), we have... 

"The frequency of the SLC24A5 111*A allele outside of Europe is largely accounted for by high frequencies in geographically proximate populations in northern Africa, the Middle East, and Pakistan (ranging from 62% to 100%)."

"The relatively high frequencies of the derived allele in Central Asian, Middle Eastern, and North Africa seem likely to be due to gene flow with European populations."

Which also doesn't rule out the probability of North Africans receiving some of their skin tone variations from so-called "Middle Easterners" as well.

Citing Rando et al. 1998 [mtDNA analysis of Northwest African populations reveals genetic exchanges with European, Near Eastern and sub-Saharan populations] along the way,...

Here is a theory: Shortly after their emergence ca. 8 ky ago or so, nomadic pastoralist Imazighen groups dispersed from where they emerged in eastern Sahara, likely in the region straddling Egypt and Sudan, and moved northward [and also possibly westward in the Sahara]. Here, they would come into contact with arriving Neolithic groups from the so-called Near East, who would have also included E-M78* carriers [along with Hg J carriers], which made its way to the “Near East” at an earlier time frame. Being nomadic, these E-M78* and E-M81 Imazighen carriers would have likely been male-biased; however, their dispersal may have included notably Hg M1 carriers from their point of origin, amongst other common L type mtDNA lineages common in north Africa. The incoming Hg J and returning Hg E carriers would have been accommodated by “Eurasian” tagged mtDNA markers that are generally common to Europeans and “Near Easterners”, along with those more commonly found in the “Near East”. These would have presumably included some, if not somewhat limited, European mtDNA markers radiated from Last Glacial Maximum refugium centers in the so-called Near East, likely radiated from the likes of Anatolia. The following might prove to be insightful, notwithstanding outdated constructs that the authors apply in the course of their analysis... 

A great number of the 99 L3E sequences in our sample from the Berbers and other Moroccans, West-Saharans, and Mauritanians seem to be of European descent in view of the numerous matches (more than one fourth) with European but not Near Eastern sequences. The average transitional distance to the nearest neighbours in the European/Near Eastern mtDNA pool is as low as .4, which would correspond to an age of 8000 years. The same figure is also obtained for the L3 sequences from the Algerian Berbers (Corte-Real et al. 1996)...

Some further Near Eastern mtDNA lineages, more similar to extant European lineages, might have come along from the Near East with the (or some) ancestors of the Iberomaurusians, but the bulk of them probably arrived in North Africa with the posterior Mesolithic and Neolithic waves. There is thus a caveat with the European appearance of North African mtDNAs: the same lineage types that came from the Near East and dispersed along the southern Mediterranean littoral around the Last Glacial Maximum (possibly spreading the Gravettian cultures) or after the Younger Dryas (bringing the Neolithic) may also have taken the northern route along the Mediterranean sea. It is therefore difficult to establish at present a clear cut between European and Near Eastern mitochondrial lineages. Nevertheless, there is strong evidence for some European genetic input into North Africa, as for example testified by Haplogroups U5 (Richards et al. 1998) and V (Vandals, Portuguese and Spanish colonization).

The Neolithic hypothesis above seems like the more plausible scenario. And to exemplify the difficulty grappling researchers in unwinding the very complex history of the north African Imazighen,... 


In summary, the mitochondrial landscape of Northwest Africa appears to be quite complex, and cannot be studied in isolation from the European, Near Eastern or sub-Saharan mitochondrial background. Population affinity diagrams reflect essentially the north-south gradient, which is evident from cluster compositions, whereas sequence comparisons employing the mtDNA database reveal the traces in Northwest Africa of (1) Paleolithic settlement(s) before the Last Glacial Maximum, (2) Neolithic waves, and (3) migrations of northern Europeans (and possibly others, such as Phoenicians, Romans, Arabs, and Iberians) in historical times.

These multiregional influences may explain the partially conflicting interpretations of North African data, which emphasize indigenous development and European/West Asian affinity (Irish, 1197, 1998) and a clear relationship to Iberians in particular (Arnaiz-Villena et al. 1995) or disclaim specific relationships to Iberians (Comas et al. 1998) and significant (Neolithic) demic diffusion from the Near East (Barbujani et al. 1994; Bosch, et al. 1997). 


These same Neolithic groups would have found their way to southeast Europe and onto islands therein, like Crete. However, because the nomadic Imazighen groups now situated in the coastal areas of northeast Africa were male-biased and with small effective population size, their mixing with the females that came along the Neolithic groups would have given the appearance of substantial intermixing. However, these nomadic pastoralist Imazighen groups would have not been the type that would have allowed arriving Neolithic groups to dominate them. So, it would appear that instead, the Neolithic elements who intermixed with them, adopted the languages and other aspects of the nomadic Imazighen groups, while their Neolithic traditions continued to stay with them. Consequently, the nomadic Imazighen groups too would be influenced by those traditions, resulting in settlement moves amongst them, like those near the oasis on the western desert of the Nile Valley. This is where they’d have likely made initial efforts to settle before moving to the far western areas. By the bronze age Holocene period, it would appear that some coastal North Africans had spilled over to southeast European areas, with Crete being an example of that. Other Imazighen nomads spread through the length of the Sahara, likely mixing with other groups therein; and again, being male-biased, they would have picked up mtDNA gene pools of those other groups. This would explain the gradient that authors like Rando et al. observed: 

The mitochondrial data of the Northwest African populations (Berber from Morocco and Algeria, Moroccans, West-Saharans, Mauritanians, Tuareg) show a mosaic composition of mtDNA types, with a pronounced gradient of sub-Saharan lineages from north to south: at the one extreme, the Berbers from Morocco have a predominantly European (Iberian) affinity, while at the other extreme, the Tuareg are closely related to sub-Saharan West Africans as represented by several Senegalese groups in this study, whereas the West-Saharans and Mauritanians are somewhat intermediate. It is remarkable that the Tuareg bear little mitochondrial resemblance to the Berber populations, although they speak a Berber language

Hg U6 would have invariably been spread across the Sahara, with relative frequency peaks in the western end of it. At any rate, subsequent intrusions into north Africa, e.g. the likes of Phoenicians, the Greco-Romans or the Vandals, would have likely left a rather limited genetic imprint only in centers of foreign administration. It is quite plausible that much of the European-specific maternal lineages came around the historic periods after those epochs, as perhaps best indicated in one of the extracts above, when the author said: "(3) migrations of northern Europeans (and possibly others, such as Phoenicians, Romans, Arabs, and Iberians) in historical times." On the other hand, when the authors said, "sequence comparisons employing the mtDNA database reveal the traces in Northwest Africa of (1) Paleolithic settlement(s) before the Last Glacial Maximum", they were likely alluding to the likes of the autochthonous north African marker of U6, which at any rate, generally comprise a relatively smaller portion of the Imazighen mtDNA gene pool. It is not clear if much earlier contacts with the likes of Cretans would have contributed to Imazighen gene pool in a substantial way, but it’s certainly possible that some degree of genetic exchange with elements therein had resulted in a portion of mtDNA gene pool spilling into north Africa, perhaps by groups returning with African ancestry. Anyway, this could very well also have contributed to the frequency of seemingly European-specific mtDNA. Contact between Cretan inhabitants and north Africans have been spoken about on many occasions, and even implicated in images of antiquity, like the example below:


The characters with frizzy-looking hair—although with the resolution of the image above, it is rather difficult to ascertain—are said to be north Africans. Other images from the Minoans seem to invoke a considerably heterogenous or "mixed" people; the following are photographs of images on Minoan sarcophagi...


Sarcophagus portion #1:

 

Sarcophagus portion #1 blown up below:




 

Sarcophagus portion #2 blown up below:



In ancient Egyptian artwork:

In ancient Egyptian art, the first group to their western desert—in an area now dominated by Imazighen speaking populations—that *tentatively appears on their records from the predynastic era onwards, are the "Tjehenu/Tehenu"; these people were generally painted in dark hue as the Egyptians themselves were. In the old Dynastic era, one comes across another group of people in the western desert area of the Nile Valley; they were presumably referred to as the "Tjamahu/Tamahu". These latter group of people were generally depicted in the light-skin tone, in a manner not different from the Aamu, generally known by many as "Asiatics". The "Tehenu" were presumably located in the coastal areas on the western desert region, while the "Tamahou" were presumably located in the more southward areas of the western desert. The latter were generally depicted sporting interesting body tattoos, and feather head gear. There are also other groups attested to in the western desert areas; namely the "Meshwesh/Mashawash" and the "Libu/Lebu (Ribu/Rebu)", notably mentioned in the New Kingdom era [see Merneptah stele for example], in the Rameside period. Any group here or any combination of these groups may have been ancestors of the contemporary north African Imazighen. Below, is a repro of a wall relief depicting what appears to be a "Meshwesh" figure under captive, and other figures from the western desert areas, possibly the "Tjamahu" (Tamahu/Tamahou)...


 

A curious feature though about the Minoan art, is the seeming consistent [though not necessarily exclusively] depictions of the male figures in dark hue, with some being even in plain black tone; this seems to be the case in the ancient Egyptian example below, and the Minoan painted counterpart underneath that...





Below, is an occasion showing individuals in plain black hue...


Relaxing on visual aids, and resuming our theory at hand...


With substantial gene flow from European maternal gene pool in the historic period, it’s likely that some of the older Eurasian mtDNA markers may have experienced unfavorable genetic drift, lowering their relative frequency. Likewise, genetic drift may have worked favorably for the more historic European markers from the Iberian peninsula. Though not exclusively, the following examples of historic events must have surely had their own role to play, in contributing to coastal northwest African gene pool,...
 
Trafficking of women from the other side of the Mediterranean sea as slaves surely must have left its own mark. Then there were also sudden waves of migration to the north African coast during the fall of direct northwest African rule in the Iberian peninsula; no doubt families who reached the north African coast had left some genetic imprint therein. And of course, again, genetic drift has its own role to play in all this.


All that aside, a look at samplings so far undertaken in coastal northwest Africa suggests that these have generally relied on sampling small, scattered populations [see Cherni et al. 2005], giving fragmented or incomplete picture of northwest African maternal gene pool structure.
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*References:

— As noted in the paragraphs.

'*' corresponds to record that was/is taken into consideration with regards to the Tjehenu/Tehenu. For instance, the "Tehenu" Palette was subsequently discussed here: The So-called Tehenu Palette