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Genomic Ancestry of North Africans Supports Back-to-Africa Migrations Brenna M. Henn
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[QUOTE]Originally posted by the lioness,: [QB] ^^^^^^ [IMG]http://picturestack.com/495/386/gGePicture3KKB.png[/IMG] ________________________________________________ http://www.ncbi.nlm.nih.gov/pubmed/20234393 [IMG]http://picturestack.com/495/386/k0iPicture4GRN.png[/IMG] The above-mentioned studies have thus revealed a dual influence in the genetic make-up of this African people. In this study, we provide new mtDNA and Y chromosome data sets of three unrelated Tuareg groups from three different countries (Niger, Mali and Burkina Faso). At the same time, we try to unravel the questions of their genetic origin, the mutual relationships among their sub-populations as well as possible links to neighbouring populations. The genetic heritage of the Tuareg population is analysed within the context of the West Eurasian versus sub-Saharan contributions to their gene pool. A total of 48% of the mtDNA haplotypes observed in the Tuareg populations could be ascribed to sub-Saharan haplogroups. Another 39%, however, were of West Eurasian ancestry (non-L types in Table 1), which is a substantial proportion considering the sub-Saharan geographical location. In fact, it has been observed that in typical North African populations there is a gradient of increasing frequency of West Eurasian lineages ranging from around 5075% in the northernmost locations.34 The Tuareg's neighbours, however, have a markedly smaller proportion of West Eurasian haplotypes (22% in Western Chad Arabs, 8% in Shuwa Arabs from North-eastern Nigeria, 7% in the Buduma from South-eastern Niger and 6% in the Kanuri from North-eastern Nigeria).35 The remaining 13% of Tuareg haplotypes belong to the typical East African haplogroup M1. Furthermore, we noticed some differences in the distribution of West Eurasian mtDNA haplogroups between Tuareg groups. Most of the West Eurasian haplogroups (30 out of 35 sequences, amounting to 6 out of 9 HVS-I haplotypes) and the East African M1 (11 out of 12 sequences but amounting to only 2 out of 3 HVS-I haplotypes) are observed in the two Tuareg populations TGos and TGor located within the bend of the Niger. Tuareg from the Republic of Niger, TTan, have much higher proportion of sub-Saharan (81%) haplogroups than of West Eurasian (16%) and East African (3%) ones. These differences in haplogroup distribution led to statistically significant genetic distances when comparing HVS-I haplotypes between Tuareg from Mali (TGos) with those from the Republic of Niger (TTan) (FST=0.048; unadjusted P-value=0.009), as well as Tuareg from Burkina Faso (TGor) with those from the Republic of Niger (TTan) (FST=0.064; unadjusted P-value=0.000), whereas Tuareg from Mali (TGos) and from Burkina Faso (TGor) are not statistically different (FST=0.012; unadjusted P-value=0.234). Similarly, analysis of MDS based on FST distances and using a large database of West Eurasian and African mtDNA sequences has shown a very good separation of the sub-Saharan and West Eurasian-North African gene pools (Figure 2). Only some East African populations are closer to the West Eurasian samples, respectively, to the North African populations analysed here. This picture is a good representation of FST values as the normalized raw stress is very low (0.01165). However, the analysed Tuareg populations are divided between two gene pools: like the sample from Libya,5 the groups located within the bend of Niger (TGor and TGos) fall into the West Eurasian gene pool, whereas the Tuareg from the Republic of Niger (TTan) and the Tuareg sample from the Watson's data set3, 4 are permeated by the sub-Saharan mtDNA gene pool. The West Eurasian component observed in the Tuareg is highly interesting. A major proportion (94%) could be allocated to haplogroups H1, H3 and V, West Eurasian lineages of Iberian origin that spread to Europe7, 10, 17, 26, 29, 36 and most probably North Africa30, 31 with the improvement of the climatic conditions after the retreat of the ice sheets 1500013000 years ago. The interpolation maps of these lineages across North Africa and Europe (Supplementary Material SM5) clearly place the Tuareg population in the path of the southern African edge of post-Last Glacial Maximum expansions. The H1 haplogroup (Supplementary Material SM5A and SM5B, with and without the outlier Norway, respectively) is as frequent in our southern Tuareg groups as in Libya and the centre of the dispersion within the Iberian Peninsula. The H3 haplogroup is almost vestigial in Tuareg (Supplementary Material SM5C), having the highest observed frequencies outside of Iberia in Algeria and Tunisia. Again for haplogroup V, Tuareg present frequencies as high as in the Basque country (Supplementary Material SM5D) [/QB][/QUOTE]
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