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The historical spread of A rabian P astoralists to the eastern A frican S ahel evidenced by the lactase persistence −13,915*G allele and mitochondrial DNA
Author(s) -
Priehodová Edita,
Austerlitz Frédéric,
Čížková Martina,
Mokhtar Mohammed G.,
Poloni Estella S.,
Černý Viktor
Publication year - 2017
Publication title -
american journal of human biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.559
H-Index - 81
eISSN - 1520-6300
pISSN - 1042-0533
DOI - 10.1002/ajhb.22950
Subject(s) - haplotype , allele , persistence (discontinuity) , allele frequency , mitochondrial dna , genetics , biology , geography , demography , evolutionary biology , gene , geotechnical engineering , sociology , engineering
Objectives Thanks to the ability to digest lactose, Arabian nomads had become less dependent upon their sedentary neighbors and some of these populations spread to Africa. When and by which route they migrated to their current locations have previously been addressed only by historical and archaeological data. Methods To address the question of Arab expansion into Africa, we collected samples from several Arabic populations, especially the Baggara in Chad and Sudan. We analyzed mutations associated with lactase persistence and reconstructed the surrounding haplotypes defined by SNP polymorphisms. We also sequenced their mitochondrial DNA to investigate relative proportions of sub‐Saharan and Eurasian origins. Results We estimated the expansion age of the −13,915*G mutation in four different Arabian datasets. The oldest age was identified in Yemen (1,356–1,799 ya) and the youngest in a Sudanese group of Rashaayda Arabs (219–312 ya). We also found a negative correlation between the frequency of the −13,915*G allele and the frequency of sub‐Saharan mtDNA haplotypes. Conclusions Even if the age of the most recent common ancestor of −13,915*G is ∼4 ka as shown in a previous study, our results suggest that its spread to Africa was more recent, which is consistent with the migrations of Arabic tribes. Because the incidence of sub‐Saharan mtDNA haplotypes is negatively correlated with the occurrence of −13,915*G, we suggest that the decrease of its frequency in Africa has been caused by progressive admixture of the Arabian nomads with sub‐Saharan populations.