Northeast African Genetic Variation

Angela

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See: Nina Holfelder et al
http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1006976

"Northeast Africa has a long history of human habitation, with fossil-finds from the earliest anatomically modern humans, and housing ancient civilizations. The region is also the gate-way out of Africa, as well as a portal for migration into Africa from Eurasia via the Middle East and the Arabian Peninsula. We investigate the population history of northeast Africa by genotyping ~3.9 million SNPs in 221 individuals from 18 populations sampled in Sudan and South Sudan and combine this data with published genome-wide data from surrounding areas. We find a strong genetic divide between the populations from the northeastern parts of the region (Nubians, central Arab populations, and the Beja) and populations towards the west and south (Nilotes, Darfur and Kordofan populations). This differentiation is mainly caused by a large Eurasian ancestry component of the northeast populations likely driven by migration of Middle Eastern groups followed by admixture that affected the local populations in a north-to-south succession of events. Genetic evidence points to an early admixture event in the Nubians, concurrent with historical contact between North Sudanese and Arab groups. We estimate the admixture in current-day Sudanese Arab populations to about 700 years ago, coinciding with the fall of Dongola in 1315/1316 AD, a wave of admixture that reached the Darfurian/Kordofanian populations some 400–200 years ago. In contrast to the northeastern populations, the current-day Nilotic populations from the south of the region display little or no admixture from Eurasian groups indicating long-term isolation and population continuity in these areas of northeast Africa.

Author summary

"Northeast Africa has geographic and historical links to Eurasia via the Middle East and the Arabian Peninsula, but the demographic history of the region itself has been more elusive. We investigate genomic diversity of northeast African populations and found a clear bimodal distribution of variation, correlated with geography, and likely driven by Eurasian admixture in the wake of migrations along the Nile. This admixture process largely coincides with the time of the Arab conquest, spreading in a southbound direction along the Nile and the Blue Nile. Nilotic populations occupying the region around the White Nile show long-term continuity, genetic isolation and genetic links to ancestral East African people. Compared to current times, groups that are ancestral to the current-day Nilotes likely inhabited a larger area of northeast Africa prior to the migration from the Middle East as their ancestry component can still be found in a large area. Our findings reveal the genetic history of Sudanese and South Sudanese people, broaden our knowledge on demographic history of humans, and quantify the impact of large-scale historic migration events in northeast Africa."


 

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