The Genetic Structure and History of Africans and African Americans

Department of Biology, University of Maryland, College Park, MD 20742, USA.
Science (Impact Factor: 33.61). 06/2009; 324(5930):1035-44. DOI: 10.1126/science.1172257
Source: PubMed


Africa is the source of all modern humans, but characterization of genetic variation and of relationships among populations
across the continent has been enigmatic. We studied 121 African populations, four African American populations, and 60 non-African
populations for patterns of variation at 1327 nuclear microsatellite and insertion/deletion markers. We identified 14 ancestral
population clusters in Africa that correlate with self-described ethnicity and shared cultural and/or linguistic properties.
We observed high levels of mixed ancestry in most populations, reflecting historical migration events across the continent.
Our data also provide evidence for shared ancestry among geographically diverse hunter-gatherer populations (Khoesan speakers
and Pygmies). The ancestry of African Americans is predominantly from Niger-Kordofanian (~71%), European (~13%), and other
African (~8%) populations, although admixture levels varied considerably among individuals. This study helps tease apart the
complex evolutionary history of Africans and African Americans, aiding both anthropological and genetic epidemiologic studies.

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    • "There is a growing literature arguing that ethno-linguistic and genetic diversity correlate. Tishkoff et al. (2009) have identified 14 African ancestral gene clusters in populations that correlate with self-described ethnicity and a shared cultural-linguistic background (cf Campbell & Tishkoff, 2008). Ashraf and Galor (2013) "
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    • "Consanguinity, ascertained by pedigree analysis, is observed in 5.7% of the population, most of which is found in the northern Sahelian regions of Cameroon where the Arabo- Muslim influence is stronger (Wonkam et al. 2013b). Because of its central location on the continent, Cameroonians cultural, linguistic, and genetic diversity mimics that of various ethno-linguistic groups found in Africa (Tishkoff et al., 2009). It is therefore anticipated that genetic studies in this population might reveal important insights to other African populations. "
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    • "Using nuclear nonrepetitive DNA sequences they found an extent of genetic differentiation among subspecies comparable to that seen among human populations. They speculated that a more geographically-informed sampling would reveal a pattern of isolation by distance (IBD) as has been described for within-continental variation in humans (Serre and P€ a€ abo, 2004; Rosenberg et al., 2005; Lao et al., 2008; Tishkoff et al., 2009). IBD describes the situation in which individuals found closer together are genetically more similar than those further apart, and it arises when the distance an individual may disperse is smaller than the continuous distribution of the organism (Wright, 1943). "
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