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Origins and Genetic Diversity of Pygmy Hunter-Gatherers from Western Central Africa

2009; Elsevier BV; Volume: 19; Issue: 4 Linguagem: Inglês

10.1016/j.cub.2008.12.049

1879-0445

Paul Verdu, Frédéric Austerlitz, Arnaud Estoup, Renaud Vitalis, Myriam Georges, Sylvain Théry, Alain Froment, Sylvie Le Bomin, Antoine Gessain, Jean-Marie Hombert, Lolke van der Veen, Lluís Quintana‐Murci, Serge Bahuchet, Évelyne Heyer,

Indigenous Studies and Ecology

Central Africa is currently peopled by numerous sedentary agriculturalist populations neighboring the largest group of mobile hunter-gatherers, the Pygmies [1Diamond J. Bellwood P. Farmers and their languages: The first expansions.Science. 2003; 300: 597-603Crossref PubMed Scopus (598) Google Scholar, 2Cavalli-Sforza L.L. African Pygmies: An Evaluation of the State of Research. Academic Press, Orlando1986Google Scholar, 3Hewlett B. Cultural diversity among African Pygmies.in: Kent S. Cultural Diversity among Twentieth-Century Foragers: An African Perspective. Cambridge University Press, Cambridge1996: 215-244Google Scholar]. Although archeological remains attest to Homo sapiens' presence in the Congo Basin for at least 30,000 years, the demographic history of these groups, including divergence and admixture, remains widely unknown [4Cavalli-Sforza L.L. Menozzi P. Piazza A. The History and Geography of Human Genes. Princeton University Press, Princeton, NJ1994Google Scholar, 5Mercader J. Under the Canopy. The Archaeology of Tropical Rain Forests. Rutgers University Press, New Brunswick2003Google Scholar, 6Phillipson D.W. African Archaeology. Cambridge University Press, Cambridge2005Crossref Scopus (7) Google Scholar]. Moreover, it is still debated whether common history or convergent adaptation to a forest environment resulted in the short stature characterizing the pygmies [2Cavalli-Sforza L.L. African Pygmies: An Evaluation of the State of Research. Academic Press, Orlando1986Google Scholar, 7Froment A. Adaptation biologique et variation dans l'espèce humaine: Le cas des Pygmées d'Afrique.Bull. Mem. Soc. Anthropol. Paris. 1993; 5: 417-448Crossref Google Scholar]. We genotyped 604 individuals at 28 autosomal tetranucleotide microsatellite loci in 12 nonpygmy and 9 neighboring pygmy populations. We found a high level of genetic heterogeneity among Western Central African pygmies, as well as evidence of heterogeneous levels of asymmetrical gene flow from nonpygmies to pygmies, consistent with the variable sociocultural barriers against intermarriages. Using approximate Bayesian computation (ABC) methods [8Cornuet J.M. Santos F. Beaumont M.A. Robert C.P. Marin J.M. Balding D.J. Guillemaud T. Estoup A. Inferring population history with DIY ABC: A user-friendly approach to Approximate Bayesian Computation.Bioinformatics. 2008; 24: 2713-2719Crossref PubMed Scopus (552) Google Scholar], we compared several historical scenarios. The most likely points toward a unique ancestral pygmy population that diversified ∼2800 years ago, contemporarily with the Neolithic expansion of nonpygmy agriculturalists [9Vansina J. New linguistic evidence and ‘the Bantu expansion’.J. Afr. Hist. 1995; 36: 173-195Crossref Scopus (174) Google Scholar, 10Rexová K. Bastin Y. Frynta D. Cladistic analysis of Bantu languages: A new tree based on combined lexical and grammatical data.Naturwissenschaften. 2006; 93: 189-194Crossref PubMed Scopus (46) Google Scholar]. Our results show that recent isolation, genetic drift, and heterogeneous admixture enabled a rapid and substantial genetic differentiation among Western Central African pygmies. Such an admixture pattern is consistent with the various sociocultural behaviors related to intermariages between pygmies and nonpygmies.