I KEEP TELLING YOU ALL NON AFRICANS ARE NEANDERTHAL HYBIDS NOW HERE IS MORE PROOF Genetic evidence for archaic admixture in Africa with ancient African hominins and the later admixture of Africans (AMH) and Neanderthals in eurasia. Department of Ecology and Evolutionary Biology, Institute for Human Genetics, University of California. Edited by Ofer Bar-Yosef, Harvard University, Cambridge, MA, and approved July 27, 2011 (received for review June 13, 2011) Abstract A long-debated question concerns the fate of archaic forms of the genus Homo: did they go extinct without interbreeding with anatomically modern humans (Africans), or are their genes present in contemporary populations? This question is typically focused on the genetic contribution of archaic forms outside of Africa. Here we use DNA sequence data gathered from 61 noncoding autosomal regions in a sample of three sub-Saharan African populations (Mandenka, Biaka, and San) to test models of African archaic admixture. We use two complementary approximate-likelihood approaches and a model of human evolution that involves recent population structure, with and without gene flow from an archaic population. Extensive simulation results reject the null model of no admixture and allow us to infer that contemporary African populations contain a small proportion of genetic material (≈2%) that introgressed ≈35 kya from an archaic population that split from the ancestors of anatomically modern humans ≈700 kya. Three candidate regions showing deep haplotype divergence, unusual patterns of linkage disequilibrium, and small basal clade size are identified and the distributions of introgressive haplotypes surveyed in a sample of populations from across sub-Saharan Africa. One candidate locus with an unusual segment of DNA that extends for >31 kb on chromosome 4 seems to have introgressed into modern Africans from a now-extinct taxon that may have lived in central Africa. Taken together our results suggest that polymorphisms present in extant populations introgressed via relatively recent interbreeding with hominin forms that diverged from the ancestors of modern humans in the Lower-Middle Pleistocene. H. sapiens hybridization It is now well accepted that anatomically modern humans (AMH) originated in Africa and eventually dispersed to all inhabited parts of the world. What is not known is the extent to which the ancestral population that gave rise to AMH was genetically isolated, and whether archaic hominins made a genetic contribution to the modern human gene pool. Answering these questions has important implications for understanding the way in which adaptations associated with modern traits were assembled in the human genome: do the genes of AMH descend exclusively from a single isolated population, or do our genes descend from divergent ancestors that occupied different ecological niches over a wider geographical range across and outside of the African Pleistocene landscape? The introgression debate is typically framed in terms of interbreeding between AMH and Neandertals in Europe or other archaic forms in Asia. The opportunity for such hybridizations may have existed between 90 and 30 kya, after early modern humans dispersed from Africa and before archaic forms went extinct in Eurasia. Recent genome-level analyses of ancient DNA suggest that a small amount of gene flow did occur from Neandertals into the ancestors of non-Africans sometime after AMH left Africa.
Posted on: Sun, 08 Sep 2013 01:15:12 +0000
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