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Diversification of present-day non-African populations and anatomically modern humans
By now many studies in different fields have led to the conclusion that present-day non-African population is the result of the diversification in several different lineages of an ancestral, well-structured, metapopulation which was the protagonist of an out-of-Africa expansion, in which it carried a subset of African genetic heritage. In this context, the analysis of ancient DNA was fundamental to test already formulated hypothesis and to provide new insights. First, it has allowed to narrow the timing and the structure of this diversification phenomenon by providing the calibration of the autosomal and mithocondrial mutation rate. Then, admixture analysis has demonstrated that many independent gene flow events, at least two, have occurred between ancestors of modern humans and archaic humans, such as Neanderhal and Denisovan populations, testifying the “leaky replacement” model of Eurasian human population history. According to all these data, the human divergence of the non-African lineages occurred around 45,000 – 55,00 BP. Besides that, in many cases ancient DNA has allowed to track historical processes which have led, in time, to the actual population genetic structure, which would have been difficult to do counting only on the analysis of present-day genomes. Among these still unresolved questions, some of the most studied are the identity of the first inhabitants of the Americas, the peopling of Europe and the origin of agriculture in Europe.