Competing Hypotheses
The multiregional hypothesis, initially proposed by Milford Wolpoff, holds that the evolution of humans from H. erectus at the beginning of the Pleistocene 1.8 million years BP has been within a single, continuous worldwide population. Proponents of multiregional origin reject the assumption of an infertility barrier between ancient Eurasian and African populations of Homo. Multiregional proponents point to the fossil record and genetic evidence in chromosomal DNA. One study suggested that at least 5% of the human modern gene pool can be attributed to ancient admixture, which in Europe would be from the Neanderthals. But the study also suggests that there may be other reasons why humans and Neanderthals share ancient genetic lineages.
The strong form of the theory has been further challenged by recent genetic discoveries regarding the non-Homo sapiens Denisova hominin, known from only one location in Siberia. Denisovan DNA was found to share 4–6% genetic affinities with modern Melanesians, but not with other extant groups, making hybridisation in Africa very unlikely in this case. Others have argued that even Denisova admixture strongly supports a single dispersal of modern humans from Africa, but a dispersal followed by two archaic admixture events: one with Neanderthals outside Africa and a second admixture event with Denisovans which has only been evidenced in New Guinea.
Other hypotheses see the emergence of Homo erectus outside Africa (in Eurasia) and then returning to colonize that continent from which the ancestors of H. erectus originated.
Read more about this topic: Recent African Origin Of Modern Humans
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