Genetic studies and fossil evidence show that archaic Homo sapiens evolved to anatomically modern humans solely in Africa, between 200,000 and 60,000 years ago,[2] that members of one branch of Homo sapiens left Africa by between 125,000 and 60,000 years ago, and that over time these humans replaced earlier human populations such as Neanderthals and Homo erectus.[3] The date of the earliest successful out of Africa migration (earliest migrants with living descendants) has generally been placed at 60,000 years ago as suggested by genetics, although migration out of the continent may have taken place as early as 125,000 years ago according to Arabian archaeology finds of tools in the region.[4] A 2013 paper reported that a previously unknown lineage had been found, which pushed the estimated date for the most recent common ancestor (Y-MRCA) back to 338,000 years ago.[5] The recent single origin of modern humans in East Africa is the predominant position held within the scientific community.[6][7][8][9][10] There are differing theories on whether there was a single exodus or several. A multiple dispersal model involves the Southern Dispersal theory,[11] which has gained support in recent years from genetic, linguistic and archaeological evidence. A growing number of researchers also suspect that long-neglected North Africa was the original home of the modern humans who first trekked out of the continent.[12][13][14] The major competing hypothesis is the multiregional origin of modern humans, which envisions a wave of Homo sapiens migrating earlier from Africa and interbreeding with local Homo erectus populations in multiple regions of the globe. Most multiregionalists still view Africa as a major wellspring of human genetic diversity, but allow a much greater role for hybridization.[15][16] Genetic testing in the last decade has revealed that several now extinct archaic human species may have interbred with modern humans. These species have been claimed to have left their genetic imprint in different regions across the world: Neanderthals in all humans except Sub-Saharan Africans, Denisova hominin in Australasia (for example, Melanesians, Aboriginal Australians and some Negritos) and there could also have been interbreeding between Sub-Saharan Africans and an as-yet-unknown hominin (possibly remnants of the ancient species Homo heidelbergensis). However, the rate of interbreeding was found to be relatively low (1-10%) and other studies have suggested that the presence of Neanderthal or other archaic human genetic markers in modern humans can be attributed to shared ancestral traits originating from a common ancestor 500,000 to 800,000 years ago
Posted on: Thu, 17 Jul 2014 16:57:02 +0000