Washington, DC — "The 'Out of Africa' hypothesis suggests that anatonomically modern humans originated in Africa about 100,000 years ago and then spread outward, and completely replaced local archaic populations outside of Africa," write the scientists in an article in the Friday, May 11 edition of Science, the journal of the American Academy for the Advancement of Science. "This proposition has been supported by genetic evidence and archeological findings."
But the authors go on to note that this theory has been challenged by arguments that modern humans evolved from several different regions. These 'multiregionalists' had, in the past, argued that some Europeans might trace their origins back to Neanderthals. Other scholars have also questioned whether the humanoid fossils found in China and other regions of Asia, such as Peking man and Java man, might indicate Asian origins for part of the population of that continent. The authors report that the theory that Neanderthals might have contributed to the development of modern humans in Europe was disproved by recent DNA analysis that was reported in the journals Nature and Cell.
Until the publication of this article, however, there had been no scientific attempt to prove the African origins of the populations of East Asia. The Out-of-Africa hypothesis argues that although there were archaic populations in Asia before this time, these were all replaced by African-origin humans who are the ancestors of the current population.
To investigate this claim, the authors sampled genetic material from more than 12,000 male individuals from 163 different populations in East Asia to see if they could detect evidence of particular Y chromosome polymorphisms that are known to have originated in Africa between 35,000 and 89,000 years ago.
The conclusions, report the team of scientists, were definitive. "Each of the 12,127 samples typed carried one of the three polymorphisms... No ancient, non-African Y Chromosome was found in the extand East Asian populations," report the authors. "This result indicates that modern humans of African origin completely replaced earlier populations in East Asia."
