At least one lineage of early humans migrated out of Africa into Asia and Europe, likely mated with Neanderthals during their travels, and then journeyed back to Africa for better weather, new DNA evidence suggests.
The findings, published in the journal Scientific Reports, help to explain why native North Africans today are genetically related to people from Europe and Asia, in addition to other Africans. It also offers strong evidence that "Out of Africa" was not a one-way trip for some human lineages that traveled back to North Africa starting around 45,000 years ago.
At the center of it all is a prehistoric individual named the Pestera Muierii Woman, or PM-1 for short. Her skull, dated to 35,000 years ago, was unearthed in the Pestera Muierii cave of Romania.
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Her "mosaic of modern human and archaic Neanderthal morphological (physical) features may be the result of Neanderthal interbreeding," senior author Concepcion de-la-Rúa of the University of the Basque Country's Department of Genetics told Discovery News.
de-la-Rúa and her colleagues extracted DNA from two of the woman's teeth and determined the ancient female's mitochondrial genome (mitogenome), i.e., a complete set of particular genes that are passed down from mothers to their daughters. The researchers noted that one component of this set, named "U6 basal," had not previously been identified in any ancient or existent humans.
Investigating the U6 mystery further, the scientists discovered that an evolved version of U6 does indeed exist today.
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"U6 is found predominantly in present-day North African populations," de-la-Rúa said, adding that the form in Pestera Muierii Woman dates to a much earlier time and therefore is "basal," or at the root of U6's emergence.
Putting the clues together, the researchers believe that the woman's Homo sapiens ancestors migrated out of Africa and, at some point, mated with one or more Neanderthals, since she appears to have been part Neanderthal. This is actually true of all people of Asian and European heritage today, who retain Neanderthal DNA in their genomes.
Migration or Vacation? Humans Left Africa, Then Returned: Page 2