People of European and Asian descent today retain Neanderthal DNA that may affect their hair, skin, fertility, predisposition to certain diseases and possibly other characteristics, a new study in the journal Nature suggests.
The genetic material inherited from Neanderthals combined with that of humans when the two species interbred 40,000 to 80,000 years ago, the study holds. The research further supports that indigenous Africans possess little or no Neanderthal DNA because their ancestors did not breed with Neanderthals, which lived in Europe and Asia.
It now appears that mating between the two species was much more prevalent than was previously suspected.
Some genetic mutations introduced by Neanderthals were not beneficial to humans. Neanderthals' contribution to modern DNA was partially removed by natural selection over time.
"Given the large amount of Neanderthal alleles (gene variants) that were swept away by selection, we think that there was a larger fraction of Neanderthal ancestry initially," lead author Sriram Sankararaman explained to Discovery News, adding that "we think that this ancestry was reduced by a third."
Sankararaman, a post-doctoral researcher at Harvard Medical School's Department of Genetics, co-authored the paper with leading evolutionary geneticists, such as Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology and Harvard's David Reich.
The researchers analyzed genetic variants in 846 people of non-African heritage, 176 people from sub-Saharan Africa and a 50,000-year-old Neanderthal.
The clearest indicator that a gene variant came from a Neanderthal was if the variant appeared in some non-Africans and the Neanderthal, but not in the sub-Saharan Africans.
Levels of Neanderthal ancestry differ in European and Asian groups, according to the study. Han Chinese people in Beijing, for example, have the most such ancestry while Puerto Ricans have the least.