An alternative to extinction is that Neanderthals were absorbed into theCro-Magnon population byinterbreeding. This would be counter to strict versions of the Recent African Origin, since it would imply that at least part of the genome of Europeans would descend from Neanderthals.
Hans Peder Steensby, while strongly emphasising that all modern humans are of mixed origins, proposed the interbreeding hypothesis in 1907, in the article Race studies in Denmark.[132] He held that this would best fit current observations, and attacked the widespread idea that Neanderthals were ape-like or inferior.
The most vocal proponent of the hybridization hypothesis is Erik Trinkausof Washington University.[133] Trinkaus claims various fossils as products of hybridized populations, including thechild of Lagar Velho, a skeleton found atLagar Velho in Portugal.[134][135] In a 2006 publication co-authored by Trinkaus, the fossils found in 1952 in the cave of Peștera Muierii, Romania, are likewise claimed as descendants of previously hybridized populations.[136]
Genetic research has asserted that some admixture took place.[137] The genomes of all non-Africans include portions that are of Neanderthal origin,[138][139] due to interbreeding between Neanderthals and the ancestors of Eurasians in Northern Africa or the Middle East prior to their spread. Rather than absorption of the Neanderthal population, this gene flow appears to have been of limited duration and limited extent. An estimated 1 to 4 percent of the DNA in Europeans and Asians (French, Chinese and Papuaprobands) is non-modern, and shared with ancient Neanderthal DNA rather than with Sub-Saharan Africans (Yoruba people and San probands).[59] Ötzi the iceman, Europe's oldest preserved mummy, was found to possess an even higher percentage of Neanderthal ancestry.[140] Recent findings suggest there may be even more Neanderthal genes in non-African humans than previously expected: approximately 20% of the Neanderthal gene pool was present in a broad sampling of non-African individuals, though each individual's genome was on average only 2% Neanderthal.[141]
More recent genetic studies seem to suggest that modern humans may have mated with "at least two groups" ofancient humans: Neanderthals andDenisovans.[142] Some researchers suggest admixture of 3.4–7.9% in modern humans of non-African ancestry, rejecting the hypothesis of ancestral population structure.[143]Detractors have argued and continue to argue that the signal of Neanderthal interbreeding may be due to ancient African substructure, meaning that the similarity is only a remnant of a common ancestor of both Neanderthals and modern humans and not the result of interbreeding.[144][145] John D. Hawkshas argued that the genetic similarity to Neanderthals may indeed be the result of both structure and interbreeding, as opposed to just one or the other.[146]
While modern humans share somenuclear DNA with the extinct Neanderthals, the two species do not share any mitochondrial DNA,[54] which in primates is always maternally transmitted. This observation has prompted the hypothesis that whereas female humans interbreeding with male Neanderthals were able to generate fertile offspring, the progeny of female Neanderthals who mated with male humans were either rare, absent or sterile.[147] However, some researchers have argued that there is evidence of possible interbreeding between female Neanderthals and male modern humans.[148][149]
No comments:
Post a Comment