Neanderthals first appeared in Europe around 300 000 years ago and were replaced by anatomically modern Humans between 45 000 and 35 000 years ago. Genetic studies if modern Human populations show that almost all non-Africans have traces of Neanderthal DNA within their genomes, but contrary to expectations, the highest proportion of Neanderthal DNA is found not in Europeans, who have relatively low levels, but among East Asians and Native Americans.
In a paper published in the journal Nature on 13 August 2015, a team of scientists led by Qiaomei Fu of the Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, the Department of Genetics at Harvard Medical School and the Department of Evolutionary Genetics at the Max Planck Institute for Evolutionary Anthropology, discuss the results of a genetic study carried out on DNA extracted from a 37 000-42 000 year old Human mandible found at the Peştera eu Oase archaeological site in Romania in 2002.
The mandible, identified as specimen Oase 1, is considered to show a mixture of morphological traits intermediate between those of modern Humans and Neanderthals, suggesting a mixed ancestry (modern Humans were well established outside of Europe by this time, ruling out the alternative scenario, that the intermediate features represent an individual evolving from Neanderthal ancestors towards modern descendants). A second specimen recovered from the same site, a cranium identified as Oase 2, also shows an admixture of Neanderthal and modern Human traits, supporting the idea of a population with mixed ancestry.
The Peştera eu Oase mandible, from which the DNA was extracted. Max Plank Institute for Evolutionary Anthropology.
Analysis of Oase 1’s mitochondrial DNA (DNA found in mitochondria, organelles outside the cell nucleus, which is only inherited through the female line, without input from male ancestors) suggests that the individual shared a common ancestor with modern Eurasians who lived around 36 330 years ago. The individual was found to be male, having both X and Y chromosomes, with the Y chromosome belonging to the F haplogroup (expand), the most common group for modern Eurasions.
The Oase 1 individual was found to share considerably more DNA with modern East Asians and Native Americans than with modern Europeans. This is initially counterintuitive, given that the specimen was found in Europe, but fits well with the current view that modern Europeans are descended primarily from invaders that arrived in the area with the Neolithic Agricultural Revolution (i.e. the introduction of agriculture to Europe).
The DNA of modern Europeans was then replaced with DNA taken from Palaeolithic and Mesolithic individuals. The Oase 1 individual was found to be equally closely related to these ancient Europeans as to modern East Asians and Native Americans, suggesting that he was a member of a population that contributed relatively little genetic material to later European populations.
Finally Fu et al. compared the DNA of the Oase 1 individual to that of DNA extracted from Neanderthal specimens. This was done by comparing the genomes Dinka people from Sudan (who are thought to have little or no Neanderthal ancestry) to that of Neanderthals in order to find alleles that distinguish the two groups (an allele is one of two or more different genes that can occur at a gene locus, for example different alleles for blue or brown eyes may be fund at the gene locus for eye colour in Humans). Fu et al. were able to find ~1.7 million alleles which differentiated the Neanderthals from the Dinka people, of which 78 055 could be fund in DNA fragments recovered from the Oase 1 individual. Of these alleles, between 6 and 9% were shared with the Neanderthals; this is at least three times the highest level of Neanderthal DNA found in any modern population, and considerably higher than that found in a number of previously examined ancient individuals from Europe and Russia.
Fu et al. further noted that much of this Neanderthal DNA was arranged into discrete segments, suggesting a recent Neanderthal ancestor, probably only 4-6 generations (i.e. less than 200 years) before the Oase I individual lived. Removal of these longer DNA segments from the study still left the individual with 4.8% Neanderthal DNA, suggesting earlier admixture between the two populations had also occurred,
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