Neanderthal genes: new data
Ability to survive in cold climates linked to Neanderthal genes
Such conclusions follow from the results of two studies aimed at determining the contribution of Neanderthals to the genome of modern humans, published in the journals Science and Nature.
According to the current hypothesis, Homo sapiens and Neanderthals had a common ancestor who lived in Africa more than half a million years ago. The ancestors of the Neanderthals were the first to leave the African continent and settle Eurasia. After the Cro-Magnons left Africa about a hundred thousand years ago and settled in the territory where Neanderthals already lived, interbreeding took place between the two branches of Homo. Earlier, the decoding of ancient DNA extracted from the skeletal remains of Neanderthals confirmed the fact of crossing of two groups, showing that on average about two percent of the genome of modern people of non-African descent belong to Neanderthal genes, and this proportion varies from person to person. The functions of some of these genes have been partially established. For example, in December 2013, it became known from a publication in Nature that the high risk of developing type 2 diabetes in modern residents of Mexico and Latin America, originating from the indigenous population of these regions, is associated with a genetic mutation inherited from Neanderthals.
New research has revealed for the first time quite significant proportions of Neanderthal DNA sites in the genome of modern humans. Thus, population geneticists from Washington State University Joshua Akey and Benjamin Vernot, whose work Resurrecting Surviving Neandertal Lineages from Modern Human Genomes was published in Science, after analyzing the data of genetic profiles of 665 inhabitants of Europe and East Asia obtained during the international project "1000 Genomes", came to The conclusion is that about one fifth (about 20 percent) of the Neanderthal genome is scattered in them. A group of researchers led by population geneticist David Reich from Harvard School of Medicine, whose work The genomic landscape of Neanderthal ancestry in present-day humans is published in Nature, analyzed the genetic data of 1004 modern humans, estimated this proportion at 40 percent.
Both groups found that the regions of the genome containing a particularly high percentage of Neanderthal alleles are rich in genes that regulate the functions of keratinocytes – epidermal cells that make up most of the outer layer of human skin and are associated with the growth of body hair. This discovery allowed scientists to assume that the genes of Neanderthals, who had already adapted to the cold climate of Eurasia, helped Cro-Magnons survive in unfavorable environmental conditions compared to Africa, which explains the preservation of Neanderthal alleles in the genome. At the same time, both Reich and Eki admit that this hypothesis is speculative and further research is needed to confirm it.
In addition, both groups noted a significant unevenness in the distribution of the "Neanderthal inheritance" across the modern genome. In the modern genome, according to the definition of the Eci, there are "giant holes", that is, areas completely free of Neanderthal genes, which indicates their "washing out" of hybrid offspring during natural selection due to the negative impact on the development of the species. So, the Eci group, for example, found that such a site is a region containing the FOXP2 gene associated with speech function in modern humans.
The discovery of the Reich group was the identification of the fact that among the genes with a high level of expression in the testicles and X chromosome, very few have Neanderthal origin, which may be, by analogy with drosophila, a marker of sterility of male hybrid offspring. "These results may partially explain the presence of regions of the modern genome that are free from the "Neanderthal inheritance", since such alleles are associated with a decrease in male fertility during the transition to the modern genetic background," the authors believe.
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