Preserved intact
Geneticists have refuted the "washing out" of Neanderthal DNA from the genome of modern humans
Ekaterina Rusakova, N+1
Paleogeneticists have made sure that the percentage of Neanderthal DNA in the genome of Homo sapiens has not changed significantly over the past 45 thousand years. The results of earlier studies showed that the amount of Neanderthal DNA in the Sapiens genome has greatly decreased over the millennia, but the authors of a new article in the Proceedings of the National Academy of Sciences (Petr et al., Limits of long-term selection against Neandertal introgression) they write that they are erroneous, since they did not take into account the transfer of genes between populations of modern people.
About 55 thousand years ago, after Homo sapiens left Africa and ended up in Eurasia, they interbred with Neanderthals living there. As a result, modern inhabitants of the planet, with the exception of Africans, inherited at least 1-2 percent of Neanderthal DNA. The amount of Neanderthal DNA varies greatly in people in different populations. Plus, as several studies have shown, over the past 45 thousand years, its percentage in the genome of modern people has been constantly falling. Perhaps this decrease is evidence that Neanderthal DNA in the genome of modern humans is constantly undergoing negative selection. But formally, no one has yet shown that negative selection can lead to such a strong "leaching" of DNA from the genome.
Researchers from the Max Planck Society Institute for Evolutionary Anthropology, led by Svante Paabo, decided to re-evaluate the percentage of Neanderthal DNA in the genome of modern humans and see if it decreases. Until recently, paleogenetics had access to the only "high-quality" Neanderthal genome, from the remains of a woman who lived in the Altai about 50 thousand years ago. But in 2017, scientists managed to sequence another genome, this time of a Neanderthal woman who lived 65-50 thousand years ago on the territory of modern Croatia. Therefore, Paabo decided to investigate both the Neanderthal genomes and the genomes of modern Africans, inhabitants of Western Eurasia (Europeans and residents of the Middle East). Scientists have created a computer simulation of gene transfer between Neanderthals and inhabitants of Western Eurasia, and gene migration between different African and Eurasian populations.
As a result, it turned out that there has not been a significant decrease in Neanderthal DNA in the genome of modern humans over the past 45 thousand years. As the authors suggest, in other studies where it is shown, gene transfer between populations of Africans and residents of Western Eurasia was not taken into account. However, negative selection of Neanderthal DNA in the Sapiens genome does occur, but less than the results of other studies have shown. Interestingly, the "leaching" of Neanderthal DNA in the sites that regulate protein synthesis is greater than in the sequences directly encoding proteins. Perhaps this indicates that the genome of Neanderthals differed from the genome of Sapiens not in protein-coding sequences, but in regulatory regions of the genome. And therefore regulatory sites were more often subjected to selection.
Earlier, geneticists showed that Neanderthals probably interbred with sapiens twice, the first time after modern humans left Africa, and then after their division into European and Asian populations.
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