The fate of Neanderthal genes
Scientists have found out that Neanderthals are gradually "dying out" in our DNA
Neanderthal DNA segments are gradually disappearing from human DNA under the influence of natural selection, which suggests that a second "extinction" awaits Neanderthals, according to an article published in the journal PLOS Genetics (Juric et al., The Strength of Selection against Neanderthal Introgression).
"On average, we have recorded a weak but widespread negative natural selection in relation to Neanderthal genes. Our population has always been larger than Neanderthals, and thanks to this, our species gets rid of harmful variations in genes faster than our "cousins", and this causes the genome to be cleared of their traces. This simple process explains why our "Neanderthal" genes look the way they are represented in our genome today," said Graham Coop from the University of California at Davis (in a press release The Fate of Neanderthal Genes – VM).
The "resurrection" and decoding of the Neanderthal genome, conducted by Svante Paabo and his team in 2009, showed that Neanderthals had contact with our ancestors and left about 2-4% of their genes in our DNA. Some of these genes, as further studies have shown, helped Cro-Magnons adapt to life in the north, giving them powerful immunity and other useful traits.
On the other hand, mathematical simulations built on the basis of this "resurrected" DNA showed that human and Neanderthal crosses should have rarely ended successfully, which forced scientists to look for the causes of this phenomenon. One of the possible reasons for this was considered the degeneration of Neanderthals due to the excessively small size of their population, or their almost complete genetic incompatibility with Cro-Magnons.
Coop and his colleagues from the 23andMe project used America's largest genomic bank to show that the first hypothesis is correct, and explained where the Neanderthal DNA actually "disappeared".
Comparing the "resurrected" Neanderthal DNA and the genomes of modern humans, scientists initially expected to see the following – the rapid disappearance of several Neanderthal variations in genes that were obviously harmful to human survival or simply led to infertility or problems with the development of the embryo. Carriers of such genes had to die more often than other people, which should have been the reason for their disappearance from the Cro-Magnon genomic fund.
But in fact, something else happened – it turned out that it was not individual Neanderthal genes that disappeared, but in fact all their traces in human DNA, only this happened very slowly and gradually.
Such "extinction" of genes means that natural selection worked against the preservation of Neanderthal variations in DNA, probably for the reason that they generally had a negative effect on the "health" of the human population and led to the defeat of their owners in the evolutionary race. This simultaneously speaks in favor of the theory of the degeneration of Neanderthals, and also explains why people today have small traces of their DNA.
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09.11.2016