Chromosome exchange
The Y chromosome of modern humans is similar to the Neanderthal one
Kirill Stasevich, Science and Life (nkj.ru ) based on the materials of Max-Planck-Gesellschaft: Y chromosomes of Neandertals and Denisovans are now sequenced.
It is now the only human species left on Earth, Homo sapiens, and once there were more of them. The most famous of the "other people" are Neanderthals (Homo neanderthalensis) and Denisovans (Homo denisovan). The remains of Neanderthals are very numerous, the remains of Denisovans are very scarce. Nevertheless, for both of them, it was possible to extract enough DNA to assess what kind of kinship they have with each other and with us.
It is believed that Denisovans and Neanderthals are closer to each other than to H.sapiens. That is, first their ancestor separated from the evolutionary branch of H.sapiens, and then this ancestor diverged into two species. On the other hand, there is a lot of evidence that all three species interbred with each other. And such a crossing did not remain without consequences: as we still carry with us the genetic inheritance of Neanderthals, so they walked with the genes of a reasonable person until they died out.
The genetic proportion of H.sapiens in Neanderthals has so far been considered very small, only a few percent. But we still don't fully know the genome of Neanderthals. And so to researchers from the Institute of Evolutionary Anthropology The Max Planck Society, the Francis Crick Institute, the Chinese Academy of Sciences, the St. Petersburg Laboratory of Prehistory, the Institute of Archaeology and Ethnography of the Russian Academy of Sciences and other scientific centers managed to read the Neanderthal and Denisov Y chromosome. DNA was taken from the remains of three Neanderthals who lived no earlier than 53 thousand years ago, and the more ancient remains of two Denisovans. The male chromosome was compared with the "Y" of modern people, both of African and non-African descent. And it turned out that the Neanderthal Y chromosome is more similar to the chromosome of modern humans than to the chromosome of Denisovans.
By the way, something similar was found in the case of mitochondrial DNA. This is DNA, which is not in the cell nucleus, but in the organelles of the mitochondria, which provide the cell with energy. In mitochondrial DNA, some proteins are encoded that are necessary for the mitochondria themselves. But the main thing is that mitochondrial DNA is transmitted only through the maternal line, because the mitochondria of the sperm do not enter the egg during fertilization. On the other hand, the Y chromosome is transmitted only through the male line. It turns out that both the maternal DNA of mitochondria and the paternal Y-chromosome Neanderthals received from a reasonable person.
However, this genetic trace was carried by the late Neanderthal generations. DNA analysis of earlier remains suggests that initially the mitochondrial DNA of Neanderthals was similar to the mitochondrial DNA of Denisovans. But then there was the migration of H.sapiens from Africa to Eurasia. Both species met, and the Neanderthals received a portion of someone else's genetic material.
The Y chromosome remained with the Neanderthals for a reason – most likely, it gave some advantages. The authors of the work believe that many unpleasant mutations had accumulated in their own Neanderthal "y" by that time, and there were few such mutations in the chromosome from a reasonable person. Therefore, among Neanderthals, those who received the "y" from H.sapiens had more chances to survive and leave offspring. But this hypothesis has yet to be tested, if possible by comparing the Y chromosomes of Neanderthals who lived at different times.
The research results are published in Science (Petr et al., The evolutionary history of Neanderthal and Denisovan Y chromosomes).
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