American researchers have proposed a method for detecting genes of other hominid species in the DNA of modern people, for which you do not need to know the genome of the "invader", according to Science Advances. This makes it possible to search for traces of hybridization of Homo sapiens with those species whose genome has not yet been deciphered, and even with those whose material evidence of life (bones, tools) has not yet been found. Scientists report that they have already found signs of interbreeding of the ancestors of modern West African peoples and a hypothetical population of unknown hominids.
It is now known that the ancestors of modern man interbred with at least Neanderthals and Denisovans (although some consider them to be a subspecies of Sapiens or Heidelberg man). These two species, in turn, had sexual relations with each other. It is logical to assume that members of the genus Homo formed interspecific pairs with someone else. But if the DNA of Homo sapiens, Neanderthals and Denisovans can still be extracted from the remains, then the genetic material of more ancient hominids is already more difficult to obtain.
To get around this problem, geneticists Arun Durvasula and Sriram Sankararaman of the University of California, Los Angeles have developed a method for searching for genes of other species in human DNA, in which there is no need to compare the genome of the one who is looking for "alien" genes, with the genome of the one from whom he received these genes.
Algorithm training and timing of divergence of different DNA variants.
To do this, they trained a model to identify fragments of the genome of Neanderthals and Denisovans in the DNA of modern humans and, by single-nucleotide polymorphisms, determine the probability that a particular piece of DNA was obtained from some other species. As the DNA of modern humans, the researchers used data from the 1000 Genomes project for the Yoruba, Mende, and two more West African peoples (a total of 405 complete genomes).
Accepted (A) and proposed in the new article (B) chronology of gene transfer from one species of people to another. UA - unknown archaic people, N - Neanderthals, D - Denisovans, W Afr - West African peoples, Eur - Europeans.
At the same time, from 2 to 19 percent of DNA similar to archaic was found in modern inhabitants of West Africa, which Neanderthals and Denisovans did not have. Geneticists tested several demographic models that could explain their presence, and concluded that the presence of archaic variants of genes is best consistent with the fact that the ancestors of the Yoruba, Mende, and two other West African peoples 43,000 years ago interbred with as yet unknown species of people who separated from the common trunk even before the appearance of the Neanderthals and Denisovans, 625 thousand years ago.
This may mean that archaic hominids existed in Africa for a very long time, until very recently in evolutionary terms. In general, the results once again make us think about how the appearance of modern Homo sapiens was formed and, in particular, pay attention to what kind of people the ancestors of various African peoples interbred with. Not much is known about this yet.
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More recently, researchers from Princeton University have identified traces of crosses of their ancestors with Neanderthals in Africans. Prior to this work, it was believed that the indigenous people of this continent had never met Homo neanderthalensis. The method used by scientists also does not require what was always needed - the reference genome of modern Homo sapiens.
Svetlana Yastrebova