Geneticists believe that modern humans did not interbreed with Neanderthals
A relative defeated a hybrid
New data obtained by a group of geneticists from the University of Cambridge and published in the Proceedings of the National Academy of Sciences, cast doubt on the theory of paleohybridization, according to which modern humans at some point could interbreed with Neanderthals. The presence of so-called "Neanderthal genes" in the human genotype is explained not by hybridization, but by the presence of a common ancestor, the authors of the article claim.
Methods for reconstructing DNA extracted from fossils continue to improve, and over the past few years, several comparative studies of the DNA of Neanderthals and modern humans inhabiting the territory of Eurasia have been published in scientific periodicals.
As the analysis showed, the genotypes of Neanderthals and modern Eurasians have from 1 to 4 percent of common genes. Since representatives of some of the most archaic from the point of view of paleogenetics, African tribes do not have such genes, it was concluded that the ancestors of modern humans who migrated from Africa to Eurasia about 90-70 thousand years ago could interbreed with Neanderthals – another kind of people who had already settled in Europe by that time.
Meanwhile, a group of geneticists from Cambridge has found an alternative explanation for this phenomenon, excluding the influx of Neanderthal genes into the human population.
"The analysis showed that the previously identified common genetic patterns, nicknamed "Neanderthal", do not represent anything special, and there is no need to explain their origin by hybridization. In other words, if a hypothetical crossing took place (and it is quite difficult to find convincing evidence that it did not exist at all), it is not as massive as it is commonly thought today," explains the lead author of the article, Andrea Manica.
According to the authors, the Neanderthal and modern man could have a common ancestor who began migrating from Africa to Eurasia about 500 thousand years ago. But just as modern Eurasians differ from each other, representatives of this ancient population of Eurasians genetically (and morphologically) also differed from each other: some parts of it were more related, some less, because according to archaeology and paleogenetics, the population of Africa itself, from where the exodus came from, was genetically strongly structured, and gene exchange between migrant groups was severely limited.
Then, about 350-300 thousand years ago, the flow of migrants weakened, and the European and African group became isolated. As a result, the first evolved into Neanderthals, and the second evolved into our ancestors, that is, modern man, while some of our African ancestors retained genetic lines close to the European, that is, Neanderthal, population, and the other part did not have such lines, or they were less pronounced.
The authors have developed a model that allows us to determine to what extent the genetic similarity of modern Eurasians and Neanderthals can be explained by hybridization, that is, by crossing different species, and to what extent by the genetic similarity with Neanderthals of some of our African ancestors, who later also began to migrate to Eurasia.
Calculations, which also take into account the subsequent evolution of different genetic lines of Eurasians, showed that when the ancestors of modern humans, some of whom carried Neanderthal-related genes, began to spread across Eurasia 60-70 thousand years ago, the frequency of occurrence of "Neanderthal genes", gradually spreading across Eurasia, eventually became higher than in Africa, which explains why some Africans have these genes less often or do not occur at all.
"Based on the theory of a common ancestor and geographical differences in genotypes, we were able to show that the Eurasian population carries more genes similar to those of Neanderthals, but it is not necessary to involve the hybridization hypothesis for this: the similarity is dictated by migration and the dynamics of the spread of these genes across Eurasia," the authors of the article summarize.
Portal "Eternal youth" http://vechnayamolodost.ru13.08.2012