Frost does not matter
Denisovans gave Inuit resistance to cold
Elena Smotrova, Anthropogenesis.roo
A research team from the UK and the USA has suggested where the Inuit of Greenland got an adaptation that allows them to better tolerate the cold. Variants of two genes important for adaptation to the cold, the Inuit probably inherited from the Denisovan man who lived in Asia several tens of thousands of years ago. ANTHROPOGENESIS.RU discussed with the first author of the article Archaic adaptive introgression in TBX15/WARS2 published in the journal Molecular Biology and Evolution, geneticist Fernando Racimo, exactly how specific gene variants affect resistance to cold and how the genes of Denisovans got to Greenland.
To conduct the study, scientists analyzed the DNA of 200 Inuit living in Greenland and compared the data with information about the genome of other living people from the 1000 Genomes project, as well as with the DNA of Neanderthals and Denisovans. As it turned out, the studied section of the genome in the variant characteristic of the Inuit is very similar to Denisov's, and sharply differs from the variants common in other modern human populations, although it is found in other peoples of America and occasionally in Eurasia. In Africa, the Denisovan variant is absent.
Inuit are a group of indigenous peoples of North America and Greenland, which is part of a larger group of indigenous peoples of the north – the Eskimos.
The intrigue is that the Inuit studied live in Greenland, and the Denisovans are described from finds in Altai. Previously, Denisov admixture was found in the inhabitants of Melanesia and Australia. It is likely that the Inuit ancestors of the Denisov heritage – an archaic variant of the TBX15/WARS2 genes – came due to the exchange of genes with other populations of Eurasia, even before migration to America. Of course, the authors do not exclude that the archaic variant came to the Inuit ancestors from some "Denisov-like" hominids unknown to science.
"We do not know exactly where the mixing could occur, but the "alien" variant of these genes can be found not only in South and North America and Greenland. With a lower frequency, but it still occurs in Eurasia, so it is possible that it got into the modern genome just on this continent, and then in some groups of people the frequency of its occurrence increased in the process of their spread to the east," explained Fernando Rasimo.
As it turned out, the "Denisovan" variant of the genes affects the distribution of fat in the human body, and thereby changes the susceptibility to cold.
Rasimo said: "As a result of various studies, we learned that a variant of genes of another species that got into human DNA plays a role in regulating the distribution of fat. However, the exact mechanism by which this happens is unknown. In fact, the results do not even mean that the frequency of occurrence of the introgressed gene has increased precisely due to the fact that it can regulate adipose tissue, but it is possible that this was one of the reasons.
As for Denisovans, we can only guess how their kind of genes would help them live in a cold climate. These conclusions will be based on the function of the gene, but it is important to note that it influenced not only the reaction to cold, but also, for example, the morphology of the face. So it's not really clear whether adaptation to low temperatures was the only reason why this gene variant is most commonly found in Inuit and other Native Americans," adds Rasimo.
The researchers note that people living in different regions may have other cases of so-called introgressive adaptation, when as a result of crossing Homo sapiens with other hominids, our ancestors got some useful quality. A number of recent studies indicate that on the way people settled from Africa, they could acquire gene variants inherent in ancient hominids that turned out to be useful. One of the most famous examples is the adaptation of Tibetans to life at high altitude, with a lack of oxygen. According to scientists, this mutation also came to Tibetans from Denisovans about 30-40 thousand years ago.
As Rasimo emphasized, people today can develop similar traits. He concluded: "Like other living beings, we humans are constantly evolving, which means that useful mutations can occur in us. For example, those who live in cold areas may develop adaptations to low temperatures."
Source: Arctic Inuit, Native American cold adaptations may originate from extinct hominids
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