2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
A research team from the United Kingdom and the United States has suggested where the Inuit of Greenland have adapted to better tolerate the cold. Variants of two genes that are important for adaptation to cold, the Inuit probably inherited from a Denisovan man who lived in Asia several tens of thousands of years ago. ANTHROPOGENES. RU discussed with one of the authors of the study, geneticist Fernando Rasimo, how specific gene variants affect resistance to cold and how Denisovans' genes got to Greenland.
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For the study, the scientists analyzed the DNA of 200 Inuit living in Greenland and compared the data with information about the genomes 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 region 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, there is no Denisovan variant.
The intrigue is that the investigated Inuit live in Greenland, and the Denisovans are described based on finds in Altai. Earlier, the Denisovian admixture was found in the inhabitants of Melanesia and Australia. Probably, the Denisovan heritage - an archaic variant of the TBX15 / WARS2 genes - came to the ancestors of the Inuit as a result of gene exchange with other populations of Eurasia, even before migration to America. Of course, the authors do not exclude that the archaic version came to the ancestors of the Inuit from some "Denis-like" hominids unknown to science.
“We do not know exactly where the mixing would have occurred, but the 'alien' variant of these genes can be found not only in South and North America and Greenland. With a lesser frequency, but it is still found in Eurasia, so it is possible that it entered 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 genes affects the distribution of fat in the human body and thereby alters the susceptibility to cold.
Rasimo said: “As a result of various studies, we have learned that a variant of genes of a different kind that got into human DNA plays a role in the regulation of fat distribution. However, the exact mechanism by which this occurs is unknown. In fact, the results do not even mean that the frequency of the introgressed gene increased precisely because it can regulate adipose tissue, but it is possible that this was one of the reasons.
As for Denisovans, we can only speculate how their genes helped them live in cold climates. These conclusions will be based on the function of the gene, but it is important to note that it influenced not only the response to cold, but, for example, the morphology of the face. So it's really unclear if adaptation to low temperatures was the only reason this gene variant is most common in Inuit and other Native Americans,”adds Rasimo.
The researchers note that people living in different regions may have other cases of the 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 of resettlement of people from Africa, they could acquire gene variants inherent in ancient hominids, which turned out to be useful. One of the most famous examples is the adaptation of the Tibetans to life at high altitudes, with a lack of oxygen. According to scientists, this mutation also came to the Tibetans from the Denisovans about 30-40 thousand years ago.
As Rasimo emphasized, people can develop similar traits today. He concluded: “Like other living things, 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.”