Cold Tolerance Among Inuit May Come From Extinct Human Relatives

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A new study, published on Wednesday in Molecular Biology and Evolution, identifies gene variants in Inuit who live in Greenland, which may help them adapt to the cold by promoting heat-generating body fat. These variants possibly originated in the Denisovans, a group of archaic humans who, along with Neanderthals, diverged from modern humans about half a million years ago.

“As modern humans spread around the world, they interbred with Denisovans and Neanderthals, who had already been living in these different environments for hundreds of thousands of years,” said Rasmus Nielsen, a professor of integrative biology at the University of California, Berkeley and an author of the paper. “This gene exchange may have helped some modern humans adapt to and conquer new environments.”

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In this study, Dr. Nielsen’s team focused on another distinct region in the Inuit genome, which seems to affect body fat distribution and other aspects of development. The researchers compared the genomes of nearly 200 Inuit with genomes of Neanderthals, Denisovans and modern populations around the world.

Strikingly, all of the Inuit studied contained the same genetic variants in this particular region of their genomes. Compared to the same region in Neanderthals and other modern populations, the Inuit region showed at most a partial match. But compared to the Denisovan genome, it “was almost a complete match,” Dr. Nielsen said.

The region in question contains genes that may play a role in dictating levels of brown fat, a type that is abundant in newborns and generates heat by burning calories. Researchers have studied brown fat for years as a possible target for obesity treatments.

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Over all, the fact that the variants are present in close to 100 percent of Greenlandic Inuit could imply that they carry some type of evolutionary advantage.

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Two years ago, Dr. Nielsen and other researchers identified another Denisovan gene, in Tibetans, that helps them use oxygen efficiently at high altitudes.

These studies are part of an emerging body of research that examines how DNA from archaic humans affects different populations today, said Sriram Sankararaman, an assistant professor of genetics at the University of California, Los Angeles, who did not participate in this research.

“Different populations have different levels of archaic ancestries. Some have more Denisovan ancestry, others have more Neanderthal, and clearly these contributions have different kinds of effects,” he said. “The next big step is to look at more genomes across diverse populations.”