Sarah Kaplan, Washington Post, October 19, 2016

Most human genomes harbor small fragments of Neanderthal DNA, the legacy of prehistoric hanky-panky between our ancestors and their hominid cousins.

For the most part, that inheritance has been detrimental. Research suggests that as much as 10 percent of the human genome was inherited from archaic hominids other than Homo sapiens, but the majority of that material was weeded out by tens of thousands of years of natural selection. The DNA that does remain has been blamed for increasing risk of depression, Type 2 diabetes, Crohn’s disease, lupus, allergies, addiction and more.

But geneticists Fernando Racimo, Davide Marnetto and Emilia Huerta-Sanchez wanted to find evidence that our archaic inheritance actually does us some good. They went looking for instances of adaptive introgression–a phenomenon in which a newly introduced piece of genetic material is so beneficial that it quickly radiates out into the entire population.

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Their results, published in the journal Molecular Biology and Evolution this week, suggest that humans have inherited helpful genetic variants associated with fat storage, respiration, skin pigmentation, liver function, immune response and keratin production.

These scraps of DNA come from both Neanderthals and Denisovans, another hominid known only from a few remains found in Russia. Tens of thousands of years after these species went extinct, their DNA may still be helping us survive the modern world.

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The main takeaway from the study, Racimo said, is that we owe more to our Neanderthal and Denisovan relatives than we think. For years, conventional wisdom about these archaic humans is that they were weaker, dumber and less evolutionarily fit than modern humans and that’s why they died out. But Racimo believes that other hominid species could have actually helped humans.

“Archaic humans expanded out of Africa before modern humans, so they had a lot more time to adapt to the particular conditions of Europe and Asia,” he said. “A shortcut to adapt to these conditions, instead of waiting for the mutations to occur, is to obtain the genetic material from these archaic human groups who were established for a long time.”

For example, the genes associated with immunity may have helped Homo sapiens resist the new pathogens they encountered as they spread around the globe.

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