Neanderthal Genes Found in Modern Human DNA, Studies Find

Neanderthals that have been extinct for 28,000 years live on in human DNA, according to research suggesting the genes may help us better survive cold weather and be linked to some present-day diseases.

The Neanderthal genes make up only about 2 percent to 4 percent of the DNA carried by a given human today, according to a paper published in the journal Science. Even so, it may be linked to the development of our hair and skin, as well as to immune disorders such as Type 2 diabetes, the research found.

New DNA techniques are reshaping knowledge of human evolution just as quickly as they’re sparking the development of medical tests and treatments. That’s allowing scientists to peek into history by comparing modern DNA with the Neanderthal genome, recently reconstructed by scientists using material from the toe bone of a female who lived 50,000 years ago.

“We’re not as beholden to ancient DNA anymore,” said Joshua Akey, an associate professor of genome science at the University of Washington in Seattle, and an author of one of the studies. “Rather than excavating bones, we can now excavate DNA from modern individuals.”

Akey’s study identified the skin and hair traits. A second report yesterday by scientists at Harvard Medical School in Boston and the Broad Institute in Cambridge, Massachusetts, found nine links between Neanderthal DNA and previously identified human genes, some of which affect immune function.

The Neanderthal DNA found in the ancient toe bone was reported in the journal Nature in December. That study suggested inbreeding may have been common for Neanderthals, and may have led to their demise. Earlier studies using less complete genetic profiles determined that Neanderthals probably mated with ancient humans as well.

Environmental Adapting

The latest DNA research supports that conclusion and suggests the Neanderthal genes left behind as a result may have aided humans in adapting to non-African environments, Akey said, adding, “What’s striking is you can really look at the distribution of Neanderthal DNA across the entire genome.”

Both studies published yesterday identified significant areas within the human genome where no Neanderthal genes appear, more than would be anticipated by chance. That suggests some mutations weren’t passed on, probably because they didn’t help survival.

The shared genes that influence hair and skin traits also influence other things, Akey said. It’s possible, for instance, that the Neanderthal genes helped alter pigmentation and moisture retention in humans, helping to increase body warmth in colder climates.

Overcoming Infertility

The Harvard study found that genes that are most active in the testes and those in the X chromosome have the least Neanderthal influence, compared to other parts of the genome. The pattern may have been a way for the body to naturally overcome infertility among different species.

That study compared the Neanderthal genome with 846 people of non-African heritage, 176 people from sub-Saharan Africa, and the genome of a 50,000 year-old Neanderthal that was published in 2013. Anything found on both the non-African heritage genomes and the Neanderthal genome, without appearing in the sub-Saharan African genomes, was likely Neanderthal-linked, they wrote.

“Now that we can estimate the probability that a particular genetic variant arose from Neanderthals, we can begin to understand how that inherited DNA affects us,” David Reich, a professor of genetics at Harvard Medical School and author of the Nature paper, said in a statement. “We may also learn more about what Neanderthals themselves were like.”

Akey and his team performed whole-genome sequences of more than 600 present-day humans from Europe and East Asia. By comparing the modern DNA with the reference genome, they were able to infer how the humans and Neanderthals interacted. What’s more, it may be possible to discover other-as-yet-unknown human ancestors by looking at modern DNA, he said.

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