Neanderthal Genes Traced to Modern Humans' Skin and Hair

Neanderthals may have gone extinct thousands of years ago, but their genomic lineage lives on, particularly in skin and hair traits, a new study published in the journal Nature found.

Led by geneticists at Harvard Medical School (HMS), the study demonstrates how some genes inherited from the early human ancestors have proven to be adaptive for modern humans, while others less so.

In the past, researchers - including David Reich, a genetics professor and senior author of the new paper - have determined that the genomes of modern humans of non-African descent are about 2 percent Neanderthal. Indigenous Africans, on the other hand, have little to no traces of the species, which lived in Asia and Europe.

But while further studies have been able to locate Neanderthal DNA in certain regions of the non-African human genome, researchers had yet to discover the biological ramifications of this heritage.

Together with colleagues from around the world, Reich analyzed genetic variants in nearly 850 people of non-African descent, 176 from sub-Saharan Africa and a 50,000-year-old Neanderthal. Those variants that appeared in some non-Africans and the Neanderthal but not in the sub-Saharan Africans were determined to be Neanderthal.

The results revealed areas in the modern non-African human genome that were heavy with Neanderthal DNA and areas that were completely void of it.

According to Sriram Sankararaman of HMS and the Broad Institute, these areas of notable absence were the "most exciting" discovery.

"It suggests the introduction of some of these Neanderthal mutations was harmful to the ancestors of non-Africans and that these mutations were later removed by the action of natural selection," he explained in a statement.

Intriguingly, the scientists found that Neanderthal heritage was greater in genes affecting keratin filaments, a protein tied to the toughness of skin, hair and nails, and is considered beneficial in colder environments because it offers better insulation. 

"It's tempting to think that Neanderthals were already adapted to the non-African environment and provided this genetic benefit to humans," Reich said.

The new study is an important one, the researcher explained, in better understanding the relationship between modern humans and the extinct species. 

"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," he said. "We may also learn more about what Neanderthals themselves were like."