Neanderthals Passed Down Genes for Hair, Skin, and Disease to Humans

If you have diabetes, depression, or Crohn's disease, you may be able to blame Neanderthals — humans' ancient long-lost cousins — for your troubles. DNA from Neanderthals, who were last seen hanging around Europe about 28,000 years ago, has been found in modern human genomes. Two new studies link some diseases, hair and skin traits, and even difficulty quitting smoking to the Neanderthals. Researchers found that the genomes of non-African people today actually contain about 1 to 4 percent Neanderthal DNA, and as much as 20 percent of Neanderthal DNA may exist in modern genomes.

Some quick history about Neanderthals and humans (a.k.a. Homo sapiens): Neanderthals were hunters who roamed across Britain to Siberia. Then, humans began to infiltrate their land from Africa, causing the Neanderthals to become extinct. But before then, those randy Homo sapiens reproduced with the Neanderthals — and the rest is history.

Researchers were interested in exactly how much humans still retain from our Neanderthal/Homo sapien ancestors, since humans had to adapt to much harsher conditions in Europe than in Africa. Studies that appear in Science and Nature come to similar conclusions: Humans kept some beneficial Neanderthal genes that affect our skin and hair, and other genes were flushed out by natural selection.

Neanderthal DNA does sit within some genes, however, such as those for keratin, a fibrous protein that makes skin, hair and nails tough and can be beneficial in colder environments by providing thicker insulation. The endurance of this Neanderthal DNA suggests that our caveman inheritance was adaptive, picked by natural selection to persist in our genome, generation after generation, because it conferred a survival advantage in individuals who carried it.

One surprising finding has to do with smoking — which was probably not a daily Neanderthal habit. However, one of the studies suggest that one of the Neanderthal genes that was passed down is the same one that has been linked to difficulty in quitting smoking. (But that's still no excuse to ignore the surgeon general's new warning.)

Other gene variants that stem from Neanderthals' influence include diseases such as type 2 diabetes, long-term depression, billary cirrhosis, and Crohn's disease. In fact, with Crohn's, "Neanderthals passed on different markers that increase and decrease the risk of disease," according to the BBC.

So, long story short, we can thank Neanderthals for allowing humans to adapt to new surroundings, but curse them for giving us some pretty serious illnesses.

“The story of early human evolution is captivating in itself, yet it also has far-reaching implications for understanding the organisation of the modern human genome,” Irene Eckstrand of the National Institutes of Health’s National Institute of General Medical Sciences, which partially funded the research, said in a statement. “Every piece of this story that we uncover tells us more about our ancestors’ genetic contributions to modern human health and disease.”

And, if you're having a bad hair day, feel free to blame it on those pesky Neanderthals.

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