We’ve known for some time that our Homo sapiens ancestors mated and mixed with Neanderthals in what would later become Europe. As a result of these mixed couplings, up to four percent of our DNA comes from this other human species. What exactly those DNA molecules changed has been fodder for speculation, but also—and luckily—the subject of scientific studies.
One such study was published last month in the journal Science, with John Capra (Vanderbilt University) as lead author. They took the vast wealth of anonymized patient data, coupled with their genetic data, and let loose some heavy statistics. Do note that this is correlation, not necessary (unique) causation, and that it only concerns clinical issues, as logged in medical records of patients. Overall, some 28,000 records were analyzed. These came only from Eurasians as they are the ones who mixed with the Neanderthals.
So what did the researchers learn? Some good things that helped us, but also some worrying findings. For instance, there is a very positive link to skin cells called keratinocytes, which help defend the body from environmental damage. The Neanderthal DNA apparently is correlated to a better protection against UV radiation (among others) and keeps those cells stronger against those exterior threats.
There is also a link with increased blood coagulation. Now that is an interesting trait to have, as it more quickly seal wounds and therefore makes it more difficult for viruses and bacteria to enter the body. Sadly, however, it can lead to hypercoagulation, leading to obstructions in the blood vessels and strokes.
Some bad surprises we inherited could be linked (this is, again, correlation, not causation) to depression and addiction to tobacco, or at least the risk of having a depression or addiction. The reason for this is not clear from my reading. Depression is an especially complex disease, and it could be correlated with other inherited traits, such as behavior or mood. Sadly, some less scientifically reputable sites ran away with this part of the research without indicating its contextual complexities.
The findings leave little doubt that the DNA from the Neanderthals was an unexpected gift, helping us survive better as a species in certain cases. But it just as clearly also imbued its negative consequences, which may only now show up clearly. Interesting research that whets the appetite for more.
Tip o’ the hat to Futurity, where I first picked up this news.