A whole range of health and psychological disorders, including depression and nicotine addiction, have been confirmed as relating the presence of Neanderthal genes in our DNA by US scientists.
The rigorous genome comparison is the first study of its kind.
It’s been known since 2010 that Eurasian genes may suffer from a series of health problems associated with Neanderthal DNA, after the fact of interbreeding with Homo sapiens was confirmed. But this was the first direct study of the two DNA types, undertaken by scientists at Vanderbilt University in Tennessee.
“Our main finding is that Neanderthal DNA does influence clinical traits in modern humans: We discovered associations between Neanderthal DNA and a wide range of traits, including immunological, dermatological, neurological, psychiatric and reproductive diseases,” senior author on the paper and evolutionary scientist John Capra said.
The study was published in the February 12 issue of the journal Science.
The new study shares some of its conclusions with previous work in the field and continues to explore the still dim area of inherited disorders from our Neanderthal forbearers.
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To arrive at their conclusions, researchers identified 135,000 Neanderthal genetic variations in modern humans, before moving onto an analysis of 28,000 Europeans’ ancestry through the Electronic Medical Records and Genomics (eMERGE) network.
“Vanderbilt’s BioVU and the network of similar databanks from hospitals across the country were built to enable discoveries about the genetic basis of disease,” Capra said. “We realized that we could use them to answer important questions about human evolution.”
The two data sets were linked to find a total of 12 traits we have a significantly larger risk of inheriting because we fooled around with our more ape-like cousins. These included everything from depression to arterial thickening, risk of heart disease, as well as nicotine addiction.
Although we know tobacco had not been brought to Europe from the Americas until relatively recently, the Neanderthal trait responsible for an increased risk of addiction probably served a completely different purpose some 50,000 years ago, scientists believe.
Researchers knew they needed to first look at things that affected our interaction with the physical environment.
“We hypothesized this because Neanderthals had been living in Central Asia and Europe for hundreds of thousands of years before our recent ancestors ever reached these areas — and thus had likely adapted to the distinct environmental aspects of these regions, compared to Africa, in terms of climate, plants and animals, and pathogens,” Capra told LiveScience.
In this way the previous hypothesis explaining our cells’ weakness to ultraviolet radiation was explained. Neanderthal DNA was found to negatively affect keratinocytes – cells that help protect our skin from such damage.
But there were also a number of surprises, such as psychiatric traits we could have inherited, both positive and negative. Heightened risk of depression is one of them, together with the nicotine addiction. It was further confirmed that, contrary to our previous suspicions, Neanderthal DNA did not directly contribute to skin color variation in modern humans. According to Capra, Neanderthals may also have had a range of skin colors.
“The brain is incredibly complex, so it’s reasonable to expect that introducing changes from a different evolutionary path might have negative consequences,” prime author and doctoral student Corinne Simonti says.