Neanderthal DNA makes up 1 percent to 4 percent of modern Eurasian genomes and as per new research, it could have a subtle but significant impact on human traits.
The Vanderbilt University study that directly compares Neanderthal DNA in the genomes of a significant population of adults of European ancestry with their clinical records confirms that this archaic genetic legacy has a subtle but significant impact on modern human biology.
Senior author John Capra noted that the 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."
Some of the associations that Capra and his colleagues found confirm previous hypotheses. One example is the proposal that Neanderthal DNA affects cells called keratinocytes that help protect the skin from environmental damage such as ultraviolet radiation and pathogens. The new analysis found Neanderthal DNA variants influence skin biology in modern humans, in particular the risk of developing sun-induced skin lesions called keratosis, which are caused by abnormal keratinocytes.
In addition, there were a number of surprises. For example, they found that a specific bit of Neanderthal DNA significantly increases risk for nicotine addiction. They also found a number of variants that influence the risk for depression: some positively and some negatively. In fact, a surprisingly number of snippets of Neanderthal DNA were associated with psychiatric and neurological effects, the study found.
"The brain is incredibly complex, so it's reasonable to expect that introducing changes from a different evolutionary path might have negative consequences," said first author Corinne Simonti.
According to the researchers, the pattern of associations that they discovered suggest that today's population retains Neanderthal DNA that may have provided modern humans with adaptive advantages 40,000 years ago as they migrated into new non-African environments with different pathogens and levels of sun exposure. However, many of these traits may no longer be advantageous in modern environments.
The study appears in Science.
