Researchers and medical professionals have long known that psychiatric and neurological diseases tend to run in families.
Some examples of these diseases include Autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), major depression, bipolar disorder, and more.
This pattern suggests heritability, and researchers have identified the genetic risk factors for developing these diseases.
But one larger overarching question still looms– why have these genetic variants not been eliminated throughout evolution?
More recent discoveries about past human socialization have helped scientists start to understand this mystery.
For example, after modern humans migrated out of Africa over sixty thousand years ago, they met and mated with Neandertals.
So, today, about forty percent of the Neandertal genome can still be identified in non-Africans.
Moreover, these individuals still carry about two percent of DNA from past Neandertals.
And while these genetic variants might have benefitted modern humans in the past, researchers today are primarily interested in understanding how Neandertal DNA has impacted the development of disease.
Seventyfour – stock.adobe.com – illustrative purpose only, not the actual person
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Most recently, an international team of scientists conducted a study to unravel the link between Neandertal DNA and over one hundred brain disorders.
The researchers also analyzed traits– including sleeping, alcohol use, and smoking– among individuals in the UK Biobank to figure out if Neandertal DNA has also contributed to behavioral variation.
And interestingly, the researchers found that Neandertal DNA is highly associated with numerous traits that are linked to central nervous system diseases.
However, the team did not find that the diseases themselves displayed a significant association with Neandertal DNA.
Still, the inquiry into Neandertal DNA did reveal other noteworthy contributions to modern human behavior– such as a greater tendency to smoke, consume alcohol, and experience abnormal sleep patterns.
“Our results suggest that Neandertals carried multiple variants that substantially increase the smoking risk in people today,” said Michael Dannemann, the study’s lead author.
“It remains unclear what phenotypic effects these variants had in Neandertals.”
However, Dannemann underscored how this finding would pave the way for future research focused on functional testing.
Perhaps most notably, though, the researchers’ discoveries concerning Neandertal DNA and links to alcohol and smoking habits may help scientists identify the evolutionary origin of reward-seeking and addictive behavior– behavioral traits that are often linked to a plethora of diseases.
“It is important to note that sleep problems, alcohol, and nicotine use have consistently been identified as common risk factors for a range of neurological and psychiatric disorders,” explained Stefan Gold, a co-leader of the study.
“On the other hand, there are some intriguing findings from anthropology that have suggested some social benefits of higher tolerance to these substances in hunter-gatherers.”
So, Gold believes that the study’s findings support his team’s hypothesis that brain diseases themselves do not have evolutionary explanations. Instead, the process of natural selection is what shapes these traits and makes modern humans more vulnerable to them today.
To read the study’s complete findings published in Translational Psychiatry, visit the link here.
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