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.
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