Scientists Say We Bred With an Extinct Human Species and It Left a Grim Change in Our Brains

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Ancient Interbreeding Leaves a Genetic Mark on Modern Mental Health

Genes inherited from our ancestors’ interbreeding with an extinct human species may have left a significant and lasting impact on our mental health, according to researchers.

Scientists Say We Bred With an Extinct Human Species and It Left a Grim Change in Our Brains

A new study, published in the journal PLoS Genetics, concludes that these genes represent one of the most widespread traces of our ancient connection with the Denisovans. These archaic humans are believed to have mated with modern humans who left Africa around 60,000 years ago.

The Denisovan Legacy and Its Global Reach

As a result of that interbreeding, we Homo sapiens appear to have inherited a genetic adaptation involved in zinc regulation. This trait may have helped early populations weather the colder climates of the time, yet it may also have predisposed us to depression and a range of other mental disorders.

The adaptation is remarkably common. Compared with other Denisovan-derived mutations, it occurs across an unusually large portion of the global population today.

Scientists Say We Bred With an Extinct Human Species and It Left a Grim Change in Our Brains “For example, a variant in the EPAS1 gene inherited from the Denisovans allows adaptation to life at altitude, but is found only in Tibetans,” explained study co-lead author Elena Bosch of the Institute of Evolutionary Biology. “However, in our case, the impact extends to all populations outside Africa.”

Genetic Detective Work

Unlike the more famous Neanderthals, little physical evidence of the Denisovans remains. Most of what we know comes from their genetic legacy, which this study significantly expands.

Through genomic analysis, the researchers identified a genetic adaptation in modern humans that closely matches a segment of the Denisovan genome. Because the variant is absent in Neanderthals, they ruled out that species as the source.

“We discovered that this mutation surely had implications for the transport of zinc within the cell,” Bosch said.

Zinc: An Essential Micronutrient

Zinc plays a vital role in human biology. It acts as a cellular messenger and is required for the proper function of hormones, enzymes, and proteins. Deficiency has been linked to growth problems and neurological disorders.

Scientists Say We Bred With an Extinct Human Species and It Left a Grim Change in Our Brains The fact that the mutation persisted suggests it once conferred an advantage. Laboratory experiments by the team showed that the gene SLC30A9 influences cellular metabolism by regulating zinc balance, offering a “possible adaptation to the cold,” said co-author Rubén Vicente, associate professor at Pompeu Fabra University in Barcelona.

Mental Health Trade-Offs

Scientists Say We Bred With an Extinct Human Species and It Left a Grim Change in Our Brains Yet the same change carries modern costs. Researchers linked the variant to increased risk of several mental health conditions, including depression, bipolar disorder, obsessive-compulsive disorder, schizophrenia, and autism.

Genetics alone does not determine mental health outcomes. Inheriting the variant may raise susceptibility, but environmental and other factors also play important roles. The precise mechanisms remain unclear, and the team plans further research.

“In the future, expanding this study to animal models could shed light on this predisposition to suffering from mental illnesses,” Vicente said.

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