Study Suggests That Ancient Interspecies Relationships May Contribute to Modern Mental Health Challenges

 

A recent study has proposed an intriguing connection between human interactions with an extinct subspecies, which inhabited Asia around 60,000 years ago, and the prevalence of depression in contemporary humans.

Researchers have identified a specific gene variant that is believed to be the result of interbreeding between humans and Denisovans, an ancient subspecies. This gene variant is thought to influence our mood and mental well-being. Individuals possessing this variant tend to exhibit lower levels of zinc in their bodies, a crucial nutrient that has been increasingly linked to mood and happiness in various studies.

SLC30A9, the gene in question, is considered the most widely distributed Denisovan gene discovered to date. It originated in Asia and has since spread to European and Native American populations. The intricate web of human evolution includes instances of gene exchange, termed "introgression," which has occurred repeatedly over the course of history.

Elena Bosch, the principal investigator at the Institute of Evolutionary Biology (IBE) and a co-leader of the study, and her research team detected an adaptive genetic variation among contemporary human populations. This variation is located in a specific region of our genome and shares remarkable similarities with the genome of the Denisovans, an ancestral population that has long vanished.

Bosch noted, "We discovered that this mutation surely had implications for the transport of zinc within the cell." In their investigation, the researchers explored Neanderthal heritage but found no evidence of the same mutation.

The research team expanded further with Rubén Vicente, the principal investigator at the MELIS-UPF, who joined the efforts to analyze the movement of intracellular zinc. Vicente explained, "Elena contacted me because her team had observed a change in an amino acid in a zinc transporter, which was very different between the populations of Africa and Asia today. From there, we started asking ourselves questions and looking for answers."

Their laboratory findings revealed that the observed genetic variant disrupts the balance of zinc within the cell, leading to a metabolic shift. This mutation appears to have assisted the Denisovans in adapting to the harsh, frigid climate that once prevailed in Asia.

The research team highlights that this variant in the zinc transporter, which is expressed in all body tissues, is associated with an increased susceptibility to various psychiatric disorders. These conditions include anorexia nervosa, attention deficit hyperactivity disorder, autism spectrum disorder, bipolar disorder, depression, obsessive-compulsive disorder, and schizophrenia.

Denisovans are believed to have been a sister species of the Neanderthals, coexisting in western Asia and Europe during a similar time period. These two subspecies diverged from a common ancestor roughly 200,000 years ago and separated from the Homo sapien lineage, which includes modern humans, around 600,000 years ago. Intriguingly, discoveries like bone and ivory beads found in the Denisova Cave suggest that the Denisovans possessed advanced tools and jewelry, shedding light on their remarkable culture and capabilities.