Nothing hits the mental illness spot like the insipid cocktail of rampant inflation, a dying planet and literal ongoing wars. Add in a dash of skyrocketing unemployment spurred on by ever-increasing epidemics and pandemics, and there is little wonder why mental health disorders seem to be on the rise among human beings. However, there might be another secret factor contributing to the development of psychological illnesses in us: our cave brains.
The history of human evolution is a complex tapestry woven with encounters, collaborations, and interbreeding with other hominid species. Among these interactions, there is one encounter that stands out — a primordial rendezvous between modern humans and the Denisovans, an extinct subspecies of archaic humans that walked the planet till at least 30,000 years ago.
Most accounts note that modern humans left Africa approximately 60,000 years ago during the "Out-of-Africa" event, eventually encountering the Denisovans in Asia. These interactions resulted in crossbreeding and the incorporation of Denisovan genetic material into the modern human genome.
While this meeting might have been profitable in some ways, recent research has also shed light on how this ancient genetic legacy may have left a lasting impact on the mental health of modern humans, including conditions such as depression and autism.
Researchers, led by Elena Bosch and Rubén Vicente, have identified one of the most widespread traces of Denisovan heritage in modern humans. This particular genetic adaptation helped ancestral Homo sapiens populations adapt to cold climates, and has to do with zinc regulation in our bodies.
Zinc is an essential trace element crucial for human health, playing a significant role in transferring information within and between cells. Vicente's team discovered that the observed Denisovan genetic variant alters zinc balance within cells, changing our metabolism to help us cope better in hostile, cold environments. However, as most of us know by now, there is no such thing as a free lunch.
Zinc transport plays a vital role in the nervous system and overall mental health. However, the Denisovan genetic variant found in the zinc transporter is also associated with a greater predisposition to various psychiatric diseases. These include the likes of depression, obsessive-compulsive disorder, schizophrenia, anorexia nervosa, hyperactivity disorder, autism spectrum disorder and bipolar disorder — conditions that hundreds of millions suffer from every year.
While being Asian-born, the Denisovan genetic adaptation is not limited to one specific geography. The variant has spread to European and Native American populations and can now be found worldwide. With prevalence in 4-6% of non-African modern humans, it one of the most far-reaching adaptations inherited from the Denisovans.
This fascinating discovery offers valuable insights into the complex history of our species and its potential influence on our well-being today. Future research, including animal models, may help uncover more about the link between this genetic legacy and mental health disorders, ultimately enhancing our understanding of the human condition.
The findings of this study have been published in PLOS Genetics and can be accessed here.
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