Humans having sex with a now-extinct subspecies they met in Asia some 60,000 years ago could be the reason one has depression, a new study has claimed.
Researchers discovered a gene variant linked to the crossbreeding of humans and Denisovans which they believe affects our mood.
Those with the variant have lower levels of zinc in the body, a nutrient that studies increasingly show is associated with mood and happiness.
Scientists said SLC30A9 is the most widespread Denisovan gene discovered to date, starting in Asia, and has spread to European and Native American populations.
The different branches of the human family tree have interbred and swapped genes, a processes known as ‘introgression’ on numerous occasions.
Elena Bosch, IBE principal investigator and co-leader of the study, and her team identified an adaptive variant among current human populations in a region of our genome that bears remarkable similarity to the genome of an extinct ancestral population: the Denisovans.
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‘We discovered that this mutation surely had implications for the transport of zinc within the cell,’ said Bosch.
Researchers did look into Neanderthal heritage but found the population was absent of the mutation.
Rubén Vicente, MELIS-UPF principal investigator, then joined the team to analyze intracellular zinc’s movement.
‘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,’ Vicente said.
‘From there, we started asking ourselves questions and looking for answers.’
His laboratory identified that the observed variant causes a new zinc balance within the cell, promoting a change in metabolism.
This led them to find that the mutation helped Denisovans cope with the cold, hostile climate that once ravaged Asia.
The team points out that the variant found in this zinc transporter, which is expressed in all tissues of the body, is associated with a greater predisposition to suffering from some psychiatric diseases.
These include anorexia nervosa, hyperactivity disorder, autism spectrum disorder, bipolar disorder, depression, obsessive-compulsive disorder, and schizophrenia.
The Denisovans are thought to have been a sister species of the Neanderthals, who lived in western Asia and Europe at around the same time.
The two species appear to have separated from a common ancestor around 200,000 years ago, while they split from the modern human Homo sapien lineage around 600,000 years ago.
Bone and ivory beads found in the Denisova Cave were discovered in the same sediment layers as the Denisovan fossils, leading to suggestions they had sophisticated tools and jewellery.
