We inherited these good and bad qualities from the Denisovans

About 60,000 years ago, modern humans left Africa. In Asia he encountered the Denisovans. That was not all peace and quiet, but there was an enormous exchange of genes. A new study shows just how great the genetic inheritance is. And it is certainly not only positive.

We still carry genes from the Denisovans – a distant ancestor – within us, but this does not apply to all people on Earth. Africans don’t have them. That and more discovered a group of Spanish evolutionary biologists from the Pompeu Fabra University in Barcelona. For example, they discovered that the genes of our distant ancestors make us better able to withstand the cold, which was desperately needed in the chilly north. To this end, the researchers studied a gene variant that is related to zinc regulation and that plays a role in metabolism within the cell. It was of course a good thing that this allowed us to withstand the cold better, but there were probably also disadvantages. This genetic adaptation makes modern humans more vulnerable to psychiatric disorders, such as depression and schizophrenia.

Not from the Neanderthals, but from the Denisovans
The way genetic diversity has evolved in human populations is something that evolutionary biologists and geneticists are very interested in. The discovery of the mutation in modern-day humans is therefore a major step forward. “We discovered through gene analysis that this specific genetic variant was added to our DNA package through cross-pollination with archaic hominins. It is very possible that we got these genes from Denisovans,” explains researcher Ana Roca-Umbert. In any case, it does not come from the Neanderthals, because they did not have this mutation among their members.

“Apparently the adaptation was beneficial to humans, because the variation in the SLC20A9 gene is still present in the DNA of many contemporary peoples,” says scientist Jorge Garcia-Calleja. “We found that this mutation undoubtedly affected the transport of zinc within the cell.”

Important messenger
The researchers discovered a mutation in an amino acid of a zinc transporter, which can be found in modern-day people from Asia, but not in people from Africa. Zinc is a trace element that is essential for human health. It is an important messenger that sends information from outside the cell to the inside, but can also perform this trick inside the cell between different parts. A zinc deficiency leads to neurological, immune and growth disorders.

Better resistant to the cold
However, science only knows in broad terms what zinc does in the body. “The regulation of zinc has been relatively poorly studied, because there were few molecular options to map the movements of zinc,” says one of the researchers. To find out more, the team manipulated the endoplasmic reticulum (a network of membranes where new proteins are made) and mitochondria inside cells and found that gene variation provides metabolic benefits in a hostile environment. “It seems very likely that the mutation leads to better cold resistance,” it said.

Geographical distribution of the substitution identified in the SLC30A9 gene in current human populations and possible scenarios of Denisovan introgression.Geographical distribution of the substitution identified in the SLC30A9 gene in current human populations and possible scenarios of Denisovan introgression.
The spread of the SLC30A9 gene around the world in current humans and possible scenarios of gene flow from one species to another, also called introgression. Image: Jorge Garcia and Elena Bosch

But zinc also plays an important role in stimulating the nervous system and as such has an effect on mental stability and health. During the study, the researchers discovered that the zinc transporter – which can be found in all corners of the body, in all types of tissue – can be linked to a greater risk of a number of psychiatric disorders, such as anorexia, hyperactivity, autism, bipolar disorder. disorder, depression, obsessive-compulsive disorder and schizophrenia.

Everywhere except Africa
The variant originated in Asia through the crossing of Denisovans and Homo sapiens, after which it also spread among European and native American populations. The gene mutation can be found all over the world, but is rare in African populations. Never before has a variant been discovered that had such a large geographic reach, according to the team. “For example, there is a known variant in the EPAS1 gene, which also comes from Denisovans and ensures that carriers can better live at high altitudes, but this mutation has only been found in Tibetans. While the variation in the SLC20A9 gene can be found everywhere in the world, except in Africa,” he concludes.