We have been suffering from mental illnesses since our brain evolved to make us more intelligent: this is the hypothesis of a study published in Cerebral Cortexwho traced an evolutionary line of human genetics discovering that mutations linked to cognitive development were almost always followed by mutations linked to the onset of mental problems, such as depression or alcohol dependence. “Cognitive progress may have come at the price of making our brain more vulnerable to mental disorders,” explains Ilan Libedinsky, coordinator of the research.
The study. The research team investigated the evolutionary origins of 33,000 genetic variants present in contemporary humans and linked to different traits – such as cognitive abilities and psychiatric conditions, as well as physical and health-related characteristics such as eye shape and cancer.
Most of these variants emerged between three million and four thousand years ago, with an explosion in the last 60,000 years – around the time of the great emigration of Homo sapiens from Africa.
Temporally related variants. Variants linked to advanced cognitive abilities emerged relatively recently compared to those of other traits: in particular, those linked to fluid intelligence, or the ability to solve new problems, were formed around 500,000 years ago.
“Only” (in evolutionary terms) 25,000 years later, on average, would variants linked to psychiatric problems emerge. This trend would have repeated itself over time: in the last 50,000 years, for example, the emergence of variants linked to language has been followed by the formation of other mutations linked to alcohol addiction and depression.
A partial view? Geneticist Simon Fisher, who was not involved in the research, recognizes the interest of the study, which “allows scientists to re-examine long-standing questions about human evolution, putting hypotheses to the test in a concrete way thanks to real data obtained from our genomes”.
However, he also underlines a weak point, recalling that this type of research is limited to examining the genetic sites that still vary from person to person today, leaving aside older changes, which have now become universal, which may have been fundamental for our evolution.
