How did evolution affect mental disorders?
Evidence of selection in the last 10,000 years
A large ancient-DNA study focused on Europe and Western Asia reports strong signatures of natural selection across roughly the past 10 millennia. By comparing allele-frequency changes in thousands of ancient people, researchers found hundreds of genetic variants under directional selection rather than random drift.
The traits most emphasized by the researchers’ genetic analyses include mental health and cognition, as well as several physiological and immune-related outcomes. The reported patterns point to decreases in risks or susceptibilities associated with mental disorders such as schizophrenia and bipolar disorder, and increases linked to cognitive traits and higher walking pace.
The same selection signals also align with changes in body composition, including a decrease in body fat percentage. But the selection picture is not uniformly “beneficial” in every biological pathway: the study also reports evidence consistent with increases in autoimmune disease.
What this means for biology and health
These findings matter because they connect demographic change and environment to specific biological pathways over a timescale relevant to modern European and Western-Asian populations. They also highlight a common evolutionary tradeoff: variants that may have improved some aspects of health—such as metabolism or neurological functioning—could plausibly affect immune regulation in ways that raise autoimmune risk.
Why it’s newsworthy now
Unlike studies that look at a single modern disease gene, this approach uses many ancient genomes across time. That helps researchers test whether selection really shifted the genetic landscape for complex traits, and whether mental health trends could plausibly have shaped (or been shaped by) evolutionary pressures.
No single variant explains complex disorders, but the directionality of the signals supports the idea that natural selection has been acting on multiple systems—brain, metabolism, and immunity—during the era after agriculture and sedentary life expanded across the region.