Evolution usually shows up over many generations, which makes it hard to catch in a living animal. Barn owls in western Switzerland are an exception. Over a few decades they have grown darker and more heavily spotted, two traits built from melanin and linked to survival. Alexandre Roulin’s group at the University of Lausanne sequenced the genomes of 3,102 birds from a long-running study of the population. They found a handful of genes with large effects behind the change. Models of random genetic drift could not explain the shift, but models that include natural selection could. In short, something is actively favoring the darker, spottier owls. What that something is remains open. Roulin suggests shifts in food supply or environmental stress, but the study does not pin it down. I flag that this is still a preprint, not yet peer-reviewed. Even so, tracing recent evolution to specific genes in a wild population this cleanly is rare.
Source: bioRxiv preprint, October 2025 (not yet peer-reviewed)
