At Siberian fur farms, silver-black foxes have been selected for friendliness toward humans for more than sixty years. Over several generations, this selection led to the emergence of "tame" pups with gentle temperaments, floppy ears and shortened snouts. A recent study showed that these changes affected a specific region of the brain — the ventromedial hypothalamus.
The scientists compared the brains of three groups of foxes: domesticated, aggressive and wild. In the ventromedial hypothalamus, known from studies in mice as a center of aggression and social responses, the friendly animals had noticeably fewer neurons expressing the estrogen receptor alpha. In experiments with mice, it is precisely these cells that trigger an immediate attack.
A reduction in the number of such neurons apparently weakens the aggressive circuit while simultaneously strengthening the tendency toward social interaction. The changes occurred quickly — over just six generations of selection. This indicates that selection pressure can restructure the brain on short timescales.
The fox experiment began in the 1950s at the Institute of Cytology and Genetics in Novosibirsk. Geneticists noticed that at fur farms some animals showed less aggression toward people. By selecting such individuals, the researchers obtained a population that resembles domestic dogs in behavior and appearance. Now neurobiologists have gained the opportunity to trace exactly which cellular changes underlie this transformation.
The results are important not only for understanding domestication. They show how ecological and social factors can influence brain development in wild species. Similar mechanisms probably operate in other mammals as well, when the habitat or the nature of interaction with conspecifics and humans changes.
The next stages of the work include searching for genetic mutations that control the development of these neurons and studying how similar changes manifest in other species. Such data will help to better understand the evolution of social behavior in nature.
Observing the foxes is a reminder: even small, targeted changes in selection can noticeably restructure the neural circuits responsible for relationships with the surrounding world.
