Tame foxes show a difference in a brain region tied to aggression in mice
· BehindLines newsroom · Updated
Researchers at Cornell University (New York State) report that the brains of foxes bred for tameness toward people differ in a deep structure called the ventromedial hypothalamus. According to the Cornell Chronicle, the results were published on 2 November 2026 in the journal Current Biology. The sample is small, and the authors do not claim to have identified the cause of tameness.
An experiment that began in the 1950s
The background is old: the experimental breeding of silver foxes started in Siberia in the late 1950s. Russian geneticists had noticed that some animals on fur farms were more tolerant of their keepers, and they bred the friendliest ones together. According to the Cornell Chronicle, after six generations some litters included pups that approached humans of their own accord. These animals also developed traits associated with domestication, such as floppy ears and shorter snouts. Only the publication of this study is new; the experiment itself is almost seventy years old.
What the team compared
The team led by Eirene Markenscoff-Papadimitriou, assistant professor of molecular biology and genetics at Cornell, examined nine silver fox brains, according to the Cornell Chronicle: three from tame animals, three from animals bred for aggression and three from wild animals. They focused on the ventromedial hypothalamus, at the base of the brain. According to the release, this region, which in mice is involved in aggression, energy use, and maternal and social behavior, had not been well studied in these foxes.
The researchers used a fluorescent RNA-labeling technique to identify cell types. They wanted to know whether the abundance of one specific type of neuron, those that express the estrogen receptor alpha, varied between the groups. In mice, earlier work by other teams using optogenetics (activating neurons with light) showed that stimulating these cells makes the animal attack another mouse.
The result and its limits
According to Cornell, tame foxes have fewer neurons expressing this receptor in the region studied. Markenscoff-Papadimitriou explains that the team wants to understand the neurological basis of the behavioral changes associated with selection. The Cornell Chronicle does not provide cell counts or the corresponding statistics; we could not access the scientific paper.
Several cautions apply. Nine brains is a small number. A correlation between fewer neurons and greater tameness does not prove that these cells cause the behavior, and the release does not claim it does. Because the aggression findings come from mice, applying them to foxes remains a hypothesis. Finally, it is still unknown why domestication would have altered this region.
Next steps
According to the Cornell Chronicle, the researchers want to understand why domestication affects this area. Anna Kukekova of the University of Illinois Urbana-Champaign may study how genome mutations influence the development of these neurons. Markenscoff-Papadimitriou sees in the work a sign that environmental pressures can reshape brain structure over relatively short timescales. The first author is Jared Klein (Cornell class of 2025). Co-authors include Andrew Miller (Cornell) and Anastasiya Kharlamova, Anastasiya Vladimirova and Darya Shepeleva (Russian Academy of Sciences). Funding came from Cornell's Center for Vertebrate Genomics.
Key points
- Publication: Current Biology, 2 November 2026, according to Cornell.
- Sample: nine brains (three tame, three aggressive, three wild).
- Observation: fewer estrogen receptor alpha neurons in the ventromedial hypothalamus of tame foxes.
- Limits: small sample, no proof of causation, the reason domestication affects this region still unknown.