Humans have been taming and domesticating wild animals over the past 15,000 years, either to put them in a farm or keep them as good ol' pets. In domestication, an animal's behavior changes, becoming less wild and more subservient to its owner.

However, another thing changes apart from behavior: appearance. For instance, dogs, rabbits, and pigs all have floppy ears and white patches, plus shorter snouts, and smaller brains. This phenomenon is called domestication syndrome, and it might also be occurring in mice.

Mice Domestication Syndrome

A team of researchers from the University of Zurich's Department of Evolutionary Biology and Environmental Studies observed wild mice that lived in a barn in Zurich, Switzerland. Within 10 years, the mice developed white patches around their typically brown fur and their snouts started to get shorter.

Why? Well, it appears being exposed frequently to humans triggered the domestication process. Apart from aesthetic changes, the mice also gradually became less fearful of people.

"The mice gradually lost their fear and developed signs of domestication. This happened without any human selection, solely as a result of being exposed to us regularly," said Anna Lindholm, an evolutionary biologist who led the study.

The experiment mirrors the result of a similar one performed decades ago. In 1959, a geneticist in Siberia tamed wild foxes and took note of the ensuing changes. Gradually, the foxes developed friendliness toward people and, astonishingly, started getting white patches, shorter snouts, curlier tails, and droopier ears.

Stem Cell Group

Why do these changes occur during the process of domesticating an animal? It appears a tiny group of stem cells is responsible. Certain aesthetic characteristics — ear cartilage, teeth dentine, and skin pigmentation — plus the stress-producing hormones seem to come from this stem cell group.

According to the study's first author, Madeleine Geiger, house mice started getting closer to humans 15,000 years ago because they were trying to get some of their food. Because of this frequent exposure, the mice became less fearful of humans and became tamer. The behavioral changes then gradually expanded into aesthetic changes, said Geiger — without human involvement, surprisingly.

Further research could shed light into which other wild animals develop a similar set of behavioral and aesthetic changes when more regularly exposed to humans. That's not saying all wild animals are susceptible to such changes, but that wild animals are inherently capable of being tamed because it might be in their biology.

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