The most famous example of domestication syndrome comes from a 1959 experiment, in which Soviet biologists Dmitri Belyaev and Lyudmila Trut took a few dozen wild silver foxes from a Siberian fur farm and began selectively breeding the tamest animals.
Domestication syndrome might in fact be an accidental side effect of breeding tamer animals
Remarkably, within just a few generations the scientists had bred docile and friendly foxes. It wasn't just their behaviour that had changed; the foxes looked different too. They had shorter muzzles, floppy ears, piebald spots and curly waggy tails.
URL: https://www.bbc.com/future/article/20210805-the-animals-changed-by-proximity-to-humans