More than fifty years ago, Russian scientists began an experiment in domestication. At that time, silver foxes had been raised for fur for about 100 years already, so their care and breeding was well known. The scientists began their project like this: they would approach the cage of a silver fox and note its response. The fox would crouch, ears flattened, snarling in fear, or else back away as far as it could until its body was vertical against the back wall of the cage. All of the foxes were frightened of the humans—but some less than others. The scientists chose the foxes that showed the least fear of humans, and bred them. Then they did the same with the pups, raising up and breeding the least-frightened of them; and so on and so on.
The original foxes were as close to wild animals as anything can be after being bred for fur for a century. Their descendants, after many generations of selection for just one thing—tameness, a liking of humans—look and act like dogs. They seek out humans, they whine and lick your face, they wag their tails. They even look like dogs—mostly, like border collies.