The key point is that the experiment offers a hint as to the stages by which domestication takes place.
"Before, we knew that dogs and wolves were descended from the same ancestor, but we didn't know how," says Hare. "What came first? The fox experiment showed that just by selecting for friendliness, all these other changes, including an increase in social skills, happened by accident."
In fact, Belyaev and Trut soon found that it was not just the foxes' personalities that were changing. Their bodies were too.
"The main surprise was that, together with changing of behaviour, many new morphological traits in tame foxes start to appear from the first steps of selection," said Trut.
Foxes are naturally more stubborn than dogs (Credit: Blickwinkel/Alamy)
The domesticated foxes had floppier, drooping ears, which are found in other domestic animals such as dogs, cats, pigs, horses and goats. Curlier tails – also found in dogs and pigs – were also recorded.
All these changes were brought on by selecting for one trait: tameability
What's more, "in only a few generations, the friendly foxes were showing changes in coat colour," says Hare.
The process seems to be ongoing. "At the more advanced steps of selection, changes in the parameters of the skeletal system began to arise," Trut wrote. "They included shortened legs, tail, snout, upper jaw, and widened skull."
The foxes started looking more delicate and, put simply, "cute".
Their reproductive habits also changed. The domesticated foxes became sexually mature about a month earlier than non-domesticated foxes. Their mating season was longer and they could breed out of season. On average, their litters had one more cub.
All these changes were brought on by selecting for one trait: tameability. This gives us a big clue to how domestication works.
