Domesticating foxes - an epic Russian experiment

A very interesting article at Scientific American details a multi-year experiment conducted in Russia which gives insight into how early humans domesticated dogs:

Belyaev and other Soviet-era biologists looked around at domesticated dogs, a species they knew had descended from wolves, and were puzzled. They could not figure out what mechanism could account for the differences in anatomy, physiology, and behavior... Belyaev hypothesized that the anatomical and physiological changes seen in domesticated animals could have been the result of selection on the basis of behavioral traits. More specifically, he believed that tameness was the critical factor...

Starting at one month of age, and continuing every month throughout infancy, the foxes were tested for their reactions to an experimenter. The experimenter would attempt to pet and handle the fox while offering it food. In addition, the experimenters noted whether the foxes preferred to hang out with other foxes, or with humans.

Then, upon reaching sexual maturity (seven to eight months), they had their final test and assigned an overall tameness score. They rated each fox's tendency to approach an experimenter standing at the front of its home pen, as well as each fox's tendency to bite the experimenters when they tried to touch it. Only those foxes that were least fearful and least aggressive were chosen for breeding...

The result of this breeding program conducted over more than 40 generations of silver foxes was a group of friendly, domesticated foxes. These domesticated foxes, which were bred on the basis of a single selection criteria, displayed behavioral, physiological, and anatomical characteristics that were not found in the wild population, or were found in wild foxes but with much lower frequency...

The domesticated foxes were more eager to hang out with humans, whimpered to attract attention, and sniffed and licked their caretakers. They wagged their tails when they were happy or excited...

More than 50 years have passed since Belyaev began his silver fox breeding program, and research with these foxes continues to uncover the genetic changes that occur with consequences for physiology, anatomy, behavior, and cognition, as a result of the process of domestication, though on a smaller scale. In 1996, the breeding population contained 700 individuals, but by 1999, it was down to 100. Because of the realities of the Russian economy and the shortage of funding for science, in order to maintain the research, some foxes had to be sold for fur, and some are now being sold as pets...

And as a bonus, this interesting tidbit:

Darwin noted, in On the Origin of Species, that “not a single domestic animal can be named which has not, in some country, drooping ears.” Drooping ears is a feature that does not ever occur in the wild, except for in elephants...

Upright ears being presumably more suited for the hazardous life in the wild.  Many of the domesticated foxes developed drooping ears.

Via Not Exactly Rocket Science.