Evolutionary biologist susan Crockford of University of Victoria, British Columbia, Canada, hypothesized that changes in the thyroid hormones turned wolves into docile dogs.
... Crockford suggests the metamorphosis could have taken place over the span of a single human life -- between 20 and 40 years.
Crockford points to a 40-year experiment by geneticist Dmitry K. Belyaev and his Siberian research group at the Institute of Cytology and Genetics, where silver foxes were selectively bred for gentleness.
As expected, each succeeding generation was more docile than the last.
What was not expected was that within 20 generations, changes in appearance emerged among the litters. Some pups displayed piebald markings, curled tails and drooping ears. Some also developed another distinctive dog behaviour: They barked.
http://www.canada.com/victoriatimescolonist/news/life/story.html?id=cf1a5ddc-9661-4d7b-98d4-a0821d96334c&k=2518 - via Scribal Terror