It has generally been assumed that the process that could transform this:

into this:

was a drawn-out evolutionary slog, taking many generations of human-canid interaction to achieve. But as Tim Flannery notes in a recent review of several new titles on the subject for The New York Review of Books, Lee Alan Dugatkin and Lyudmila Trut’s How to Tame a Fox (and Build a Dog): Visionary Scientists and a Siberian Tale of Jump-Started Evolution offers a fascinating look at the groundbreaking discovery that revealed that the process of domestication, once thought to have taken thousands of years, could be compressed into decades:

“Profound insights into how dogs evolved from wolves come from a remarkable, multidecade experiment on foxes that was carried out under the supervision of the Russian geneticist Dmitri Belyaev from the 1950s onward. … Belyaev’s experimental method was simple in the extreme. Out of the thousands of silver foxes held at a fur farm, he simply selected for ones that were calmer than normal in the presence of humans. After just a few generations of selective breeding, some offspring of these slightly tamer foxes started to seek out human company. Breeding these individuals produced foxes that showed changes in their reproductive systems that are typical of domesticated animals, which often bear more than one litter per year. Astonishingly, a few of the selected foxes even began to wag their tails and bark—characteristics otherwise seen only in dogs.

…

By demonstrating that a simple selection mechanism could, over an exceedingly brief time, have such a large effect, Belyaev’s experiment had a major impact on our understanding of how the dog–human relationship began.

The NYRB article has more on the book and the Russian experiments and their groundbreaking revelations about about the genetic and behavioral evolution of domesticated animals, but for more background check out the video below consisting of excerpts from a Soviet-era film made for the 1977 International Congress of Genetics, held in Moscow, about experiments in domesticating the silver fox: