ABOVE: FLICKR.COM, ZOOFANATIC

Apaper published yesterday (December 3) in Trends in Ecology and Evolution criticizes a famous experiment on fox taming and casts doubt on domestication syndrome, the idea that a variety of physical traits change when an animal goes from wild to tame.

In the 1950s, geneticist Dmitri Belyaev conducted a well-known animal domestication experiment at the Institute of Cytology and Genetics in Novosibirsk, Russia, in which he tamed silver foxes (Vulpes vulpes) by selectively breeding the friendliest ones.

Within 10 generations, the foxes showed dog-like behaviors, such as seeking out human contact and licking people’s hands and faces. Their appearance also changed—they developed tails that curled up, spotted coats, and floppy ears similar in appearance to other domesticated animals such as dogs, cows, and pigs. This led Belyaev and other researchers to suggest that certain physical traits evolve with tameness, a phenomenon that came to be known as domestication syndrome.

But Belyaev’s foxes weren’t wild to begin with, say the authors of the new study, led by geneticist Elinor Karlsson at the University of Massachusetts Medical School and the Broad Institute of MIT and Harvard. Genetic testing suggests that the foxes Belyaev obtained were from a Canadian fur farm, where farmers may have already been breeding animals to have unusual spotted patterns. And Belyaev started his experiment with a relatively small population of 130 foxes, which could have made traits such as spots spread more quickly.

Researchers had already raised questions about the foxes’ tameness in the past. When the late Raymond Coppinger, a dog evolution researcher at Hampshire College, visited the International Fox Museum and Hall of Fame on Prince Edward Island, Canada, he was taken aback to see pictures of spotted foxes that looked just like Belyaev’s foxes, reports The New York Times.

“The paper provides the final nail in the coffin to the idea of a universal set of traits characterizing all domesticated animals,” Marcelo Sánchez-Villagra, a paleobiologist at the University of Zurich who studies domestication and was not involved in the study, tells the Times.

Additionally, Karlsson’s team did not find conclusive evidence that dogs hold their tails differently from wild species of foxes or wolves, and found limited evidence that it happens in other mammals.

“Our main point is not that domestication syndrome doesn’t exist, but just that we don’t think there is enough evidence to be confident it does exist,” Karlsson tells The Washington Post.

Emily Makowski is an intern at The Scientist. Email her at emakowski@the-scientist.com.