The goal of Soviet zoologist Dmitry Belyaev’s 60-year experiment with silver foxes (Vulpes vulpes) in Siberia was to reveal the evolutionary and genetic bases of domestication.

The experiment, begun in 1959 at the Institute of Cytology and Genetics in Novosibirsk, Russia, was based solidly in conventional Darwinian evolution: The researchers would selectively breeding the friendliest foxes and track the inherited characteristics that accompany tameness.

Those least afraid of people were chosen to reproduce. His goal was to simulate the process that turned fierce ancient wolves into the dogs now known as our best friends.

The experiment worked, famously well. In 10 generations, Belyaev’s lineage of foxes became tame, seeking attention from people and wagging their tails when scientists approached.

But this wasn’t the only way the foxes changed. In 1979, Belyaev noted that some of the foxes had begun to look different, developing curly tails, spotting on their coats and floppy, puppy-like ears. Later, other scientists began noticing some of these same traits in other domesticated species — pigs and goats, birds and fish — which seemed to point to a common genetic path that animals take as they change from wild to tame to domesticated.

Jason Bittel, “Tame foxes taught us about animal domestication. But did we get the story wrong?” at Washington Post

Tame foxes would be a good experimental subject for Belyaev’s purposes because, unlike dogs or cats, foxes are not considered easy to tame. Things went well for decades; the drift toward cute and cuddly came to be called “domestication syndrome.”

Here’s the traditional view:

Now here’s what happened recently: Elinor Karlsson, a biologist at the University of Massachusetts Medical School in Worcester looked into the matter a little more closely:

It’s no secret that the foxes weren’t truly “wild,” Karlsson says. The Soviet foxes originally came from fur farms on Prince Edward Island in Canada, with selective breeding dating back to at least the 1880s. One of Karlsson’s colleagues, on vacation on the island, stumbled across fur farm photographs from the 1920s during a visit to a local museum. Those foxes appeared tame with spotted coats — one of the same domestication traits claimed as a by-product of the Russian experiment that supposedly took generations to emerge.

“These photos dated from decades before the project had even started,” Karlsson says. The images “seemed to raise a lot of questions about exactly what had happened during the course of that project in terms of genetic changes in that population.”

Jake Buehler, “Russian foxes bred for tameness may not be the domestication story we thought” at ScienceNews

Maybe “domestication syndrome” didn’t even exist, she says. These physical traits were not rare in the fur farm population in Prince Edward Island. In any event, as she and her colleagues say in an open-access paper in Trends in Ecology and Evolution, the evidence for a single, specific domestication syndrome is weak: “The defining characteristics vary widely and have not been observed in most domesticated species. Many studies fail to distinguish traits that accompanied domestication from those only in modern breeds, and some traits are reported anecdotally without any accompanying frequencies or measurements.”

For example, Karlsson and her colleagues didn’t find evidence that dogs differed much from wild canids (wolves, coyotes, etc.) in the way they held their tails. So if the tame foxes have curly tails, that fact may be unrelated to their friendliness to humans.

That in turn means that physical traits associated with tameness may be hard to generalize:

“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 [New York] Times.

Emily Makowski, “Famous Fox Domestication Experiment Challenged” at The Scientist

So we are back where we started. The foxes are tame. But why are they tame? Other foxes are decidedly not tame. Why is it so easy to “tame” dogs and cats but not wolves and bobcats? Appearance doesn’t seem to matter much:

The remarkable thing about all this is that some animals that seem almost indistinguishable from their domesticated counterparts can prove to be incurably wild. The difference between foxes and dogs doesn’t seem like very much, domestic pigs seem superficially very similar to the impossibly wild peccaries and warthogs, and zebras can even interbreed with the fully domesticated horses and donkeys…and yet outside a couple isolated cases of taming zebras, the species has proven completely impossible to domesticate.

Alasdair Wilkins, “Why some animals can never be domesticated” at Gizmodo

There are, as always, some clues to evaluate. Evolutionary physiologist and geographer Jared Diamond offers six criteria for tameness, of which the last and most interesting is the social structure of the animal’s natural life:

Lastly, with the exception of the cat, all the major domesticated animals conform to a social hierarchy dominated by strong leadership. This has allowed us to easily modify them so that they’ll recognize their human caretaker as the pack leader.

Natalie Wolchover, “Why Can’t All Animals Be Domesticated?” at LiveScience

However, the cat may not be as much of an exception as sometimes supposed. According to recent research, cats do bond with people and recognize their own names as signals. The cat expects humans to take care of him as a cat cares for her kitten; it is a relationship he understands but pack obedience is neither sought nor expected. But we still come back to: Why is the domestic cat easily tamed and the bobcat not? Selective breeding no longer seems a clear answer.

Nonetheless, the hope to find a gene that explains domestication thrives and is even applied to humans. Current buzz centers on a gene, BAZ1B, which controls 40% of neural crest cells in an embryo. These genes have changed in both modern humans and domesticated animals::

Some variants of those genes are found in nearly every modern human, but either weren’t found or were not as prevalent in the DNA of their extinct Neandertal or Denisovan cousins (SN: 9/19/19), the team says.

That all adds up to one thing: “We’re giving the first proof of self-domestication in humans,” says neuroscientist Matteo Zanella of the University of Milan. Tina Hesman Saey, “A gene tied to facial development hints humans domesticated themselves” at ScienceNews

But wait.

But Zanella and his colleagues’ conclusion is a giant leap from their research on cells growing in laboratory dishes, says Kenneth Kosik, a neuroscientist at the University of California, Santa Barbara. “It’s a very seductive paper,” full of interesting ideas and reams of data, he says. But tying human evolution, domestication and development of facial features together based on the activity of one gene is an overinterpretation, Kosik says. “Those kinds of jumps just don’t belong in a scientific paper.”

Tina Hesman Saey, “A gene tied to facial development hints humans domesticated themselves” at ScienceNews

Bravado can do a lot of things but it is a poor substitute for insight. There is no mystery in why animals snarl, attack, and flee. We are still trying to understand the ones who choose to live with us.

Further reading: Researchers: Apes are just like us! And we’re not doing the right things to make them start behaving that way…
animal intelligence

and

The real reason why only human beings speak. Language is a tool for abstract thinking—a necessary tool for abstraction—and humans are the only animals who think abstractly.