What does it take to domesticate an animal?

November 6, 2015

Dear Cecil:

How long does it take to "officially" domesticate an animal? What is the last wild animal humans have domesticated? If we tried long enough, could we end up with domesticated koalas or beavers?

— Dane Coffey, Bella Vista, Arkansas




Cecil replies:

“Officially”? There’s not exactly a UN Bureau of Domesticated Animals where species register once they’ve become housebroken. But sure, plenty of animals are ripe for domestication, given enough time. Maybe eventually we could train those beavers of yours to replace the Army Corps of Engineers.

First, though, let’s make something clear about domestication. In brief, it’s not the same thing as taming, which is the easy part — what you do when you (e.g.) take a baby tiger from the jungle and hand-feed her through cubhood. By the end of this process, ideally, she’ll be amiable enough to star in your Vegas stage act.

But say that tiger then has cubs of her own. They won’t have inherited any of their mother’s ease around humans. Taming refers to learned behavior, whereas domestication indicates an actual shift in the animal’s genome that takes generations to come about. Scientist-author Jared Diamond argues in his blockbuster Guns, Germs, and Steel that this distinction disqualifies certain well-known working animals, notably the draft elephants of South and Southeast Asia — they’re not bred by humans but rather plucked from the wild a la carte and trained. A domesticated animal, as Diamond puts it, is one “selectively bred in captivity and thereby modified from its wild ancestors, for use by humans who control the animal’s breeding and food supply.” (Plants can undergo a similar process, of course — the domestication of cereal crops like wheat has had a not insignificant effect on human history — but we’ll focus here on fauna.)

As to your question, there’s an easy answer: the last wild animal to be domesticated was the silver fox, and it took a startlingly short time. In the late 1950s a Soviet biologist named Dmitry Belyaev rounded up about 150 of the animals with the goal of, essentially, replicating and observing the process by which, 10,000 years before, some wolves became dogs. As he bred each successive generation of kits, Belyaev selected for one trait: how the animals got along with humans.

The results were remarkable: by 1964, Belyaev had produced fourth-generation foxes as friendly as dogs — tails wagging, the whole shebang. But it wasn’t just their behavior that changed. Belyaev noticed a phenomenon identified earlier by Darwin: domesticated mammals share certain physiological qualities that set them apart from their wild forebears. They’re smaller, with smaller brains and teeth; their fur has white spots or patches; their ears are floppier. Between their juvenile morphology and their friendly behavior, it’s as though domesticated animals are wild ones that have been stunted, forever stuck in adolescence. The ears of Belyaev’s foxes began to droop after just nine generations.

By the time National Geographic checked in on this long-running experiment, in 2011, researchers had identified two regions of the domesticated foxes’ genomes that differed from those of their wild relatives. It was once thought there might be a single gene responsible for domestication, though it’s beginning to look like it’s actually a far more complex process of genetic change.

The ease with which Belyaev pulled this off makes it sound as if, with a little effort and a healthy research budget, you can domesticate whatever you please. But Diamond believes there are a few prerequisites. Domesticable animals, he thinks, should:

Grow quickly. Nobody wants to wait around 15 years for an elephant to mature.
Breed in captivity. (Difficulties on this front apparently thwarted Belyaev’s attempts to domesticate otters.)
Be efficient eaters, in terms of biomass conversion, and not picky, either. This rules out your koalas.
Have reasonably decent personalities, which rules out grizzly bears and Dick Cheney.
Not be too nervous.
Come from a social structure with a “well-developed dominance hierarchy,” which humans can then insert themselves at the top of. (This would seem to rule out cats, but Diamond suggests the reason cats were domesticated is that we never tried to herd them; they’ve only ever been pets.)
So domestication is a highly contingent process by which humans have sometimes manipulated evolution to benefit ourselves. Or animals have, to benefit themselves. One hypothesis has it that the process by which wolves became dogs sprang from their own initiative, whereby the less aggressive among them realized a selective advantage in hanging around people — namely, the buffet possibilities presented by human garbage. Humans subsequently did their part by adopting and breeding the friendliest pups.

Researchers continue to be intrigued by the self-domestication hypothesis. These days they’re looking at it to explain certain traits observed in bonobos, vis-a-vis their violent cousins chimpanzees, from whom they split taxonomically about a million years ago. The bonobos are peaceful and, in line with Darwin’s observations, display those familiar differences in morphology. Have they domesticated themselves, and why? The import of this question is obvious. Certain hominids abandoning aggression, embracing sociality, becoming more … evolved? Sound familiar?

— Cecil Adams