What the Fox Genome Tells Us About Domestication

After only a few decades of domestic breeding, friendly foxes have social behavior woven into their genes

Many friendly foxes carried a version of a gene that differed from their feral counterparts. (Minette Layne/Flickr)
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It took humans several millennia to turn feral wolves into man’s best friend. But in just 60 years, scientists did the same with foxes. Because of this, researchers can now see, for the first time, how domestication leaves its mark on a friendly fox’s genes.

In a study published this week in the journal Nature Ecology and Evolution, researchers sequenced the genomes—or genetic roadmaps—of several groups of red foxes (Vulpes vulpes) that varied in demeanor and found specific groups of genes that differed between the fierce and the friendly. To the delight of those doggedly investigating how canines became domesticated, many such genes matched up with those previously identified in studies of dog domestication.

Luckily, researchers had easy access to foxes bred to behave differently. Beginning in 1959, Russian geneticist Dmitri Belyaev used fox breeding as a sped-up way to study the evolutionary meanderings that dogs underwent on the path into human homes. Even back then, he suspected socialibility was a genetic trait—that the lone wolf and cuddly lap dog behave differently because their genes dictate as much. Though he didn’t live to see his hunch confirmed, his purposeful experimentation would be a genetic jackpot for researchers looking into the genes that drive an animal’s amicability.

Belyaev’s foxes—which sport a mutation that makes their coats silver instead of red—were split into two separate lineages: friendly and aggressive. At each reproductive crossroads, he and his researchers selected only the most docile and the most feral of the bunch and mated these individuals to each other. Within ten generations, they bred a wide-eyed group of tail-wagging foxes that not only tolerated the presence of humans, but eagerly sought it out.

Belyaev died in 1986 after dedicating the last third of his life to his growing fox colony, but other scientists, like Anna Kukekova, a biologist at the University of Illinois and author of the new study, were quick to take up the mantle.

Kukekova and her team sequenced the genomes of foxes from three groups: Belyaev’s two original lineages of combative and docile foxes, and traditionally farm-raised foxes that hadn’t been selected for temperament.

The sequences revealed 103 genetic regions that differed among the groups. Encouragingly, 45 of these genetic locales overlapped with previously identified regions in studies of dog domestication—both reconfirming the merit of previous work using canine genetics and establishing new connections.

In an interview with Carolyn Y. Johnson of the Washington Post, Bridgett vonHoldt, a biologist at Princeton University who was not involved in the study, confirms the likely overlap in genes responsible for the transition of feral to friendly in both wolves and foxes. Domestication—it seems—targets similar groups of genes, even across species.

An additional 30 genes had previously been linked to fox temperament. Of these genes, one in particular stood out: SorCS1, which is involved in ferrying chemical signals between brain cells. Most of the tame foxes carried a version of the gene that was different from that of their feral counterparts—but the link is complicated. Unsurprisingly, one gene can’t fully explain the vast split in behavior, and it is most likely only one piece of an extremely complex puzzle. Still, this might hint at a logical connection between domestication and how foxes learn.

A full genetic understanding of domestication is a long way off, explains geneticist Elaine Ostrander of the National Human Genome Research Institute in Bethesda, Maryland, in an interview with Tina Hesman Saey of Science News.

Ostrander likens the process to zooming in on a map: “Before you get to the right house, you have to get to the right street. Before you can get to the right street, you have to get to the right city, state and so on,” she says. Basically, fox geneticists have zeroed in on a county; it remains to be seen whether they will find domestication’s correct address.

About Katherine J. Wu
Katherine J. Wu

Katherine J. Wu is a Digital Editor at PBS NOVA and Story Collider producer. She holds a Ph.D. in Microbiology and Immunobiology from Harvard University. Previously, she served as a AAAS Mass Media Fellow at Smithsonian magazine.

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