DNA might reveal how dogs became man’s best friend.
A new study shows that some of the same genes linked to the behavior of extremely social people can also make dogs friendlier. The result, published July 19 in Science Advances, suggests that dogs’ domestication may be the result of just a few genetic changes rather than hundreds or thousands of them.
“It is great to see initial genetic evidence supporting the self-domestication hypothesis or ‘survival of the friendliest,’” says evolutionary anthropologist Brian Hare of Duke University, who studies how dogs think and learn. “This is another piece of the puzzle suggesting that humans did not create dogs intentionally, but instead wolves that were friendliest toward humans were at an evolutionary advantage as our two species began to interact.”
Not much is known about the underlying genetics of how dogs became domesticated. In 2010, evolutionary geneticist Bridgett vonHoldt of Princeton University and colleagues published a study comparing dogs’ and wolves’ DNA. The biggest genetic differences gave clues to why dogs and wolves don’t look the same. But major differences were also found in WBSCR17, a gene linked to Williams-Beuren syndrome in humans.
Williams-Beuren syndrome leads to delayed development, impaired thinking ability and hypersociability. VonHoldt and colleagues wondered if changes to the same gene in dogs would make the animals more social than wolves, and whether that might have influenced dogs’ domestication.
In the new study, vonHoldt and colleagues compared the sociability of domestic dogs with that of wolves raised by humans. Dogs typically spent more time than wolves staring at and interacting with a human stranger nearby, showing the dogs were more social than the wolves. Analyzing the genetic blueprint of those dogs and wolves, along with DNA data of other wolves and dogs, showed variations in three genes associated with the social behaviors directed at humans: WBSCR17, GTF2I and GTF2IRD1. All three are tied to Williams-Beuren syndrome in humans.
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“It’s fascinating that a handful of genetic changes could be so influential on social behavior,” vonHoldt says.
She and colleagues propose that such changes may be closely intertwined with dog domestication. Previous hypotheses have suggested that domestication was linked dogs’ development of advanced ways of analyzing and applying information about social situations, a way of thinking assumed to be unique to humans. “Instead of developing a more complex form of cognition, dogs appear to be engaging in excessively friendly behavior that increases the amount of time they spend near us and watching us,” says study coauthor Monique Udell, who studies animal behavior at Oregon State University in Corvallis. In turn, she says, that gives dogs “the opportunities necessary for them to learn about our behavior and what maximizes their success when living with us.”
The team notes, for instance, that in addition to contributing to sociability, the variations in WBSCR17 may represent an adaptation in dogs to living with humans. A previous study revealed that variations in WBSCR17 were tied to the ability to digest carbohydrates — a source of energy wolves would have rarely consumed. Yet, the variations in domestic dogs suggest those changes would help them thrive on the starch-rich diets of humans. Links between another gene related to starch digestion in dogs and domestication, however, have recently been called into question (SN Online: 7/18/17).
The other variations, the team argues, would have predisposed the dogs to be hypersocial with humans, a trait that humans would then have selected for as dogs were bred over generations.