Dog lovers have long assumed that the dog breed determines its temperament. But a sweeping study comparing the behavior and ancestry of more than 18,000 dogs shows that while ancestry influences behavior, breed has far less to do with a dog’s personality than is commonly believed.1.
“If you adopt a dog based on its breed, you get a dog that looks a certain way,” said study co-author Elinor Karlsson, a computer biologist at the University of Massachusetts in Worcester. “But as for the behavior, it’s a bit of luck of the draw.”
Form over function
That’s partly because varieties are a modern invention. Humans have shaped how dogs look and behave since domestic dogs first evolved from wolves more than 10,000 years ago. But for most of that time, these efforts focused on dogs’ working ability — how well they herded livestock, guarded against danger, or pulled sleds, for example.
Breeds as we see them today — distinctive canines like beagles, pugs, and Labradors — are a byproduct of more recent evolutionary interference. About 200 years ago, dog enthusiasts in Victorian England began inventing breeds by actively selecting for dog characteristics they found aesthetically pleasing.
These experiments created today’s varieties. Today’s purebred dogs are defined by their appearance, but the breed is also thought to influence temperament. For example, the American Kennel Club describes pugs as “mischievous” and border collies as “affectionate.”
But, as Karlsson points out, “anyone who has had eight dogs of the same breed will tell you all about their different personalities”. To get a better idea of how breed affects behavior, Karlsson and her colleagues surveyed thousands of dog owners about their pets’ backgrounds and activities, ranging from whether they tended to eat grass to how likely they were to chase toys. . The researchers then sequenced the DNA of a subsection of the study dogs to see if ancestry could be linked to behavior.
The team found that some traits are more common in certain breeds. For example, compared to a random dog, German Shepherds were easier to steer; beagles, not so much. And the authors’ genetic studies revealed that mixed-breed dogs of certain ancestry were more likely to act in specific ways. For example, mutts with Saint Bernard ancestry were more affectionate, while mutts descended from Chesapeake Bay retrievers had a penchant for breaking doors.
But on average, the breed accounted for only about 9% of the variation in how a dog behaved, some “much smaller than most people, including me, expected,” Karlsson says. Particularly low was the association between breed and how likely a dog was to exhibit aggressive behavior, which could have implications for how society treats “dangerous” dog breeds, says Evan MacLean, a comparative psychologist at the University of Arizona in Tucson, who was not involved. in the study.
“We talk about breeds as if they were categorically different,” he says. “But in reality, that’s not the case.”
Genetic analysis revealed 11 regions of the genome associated with specific behavior. For example, a tendency to cry was associated with a region near two genes whose human analogs are involved in speech. The most significant link was between a region of the genome involved in cognitive performance in humans, but dogs were more likely to get stuck behind objects.
These genetic traits have been around for much longer than breeds have existed, says Kelsey Witt, a population geneticist at Brown University in Providence, Rhode Island. “At first glance, it seems surprising that race is not a good predictor” of behavior, she says. “But when you consider how recent varieties are, it makes sense.”