A new study that combined genome sequences from more than 2,000 dogs with survey data from another 18,000 pooches has come to a conclusion that upends more than a century of established thinking about dog behavior, finding that a dog’s breed contributes little to its behavioral tendencies.
The six-year study was a huge undertaking involving researchers from across the United States, led by lead author Elinor Karlsson, director of the Vertebrate Genomics Group at the Broad Institute of MIT and Harvard.
Dogs and behavior
The new study, published in Science, was the culmination of a project that began years ago as a survey of compulsive behaviors in dogs, Karlsson told a news conference. Dogs are an excellent model of human behavior – they are closely linked to human society and are even treated for behavioral disorders with human psychiatric drugs. Karlsson hoped that understanding the reasons why dogs whine, bark and play fetch at the genetic level could also be informative for understanding the genetics of human behavior.
His early efforts to understand canine genomics were crippled by a lack of access to canine DNA. Karlsson found that each time she shared the topic of her search with others, there was only one result. “They immediately pulled out their cell phone, showed me a picture of their dog, and started telling me all about their dog’s behavior,” she says. Karlsson realized that owner enthusiasm was, in fact, the perfect way to access more information about dogs.
His team created a website, called Darwin’s Ark, where owners could (and still can) upload information about their dogs to the site, answering a survey of over 100 questions about their dog’s appearance and behavior. .
Karlsson, despite her status as an expert in canine genetics, had never owned a dog. So she recruited Marjie Alonso, then executive director of the International Association of Animal Behavior Consultants, to learn more about canine behaviors. Alonso’s insights helped develop the structure of Darwin’s Ark, designing questions that would go to the heart of dog behavior, without being overshadowed by the personality and intent that owners often graft onto dog’s actions. their dog.
What’s in a breed?
Initial data from the study presented the associations between genomic variation in single-breed dogs and the responses that owners of those dogs submitted to the survey. The division of domestic dogs into distinct breeds has become commonplace, but modern breed classifications are less than 200 years old. This represents 50 to 80 generations of dogs, compared to the thousands of generations accumulated over the more than 10,000 years of dog domestication. What effect did this relatively short period have on canine genetics? A solid selection of breeds for looks – think hulking Great Danes, wiry Airedale Terriers or bent-faced Shar Pei – were highlighted in the team’s findings. Physical traits, like height and length of fur, have shown strong ties to different breeds. Certain motor patterns also showed links – Alaskan Malamutes were more likely to howl, while Labrador Retrievers were, unsurprisingly, more likely to retrieve.
But the vast majority of behavioral traits showed little differentiation between breeds and no behavior was breed-exclusive – while Labradors were considered the least likely to howl, 8% of owners said their Labs did. . For Karlsson, this was not surprising: “The problem with complex characters is that selecting them takes time. And so, the idea that they were created within the last 160 years when these races appeared didn’t make sense.
The team compared their responses to breed standards as defined by the American Kennel Club, which assigns each breed a three-word character profile (Shiba Inus are active, alert and attentive, Chihuahuas are charming, graceful and impertinent) and the dog breed encyclopedia. the Encyclopedia were found to be slightly more consistent with the team’s findings. The survey questions were divided into eight “factors,” which captured key aspects of dog behavior. Nine of the ten rankings of the Encyclopedia correlated with at least one study factor. But all of these findings had one major flaw — owners’ reports of their pets’ behaviors are likely influenced by breed stereotypes that Karlsson and his team were trying to counter. This is where mutts came in handy.
Half of the dogs submitted to Darwin’s Ark were mixed-race mutts. The team took a sample of these pooches who had no easily guessable lineage and sequenced their genomes to determine their exact breed composition.
This analysis showed game-changing results. While owners of purebred Golden Retrievers were more likely to say their dogs were friendly to strangers, having Golden Retriever ancestry did not make pooches more or less likely to growl at the postman. The team conducted an extensive genome-wide association study (GWAS) involving these pooches. This analysis showed that, on average, a dog’s breed predicted only 9% of its resulting behavior.
For a few factors, certain racial ancestries had an impact. For example, having Collie ancestry made a dog more likely to be tender (responding to human commands) while dogs with Shar Pei in them were immune to the temptation of a discarded toy. But other behavioral factors, which conventional wisdom has decided are race-related, showed no connection. Breed mattered to an insignificant degree in deciding whether a dog was sociable with other dogs or easily stimulated in different settings.
Heritability of dog traits
So what influences dog behavior? It is important to remember that the study does not suggest that genetics as a whole is unimportant in determining behaviors. The heritability of a trait is the extent to which genetics influence variation in that trait – the heritability of submission, for example, was 30%, suggesting that almost a third of the variation in dogs is due to their genes.
What the study says is that these influences are more likely to have been accumulated over the thousands of years preceding the emergence of the breed, rather than more recently. For Alonso, the message of the study is clear: “Dogs are individuals”. If you’re choosing a dog, breed isn’t entirely unimportant – it’s probably a bad idea to get a husky if you can only spare 15 minutes a day for walks – but breed is not the end of everything. “I don’t think we should really decide that breeds are the things that will tell us whether or not we’re going to be happy with a dog or whether a dog is going to be happy with us,” Alonso says.
The study could have implications for legislation on ‘dangerous breeds’ of dogs. While the team explained that aggression itself was difficult to measure, their agonistic threshold proxy factor – essentially the likelihood that a dog would react negatively to a stimulus – showed almost no link to breed. When it comes to genetics, says Karlsson, a race-based restriction “doesn’t seem to make much sense to us.”
But more broadly, these findings could have major implications for how we select and treat man’s best friend. Rather than expecting to adopt a Labrador and end up with a greedy and friendly pet or predicting an intelligent, independent and stubborn dog when buying a West Highland Terrier, owners should work more dog per dog. “You adopt an individual,” summarizes Karlsson, “with whom you will have to learn to live.
Reference: Morrill, K, Hekman, J, McClure, J et al. Inclusive canine ancestry genomics challenges popular breed stereotypes. Science; 376. doi: 10.1126/science.abk0639