How Genetics Challenges Dog Breed Stereotypes

Humans domesticated dogs at least a few thousand years ago, but most modern breeds have only been around for about 160 years. Interestingly, purebred dogs currently only make up a fraction of dogs in existence. Around 80% of all dogs are free-roaming “village dogs.” In the U.S., around half of all companion dogs are mixed-breed or mutts. Unlike modern dogs bred for physical appearance, dogs bred prior to the 1800s were mostly selected for certain uses to humans (e.g., hunting, herding). Since then, stereotypes about breeds have become widespread. For example, you might be familiar with the stereotypes that pit bulls are “aggressive,” terriers “high energy,” and German shepherds “obedient.”

A group of scientists collaborated to test the accuracy of dog breed stereotypes. Specifically, they surveyed the human guardians of about 18,000 dogs and sequenced the DNA of 2,155 dogs. Ultimately, they found that while genes explain more than 25% of the variation in certain behavioral traits, the stereotypes that are tied to certain breeds are largely wrong.

To recruit dogs for the study, the researchers solicited their human companions to enroll in “Darwin’s Ark,” an open data resource for collecting human-reported phenotypes and genetic data in dogs. Human volunteers completed 12 short surveys on their dog’s behavioral and physical traits and then received a DNA kit to swab their dog’s saliva. Once they collected the data, the researchers were able to identify eight broad dimensions of dog behavior, including:

• How comfortable the dog is around people, especially strangers
• How easily excited the dog is
• How much the dog enjoys specific “motor patterns,” like playing with toys
• How responsive the dog is to training
• How easily the dog gets scared
• How social the dog is with other dogs, particularly unfamiliar dogs
• How much the dog interacts with its typical, daily environment
• How much the dog asks for physical contact from humans

Although most of these traits were genetic (transferred from parent to offspring), the researchers found that dog behavior isn’t a reliable way to differentiate breeds. Further, a dog’s breed offers little in the way of predicting behavior for individual dogs, explaining a mere 9% of the behavioral differences even for those within the same breed. For behaviors that were more strongly influenced by genetics, such as responsiveness to direction and commands, knowing a dog’s breed ancestry made predicting his or her behavior slightly more accurate. However, this knowledge was nowhere near enough to “define” a dog by breed. Furthermore, breed offers practically no insight into other, less strongly genetically influenced traits (for example, how easily a dog gets scared).

Thus, in modern dogs, there are only subtle behavioral differences among breeds. More importantly, knowing an individual dog’s breed offers little to no information as to how that dog will behave. Dog behavior, then, is what geneticists refer to as “multifactorial,” or a combination of genes, the environment an individual dog lives in, and other physical traits like age and sex. These differences most likely developed over thousands of years, and the research team didn’t find evidence that the behaviors they studied are a result of intentional selection by breeders (although they didn’t rule this out entirely).

What does this mean for animal advocates? Foremost, this study provides evidence that breed (and possibly breeding) doesn’t tell us what kind of personality we will get when seeking a companion dog. Given that breeding has led to severe health problems in many purebreds (such as hip and joint pain in German shepherds and heart failure in Great Danes), advocates could use this work to provide a practical argument against breeding — especially if the desired effect is some specific personality trait. This advocacy is increasingly urgent given the conditions faced by dogs through forced breeding in “puppy mills.”

Additionally, for humans nervous about adopting certain breeds for fear of some innate behavioral problem, this work is a step toward putting that rumor to rest. Many of the dogs who have a hard time finding homes are seen as “problems” or “dangerous” due to their breed, an unfortunate consequence of such breed-based stereotyping. Even in this study, breed stereotypes were evident. For example, guardians of purebred golden retrievers tended to say that their dogs were not fearful of strangers; meanwhile, this same trait was not widely seen in mutts with strong golden retriever ancestry. In other words, it’s most likely the environment, not the dog, influencing behavioral issues. 

Finally, this research encourages humans to treat dogs as individuals with dignity. Instead of seeing them as inevitable products of their genes, we should respect them as “persons” in their own right, worthy of care and humanity.