While we know that our relationship with dogs is truly the world’s oldest friendship, researchers are still trying to determine how it started, and, in some cases, who domesticated whom. Regardless, it’s clear that our two species have had profound effects on one another.
The connections between us feel bone deep, and now, it seems, science is validating that perception. The results of a new study, “Evidence of large genetic influences on dog ownership in the Swedish Twin Registry has implications for understanding domestication and health associations,” suggest that an affinity for dogs has a genetic basis.
The team, which included researchers from Uppsala University and the University of Liverpool, was led by Swedish molecular epidemiologist Tove Fall, famous for the 2015 study demonstrating that the risk of childhood asthma is reduced by early contact with dogs.
Based on the observation that children who grow up with dogs are more likely to have dogs as adults, the question the team focused on was whether this was a result of nature (genes) or nurture (individual experience). Identical twins share an entire genome and fraternal twins share half, which makes them ideal candidates for studies that seek to ferret out influences inherent in these sorts of questions. Sweden offered the researchers a rich context for this work; it has the largest twin registry in the world, and dog registration is mandatory, giving the researchers two reliable data sets for this first-of-its-kind investigation.
The final study group comprised 50,507 pairs, in which information on both twins was available for 35,035 of the pairs. The results indicated that heritability could be estimated at 57 percent for females and 51 percent for males, with environmental factors accounting for ownership only in early adulthood. Interestingly, when it came to favored dog breeds in Sweden, the most common was mixed, followed by Golden Retrievers and German Shepherds.
As Dr. Fall noted, “We were surprised to see that a person’s genetic make-up appears to be a significant influence in whether they own a dog. As such, these findings have major implications in several different fields related to understanding dog-human interaction throughout history and in modern times. Although dogs and other pets are common household members across the globe, little is known [about] how they impact our daily life and health. Perhaps some people have a higher innate propensity to care for a pet than others.” This is important in light of the plethora of health benefits derived from living with dogs, including an improved perception of well-being and even increased longevity.
The study’s authors concluded that there is evidence of a genetic factor in our choice to keep dogs, but didn’t identify the specific genes involved. They expect that, as with other personality-related traits, future work will show a polygenic influence—genes whose individual effect is too small to be observed, yet in concert with others, produce a perceptible variation—and that those genes will also be pleiotropic, meaning they will have multiple effects (in addition to being responsible for an affinity for dogs).
Keith Dobney, zooarchaeologist from the University of Liverpool and study co-author, noted that this work “has major implications for understanding the deep and enigmatic history of dog domestication … modern and ancient genetic data are now allowing us to directly explore why and how.”
We’ll definitely stay tuned for future studies into the biological mechanisms of our relationship with dogs, but really, the only proof we need of its existence is waiting by the door for her walk.