Could genetics explain why some people are dog lovers and others cat lovers?
Yes — well, partly — according to new research from a team of Swedish and British scientists. After conducting a study involving more than 35,000 pairs of twins, the researchers say they believe genetic variation may explain as much as half of people’s propensity to own a dog.
“The study has major implications for understanding the deep and enigmatic history of dog domestication,” says Keith Dobney, one of the study’s authors and a zooarchaeologist at the University of Liverpool, in a released statement. “Decades of archaeological research have helped us construct a better picture of where and when dogs entered into the human world, but modern and ancient genetic data are now allowing us to directly explore why and how.”
A 15,000-year relationship
As Dobney and his colleagues explain in their paper, the relationship between humans and dogs goes back at least 15,000 years in Europe and 10,000 years in the Americas.
“Over the subsequent millennia this ‘special relationship’ developed apace throughout most cultures of the world and is as strong and complex today as it has ever been,” they write. “Dogs have long been important as an extension to the human ‘toolkit,’ assisting with various tasks such as hunting, herding, and protection, as well as for more social activities such as ritual and companionship.”
In recent years, research has also begun to suggest that dogs may offer their humans health benefits. Today’s dog owners tend to be more physically active, for example, and to report a greater sense of well-being than people who don’t own a dog. Some studies have even linked dog ownership to a longer life, perhaps because it protects against heart disease.
Yet, as Dobney and his colleagues point out, it’s “difficult to disentangle” whether the “health differences between dog owners and non-dog owners reflect effects of dog ownership itself, or underlying pre-existing differences in personality, health and genetics.”
It was for that reason that the researchers decided to conduct the current study. They wanted to see if they could determine how much of our willingness to own a dog the result of environmental factors — particularly growing up with a pet dog during childhood, which has been shown to be associated with dog ownership in adulthood — and how much might be the result of genetics.
How the study was done
The data for the study comes from information collected on 35,035 pairs of twins in the Swedish Twin Registry. All the twins were born between 1926 and 1996, and all were alive in 2006. Almost 12,000 were identical twins, which meant they shared their entire genome. The rest were nonidentical, including 10,000 twins of opposite gender. They shared about half their genes, like other siblings.
Almost 10 percent of all the twins had been dog owners at some point between the years 2001 and 2016. The researchers were able to determine that fact because Swedish law requires that every dog in the country be registered with the Swedish Board of Agriculture.
The researchers then compared dog ownership between the identical and nonidentical twins. They found that if one twin owned a dog, the other twin in the pair was much more likely to also own a dog if the twins were identical than if they were nonidentical.
With the aid of some complex mathematical modeling, they came up with a precise measure of that inheritability.
“We found that additive genetic factors largely contributed to dog ownership, with heritability estimated at 57 per cent for females and 51 per cent for males,” the researchers write in their study.
The study has several limitations. Most notably, dog owners in the study could have been misclassified as nonowners, either because their spouse or someone else in their household registered the dog or because they didn’t obey Swedish law and never registered their pet. Indeed, surveys have found that only about 83 percent of Swedish dog owners register their pets.
Still, the study’s findings are similar to those of a 2012 American twin study, which suggested as much as 37 percent of the propensity of people to own pets is influenced by genetic rather than environmental factors.
“These kind of twin studies cannot tell us exactly which genes are involved, but at least demonstrate for the first time that genetics and environment play about equal roles in determining dog ownership,” said Patrik Magnusson, the current study’s senior author and an epidemiologist at the Karolinska Institute in Sweden, in a released statement.
“The next obvious step is to try to identify which genetic variants affect this choice and how they relate to personality traits and other factors such as allergy,” he added.
FMI: The study was published in the journal Scientific Reports, where it can be read in full.