Some people own dogs, others don’t. How come?

A group of researchers in Great Britain and Sweden wondered why.

After all, there would seem to be a lot of factors that make owning a dog a no brainer: as the earliest domesticated animals, dogs have been providing humans with both help (as working dogs of various types) and companionship for at least 15,000 years. Today, some 43 million households in the US alone have one or more pet dogs. And the health benefits of dog ownership—everything from better emotional health to living longer—have been widely trumpeted in recent years.

Seriously, why doesn’t everybody just get a dog?

According to a new joint study by British and Swedish researchers, the decision to get a dog is less a choice than it is a genetically determined preference—in other words, it’s built into our DNA.

The researchers mined the Swedish Twin Registry, the largest data registry on twins in the world, to determine how the influences of environment and genetics on dog ownership differed. Twin studies are especially suited for this type of research because they allow researchers to examine the overall role genes play in the development of a trait or disorder.

Comparisons between monozygotic (MZ, or identical) twins and dizygotic (DZ, or fraternal) twins are conducted to evaluate the degree of genetic and environmental influence on a specific trait. MZ twins are the same sex and share 100% of their genes. DZ twins can be the same- or opposite-sex and share, on average, 50% of their genes.

The final dataset included 85,542 twins from 50,507 twin pairs with known zygosity, both MZ and DZ, where information on both twins were available in 35,035 pairs.

Information about dog ownership was compiled from Swedish national dog registries collected from  2001 through 2016.

The researchers found that genetic factors largely contributed to dog ownership, with 57% of females and 51% of males showing an inherited preference for dog ownership.

Among their key findings:

• Identical twins are more likely to agree on dog ownership than nonidentical pairs
• It’s impossible to say which genes are involved in the preference

NEWStat reached out to Tove Fall, VMD, PhD, lead author of the study, to find out more. Fall is a veterinarian and a professor of molecular epidemiology in the Department of Medical Sciences and the Science for Life Laboratory, Uppsala University, in Uppsala, Sweden.

NEWStat: What compelled you to investigate a possible genetic angle in who owns dogs?

Tove Fall: Our previous research has shown that dog owners live longer, and I was curious whether people who get a dog are already different before they get a dog. [This study] was the first step in disentangling that. Also, as a veterinarian, I have noticed how different [people’s] attitudes are toward pets.

NEWStat:Were you surprised to discover that genetics might play a role in dog ownership?

TF:I wasn’t surprised that it played a role, but I was surprised at the magnitude. Most social behaviors have a heritable component of about 30%, and [that] was the heritability I expected.

NEWStat:Do your findings have any bearing onthe health benefits of owning a dog?

TF: We need to investigate which genetic variation is linked to dog ownership and what other phenotypes are affected by those genetic variants to understand more about the mechanism.

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