D: Sorry I’m late this morning Yaël. I had to take my dog, Max, to the vet.

Y: Oh, that’s OK, Don. Say, have you ever thought about why you own a dog?

D: Sure I have, we wanted our kids to have the experience of growing up with one.

Y: Some scientists think that there may be a deeper explanation. In 2019 a team of Swedish and British scientists published a study claiming that whether we chose to own a dog may be influenced by our genes.

D: That’s hard to believe. What’s their evidence?

Y: The study was based on a database of twins maintained by the Swedish government. There are two kinds of twins. Identical twins have all of the same genes. Fraternal twins are no more genetically similar than other siblings, but usually grow up in the same environment. The researchers used this difference to tease apart environmental from genetic influences on dog ownership. They combined the data on twins with data on dog ownership also obtained from Swedish national registries, and studied dog ownership in more than thirty-five thousand twin pairs.

D: Now I see. If identical twins are more likely than fraternal twins to both own dogs, that would be evidence for a genetic influence on dog ownership over and above influences from the twins shared upbringing.

Y: That’s right, and, using this reasoning, the researchers’ analysis showed that there was, indeed, a significant genetic influence on dog ownership that was stronger in women than in men.

D: Maybe this new finding can tell us something about how the partnership between humans and dogs evolved.