It is not hard to construct a Darwinian explanation of pet ownership. Domestic dogs and cats, the argument would run, are the “cheesecake” of the parental instinct: human creations designed to hijack our evolved dispositions in order to deliver large quanta of adaptively useless pleasure. Cheesecake, while providing little nutritional value, takes advantage of our desire to gorge on fats and sweets (which were hard to come by in the prehistoric past and had to be consumed at every opportunity). Pets capitalize on our innate urge to care for small, helpless creatures. They’re like babies, only better: they don’t grow up, they don’t need a lot of looking after, and they’re even cuddlier than the originals, because they have fur.
It’s no wonder, on this account, that pet ownership has expanded in this country as fertility rates have declined. As of 2008, 18 percent of American women ages 40-44 were childless, up from 10 percent in 1976. Meanwhile, pet ownership has risen from 56 percent of all U.S. households in 1988 to 62 percent today.
But I don’t believe that pets are merely a substitute for the children we’re not having, not even from an evolutionary perspective. Dogs were domesticated at least 15,000 years ago, cats some 10,000 years ago. Human evolution, particularly psychological evolution, appears to happen a lot faster than we used to think. While we’ve shaped the evolution of other species to fit our needs–bred them, in other words–we have surely been adapting to their presence, as well. Cows, pigs, sheep, and goats have also been part of human society for about 10,000 years; donkeys and horses for about 6,000 years. People who get along with animals–people who understand them, who like to be around them, and who enjoy making them happy enough to be healthy and fertile–have clearly stood a better chance of survival than people who don’t.
So what happens when the animals we’ve adapted to being around are taken away? Over the last couple of centuries, proximity to farmyard creatures has ceased to be the human norm. If ownership of cats and dogs is a substitute for anything, it’s probably for that. We don’t need only children in our lives, we also need animals. I’m not suggesting that there really is a pet gene, but I do believe the love of animals, and the propensity to form familiar relationships with them, is deeply intertwined in what it means to be human, not only culturally but genetically. Our pets are not frills or consolation prizes; they’re essential parts of who we are.
