And they called it puppy love
In 2014, researchers reported on a group of capuchin monkeys in Brazil that had adopted an infant marmoset (a much smaller monkey), which they carried about, cared for and played with for over a year. Perhaps surprisingly, this was the first confirmed record of a long-term pet-like association developing between two animal species not under the direct supervision of human caretakers.
There are certainly plenty of other well-documented stories of chummy inter-species relationships (check out YouTube for “weird animal friendships”), but in each case the animals involved have spent most or all of their lives under close human supervision. Even the capuchin-marmoset association wasn’t established under entirely natural conditions as it occurred in a biological reserve where the animals were being provided with food as part of an ecotourism development project.
So it seems that only humans regularly bring animals into their lives for non-utilitarian purposes … that is, primarily as pets rather than as sources of food or labor.
More to the point, why do we so love our pets? Why do we invest so much of our time and resources to feed them, play with them, take them on walks, pay their veterinarian bills, and post reams of their cute photos and videos online?
Well at least for dogs and cats, the answer seems obvious, doesn’t it? They’re furry, warm and friendly. They’re sweet, funny, playful, mischievous, loyal, beautiful, goofy, energetic, crazy, brave, adorable, adventuresome, cuddly and loving. We just can’t help ourselves.
In 2011, University of Nevada researchers Peter Gray and Sharon Young published a cross-cultural study of pet-keeping practices in 60 societies from around the world. Dogs were the most commonly kept pets, followed by birds, cats and a wide array of other animals stretching from caimans and tortoises to ostriches and bats.
Digging a little deeper into the data on the human-canine relationship, they found that although people lived with dogs in 53 of the cultures, they were only treated as pets in 22 of them. But even there, dogs were primarily kept for their value in hunting, herding, defense and other utilitarian functions and were not considered members of the family circle, as seems the norm in so many Western households.
In fact Gray and Young found that dogs were played with in just three of the 60 cultures, leading the researchers to conclude that the resources and attention given to pets in the U.S. and Europe represents something of a cultural anomaly when considering the full spectrum of human societies.
Then too, even in the most pet-friendly of cultures, many people can’t envision why anyone would ever want to invite an animal into their household. They are messy, demanding and potentially aggressive. What’s to like?
For many years, Western psychologists largely accepted the view that pet-keeping offered us significant health benefits in the form of reduced stress due to the companionship they offer and the increased physical activity they commonly engender.
But recent research is at best equivocal on such benefits. Although some studies have found pet-owners profit from lower blood pressure, higher self-esteem and fewer visits to the doctor, other investigations have found indicators of generally poorer psychological health in pet-owners and no differences between pet-owners and non-owners in longevity.
Western Carolina University’s Harold Herzog has studied the biology and culture of pet-keeping for many years and has concluded that “the existence of a general beneficial ‘pet effect’ on human health and happiness is not a well-established fact but a hypothesis for which there is some support.”
In a 2014 paper, Herzog argued that while humans do possess a variety of innate traits that would favor attachment to members of other species (such as our parental urges and attraction to creatures with infantile features), the practice of pet-keeping has a strong culture-specific component; it is a “product of social learning” from other members of the community in which one lives.
In modern lingo, it’s a meme — a rather contagious culturally-based behavior, more prevalent in some societies than in others.
Which is not to say our love of pets hasn’t a biological basis. Epidemiological studies have shown that pet-keeping in Western societies tends to run in families. There’s a genetic component underlying how predisposed one might be to fall to pieces over a beagle puppy.
And there’s also the hormonal angle. In 2015, researchers reported that oxytocin, the hormone most commonly associated with mother-infant bonding and romantic love, spikes in the brains of both dogs and their owners when they interact.
As Duke University’s Evan MacLean puts it, “Our relationship with dogs are very much like parent-child relationships. We respond to our dogs quite a bit like human children … One evolutionary scenario might be that dogs found a way to hijack these parenting responses and … over time may have taken on more childlike and juvenile characteristics to further embed themselves into our lives.”
Ken Baker is a scientist and a retired biology professor. If you have a natural history topic you’d like the author to consider for an upcoming column, email your idea to firstname.lastname@example.org.