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My friend and fellow dog lover Edie, an occupational therapist in Massachusetts, has been looking for a mate for nearly 10 years. She finally thought she’d found one in Jeff, a nice guy, generous and funny, who teaches high school. They dated for several months, and just as there was talk about a future, it occurred to Edie that Jeff hadn’t really bonded with her yellow Lab, Sophie. In fact, as she thought more about it, she wasn’t sure Jeff was a dog guy at all.

She confronted him about this at dinner one night, and he confessed, in some anguish, that he didn’t love Sophie, didn’t love dogs in general, never had.

They broke up the next week. More accurately, she dumped him. “What can I say?” Edie told me, somewhat defensively. “Sophie has been there for me, day in and day out, for years. I can’t say the same of men. She’s my girl, my baby. Sooner or later, it would have ended.”

Having just spent two months on a book tour talking to dog lovers across the country, I can testify that this story isn’t unusual. The lesson Edie gleaned, she says, was that she should have asked about Sophie first, not last.

In America, we love our dogs. A lot. So much that we rarely wonder why anymore.

This, perhaps, is why God created academics.

John Archer, a psychologist at the University of Central Lancashire, has been puzzling for some time over why people love their pets. In evolutionary terms, love for dogs and other pets “poses a problem,” he writes. Being attached to animals is not, strictly speaking, necessary for human health and welfare. True, studies show that people with pets live a bit longer and have better blood pressure than benighted nonowners, but in the literal sense, we don’t really need all those dogs and cats to survive.

Archer’s alternative Darwinian theory: Pets manipulate the same instincts and responses that have evolved to facilitate human relationships, “primarily (but not exclusively) those between parent and child.”

No wonder Edie ditched Jeff. She was about to marry the evil stepfather, somebody who wasn’t crazy about her true child.

Or, to look at it from the opposite direction, Archer suggests, “consider the possibility that pets are, in evolutionary terms, manipulating human responses, that they are the equivalent of social parasites.” Social parasites inject themselves into the social systems of other species and thrive there. Dogs are masters at that. They show a range of emotions—love, anxiety, curiosity—and thus trick us into thinking they possess the full range of human feelings.

They dance with joy when we come home, put their heads on our knees and stare longingly into our eyes. Ah, we think, at last, the love and loyalty we so richly deserve and so rarely receive. Over thousands of years of living with humans, dogs have become wily and transfixing sidekicks with the particularly appealing characteristic of being unable to speak. We are therefore free to fill in the blanks with what we need to hear. (What the dog may really be telling us, much of the time, is, “Feed me.”)

As Archer dryly puts it, “Continuing features of the interaction with the pet prove satisfying for the owner.”

It’s a good deal for the pets, too, since we respond by spending lavishly on organic treats and high-quality health care.

Psychologist Brian Hare of Harvard has also studied the human-animal bond and reports that dogs are astonishingly skilled at reading humans’ patterns of social behavior, especially behaviors related to food and care. They figure out our moods and what makes us happy, what moves us. Then they act accordingly, and we tell ourselves that they’re crazy about us.

“It appears that dogs have evolved specialized skills for reading human social and communicative behavior,” Hare concludes, which is why dogs live so much better than moles.

These are interesting theories. Raccoons and squirrels don’t show recognizable human emotions, nor do they trigger our nurturing (“She’s my baby”) impulses. So, they don’t (usually) move into our houses, get their photos taken with Santa, or even get names. Thousands of rescue workers aren’t standing by to move them lovingly from one home to another.

If the dog’s love is just an evolutionary trick, does that diminish it? I don’t think so. Dogs have figured out how to insinuate themselves into human society in ways that benefit us both. We get affection and attention. They get the same, plus food, shelter, and protection. To grasp this exchange doesn’t trivialize our love, it explains it.

I’m enveloped by dog love, myself. Izzy, a border collie who spent the first four years of his life running along a small square of fencing on a nearby farm, is lying under my desk at the moment, his head resting on my boot.

Rose, my working dog, is curled into a tight ball in the crate to my left. Emma, the newcomer who spent six years inside the same fence as Izzy, prefers the newly re-upholstered antique chair. Plagued with health problems, she likes to be near the wood stove in the winter.

When I stir to make tea, answer the door, or stretch my legs, all three dogs move with me. I see them peering out from behind the kitchen table or pantry door, awaiting instructions, as border collies do. If I return to the computer, they resume their previous positions, with stealth and agility. If I analyzed it coldly, I would admit that they’re probably alert to see if an outdoor romp is in the offing, or some sheepherding, or some beef jerky. But I’d rather think they can’t bear to let me out of their sight.