Let’s face it: On paper, at least, pets may seem like something of an indulgence.

In return for a lifetime of food and affection and healthcare, they don’t seem to offer anything of practical value.

Of course, we don’t mean animal companions aren’t good for us. Scores of studies suggest they’re a boon for both mental and physical health. They may even help us sleep at night.

But when was the last time you saw a chihuahua pulling a plow through a field? Or a golden retriever unloading groceries from the car?

(Okay, maybe that one time)

Golden retriever dogs carry grocery bags When the groceries arrive, these golden retrievers are happy to lend a hand. (Photo: Snapshot from YouTube video/George Best)

So what do pets really give us? Well, that depends on who you ask.

Some people wouldn’t think of making their cat earn her keep and simply appreciate her for being her enigmatic, window-haunting self. Others don’t understand why we heap so much time and money on pets in return for so little.

Cat behind blinds in window The only job cats seems to take seriously is creeping out the occasional passerby. (Photo: colobok34/Shutterstock)

Well, it turns out, some people may be genetically disposed to appreciate animals — likely because animals first finagled their way into our ancestors' lives by offering a very palpable service.

Somewhere between 15,000 and 5,000 years ago, writes John Bradshaw, author of the bestseller "In Defence of Dogs," humans started domesticating animals. Keeping them from breeding with their wild counterparts was essential since it would have set animal husbandry back generations.

So, to make sure the wild stayed wild — and the domestic stayed domestic — a fortunate few animals were allowed to live indoors and more closely alongside humans.

Eventually those sheltered animals did what animals do: They bonded with people. That group of animal-keeping humans may have prospered quite apart from their non-farming counterparts, the hunters and foragers.

"Groups which included people with empathy for animals and an understanding of animal husbandry would have flourished at the expense of those without, who would have had to continue to rely on hunting to obtain meat. Why doesn’t everyone feel the same way? Probably because at some point in history the alternative strategies of stealing domestic animals or enslaving their human carers became viable.

"The very same genes that today predispose some people to take on their first cat or dog would have spread among those early farmers."

So what started as humans appreciating a real service provided by animals — guarding crops, tilling soil, providing food — may have, over time, become an appreciation for animals in general.

Maybe that’s why efforts to create mechanical companions, like Sony’s robotic dog Aibo, have yet to catch on. It may walk like a dog and bark like a dog and even, roughly, look like a dog. But our genes tell us it isn’t a dog.

Sony Aibo with ball Sony is planning to launch a new, more service-oriented version of the cyber-dog that flopped more than a decade ago. (Photo: ilterriorm/Shutterstock)

And maybe that’s why, in order to sell Aibo, Sony seems to be taking a page from our evolutionary history. The latest incarnation of the robo-dog promises a sophisticated artificial intelligence, allowing the cyber-pooch to help us out around the house. Think dimming lights, turning up music, fetching slippers.

But will the sum of its parts add up to a soul? Will we be able to appreciate and bond with this creature the way our ancestors did with real animals?

It’s hard to imagine even the most space-age cyberdog being able to learn that very old trick.