Human Nature


Our creepiest genetic invention, the dog.

Dogs: Made to order

Have you heard the latest news? We’ve decoded the DNA of dogs. Here’s how the media-approved version of the story goes: We’re showing our love for “man’s best friend” by discovering and treating the genetic causes of his ailments. In return, we’ll learn to treat the same ailments in ourselves.

It’s a heartwarming story, but it’s a fraud. The reason we targeted the dog genome for decoding is that it’s useful for genetic research. The reason it’s useful for genetic research is that dogs are neatly divided into breeds, each of which is plagued by specific diseases. And the reason dogs are divided into diseased breeds is that we made them that way. Dogs are the world’s longest self-serving, ecologically reckless genetic experiment, perpetrated by the world’s first genetically engineering species: us.

Dogs were just a loose category of wolves until around 15,000 years ago, when our ancestors tamed and began to manage them. We fed them, bred them, and spread them from continent to continent. While other wolf descendants died out, dogs grew into a new species. We invented the dog.

We didn’t pick just any wolves for this project. We picked the ones that could help us and get along with us. Dogs are dumber than monkeys and other mammals in many ways, but they excel at one thing: interpreting human behavior. Three years ago, scientists tested this talent in wolves, adult dogs, puppies raised in households, and puppies raised in kennels. The wolves couldn’t read humans well, but the puppies could—even the puppies raised in kennels. Through selection, we’ve hardwired human compatibility into dogs. We’ve made a species in our image.

But that wasn’t enough. We had specific needs. We bred hunting dogs, herding dogs, sled dogs, and guard dogs. (We also tried a few unauthorized uses.) We turned reproductive separation and inbreeding into a science, multiplying and dividing the species into more than 400 breeds. The American Kennel Club sorts them into the Sporting Group, Working Group, Herding Group, Hound Group (whose ancestors were “used for hunting“), Terrier Group (whose ancestors “were bred to hunt and kill vermin“), and Toy Group. “The diminutive size and winsome expressions of Toy dogs illustrate the main function of this Group: to embody sheer delight,” says the club’s Web site. Every dog has his duty.

Each need, each breed, called for special traits. We bred collies for vigilance, Rottweilers for aggression, retrievers for obedience. In a span of decades, we bred ferocity into Dobermans and then, with equal deliberateness, bred it out. We treated dogs like guns. We designed and bought them for protection, then complained when they hurt us. When cities banned pit bulls, we bought Rottweilers. It was as easy as replacing an illegal assault weapon with a legal one.

Not all our designs were utilitarian. We made some breeds just for fun. Some, like the Pharaoh Hound, were thought to be ancient because they looked like dogs drawn on Egyptian tombs. But last year, when we checked their DNA, we found no evidence they were older than modern breeds. Apparently, breeders crafted them by mating dogs that looked like the drawings. Life imitated art.

In the course of engineering dogs to look, feel, and act as we wanted, we ruined millions of them. We gave them legs so short they couldn’t run, noses so flat they couldn’t breathe, tempers so hostile they couldn’t function in society. Even our best intentions backfired. Nature invented sexual reproduction to diversify gene pools and dilute bad variants. By forcing dogs into incest (which we ban among humans, in part for biological reasons), we defied nature. We concentrated each bad gene in a breed, magnifying its damage: epilepsy for springer spaniels, diabetes for Samoyeds, bone cancer for Rottweilers. That’s why the dog genome is so nifty: We can find disease genes just by comparing one breed’s DNA to another’s.

Well, too bad for the dogs. But three cheers for us and our experiment. “The dog genome is a wonderful playground for geneticists,” exults the New York Times. “A treasure trove,”  says  the San Francisco Chronicle. “A convenient laboratory,” agrees Reuters.

Man’s best friend, indeed.