“Find out where all the short-legged dogs come from,” an acquaintance told me, just before I left for Rarotonga, the capital island of the Cook Islands. Given that I was going to work as a veterinarian and that I had volunteered to collect DNA samples for the canine genome project, the request didn’t come entirely out of left field. Still, it seemed like some sort of inside joke.
Once I arrived, everything began to make sense. There are a lot of dogs on the island, most of them reminiscent of dingoes, like feral dogs the world over. But a good third of them have legs almost as short as a dachshund’s—though straight and lovely rather than crooked like those of most dwarf breeds. I guessed that these short-legged dogs descended from some distant European ancestor, some basset hound on holiday. But that thought only proved how little I knew about the origins of dogs and other domesticated animals.
Short legs, it turns out, aren’t that rare. The characteristic may even be a function of domestication. Animals don’t just become tame when they adapt to human society. They often become smaller, spotted, pug-nosed, floppy eared, oversexed, and small brained. They do this no matter what the species, genus, or taxon—dog, cat, cow, horse, sheep, pig. When natural selection narrows its focus on a single trait—docility—a suite of other traits tumble along behind. And those traits offer insight into biological development.
“Not one of our domestic animals can be named which has not in some country drooping ears,” Charles Darwin noted in The Origin of Species. His theory of natural selection was based in part on what he observed in domesticated species. Now genes dominate evolutionary theory, but some scientists argue that geneticists are missing something: DNA sequences alone can’t explain the many forms that species take. By looking closely at domesticated animals, they say, we may be able to unlock the mystery of how genotypes give rise to phenotypes—how nearly identical stretches of DNA can create radically different dogs.
The dogs of Rarotonga live in a state of pleasant anarchy. They wear no leashes, and few are collared. They are not so much owned by individuals as by everyone. Anthropologists call such arrangements community domestication. Some dogs are fed; many forage on coconuts, fruit, and garbage. Walk to the beach and you will accumulate dogs, gamboling with one another and with you. Once at the beach, they sit by your towel or wander into the shallow lagoon to fish. They wade out, noses pointed toward the water. If a fish comes by, a dog will pounce with both forefeet. Then it will carry the catch back to the beach and eat.
They are nice dogs and easy to work with, and they became my scientific subjects calmly and gracefully. The canine genome project is a multinational collaboration similar to the Human Genome Project. The DNA samples I was collecting were for Marcia Eggleston’s veterinary genetics lab at the University of California at Davis. Eggleston’s part of the project was aimed at finding genetic markers that would help biologists zero in on the genes that cause defects in purebred dogs, such as hip dysplasia and epilepsy. Other labs could then compare DNA sequences from purebred dogs; wild canids such as wolves, coyotes, and dingoes; and feral dogs. Most inherited diseases are associated with inbreeding, so the diseases don’t exist in wild canids and should be less common in feral dogs. By comparing their genes, biologists hope to identify and map defective sequences.
Eggleston’s lab had a good deal of purebred dog DNA and just enough wild canid DNA. But her only samples of feral dog DNA were from Bali and South Africa, where veterinarians had taken samples while spaying and neutering street dogs. Now I would do the same in the Cook Islands.
At my clinic, the cages were always full: We desexed dogs and cats and treated animals poisoned by fish, hit by cars, or made ill by intestinal parasites. (Our services were free, but we ended up with a lot of fruit and coconuts.) The DNA sampling involved no more than twirling a cytology brush, which looks like a miniature test-tube brush, between a dog’s cheek and gum. Afterward, each subject sat for a digital portrait. I labeled samples with dog names and Zip disks with pictures and shipped everything back to the States.
Word got out of my interest. Rarotonga is like a small town, and each new veterinarian at the clinic is profiled in the local paper. The islanders found it amusing that their dogs were the objects of scientific scrutiny. A few brought their animals in just for the sampling. Cook Islanders have a dry sense of humor and like to flaunt cultural differences to provoke reactions. One fellow at first refused to let me spay his dog, for if all the dogs were desexed, where would the islanders get more dogs? And if there were no more dogs, what would he eat?
I had been working on the island for two weeks when I received the phone call that revamped my worldview. Gerald McCormack, Rarotonga’s national naturalist, author of the local nature guidebook, and director of the Cook Islands Natural Heritage Project, wanted to know the results of the canine DNA analysis. What did they show about the origins of the short-legged dogs? My answer was sketchy at best, so I tried to mollify him by saying that they were probably all descendants of some European import. “Quite possibly not,” he said. “Read Cook’s journals.”