Labradors may be the most popular breed of dog, but the most populous kind is no breed at all. That distinction goes to the humble village dog scratching out a semiwild living in and around human settlements.
While a postdoc at Cornell University a few years ago, Adam Boyko became curious about the little-studied village vagrants. Though dogs were first domesticated 20,000 to 15,000 years ago, most breeds go back only a few hundred years. Perhaps village dog DNA might shed light on the long, early history of domestication, when canines were hanging around humans yet not under our domain. But how to get samples?
As it happened, around the same time Boyko's brother Ryan had married, and he and wife Corin were looking for a cheap honeymoon off the beaten track. The three Boykos decided to merge their two quests. Adam—now at Cornell's College of Veterinary Medicine—obtained a grant, then enlisted Ryan and Corin to spend their honeymoon traveling around Egypt, Uganda, and Namibia, befriending villagers and local vets. They collected DNA from more than 300 village dogs.
When the samples were analyzed, most of the village dogs turned out to be as closely related to wolves as they were to fully domesticated dogs. Rather than being mixed-breed mutts that had gone feral in historical times, the village dogs had been eking out an existence on the human fringe for millennia. Their genomes thus reflected a state of early domestication, before artificial selection and inbreeding directed by humans had taken over. "When you are looking at village dogs," Adam Boyko says, "you have something more akin to natural selection, albeit in an environment that's managed by humans."
Unexpectedly, the study also helped to challenge the reigning view on the place where dogs first appeared. Fossil evidence had already pinned the transition from wolf to dog somewhere in Europe or Asia, and a 2002 study had shown that East Asian village dogs were more genetically diverse—an indication that wolves had first been domesticated in East Asia. But the Boykos' 2009 work found that the African village dogs were just as diverse as the East Asian ones. Some also carried a genetic signature shared with Middle Eastern gray wolves, supporting research by Robert Wayne and Bridgett vonHoldt of UCLA that points to the Middle East as the likely cradle of dogs.
The Boykos continue to expand their sample collection, with another expedition planned for Africa. And they've also begun using the same techniques to solve a related mystery: the strange disappearance of native dogs in South America. We know from the historical record that Native Americans had dogs. But previous population surveys in the Americas turned up only dogs with European heritage. "How do you ship so many dogs across the world that they completely replace the native dogs?" Boyko wonders, suspecting that in fact there may still be village dogs with native DNA in the remotest areas of the continent. So in August the three Boykos packed their bags and headed into the jungles of Peru, searching for the lost American dog.