Scientists agree on two things about dogs: they descend from wolves, and they were the first animals humans domesticated. Beyond that, nearly everything about how it happened is still in dispute, according to a CBC Ideas examination of the competing theories.
The gap at the center of the debate is a strange one. Genetically, dogs and wolves are nearly the same animal. Behaviorally, they are nothing alike. “There’s a really complex interaction that gets us from gene to behaviour,” Kathryn Lord, an evolutionary biologist at the University of Massachusetts Medical School, told CBC. From wolf to dog, the question is how that small change in genes “interact[s] with early development and environmental change to get us this really very different animal.”
Dr. Lord knows the wolf side of the equation firsthand. She began rearing wolf pups in 2004, living in such close quarters that hungry pups, fed by bottle every four hours, would “snarfle into your ear” while she slept. Asked how many pups she has raised, she laughed. “I think it was … 42?” she said. “Enough that I’ve lost track.”
The leading account of domestication comes from Raymond Coppinger, who taught Dr. Lord at Hampshire College in Massachusetts. His hypothesis holds that certain ancient wolves survived better by scavenging human leftovers than by hunting. That meant lingering near prehistoric settlements despite the natural wolf instinct, which scientists call flight distance — how close a wolf will let something frightening come before it runs, and how far it runs. The less timid wolves got first access to the refuse.
Once wolves stopped hunting, the theory goes, a cascade of other changes followed. “You no longer need as much parental care,” Dr. Lord said. Wolves take two or three years to learn to hunt well, and pups must stay with their parents that long, so wolves breed only once every year or two. Dogs living wild can reproduce every eight months and finish raising pups at 10 weeks.
Researchers know this from studying free-ranging dogs — village scavengers that make up an estimated 80 percent of the world’s dogs. Mr. Coppinger and his wife and co-author, Lorna Coppinger, spent years observing them in Vietnam, India, Tanzania and Mexico. “Free ranging dogs are the forgotten dog,” Sarah Marshall-Pescini of the Wolf Science Center in Austria told CBC. “If we have any possibility of looking at how dogs used to live, that’s a closer model than our Western childlike way of treating dogs.”
At the Austrian center, a hand-raised pack of wolves and a pack of dogs live in separate forested enclosures of about one hectare each, allowing tests of how the two cooperate. In one task, two animals must pull ropes together to earn food. The results upend the familiar picture. “Wolves are outstandingly co-operative,” Dr. Marshall-Pescini said, and tolerant about sharing food — predictable, since they hunt together and share carcasses. Dogs, by contrast, are possessive, with strict hierarchies over who eats.
Wolves also escalate aggression slowly, step by step, to preserve the pack. Dogs escalate fast. “There is this idea that from wolves to dogs, dogs are a nicer version than wolves — less aggressive, more tolerant, a more fuzzy, cuddly kind of animal,” Dr. Marshall-Pescini said. “I actually don’t think that’s true.”
She conceded the finding surprised her, too. “I wouldn’t have suspected,” she said. “But this more tolerant version of dogs and ‘big bad wolf’ thing really falls apart.”