Horses and other animals typically used for transport are products of directed domestication: Humans take an animal out of the wild with a specific use in mind, and breed subsequent generations for that purpose.
In commensal domestication, however, humans unintentionally create an environment that attracts the animal. Over generations, the human appreciates some benefit that the animal provides and encourages its presence while the animal becomes separated from others of its kind in the wild.
Cats are an example of commensal domestication. Once humans took up agriculture and began storing grain, the ready food source attracted rodents, which attracted cats.
Dogs may have undergone a similar process. “We see how it could have happened in wolves,” says Larson. “There was a population that just started hanging out with us, subsisting off the environment we were creating. Only after generations did humans start intentionally creating populations, and only long after that do we get crazy things like Labradoodles.”
Other researchers, however, including PennVet’s Serpell, doubt human hunter-gatherers would have tolerated large predators near their camps — or that the resource-frugal humans would have left behind enough potential food to sustain a wolf-sized animal. Instead, they argue, it’s possible that prehistoric humans, like many more recent hunter-gatherer groups, had a custom of adopting baby animals. A hand-reared ancestral wolf, Serpell argues, would develop an intense, familial bond with humans.
“That animal, as an adult, would be sufficiently socialized to be safe” in the eyes of the hunter-gatherers, says Serpell.
Meanwhile, other researchers argue that debating the how or why of domestication is beside the point.
“I think of domestication as a multispecies process,” says Losey. “It’s not something we did to wolves. It’s something we’ve done together.”
If two apex predators managed to find mutual benefit in a close relationship once, as early research held, or twice, as the newest analysis indicates, why not three or four or 10 times?
“In some ways, we have embedded the idea that domestication is so complicated and rare and unusual that it could have only been done once,” says Losey. “I don’t see that. I think there were probably hundreds, if not thousands, of domestications that lasted only a few generations. For whatever reason, they didn’t persist.”
As our oldest companion outside our own species, the story of dogs is most closely linked with our own. (Sorry, cat fanciers.) The more collaborative, more precise direction research is heading promises at last to tell us the opening chapter of that long relationship.
“We need to reconsider how we think of dog domestication,” says Losey. “It’s an ongoing process that continues today ... and it’s a process that has no end. It’s an evolutionary partnership.