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National Geographic headlined a commentary published March 3, "We didn't domesticate dogs. They domesticated us."
The National Geographic authors summarized what they said is the "most common" model for dog domestication:
some hunter-gatherer with a soft spot for cuteness found some wolf puppies and adopted them. Over time, these tamed wolves would have shown their prowess at hunting, so humans kept them around the campfire until they evolved into dogs.
They proceed to pick holes in this argument.
First, they characterize early human populations as "not very tolerant of carnivorous competitors". Humans, they say, were already successful hunters and wolves eat a lot of meat-- and don't share well-- so no gains would be likely by hunting with them.
Finally, they add
Humans have a long history of eradicating wolves, rather than trying to adopt them. Over the last few centuries, almost every culture has hunted wolves to extinction....If this is a snapshot of our behavior toward wolves over the centuries, it presents one of the most perplexing problems: How was this misunderstood creature tolerated by humans long enough to evolve into the domestic dog?
Their answer:
Most likely, it was wolves that approached us, not the other way around, probably while they were scavenging around garbage dumps on the edge of human settlements. The wolves that were bold but aggressive would have been killed by humans, and so only the ones that were bold and friendly would have been tolerated.
This proposal is closely allied with an argument by biologist Raymond Coppinger included in a 2008 Nature special, Dogs that Changed the World. The PBS website documenting this special starts similarly:
Traditionally, the experts studying the evolution of modern dogs believed that domestication was a conscious effort of humans. The theory was that ancient people took wolf pups from their dens, adopted them, fed them, trained and tamed them.
Coppinger argued that the inherent difficulty in taming wolves-- something he was experimenting with, assisted by graduate students-- made this unlikely. Taming wolf cubs was impossible if they were older than 19 days-- and even then, he said, you wouldn't want to take away a bone, or get in the wolf's way if it was getting serious about courtship.
Coppinger floated the argumen that wolves might have been drawn to the edge of human settlements where garbage would have fed smaller animals. The wolves who stayed-- and tamed themselves-- would have had a shorter "flight distance": how close the animal would allow a human to come before fleeing. Wolves with shorter flight distance would have been able to stay close to settlements, foraging in a new, human-created niche.
If this new perspective is accurate, in order to understand dog domestication, we need to understand wolf behavior more than human behavior.
Following Coppinger's lead, U Mass Amherst doctoral candidate Kathryn Lord conducted research on how dog puppies and wolf cubs develop published in the journal Ethology in December 2012. Lord emphasized the importance of the "critical period of socialization" early in the animal's life:
When the socialization window is open, wolf and dog pups begin walking and exploring without fear and will retain familiarity throughout their lives with those things they contact. Domestic dogs can be introduced to humans, horses and even cats at this stage and be comfortable with them forever. But as the period progresses, fear increases and after the window closes, new sights, sounds and smells will elicit a fear response.... [Dogs and wolves] enter the critical period of socialization at different ages. Dogs begin the period at four weeks, while wolves begin at two weeks....wolf pups are still blind and deaf when they begin to walk and explore their environment at age two weeks.
Unlike dogs, wolves explore a world they experience as frightening:
"When wolf pups first start to hear, they are frightened of the new sounds initially, and when they first start to see they are also initially afraid of new visual stimuli. As each sense engages, wolf pups experience a new round of sensory shocks that dog puppies do not."
There is one small problem: Coppinger's model was based on dating domestication of dogs somewhat later than now seems to be the case.
But the basic idea-- that ancestral dog populations came from wolves who chose to live near human camp edges-- can survive independent of this dating. Contrary to what the National Geographic commentary suggested, this actually seems to be the current consensus model.
In October 2010, Archaeology magazine online quoted University of Victoria zooarchaeologist Susan Crockford who suggests the same scenario:
dogs descend from wolves that gathered near the camps of semi-sedentary hunter-gatherers, as well as around the first true settlements, to eat scraps. "The process was probably driven by the animals themselves," she says. "I don't think they were deliberately tamed; they basically domesticated themselves." Smaller wolves were probably more fearless and curious than larger, more dominant ones, and so the less aggressive, smaller wolves became more successful at living in close proximity to humans.
Research on dog genomes, published in Nature in January, seems to support this scenario. It shows that dogs have genetic changes that allow them to digest starches more easily than wolves can. For scavengers eating scraps at the edge of human settlements, this made more of the trash into potential food.
As the LA Times noted in its coverage of the report, "No one knows for sure when or where the first dogs came to be, but most evolutionary biologists agree that the wolf probably made the first move and that the draw was the food humans discarded".
So some wolves domesticated themselves by adapting to new conditions created by humans, never intended to produce that effect.
A provocative argument by Colin Groves of the Australian National University more than a decade ago went even further, suggesting that humans were "domesticated" as a result of the actions of dogs.
At the time, Michigan University's C. Loring Brace characterized the argument as "an amusing but highly improbable trial balloon".
Groves built on a general observation that brain size sometimes (not always) is reduced in domesticated animals:
Dr Groves believes early humans came to rely on dogs' keen ability to hear, smell and see - allowing certain areas of the human brain to shrink in size relative to other areas.
"Dogs acted as humans' alarm systems, trackers and hunting aids, garbage disposal facilities, hot-water bottles and children's guardians and playmates. Humans provided dogs with food and security. ...Humans domesticated dogs and dogs domesticated humans."
Dog domestication-- so much earlier than any other incident of animal domestication in human history-- may be unlike these later activities: domestication as an unintended consequence of human entanglement with non-human animals.
This doesn't mean it has nothing to say about later domestication. Indeed, it may be that this unintended process of co-habitation made early humans see the other animals around them differently: as potential participants in shared lives.
Dogs may have not only domesticated themselves: they may have invented the concept of domestication itself.
