From scavenger to household royalty: How dogs evolved from wolves to pampered pets
Dogs and their wolf ancestors have a small genetic difference, but differ vastly in behaviour
*Originally aired on March 1, 2021.
Kathryn Lord isn't quite sure. As she counts them up in her head she chuckles.
"I think it was … 42?"
It's not that she's forgotten the experience. When you hand raise wolf pups, you live in close quarters for weeks. It's intense. The musky, mildly skunky smell. The sharp teeth. If you're sleeping when they're hungry, ready for another bottle — which is every four hours — they "snarfle into your ear." If you don't sit up immediately, says Lord, you end up with pierced ears.
So, how many wolf pups?
"Enough that I've lost track."
Kathryn Lord began rearing wolves in 2004 under the guidance of Jacinthe Bouchard, a noted animal behaviourist in Quebec.
Lord was a grad student researching how dogs and wolves develop during the first weeks of life. By then she was set on her path. It began in her freshman year at Hampshire College in Massachusetts. In her first semester she signed up for a course in animal behaviour. Her professor was Raymond Coppinger, an influential thinker in the field of dog domestication.
For Lord, an evolutionary biologist at the University of Massachusetts Medical School, the mysteries of dog evolution still fire her curiosity. While the genetic difference between dogs and their wolf ancestors is small, the behavioural differences are vast.
"There's a really complex interaction that gets us from gene to behaviour," she says. From wolf to dog, "how does the evolution of that small change in genes interact with early development and environmental change to get us this really very different animal?"
Developing an evolutionary advantage
According to Coppinger's hypothesis of dog domestication certain ancient wolves found they could survive better by scavenging the leftovers of humans rather than by hunting. This meant hanging around the settlements of prehistoric hunter-gatherers. Normally wolves avoid human contact.
"We call it flight distance. How close will you let something frightening approach before you start to run? And how far away will you run, once you start running?"
Wolves run far away when they sense someone approaching, often before the person even sees them. In Coppinger's prehistoric scenario, some wolves are less timid. When they do scramble for safety, it isn't far. By acting less like wolves, they gain an evolutionary advantage: the first chance at human refuse.
As wolves evolve into dogs, this shift from hunter to scavenger triggers a cascade of other changes.
"You no longer need as much parental care," says Lord.
"Wolves don't get really good at hunting till they're two or three years old. It's like a professional sport. It's really complicated to do well. Part of it is learned. They have to stick around mom and dad until they're good at it. This leads to wolves having to spread out their litters," that is, reproduce less frequently.
Wolves bear their young once every year or two. Dogs living in a natural state may reproduce every eight months. Unburdened by the need to teach them to hunt, they finish raising their pups at 10 weeks.
Disbelief of the 'big bad wolf'
Researchers know this by studying free ranging dogs. These are village dogs that survive by scavenging from nearby human settlements. They comprise an estimated 80 per cent of the world's dogs. Raymond Coppinger, and his wife and co-author Lorna Coppinger, spent years observing village dogs in Vietnam, India, Tanzania, and Mexico.
"Free ranging dogs are the forgotten dog" says Sarah Marshall-Pescini of the Wolf Science Center (WSC) in Austria.
"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."
In addition to field studies of village dogs, scientists at the WSC study the social behaviour of wolves and dogs in a controlled environment. A pack of wolves and a pack of dogs live separately in forested enclosures of approximately one hectare. The animals are hand raised and socialized to accept humans. That allows the researchers to observe and care for them in close quarters. It also enables them to conduct tests that measure how well they co-operate.
For example, there is a rope pulling task in which two dogs or two wolves must co-operate to earn a food reward.
"Wolves are outstandingly co-operative" says Marshall-Pescini. "They are pretty tolerant of each other when it comes to sharing food, which makes sense if you think that they have to hunt together and then share carcasses. Whereas dogs can be quite possessive and there is a strict hierarchy that dictates who has access to food."
The researchers at the WSC find that wolves are more measured in their aggression, escalating slowly in a series of steps. This stems from the need to maintain pack cohesion. Dogs on the other hand escalate aggression rapidly.
"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. I actually don't think that's true," says Marshall-Pescini.
This came as a surprise.
"When I imagined wolves and dogs before studying them, I wouldn't have suspected. But this more tolerant version of dogs and 'big bad wolf' thing really falls apart."
Which is not to say they don't have sharp teeth, even as pups.
Guests in this episode: (in order of appearance)
Angela Perri is an archaeologist at Durham University, U.K.
Sebastian Dicenaire is a French playwright and audio producer living in Brussels
Greger Larson is director of the Palaeogenomics & Bio-Archaeology Research Network at the University of Oxford, U.K.
Kathryn Lord is an evolutionary biologist at the Karlsson Lab of the University of Massachusetts Medical School and the Broad Institute.
Mietje Germonpré is a palaeontologist at the Royal Belgian Institute of Natural Sciences in Brussels.
Sarah Marshall-Pescini is a behavioural scientist at the Wolf Science Center in Austria, and the Domestication Lab at the University of Veterinary Medicine in Vienna.
Giulia Cimarelli is a biologist at the Wolf Science Center, and a postdoctoral fellow at the Domestication Lab at University of Veterinary Medicine, Vienna.
* This episode was produced by Neil Sandell. Find him on Twitter.
How to Tame a Fox (and Build a Dog) by Lee Alan Dugatkin and Lyudmila Trut (U of Chicago Press).
What Is a Dog? by Raymond Coppinger and Lorna Coppinger (U of Chicago Press).
Music by: (under Creative Commons license)
Blue Dot Sessions: "A Palace of Cedars", "Hickory Interlude" CC BY-NC 4.0
Podington Bear: "Cracked Nut Suite" CC BY-NC 3.0
Soularflair: "Even in My Dreams" CC BY-NC-ND 4.0
Neil Sandell wishes to thank these people who offered their time and insights:
Lee Alan Dugatkin
Christoph Jung & Daniela Pörtl