There are so many different breeds of dogs today, it’s almost hard to believe they are all the same species: Canis familiaris. When you look at a Pug or an Afghan Hound, it may be even harder to believe dogs are closely related to gray wolves (Canis lupus). But in fact, they share a common ancestor. Although there’s still much debate about the details, the scientific community agrees that dogs were likely the first domesticated animal. But how did the domestication of dogs from wolves occur?
What Is Domestication?
A domesticated animal is one that has, through evolutionary processes, been reshaped to adapt to a human-made environment. This means the domesticated species has new traits compared to its wild counterpart, including different genes, physiology, and behavior. It’s a development that takes many, many generations. In fact, it was about 30,000 years ago when the domestication of dogs from wolves first began. Recent genetic evidence suggests it could’ve even been 40,000 years ago.
But what was the initial trigger that started ancient wolves along the pathway to dogs. Could it have been humans raising wolf pups, humans and wolves hunting together, or did wolves do this all by themselves?
Two Phases of Dog Domestication
To complicate the situation further, scientists believe that dogs were domesticated in two phases. The first phase lasted until about 15,000 years ago, and the second began right after that. Scientists agree on what happened during the second phase because it’s marked by plenty of archaeological evidence. We know that humans were selecting for certain behavior traits in early dogs, so they could use them for different functions such as livestock guarding or hunting.
According to Vanessa Woods, director of the Duke Puppy Kindergarten at Duke University and co-author of “The Genius of Dogs” and “Survival of the Friendliest,” the dates may change, but the consensus is clear. “As new discoveries are made, and genetic techniques improve, these timelines may shift. But there’s broad agreement that humans began intentionally selecting for traits—like coat color, size, or behavior—much later, after the initial phase.”
Did Humans Domesticate Dogs?
So, what happened during the first phase? There are currently several competing hypotheses. Two are the hunting hypothesis and the pup-adoption hypothesis. They involve humans artificially selecting for certain traits, just as in the second phase. Whereas the third hypothesis states that early dogs domesticated themselves. Deliberate human intervention was not involved.
The hunting hypothesis suggests that humans chose less aggressive wolves to help with hunting. These were the people responsible for the domestication of dogs from wolves. Although humans used early dogs as hunting partners in the second phase of dog domestication, it seems less likely in the first phase. First, humans didn’t use tools like arrows yet that would make tracking and retrieval useful skills from their canine partners. Also, wolves and humans would have been competing for the same food sources. It’s possible humans would’ve been more interested in eradicating wolves than working with them.
Could Dogs Have Self-Domesticated?
The pup-adoption hypothesis states that humans adopted and hand-reared wolf pups. Those pups that bonded with humans would have been kept for the next generation. Those that didn’t socialize well would not. In time, the tamer wolves became reproductively isolated from non-socialized wild wolves, so after enough generations, dogs were formed. However, there is little evidence of humans keeping pets during this time period. And although wolf pups are undeniably cute, was there enough advantage to raising them to justify sharing food with them?
Then there is the self-domestication hypothesis. In this scenario, wolves that were less fearful of humans started scavenging on food waste and leftovers near human campsites. Humans would have killed or chased away the more aggressive wolves, leaving only the more tolerant ones. Over time, these friendlier wolves would have become reproductively isolated from the wild, intolerant wolves living outside the settlements. From there, primitive dogs would eventually have arisen.
New Support for Dog Self-Domestication
Woods feels the idea of humans actively domesticating wolves is highly unlikely. Wolves were larger during the Ice Age, and potentially dangerous predators. She believes wolves likely domesticated themselves. That natural selection for friendliness could have led to behavioral, cognitive, and physical changes. These could include things like patchy coats and floppy ears, commonly seen in domesticated animals. “Once these proto-dogs had evolved these new cognitive and physical traits, they would have stood out from their wild counterparts,” she says. “They could digest starch, bark to alert humans of threats, and even serve as hunting companions – or, in hard times, as food. We call this evolutionary strategy ‘survival of the friendliest.’”
On the other hand, Dr. Alex Capaldi, PhD, Associate Professor of Mathematics and Statistics at James Madison University, believes each of the main hypotheses has their pros and cons. “Humans and ancient wolves were interacting in many locations and times. Ultimately, I believe it’s not really a question of which of these processes led to dog domestication,” he says. “They all probably played some role. Instead, it’s a question of which was the largest factor.”
Would Self-Domestication Take Too Long?
Still, Dr. Capaldi’s latest research study in Proceeding of the Royal Society B provides support for the self-domestication hypothesis by countering one of the common objections – that it would take too long to occur. Using a statistical model, Dr. Capaldi and his team looked at potential evolutionary timelines for dog self-domestication. If wolves chose to stay near human settlements, and they selected mates with a similar temperament, then there was more than enough time for the early dogs to domesticate themselves. In fact, with mate selection factored in, the computer simulation evolved a sustainable dog population 74.2% of the time in a suitably short time period (median of 8,030 years).
Dr. Capaldi points out this isn’t proof for one hypothesis over the other. But it does show that self-domestication was possible in that 15,000 or so years over which the first phase occurred. However, there are other criticisms to the self-domestication hypothesis to be overcome. For example, whether early humans would’ve had enough food scraps available for the wolves to want to hang around.
What Does Dog Domestication Tell Us About Dogs?
If it’s such a murky topic, why are scientists pursuing answers to the questions of dog domestication? Because it gives us clues as to how domestication may have occurred in other species. It also provides insight into human evolution. There are some scientists who believe humans self-domesticated too, selecting for tolerance and cooperation. So the more we learn about dogs, the more we learn about ourselves.
And what does it tell us about dogs? Learning more about the domestication of dogs from wolves can help us understand why humans bond so closely with dogs. According to Woods, it helps explain why dogs can read our gestures, share our homes, and become part of our families. “Their evolutionary journey is built on a partnership based on mutual benefit and emotional connection. That’s why they’ve become the second most successful large mammal on Earth – second only to us.”