About 15,000 years ago, some bold and friendlier-than-average wolves started hanging around the edges of human campfires, perhaps begging for scraps. It was a successful evolutionary strategy: Today, those wolves' descendants—domesticated dogs—are thriving, having followed their human companions to every corner of the globe.
Brian Hare, PhD, the director of the Duke Canine Cognition Center at Duke University, wants to understand the effects of that evolutionary journey. Hare, a cognitive neuroscientist whose works spans comparative psychology and evolutionary anthropology, is interested in the temperamental, physical and cognitive changes that come with domestication.
Over the years, he's found evidence that dogs are surprisingly smart when it comes to understanding human behavior. In one early series of studies, for example, Hare found that dogs can spontaneously follow a person's pointing finger to find a hidden treat, a task that's easy for a human toddler but impossible for a chimpanzee—humans' closest living relative on the evolutionary tree.
In his most recent line of work, Hare is going beyond dogs to explore the effects of domestication on a broader scale. He believes that Homo sapiens didn't just domesticate dogs, cows, sheep and other animals—we domesticated ourselves as well, becoming a friendlier species over time. And our increased amiability, he says, may have been the key to our incredible evolutionary success.
You titled a recent paper "Survival of the Friendliestopens in new window." How did becoming "the friendliest" help our ancestors survive?
An amazing revelation over the last 10 years has been that there were many human species around 100,000 years ago—at least five. So how, in the last 100,000 years, did our species go from being no different than any of those other [long-gone] human species to completely taking over the whole planet?
If you think about it, if you can become more tolerant and friendly with strangers, then you can interact with thousands instead of hundreds of people in your lifetime. And you will be introduced to innovations from hundreds of miles away instead of just dozens of miles away. And you might improve on those innovations, then pass them on to another group.
So, innovation explodes if you can become friendly enough to network with strangers. That's where our hypothesis, the survival of the friendliest, comes from.
What evidence do you and others have that our ancient ancestors became friendlier over time?
When you breed animals to be friendlier, it changes more than their behavior: You change what they look like, their physiology and potentially their cognition.
The work of Dmitry Belyaev was seminal in making that argument. [Belyaev was a Russian geneticist who in the late 1950s began breeding foxes by selecting for friendliness. He found that after just 20 generations, the foxes bred for friendliness became more doglike not only in their temperament but also in physical characteristics—they began to develop the white spots, floppier ears, and shorter, narrower faces that are all characteristics of domestic dogs.]
What connects everything together is development. If you change the neural hormones that are responsible for aggressive behavior or friendly behavior [such as by increasing serotonin levels in the brain], then early in development those same neural hormonal pathways are involved in a lot of other things.
So, there's this pattern: Selecting for friendliness changes development and has cascading effects on all aspects of animals' physiology, psychology and morphology.
For animals to develop friendliness, it doesn't have to involve human intervention, either. It can be favored by natural selection. For example, you see the same physical and temperamental changes among bonobos, which are genetically almost identical to chimpanzees but are xenophilic (liking strangers rather than fearing them). We believe that's because bonobos' early ancestors had a more predictable source of food where they live south of the Congo River, and so natural selection could favor friendliness.
So, what about our own species? We've looked in the fossil record and, if we're right, we would also see some of these same morphological changes over the last 100,000 years. We have evidence for some of them—for example Homo sapiens' faces have become shorter and narrower, just as seen in domestic species—and we're continuing to look for others.
So far this sounds like a warm-and-fuzzy story—humanity's friendliness has ensured its survival. But you caution that this self-domestication hypothesis also has a dark side. What is it?
The same mechanism that allows our friendliness is also tightly intertwined with the worst part of our nature.
Something that is completely unique to our species is that we are attracted to strangers—but only those that we identify as being part of our group. Bonobos are xenophilic, they like all strangers. And chimpanzees are fearful of all strangers. But we are capable of both of those responses.
When you select for friendliness, in a variety of different animals we've compared, you see changes in how the animals deal with others in terms of social cognition. In the case of humans, I think, we gained this incredible enhancement in how we use our theory of mind—how we understand the emotions, beliefs or intentions of other humans.
The flip side of that is if we find new strangers threatening, we can dampen that response and not attribute a human mindset to them. We can dehumanize them and treat them as if they were a rock or a chair. That's where you can get people doing horrific things to one another.
If that's correct, it has big implications for how we think about becoming a friendlier species. There's nice evidence that we can immunize ourselves from some of the worst of our human nature, and it's similar to how we make sure that dogs are not aggressive to one another: We socialize them. We want puppies to see the world, experience different dogs and different situations. By doing that for them when they're young, they aren't threatened by those things. Similarly, there is good evidence that you can immunize people from dehumanizing other groups just through contact between those groups, as long as that contact results in friendship.