TO: The endurance of the most social, bold dogs is what you call "survival of the friendliest."
BH: Exactly. Since Herbert Spencer coined the phrase "survival of the fittest," people often think of the Hobbesian notion of nature as red in tooth and claw. And, of course, many species do use aggression to stay on top. But nature is also replete with examples of species evolving to be friendlier, more tolerant and social. In those cases, the ones which are able to survive by being friendly can outcompete those which are less friendly.
Dogs as a species became more tolerant and as a result are one of the most successful mammals in the history of the planet—in terms of quality of life, numbers, distribution. I don't think there's any place where humans have gone that dogs have not also gone—even space! If you compare dogs with wolves, that population that decided to eat garbage, boy did they make the right decision.
TO: What do you mean when you suggest that humans, too, are self-domesticated?
BH: Selection of friendliness over aggression was what made dogs happen. And in our ape family, it seems that bonobos have been selected to be more friendly. That then makes us look at our own species; does that mean that we have been under selection to be less aggressive and more tolerant? That is how we went from having a dispersed distribution to being able to live in very high-density populations since the agricultural revolution.
TO: What do you make of the hypothesis that dogs played a role in domesticating us?
BH: I don't think that hypothesis is any less plausible than others I've heard that attempt to explain the transition from foraging to settled agriculture. When humans became more sedentary, dogs started appearing. Humans who were tolerant toward dogs would have had hunting partners, a home alarm system, and when things got tough, an emergency (and portable) food supply.
What's required for civilization is tolerance, so maybe these advantages pushed humans toward being more tolerant. I'm not saying it did everything, but it could have played a role. Now, it's another question how you test any of this.
TO: You suggest the increasing overlap between human and wild territory may put us on the cusp of another domestication event.
BH: Take the coyote. The coyote evolved in the western United States. There were no eastern coyotes, but now they have moved into the eastern United States. How is it that coyotes that were living in places like Yellowstone National Park now live on Manhattan Island? It must have required some type of evolution in terms of how they deal with interactions with people. Is this the same process that happened with proto-dogs? I don't know. But creatures evolve to take advantage of any niche that exists—even in high-density urban areas.
TO: Though they're impressively clever in many ways, dogs come up short in other aspects, finding it difficult to learn how to pull a rope to bring food nearer to them, for example.
BH: Yes, that is one of the areas where the only way to describe it is that they're a bit vapid. This concept of connectivity is just too much for them, which is why they end up wrapping their leads around posts. But they overcome their weaknesses by depending on humans.