The point is, then, that if dogs were indeed domesticated more than 100,000 years ago, as Wayne's data suggest, there wasn't much selective breeding going on for most of those 100,000 years. Rather than diverging into separate lines, the dog gene pool remained a well-mixed soup in a bowl of global dimensions. There was considerable gene flow throughout the population, which would not have been the case had early human beings been trying to direct the breeding of their dogs or to develop special lines with certain selected characteristics. Wayne's study also suggests that for a long time the genetic difference between a dog and a wolf was too small to cause any striking morphological change that would show up in the fossil record.

Even if the step from wolf to dog was a small one, it apparently didn't happen very often. Wayne found that the dog mitochondrial DNA sequences fell into four major groups. If there had been a continual influx of new wolf blood into the dog population (that is, if the dog had been reinvented again and again from wild populations at different times), such distinct grouping would not have occurred. Wayne's conclusion is that the earliest dogs "must have been integrated somehow into human society" to keep them genetically isolated from the surrounding population of wild wolves, and also that the domestication of dogs from wild populations must have been "a rare event"—something that happened only a few times in history.

That it happened at a time when "humans were barely human," as Gregory Acland—a veterinarian who works with Aguirre at Cornell's Center for Canine Genetics and Reproduction—puts it, raises an interesting possibility. It suggests that early man may not have sought to domesticate dogs at all. Rather, proto-dog found it in his interest to hang around people, and somehow persuaded them not to throw rocks at him or eat him.

That is a teleological statement, of course; if this scenario is correct, there was no conscious intent on the part of the dogs. But there was arguably little or no conscious intent on the part of the people, either. The wonder and beauty of natural selection is that it is creative; it crafts solutions that for all intents and purposes seem to reflect intelligence—"unthinking" intelligence, as the philosopher Daniel Dennett aptly put it. The evolutionarily correct way to state all this is that human beings, with their campfires and garbage heaps and hunting practices, but above all with their social interactions, represented an ecological niche ripe for exploitation by wolves. Or at least by those wolves that through some chance modification in their genetic makeup were able to exploit that niche and then prospered to pass on those traits to their offspring. Although wolves today are the most widespread wild land mammal in the world—with a range that extends from North America to Europe to Asia, encompassing everything from semi-desert to tundra to subtropical forest—their total population probably numbers no more than 150,000. In the United States there are about 50 million owned dogs and millions more unowned—eloquent evolutionary testimony to the wisdom of mooching off people rather than fighting it out in the wild.

Dogs and Determinism

What is so exploitable about human society? And how do dogs manage to exploit it? We are, as the animal behaviorist John S. Kennedy called us, "compulsive" anthropomorphizers—always on the lookout for behaviors that mimic, even superficially, human social phenomena such as loyalty, betrayal, reciprocity. These are useful things to look out for when one is a group-dwelling animal whose survival is threatened less by ravenous wild beasts than by back-stabbing fellow group dwellers. Our cognitive ability to ascribe motives to others is a large part of what makes us human. But it truly is compulsive. Human beings do it so instinctively that they are forever ascribing malignant or benignant motives even to inanimate forces such as the weather, volcanoes, and internal-combustion engines. Our very cleverness is the start of our undoing when we're up against an evolutionary sharpshooter like the dog. We are primed to seize on what are, in truth, fundamental, programmed behaviors in dogs and read into them extravagant tales of love and fidelity. Often dogs need do no more than be their simple selves to amaze and beguile us.