But when we look back at our relationship with wolves throughout history, this doesn't really make sense. For one thing, the wolf was domesticated at a time when modern humans were not very tolerant of carnivorous competitors. In fact, after modern humans arrived in Europe around 43,000 years ago, they pretty much wiped out every large carnivore that existed, including saber-toothed catsand giant hyenas. The fossil record doesn't reveal whether these large carnivores starved to death because modern humans took most of the meat or whether humans picked them off on purpose. Either way, most of the Ice Age bestiary went extinct.

The hunting hypothesis, that humans used wolves to hunt, doesn't hold up either. Humans were already successful hunters without wolves, more successful than every other large carnivore. Wolves eat a lot of meat, as much as one deer per ten wolves every day—a lot for humans to feed or compete against. And anyone who has seen wolves in a feeding frenzy knows that wolves don't like to share.

Humans have a long history of eradicating wolves, rather than trying to adopt them. Over the last few centuries, almost every culture has hunted wolves to extinction. The first written record of the wolf's persecution was in the sixth century B.C. when Solon of Athens offered a bounty for every wolf killed. The last wolf was killed in England in the 16th century under the order of Henry VII. In Scotland, the forested landscape made wolves more difficult to kill. In response, the Scots burned the forests. North American wolves were not much better off. By 1930, there was not a wolf left in the 48 contiguous states of America.  (See "Wolf Wars.")

If this is a snapshot of our behavior toward wolves over the centuries, it presents one of the most perplexing problems: How was this misunderstood creature tolerated by humans long enough to evolve into the domestic dog?

The short version is that we often think of evolution as being the survival of the fittest, where the strong and the dominant survive and the soft and weak perish. But essentially, far from the survival of the leanest and meanest, the success of dogs comes down to survival of the friendliest.