Long before history began, our ancestors began an unwitting scientific experiment. Somehow humans managed to domesticate the wolf, and the two-legged masters began breeding their four-legged companions in a primitive form of genetic engineering that would, thousands of years later, result in Lassie, pooper scoopers and the Taco Bell chihuahua.
That it happened more or less this way is not in doubt. Where, when and why it happened are other matters. Until last week the theories had been wide ranging and contradictory. Depending on whom you asked, wolves became dogs either independently in several places or in a single location. The...