Of the billion dogs in the world, three-quarters of them look as much alike as do the individuals of any other species. A few years ago we asked a Navajo shepherd what a Navajo sheepdog looked like. He said, “A Navajo sheepdog is not too big and not too small.” To us the Navajo sheepdogs were identical in size and shape and color variations with the sheepdogs of Sonora and the village dogs in the mountains of Venezuela or the ones we worked with in eastern and South Africa or saw in India and China. That is true of the majority of dogs in the world—they are not too big and they are not too small. One of the most fascinating details about that 75 percent of the dogs in the world that control their own reproductive life is: They all look similar.

For a biologist, that kind of uniformity implies the process of natural selection. Their size and shape (and even color) indicate an adaptation to a niche. The village dog is not a blending of purebreds that was created by artificial selection. The village dog is the animal that evolved on its own, with no reproductive control by humans, and is adapted to the niche in which it makes its living. The message is, those look-a-like dogs have evolved right there in their niche and are uniquely adapted to this niche. They are not escapees from irresponsible dog owners. They are a natural species that lives close to humans, finds its own food, and mates perfectly well without human control.