As I write this chapter in a third-floor garret, my family's dog Riley naps on a rug in front of a fireplace on the first floor. We enjoy having him in our lives because he bubbles with affection, cheers us when we are low, and enlivens our walks and runs. We love him, even though he is undistinguished by the usual measures of canine fame. He carries no proud pedigree and has won no shows. He came to us not from an elite kennel but from a shelter, and his ancestry remains a mystery. He might be a flat-coated retriever, he might have sprung from a Labrador retriever that coupled with another breed, or he might belong to some other clan. He is the most ordinary of dogs.

He is also extraordinary, for he belongs to one of the first species of domesticated animal. Domestication refers to the process through which species adapt other species to live and reproduce in captivity. In the domestication hall of fame, the plaque for dogs greets us as soon as we enter. Dogs hold pride of place because in addition to being one of the first domestic species, they experienced two dramatic transformations. One transformation saw one or more populations of wolves evolve into dogs. It is remarkable that descendents of wolves could become companions we trust around our babies, especially since the first domesticators had no example of other domestic animals to inspire them.