In contrast to wild animals living in zoological settings that have scientific value as representatives of particular species, or with domesticated work animals and those kept for their value as commodity producers, a pet is any domesticated animal or wild animal living in a domestic setting that is cared for, enjoyed, and valued for a unique set of characteristics that differentiates it from other members of the same species. Mitochondrial canine DNA evidence suggests that humans have kept dogs, the first animals to emerge as pets, for tens of thousands of years. Many pets are valued solely for their role as companions, treated by those who care for them with affection as though they were friends or family members. Some pets are also working animals: They hunt, herd, perform search and rescue operations, control traffic, protect homes from pests and strangers, or otherwise serve to extend human capacities...