New York anthropologist Krystal D’Costa wrote last month about a paper by Pat Shipman arguing that our special connection with animals is one of the key traits that distinguish humans from all other creatures on Earth. Anthropologists, philosophers, and others have ruminated for centuries on what defining characteristics make us “human.” Traditionally, the big three traits of humans have been sophisticated communication, tool use, and domestication of animals. Shipman argues that the fact that people take domestication one step further and adopt pets as family members is a fourth distinguishing trait of human beings.