Michel Foucault argued that in the nineteenth century, the species became a population and became subject to political management. Foucault’s claim defines the political stakes of this book, whose point of departure is the loss of a theological ground for the species concept. As species become targets of political power, they become mutable and historically contingent. The book argues that a result is that species come to be identified with aesthetic categories and with symptomatic or unmotivated behaviors.