The post-Darwinian theory of atavism forecasted obstacles to human progress in the reappearance of throwback physical or cultural traits after several generations of absence. In this original and stimulating work, Dana Seitler explores the ways in which modernity itself is an atavism, shaping a historical and theoretical account of its dramatic rise and impact on Western culture and imagination. Examining late nineteenth- and early twentieth-century science, fiction, and photography, Seitler discovers how modern thought oriented itself around this paradigm of obsolescence and return-one that served to sustain ideologies of gender, sexuality, and race. She argues that atavism was not only a discourse of violence-mapping racial and sexual divisions onto the boundary between human and animal-but was also an illustration of how modern science understood human being as a temporal category. On one hand, atavism positioned some humans as more advanced than others on an evolutionary scale. On the other, it undermined such progressivism by suggesting that because all humans had evolved from animals they were therefore not purely human. Atavism thus reveals how scientific theories of a recurrent past were a significant feature of modernity. At the beginning of the twentieth century, atavistic theory had widespread social and economic effects on the taxonomies of medicine, the logic of the welfare state, conceptions of the modern family, and images of the abnormal. Investigating the cultural logic of science in conjunction with naturalist, feminist, and popular narratives, Seitler exposes the influence of atavism: a fundamental shift in ways of knowing-and telling stories about-the modern human.