Eugenic thought and practice swept the world from the late nineteenth to the mid-twentieth century in a remarkable transnational phenomenon. Eugenics informed social and scientific policy across the political spectrum, from liberal welfare measures in emerging social-democratic states to feminist ambitions for birth control, from public health campaigns to totalitarian dreams of the “perfectibility of man.” This book dispels for uninitiated readers the automatic and apparently exclusive link between eugenics and the Holocaust. It is the first world history of eugenics and an indispensable core text for both teaching and research. Eugenics has accumulated generations of interest as experts attempted to connect biology, human capacity, and policy. In the past and the present, eugenics speaks to questions of race, class, gender and sex, evolution, governance, nationalism, disability, and the social implications of science. In the current climate, in which the human genome project, stem cell research, and new reproductive technologies have proven so controversial, the history of eugenics has much to teach us about the relationship between scientific research, technology, and human ethical decision-making.