While the idea of improving humans through selective breeding is at least as old as the ancient Greeks, it gained widespread prominence after 1869. In 1883, Sir Francis Galton coined the word "eugenics," from the Greek word eugenes, meaning "well-born" or "hereditarily endowed with noble qualities," to describe this new science of directed human evolution. Galton's work, and the subsequent rediscovery of Gregor Mendel's genetic studies, convinced many scientists and social reformers that eugenic control over heredity could improve human life.

Galton's ideas swept America during the Progressive Era of the early twentieth century. At that time, many scientists and laypeople believed that eugenics could facilitate social progress by eradicating problems ranging from alcoholism and prostitution to poverty and disease. What better way to prevent such misfortunes, eugenicists asked, than to prevent the birth of people genetically susceptible to them? Eugenics seemed to offer an efficient and humane solution to...