Genetics and human anthropology were often deeply racist disciplines before World War II; hierarchies of intelligence and ability among races were drawn up, and it was thought that the unfit should be weeded out of the population. These ideas were not the sole property of Nazi Germany, but were endorsed widely in the USA and Europe. The Holocaust and other massacres in the name of racial purity buried such notions for decades, but the author shows here how they are returning in the work of often well-meaning scientists. Exploiting as they do anxieties about race, social breakdown and nationalism, these ideas are increasingly less marginal. This book analyzes such ideas and their defenders in a powerful expose of resurgent racialism in science.