A popular pseudoscience was leaving its mark on American culture a century ago in everything from massive reductions in quotas for immigration to the U.S., to thousands of "fitter family" contests at county fairs, to a growing acceptance of birth control by those who thought it could curtail the fertility of "undesirables."

These are just a few examples of the influence of eugenics in the early 20th century. The idea of scientist Francis Galton, eugenics suggested that negative traits could be bred out of the human species by discouraging reproduction by those considered inferior. It laid the groundwork for forced sterilization laws in the U.S. and Nazi "racial hygiene" programs and the Holocaust. [...]

Galton credited reading his cousin Charles Darwin's "On the Origin of Species" (1859) about the theory of natural selection with initiating him into "an entirely new province of knowledge," paving the way for his studies of inheritance.