The term eugenics was first used in 1883 by Francis Galton, an English scientist and statistician. Galton defined eugenics as “a brief word to express the science of improving stock, which is by no means confined to questions of judicious mating, but which, especially in the case of man, takes cognisance of all influences that tend in however remote a degree to give to the more suitable races or strains of blood a better chance of prevailing speedily over the less suitable than they otherwise would have had.”  

While Galton coined the term at the turn of the 19th century, ideologies around biological superiority and inferiority behind it existed well before the term. Importantly, scientific and medical racism, exclusionary immigration, and colonization all rely on eugenic ideals. 

In the 1750s, evolutionary scientist Karl Linneaus sought to use his model for animal and plant classification to understand human hierarchy. He built a framework for scientific racism, asserting that there were four different human “varieties'' based on physical traits like hair, skin color, and behavior. In this, he generated a hierarchy where European people are “white and wise,” whereas African people are “black and neglectful.” He leveraged his scientific training to justify his racism, arguing that human traits, including behavior, are biological, a crucial tenet of eugenics. 

Scientists built upon this framework as theories about genetics and evolution developed. Without a clear understanding of a biological mechanism in the late 19th and early 20th centuries, scientists like Gregor Mendel and Charles Darwin began to propose that certain traits like pea shape or beak size are heritable, passed down from generation to generation. Francis Galton sought to apply that thinking to humans and posed that traits like intelligence or criminality were passed down.

These ideas were not sequestered in the scientific community but were legitimated through scientists’ work. On a legislative level, U.S. immigration law in 1882 explicitly banned the entry of people identified as “likely to become a public charge” or “idiots, lunatics, and convicts.” Lawmakers relied on the belief that some people were biologically inferior and genetically destined to be a burden on society, most often on the basis of ethnicity and class. Without ever explicitly using the term eugenics, this law reflects how officials in positions of power conceptualized poor immigrants as biological threats to the economy and national “gene pool.”