Eugenics: Pseudoscience, Racial Theory, and Crimes Against Humanity

Core Idea

Eugenics — the attempt to improve the human genetic makeup through selective breeding — emerged in the early 20th century from misapplication of Darwinian theory. Scientists like Karl Pearson developed statistical methods for studying heredity, which seemed to show that intelligence, criminality, and moral worth were heritable traits. Eugenics had wide appeal: progressives saw it as rational improvement; conservatives used it to defend class and racial hierarchies. Eugenics movements in the US, UK, and Scandinavia led to forced sterilization laws. Nazi eugenics took racial eugenics to its horrific conclusion: the regime sterilized hundreds of thousands and murdered millions on the basis of presumed genetic deficiency. After WWII, eugenics became taboo in most of the world — it was discredited both scientifically (the genetics was crude) and morally (its association with genocide). Yet eugenics reveals a profound danger: scientific authority can be misused to justify atrocity. It shows how scientific ideas can become entangled with racism and used to legitimize violence. It also reveals the difficulty of distinguishing legitimate medical genetics from eugenic thinking — modern genetic testing, gene therapy, and prenatal screening raise eugenics-adjacent questions about what traits are 'worth' inheriting, and whether society should guide human genetic evolution.

Explainer

Eugenics — the project of improving the human species through selective reproduction — was not a fringe movement. In the early 20th century, it attracted leading scientists, progressive reformers, and respectability across the political spectrum. Francis Galton coined the term in 1883, and eugenics developed as an academic discipline with journals, societies, and international congresses. The claim was that modern medicine and social welfare were allowing 'unfit' individuals — the cognitively disabled, criminals, the poor — to survive and reproduce at rates that would degrade the species. Scientific management of human reproduction was the proposed solution.

The genetics was crude. Eugenicists assumed complex traits were controlled by simple genetic factors, making them highly heritable and easily selectable. They used correlation between family members as evidence of heritability without separating genetic from environmental transmission. They defined 'fitness' in terms of culturally valued characteristics — intelligence as measured by early IQ tests, respectable behavior as defined by dominant norms — and assumed these had straightforward biological bases. Karl Pearson developed statistical methods for studying heredity that appeared rigorous; in practice they were applied to categories that were culturally constructed and measurements that reflected social position as much as biology.

Eugenics programs in liberal democracies preceded the Nazi atrocities. In the United States, roughly 30 states passed forced sterilization laws by 1933, upheld by the Supreme Court in Buck v. Bell (1927). Approximately 65,000 Americans were forcibly sterilized; Sweden sterilized roughly 63,000 people between 1935 and 1975. Nazi Germany's 1933 hereditary health law was explicitly modeled on American eugenic legislation. The Nazi racial hygiene program sterilized an estimated 400,000 people and murdered hundreds of thousands of people classified as cognitively or physically disabled under the 'T4' program — a precursor to the Holocaust.

After WWII, eugenics was discredited both scientifically and morally. The science was wrong: modern genetics understands complex traits as polygenic, massively environmentally influenced, and technically impossible to select for in simple ways. The morality was monstrous: the history left no doubt about where scientific authority to classify humans by fitness leads. Yet the history does not end there. Prenatal genetic testing, preimplantation genetic diagnosis, and emerging gene-editing technologies raise analogous questions about which traits are worth selecting for, and who decides. The difference between state coercion and individual choice is real — but so is the question of whether choices made under social pressure and insurance incentives are as freely chosen as they appear.