The pseudoscience of eugenics, founded on the mistaken notion that nature envisions some “right” combination of genes, and that selective breeding can improve the human race, is making a comeback. While the heyday of eugenics was a century ago, the idea was never really forgotten.

In the 19th century, the modern science of biology was in its infancy, but took a leap forward with the work of pioneering researchers like Charles Darwin and Alfred Russel Wallace. But other thinkers, like Darwin’s cousin, Francis Galton, took things further by supposing that, just as farmers breed animals to improve or weed out various traits, humans could be guided to make “better” offspring.

When the Nazis came to power in the 1930s, they took eugenicist ideas and ran with them, justifying their hatred of certain groups—Jews, Roma, gay people, the disabled—as supposedly backed by science, anchored to the notion that some people were naturally superior to others. In this distorted way of thinking, violence against the unfit was justified, even noble.

While eugenics largely fell into disrepute in the wake of Nazism, it never disappeared. Nor was it something the Nazis invented: In the early 20th century, most of the literature on eugenics was published in the United States, where it eventually underpinned sterilization campaigns against people with disabilities, fueled racist immigration policies, and, more recently, inspired efforts like the “Repository for Germinal Choice,” which collected and preserved the genetic material of leading thinkers, including Nobel laureates, by storing their sperm.

These sentiments, coming from the most powerful people in Washington, D.C., and in the tech world are echoed on social media and in the wider world. They stoke xenophobic conspiracies like the “great replacement theory,” which holds that whites are being driven to extinction by non-white immigrants, and that breeding programs and restrictions on immigration are needed to ensure that whites retain a dominant position.

This discourse has, for many, a starkly familiar flavor, echoing some of the statements made by eugenicists a century ago. Despite a half century of science showing that the ideas behind eugenics have no basis in fact, it continues to surface in Washington and across political lines. As Rebecca Sear, an evolutionary anthropologist at Brunel University in the United Kingdom, who has published extensively on eugenics, puts it: “In the 21st century, eugenics is experiencing a fully-fledged revival.”