How was Charles Darwin’s theory of natural selection connected to eugenics?

Charles Darwin’s theory of natural selection was not a blueprint for eugenics, but its concepts were misappropriated by others to justify the movement. Darwin’s cousin, Francis Galton, who coined the term eugenics in 1883, was deeply influenced by Darwin’s work on evolution and sought to apply those principles to human society.123

The connection was primarily established through the following interpretations:

• Misapplication of "Survival of the Fittest": Proponents of social Darwinism argued that the "survival of the fittest" logic—which Darwin observed in nature—should be applied to human populations. This led to the belief that society should actively intervene to favor "more suitable" individuals while discouraging the reproduction of those deemed "less fit".14
• Control of Evolution: Darwin had suggested that humans, unlike other species, could potentially control their own future evolution through selective reproduction. Eugenicists seized upon this idea to promote positive eugenics (encouraging "good stock") and negative eugenics (prohibiting breeding among the "defective").24

It is essential to recognize that these applications were ethically flawed and scientifically misguided, ultimately leading to human rights abuses, including compulsory sterilization and, in the case of Nazi Germany, the horrific extermination of entire groups of people.14