Rutherford, a geneticist, offers a thought-provoking scientific analysis of eugenics, which he calls "a defining idea of the twentieth century." 

The book covers a wide range of topics related to eugenics, including gene editing technology, embryo selection, IQ, heritability, and complex polygenic traits. Rutherford, who argues passionately against eugenics, warns of the dangers of using eugenic ideas to try to manipulate or control polygenic traits, as this could lead to unintended consequences and ethical dilemmas.