<p>Hereditarianism, the belief that genetic factors significantly influence differences in behavioral traits and social outcomes, remains relevant in the age of polygenic embryo screening and social science genomics. Although early twentieth-century monogenic versions of hereditarianism—suggesting specific genes for traits like feeble-mindedness, nomadism, and pauperism—may now seem outdated, similar reasoning persisted into the early twenty-first century through candidate gene studies. With the advent of high-resolution genomic association studies, the understanding of complex traits has shifted toward a massively polygenic architecture, moving away from the "gene for X" paradigm. Nevertheless, the aspiration to identify purely genetic causes persists, and a more nuanced form of hereditarian theory continues to exist. This paper explores the evolution of hereditarianism in its various forms, examining its connections to racism and anti-egalitarian politics. In a sense, this work is an extension of the twentieth century critique of hereditarianism, in line with key figures like Richard Lewontin and Stephen Jay Gould. The paper begins with early twentieth-century eugenics and the hereditarian approach to IQ in the United States, progresses to modern scientific racism, and concludes with an evaluation of causal claims in contemporary social science genomics. A consistent theme across these periods and fields is the belief in the potential for genetic explanations of social inequalities both within and between groups.</p>