Much has been written about the relationship between biology and social science during the early twentieth century. However, discussion is often drawn toward a particular conception of eugenics, which tends to obscure our understanding of not only the wide range of intersections between biology and social science during the period but also their impact on subsequent developments. This paper draws attention to one of those intersections: the British economist and social reformer William Beveridge’s controversial efforts to establish a Department of Social Biology at London School of Economics during the 1920s and 1930s. Featuring a fully equipped laboratory headed by a leading geneticist, the Department of Social Biology was Beveridge’s attempt to "cross-fertilise" biology and social science and, in so doing, take the ideological heat out of social scientific, in particular economic, methods of investigation. Exploring why Beveridge’s project failed and throwing light on its long-term legacies, this paper considers what we can learn from the short-lived Department of Social Biology.