It is (or used to be) a commonplace of Marxian commentary that Marx did for human history what Darwin had done for the organic world. Possibly the most famous instance of this is Engels' "Speech at the Graveside of Karl Marx" (1883, 429–30). But Marx himself also made claims for connections and parallels between natural selection and historical materialism, one example being the above epigraph. Unfortunately, these claims seem never to have progressed beyond general observations. In this essay I want to develop a more detailed connection between the two theories.