Is there a queer Darwin? It is often assumed that Darwinian biology is an ally of conservative approaches to sexuality and gender. The Christian legal framework known as natural law philosophy, for instance, reads Darwin as a champion of heterosexual coupling, proving the biological imperative of straight sex. Some feminist readings of Darwin (such as that of Elizabeth Grosz) find in Darwin a confirmation of the necessity of sexual difference organized around masculinity and femininity—an approach Myra Hird has called the “ontology of heterosexuality.” But these interpretations are incorrect. Schaefer argues that far from being an advocate for the ontology of heterosexuality, Darwin provides tools to demolish it. Turning to his research on barnacles and orchids and his speculation on the sources of organic variation, this essay highlights the irreducible importance of diversity and change for Darwin's framework. The ongoing ferment of variation that is the guideline of all life on earth extends not only to the morphology of sex organs but to desire itself. Darwin shows that the ontology of heterosexuality is an arbitrary snapshot, a single moment in the fluid trajectory of life, rather than a law that can be arbitrarily cast over the whole arc. In this, Darwin supports Eve Kosofsky Sedgwick's first axiom for queer theory: “People are different from each other.” The essay concludes by connecting a Darwinian approach to sex with José Esteban Muñoz's call for a queer ecstasy that anticipates the futurity of desire.