Abstract: Infanticide by males has been the subject of intense empirical and theoretical study for decades. However, a related phenomenon, male-mediated prenatal loss, has received considerably less attention. Male-mediated prenatal loss occurs when inseminated or pregnant females terminate reproductive effort following exposure to a non-sire male, either through implantation failure or pregnancy termination. Male-mediated prenatal loss encompasses two sub-phenomena: sexually selected feticide and the Bruce effect. In this talk, I will walk through three different evolutionary scenarios in three species of primate - the yellow baboon, the gelada, and the chacma baboon - to lay out a framework that explains the relationship between infanticide, feticide, and the Bruce effect and describes the proximate and ultimate mechanisms involved for each. I argue that male-mediated prenatal loss may have played a greater role in mammalian social evolution than has previously been documented.