M onogamy literally means “one marriage” in Greek, and implies mating for life: one love, one sexual partner—forever. Yet most people today think of it as committing to one person at a time. You can have many loves and many sexual partners over the course of a lifespan, as long as you are faithful to each person along the way, otherwise known as serial monogamy. Along with this focused attention on just one person comes the assumption that both parties understand what is outside the bounds of