Dan Franks: University of York

Why females of some species cease ovulation before the end of their natural lifespan is a longstanding evolutionary puzzle. In humans as well as some natural populations of cetaceans and insects, reproductive aging occurs much faster than somatic aging and females exhibit prolonged post-reproductive lifespans (PRLSs). Determining the mechanisms and functions that underpin PRLSs has proved a significant challenge. Here we bring together both classic and modern hypotheses proposed to explain PRLSs and discuss their application with particular reference to our studies of killer whales. In doing so we highlight the need to consider multiple interacting explanations for the evolution of PRLSs.