The Cultural Evolution of Low Fertility 1 Running head: THE CULTURAL EVOLUTION OF LOW FERTILITY Influences on Communication about Reproduction: The Cultural Evolution of Low Fertility

Kin altruism appears to influence an individual’s evaluation of the reproductive decisions of other people. Playing the role of an older woman advising a younger woman about reproduction influenced female participants’ self-reported beliefs about the decision. Women randomly assigned to the group with the task of advising a daughter were more inclined to believe that the choice consistent with the pursuit of reproductive success was correct, whether this meant reproducing soon or postponing reproduction. We explore the implication of this communication bias on the cultural evolution of reproductive norms and find that such a bias could, at least in part, explain the demographic transition and other changes in reproductive decisions that occur as societies modernize and social networks become less kin-based.