[This is a joint talk with the Garrod Research Seminars]

Here we examine the evolution of religious celibacy from an evolutionary perspective. We use this issue to address the wider question of whether fitness considerations underly the evolution of cultural traits.   We use the tools from behavioural ecology. We model how sending a child to the monastery, to live a celibate life, could evolve as a mechanism to enhance inclusive fitness. If close kin benefit from the decision and the decision is made by parents rather than the boy himself, then sending more than a negligible proportion of sons to the monastery to live as monks can be favoured by selection.  We test the model with demographic data from Western China, where a significant number of young boys were sent to live as monks in Tibetan monasteries.  We show that the decision to send a son to monastery was not costly to the parents of monks in terms of inclusive fitness and thus can evolve by kin selection.  Thus monasteries represents an example of a complex institution that may have arisen due to kin-selected benefits.