Přednáška: Erhao Ge – From Piety to Altruism: Exploring Religious Signalling and Prosociality in Evolutionary Anthropology

Few studies have examined how costly religious behaviours that signal qualities or commitment are influenced by the context of the signalling system and the perception and behavioural feedback of recipients. Here, we first investigate whether individuals in small, stable communities engage in more costly behaviours in economic games compared to those in larger, less stable communities, where people are less familiar with each other, to gauge how reputational concerns in varying contexts affect the decisions of signallers. We conducted a public donation game involving 501 participants from 17 communities in northwestern China, ranging from small villages to large cities. Our findings indicate that higher donations came from individuals in smaller, more stable communities. Secondly, we compare the effectiveness of occasional public displays against regular but less public acts for gaining prestige recognition and forming social relationships in a real-world setting, to understand how receivers perceive these signals and modify their behaviour accordingly. Data on religious engagement, from regular low-cost practices to infrequent high-cost pilgrimages, were collected among residents of an agricultural Tibetan village, along with information on their reputational status and social support networks. We observed that participation in distant pilgrimages enhances the perception of all prosocial traits, while daily practices are positively linked to being recognised for devoutness, but not other qualities. We found that peers are inclined to form social bonds with more religious individuals. However, the benefits of these relationships depend on gender and the frequency/costliness of religious practices. These highlight that the cost-benefit ratio of signals is likely socio-economically dependent, and the effectiveness of signals may vary based on their scope and continuity. Furthermore, the role of extremely costly acts, specifically sending a boy to become a celibate monk, thus sacrificing reproductive opportunities, remains unclear. It has been speculated that this could relate to sibling competition over family resources, implying that celibacy might offer inclusive fitness benefits. We present socio-demographic data from 530 households in 21 natural villages within an agropastoralist Buddhist Tibetan community in China. We explore the potential link between wealth and having a monk brother, and the reproductive success of families with a monk. Our findings reveal that later-born boys are more likely to become celibate monks, and brothers of monks tend to be wealthier. Men with a monk brother have more children, and grandparents with a monk son do not have fewer grandchildren. This suggests that the parental preference for this practice may offer a potentially effective strategy to mitigate sibling competition and enhance inclusive fitness outcomes.