Ancestral Beliefs and Fertility in Sub-Saharan Africa

This paper contributes to the explanation of the puzzle of persistently high fertility in sub-Saharan Africa. I focus on the impact of a belief system that emphasizes the role of ancestors, who influence people’s lives and have a strong interest in the continuation of their lineage into which they may be reincarnated. I combine first-hand data with original ethnographic information and both historical and contemporary surveys to show: 1) a strong, positive relationship between ancestral beliefs and fertility in different contexts and time periods; and 2) that this relationship is specifically driven by the motive to continue one’s lineage. I test the specific predictions of a simple model of fertility in which children area public good for a family with ancestral beliefs because they continue the family line. However, whether one’s children continue one’s lineage depends on the kinship system: while this is the case in a patrilineal system, children only continue the mother’s lineage in matrilineal societies. The model predicts that 1) ancestral beliefs have a stronger positive influence on fertility in patrilineal societies; and 2) in groups with ancestral beliefs, very specific free-riding behaviors emerge: in patrilineal societies, male fertility decreases with the number of brothers, whereas in matrilineal societies, female fertility decreases with the number of sisters (but not brothers). These predictions are supported by the data.