Abstract
Life history theory anticipates that organisms trade offspring quantity for offspring quality. In modern human societies this tradeoff is particularly acute because of increased returns on investments in embodied capital. Religious people, however, despite having more children than their secular counterparts, do not appear to suffer lower quality offspring. To explain this apparent paradox of religious fertility, we propose a religious alloparenting hypothesis, which hypothesizes that higher levels of alloparenting in religious communities enable religious individuals to support larger families without reducing offspring quality. Using data from a large national sample whose population is roughly half religious and half secular (N = 12,980; New Zealand), we demonstrate that, after adjusting for denominational, environmental, ethnic and other demographic differences, religious identification is associated with an increased likelihood of having at least one child, and religious identification and ritual frequency are positively related to offspring number among people with at least one child. Consistent with the religious alloparenting hypothesis, religious identification and ritual frequency are also positively associated with alloparenting among community members who do not currently have young children of their own. These are the first findings to reveal that religious cooperation extends to alloparenting; however, whether or not the levels of alloparenting in religious communities are sufficient to mitigate the costs of higher relative fertility remains a critical consideration for future research.