I study religions from the evolutionary perspective, using the theory of sexual selection as the main theoretical framework. This theory allows to see religious thinking and behavior as traits preferred during human evolution due to a direct impact on an individual's reproductive success. Thus, religion could have evolved as a cultural factor shaping the reproductive strategies of its devotees so as to optimize the number and quality of offspring within their socio-ecological context.

In order to empirically examine the reproductive function of religion, involving parental investment, I focus on the diversity of religious norms and practices across cultures concerning child-care support from "non-mothers" (so-called alloparenting) and from the father by increasing paternity certainty through the restriction of female sexuality.