Why and how do religious individuals, and some religious groups, achieve higher relative fertility?

Across the contemporary world, religious individuals tend to exhibit higher relative fertility than their secular counterparts, while religions vary substantially in mean fertility levels. Across all biological taxa, organisms sacrifice quantity for quality of offspring. If all things were equal, then, religious individuals would be expected to produce lower-quality offspring and religions with high fertility levels would be expected to be lower-quality populations. Studies of modern populations demonstrate that humans sacrifice quantity for quality of offspring, yet children born to religious parents do not appear to suffer. I propose the Alloparenting Signaling Model, which asserts that religious cultures function as cooperative breeding niches that motivate alloparenting from large kin networks, as well as unrelated co-religionists, to enable high-quantity, high-quality reproductive strategies, and that shared parental care partially explains successful religions. Evaluating this model will require methods from human behavioral ecology as well as traditional ethnography.