Religious doctrines that boost fertility outcompete rival religious groups demographically.

Evidence

It is no accident that religious conservative attitudes on women’s rights, contraception, abortion, and sexual orientation are conducive to maintaining high fertility levels. The reproductive advantage of prosocial religions is therefore another key factor that explains the latter’s cultural survival and expansion. Culturally transmitted prosocial religious beliefs and practices appear not only to have effects on cooperation and trust, but they also have direct Darwinian fitness consequences that contribute to the demographic growth and stability of large cooperative groups. Of course, not all religions encourage reproductive success (consider the Shakers, who banned sexual intercourse). However, I hope it is clear by now that in the logic of cultural evolution, there is no reason to expect that all religious groups reproduce at high levels. The logic is simply that those religious groups with beliefs and practices that promote population growth (be it by conversions, or higher fertility rates, or both), all else being equal, would outcompete their rivals—including religious rivals like the Shakers and the self-castrating Skoptsy—and take a larger share of the religious market, and ultimately the world’s population. — Norenzayan, Ara, Big gods - how religion transformed…, 499

Categorization

• XREF: Connects to the reader’s framework: conservative reproductive doctrine as a cultural survival mechanism complementing the Big God moral-enforcement mechanism; also relevant to Baumard’s partner-choice lens on costly signals.
• ADDENDUM: Relates to ‘On Sacrifice’ — the Shakers and Skoptsy as extreme self-limiting religious groups parallel sacrificial dynamics of giving up reproductive capacity for devotional identity.