Islamic conversion in Africa spread via the economic trust its institutions enabled.

Evidence

Returning to Ensminger’s analysis of the spread of Islam into Africa, it is apparent that belief in an all-powerful Allah who knows everything and cares about morality, supported by credible displays of sincere devotion that included charity, fasts, daily prayer, and restrictions on diet and sexual behavior, permitted greater trust, shared rules of economic exchange, and the use of credit institutions among newly converted Muslims. This facilitated more trade and greater economic success. Kenyan pastoralists, as well as other local African groups, began adopting the religious beliefs along with the associated institutions and rituals. — Norenzayan, Ara, Big gods - how religion transformed…, 353

Categorization

• XREF: Concrete historical case for the reader’s partner-choice/Big God integration: moralizing deity plus costly rituals lowering transaction costs among strangers.
• QUESTION: Would trace how the fumi-e, as an enforced public display, inverts this voluntary costly-signaling logic under coercion.