I have to protest the idea that religion as an utilitarian code for social and physical life. A lot of it is purely arbitrary.

For example the Trobrian islanders' culinary taboo was that the higher up one was in the social stratification, the less things one was allowed to eat... Is it of practical rather than symbolic use ?

As for sexual life, there is a Pacific society where in order to maintain fertility, young boys are to perform fellatio on teenagers... Abrahamic confessions do not as much forbid contraception (which was mostly unknown at the time of their foundation) as promote the sacred aspect of the male gametes, based on the belief that it constitutes human life (whereas the Trobrians believe the males have no role in reproduction)...

Organised, written religion is needed when a society gets to large to properly enforce behaviour according to shared, non-codified social norm ; as such, it is a primitive form of law. It is clear that the Koran was at heart a codification of the laws Muhammad needed to rule over his people.

But this doesn't prevent much of religious rules from being arbitrary. Agreeing on arbitrary rules is as useful when it comes to social and political norms as for language definition.

Un roi sans divertissement est un homme plein de misères