Cultah

Culture is a pretty vague and poor explanation. Never properly defined, effects or transmission certainly arent elucidated in any mechanistic way like you claim we must do with genes, and generally predicts little as a result. Every time we try to isolate culture it is assumed it still got in somehow. It's a god of the gaps kind of argument.

And most the of time it is confounded by genetic factors. The lower inbreeding among the Shia versus Sunni being one.

And in fact, our inability to even isolate or effectively change culture to the point where these gaps close means it's practically indistinguishable from a genetic effect. Every time we try, some subtler form of culture is assumed to be worming its way in. It acts like genes at this point

sorry but culture is an empty explanation without much going for it. Cant even define culture much less make predictions of it. You just use it as an equality of the gaps.

As @sentientist says