he IQ is below 100 because 2nd cousin and even first cousin marriages are frequently the norm. Marriages within the clan is also preferred or almost required in some Islamic places like somalia.
Consanguineous marriage would produce offspring well below 100, like in Pakistan. Malaysia and Indonesia do not have high rates of cousin marriage, despite being Muslim. And yet, Israel does...so it’s not simply a Muslim thing. Regardless. IQ tends to be higher in places with winters, and it takes a mean IQ of at least 90 to maintain a republic. Same reason caudillos work better in South America.