"If there are two things that characterize Islamic culture, they are terrorism and inbreeding. The latest research shows that these two things might be closely connected . . . First cousin marriages have been the tradition in many Muslim families for innumerable generations. Such marriages increase the risk of negative mental and physical consequences . . . Risk of mental retardation increases with 400 percent (Proceedings of the National Academy of Science, 1978 Effect of inbreeding on IQ and mental retardation). Research shows that the IQ is 10-16 points lower in children born from blood related parents and that abilities related to social behavior and empathy develops slower in inbred babies (Indian National Science Academy, 1983 Consanguinity Effects on Intelligence Quotient and Neonatal Behaviours of nsari Muslim Children [pdf]). Such facts might make several pieces fall into place for many people . . . People with low intelligence (because of inbreeding) might also be easier to brainwash with fundamentalist Islam. "
From Internet sources. My emphasis.
Shame be upon the Islamists.
Not sure intelligence has anything to do with it. But I wouldn’t be surprised if genetics plays a role in lifestyle and spiritual disposition.