Fully half of all registered marriages in Pakistan are between FIRST COUSINS. Men marrying their nieces is not at all unusual!
This has been going on with the Sunnies for hundreds of years. Not quite so much with the Shia, closer to a quarter of the marriages are between first cousins.
Think about it. Your wife and you share grandparents. Think about that. Now, consider that those grandparents also share grandparents!!
Family trees like telephone poles. Generation upon generation, all the way to Esau and Ishmael.
Why do we wonder that they are so easily led into madness?
Mamzelle, you are absolutely correct about inbreeding. But there is much more to the demography.
Polygamy is a hideous social dynamic hardly ever discussed academically or religiously. Where it exists far too many men never have a wife or family, a recipe for violence/conquest. The wealthy men who do have wives acquire and dispose of women according to their fertile years. OBL had 53 brothers and sisters. This causes even more men to be useless, angry drones.
No father can properly raise several dozen children. Mothers must compete viciously for their child’s favorable outcome, so they inadvertently earn the distain accorded “trecherous” women.
In his Satanic wisdom, Mohammed designed an insatiable mercenary force with a sexual imperative to conquer, and if that is impossible they can have boys and female domesticated animals.
Criticizing polygamy should be acceptable due to genetics, anthropology and history. It’s been a colossal failure in other societies besides Muslim.
If you search for “Middle East consanguinity” you find all sorts of scholarly articles on the subject. It isn’t pretty.