Cousin marriages has negative impact on intelligence, sanity, health and society. In Pakistan, 70 percent of all marriages are between first cousins (so-called "consanguinity") and in Turkey the amount is between 25-30 percent. Across the Arab world today an average of 45 percent (in some parts up to 70 percent) of married couples are related.
This phenomenon is allowed for by Islam's marriage law, which is delineated in Qur'an 4:23-34, making this something for which Sharia opens the door.
The lowered intelligence, psychiatric diseases and low status that result from handicaps that afflict many Muslim children as a result of inbreeding may increase the chances of luring people into becoming suicide bombers.