This might explain a few things.

Massive inbreeding within the Muslim culture during the last 1.400 years may have done catastrophic damage to their gene pool. The consequences of intermarriage between first cousins often have serious impact on the offspring’s intelligence, sanity, health and on their surroundings.

The Muslim culture still practices inbreeding and has been doing so for longer than any Egyptian dynasty. This practice also predates the world’s oldest monarchy (the Danish) by 300 years.

A rough estimate shows that close to half of all Muslims in the world are inbred: In Pakistan, 70 percent of all marriages are between first cousins (so-called “consanguinity”) and in Turkey the amount is between 25-30 percent (Jyllands-Posten, 27/2 2009 More stillbirths among immigrants”

Statistical research on Arabic countries shows that up to 34 percent of all marriages in Algiers are consanguine (blood related), 46 percent in Bahrain, 33 percent in Egypt, 80 percent in Nubia (southern area in Egypt), 60 percent in Iraq, 64 percent in Jordan, 64 percent in Kuwait, 42 percent in Lebanon, 48 percent in Libya, 47 percent in Mauritania, 54 percent in Qatar, 67 percent in Saudi Arabia, 63 percent in Sudan, 40 percent in Syria, 39 percent in Tunisia, 54 percent in the United Arabic Emirates and 45 percent in Yemen (Reproductive Health Journal, 2009 Consanguinity and reproductive health among Arabs.).

A large part of inbred Muslims are born from parents who are themselves inbred – which increase the risks of negative mental and physical consequences greatly.