Originally Posted by CarlosTheGaucho

This is a major issue in the Islamic world.

The tradition comes from the Sunna of Mohammad. According to the doctrine of Islam, every Muslim is commanded in 91 verses in the Qu'Ran to emulate Mohammad in everything he ever did or said.

Since Mohammad married (as one of his many wives) a first cousin, you've got a wide spread, 14 centuries long tradition of inbreeding on a mass scale in the Islamic world.

Sha'ria, as a manual how to run an Islamic civilization approves (even not prescribes) of a first cousin marriage. An estimate is that about one half of the Islamic population originating in the Middle East stems from in-bred relationships.

The figure for Saudi Arabia is approx. 67 pct. Pakistan about 55 pct. etc. etc.

Inbreeding also most often contributes to generally lower average IQ (10-15 points drop), so this negatively affects the average IQ in many of the Islamic countries and communities.

This is also a reason why for example Islamic immigration to Denmark has a devastating effect on the social, healthcare, and educational system. About 30 pct. of birth defects in Denmark annually are to come from its Islamic diaspora, and it's very difficult to educate or to employ a group of population with an IQ range of 80 -85.

I've heard somebody that was managing Pakistanis in London and couldn't believe that grown men wouldn't be able to mentally accomplish tasks easy enough for a 10 years old to solve, then I realized that about 55 pct. of Pakistanis come from in-bred relationships and it started to make sense.