I too found the study on consanguinity quite out of context. Ok, its true, so?
I dont think people with down syndrome and other important genetical defects are capable of handling war, even just soldieering, and being a stupid inbred is not a direct path to religious fanatism. As lombardsoup implied "without sources" () joining ISIS #1 reason is probably not poor intellect, but you can keep believing that if that saves you some brain cells.
First of all, the way these Arab fanatic groups are organized (or, as it happens,
not organized) being a stupid inbred is not a disadvantage. On the contrary. It's also not a direct path to religious fanaticism, but it sure helps. It's easier to sell it to a retard than to an educated, intelligent person -- obviously.
The #1 reason for anyone joining ISIS is, in-deed, poor intellect. What
else could it be? They have no hope of success, they're a fanatical religious organization (and believing in that crap takes a person with limitations on either their intellectual capacity or intellectual honesty, or if you're a real winner, both), many of their acts
are plain stupid, the list goes on.
What legit reason could there be for joining ISIS that didn't come to be as a direct result of poor intellect?