Anyway, you can further analyze IQ along with impulse control and propensity towards violent behavior to construct a two-dimensional matrix:
Intelligence - high / low
Sociability - high/low
If you evenly divided the global population into these 4 quadrants (big assumption, but useful for a preliminary examination), it would leave you with around 25% in the low IQ, high violence sector.
Another point to consider is that the nake ape still competes over scarce resources, including favorable weather & environment. That means the nicest, best zones (ie Europe, N America, Japan, AU, SA, etc) are controlled by the highly intelligent who developed the most effective weaponry and claimed the areas for themselves.
The flip side, of course, is that the world's very worst areas to live are inhabited by low IQ, highly violent animals. Now, when you combine those with both a low IQ and a high degree of violence, you get a culture that is both depressing and savage. If you found yourself in one of those places without possible recourse, to which avenue would you gravitate?
Why, wouldn't it be a violent, thug based theology promising the world's losers a huge payoff - both here and an afterlife? This is Islam; nothing more than a manifestation of a promise to those who are both stupid and dangerous.
Very well put.