I agree that a lot of the low black IQ is cultural. But not all of it. Different races have different IQ ranges. It's heredity....were the skills their ancestors needed to survive intellectual, analytical skills? Were they skills of working together and adapting to a less challenging environment? etc
In our politically correct world, we can't acknowledge that different ethnic groups have tendencies to different skill sets. It's a crime, because learning is no longer being geared to potential.
this is required reading
http://www.americanthinker.com/2011/04/the_keystone_of_the_islamic_mi.html
it explains much for the muslim/arab world and why they lash out the way they do