The Bell Curve has been thoroughly debunked I believe. Genetics aren't nearly as important as environment for IQ scores, as proven by adopted children.
A few things to bear in mind, race is far more of a cultural construct than a genetic one. Compared to other species we don't show much genetic variation, and people of African descent are much more genetically diverse than the rest of humanity. Another is that IQs have been rising steadily around the world, proof that environmental factors such as nutrition and education have a a large effect.