It is 100 percent genetic.
I have said it before on here and will defend my opinion to the death. But before you read my answer bear in mind I am not a racist!!!!
The problem with coloured folk, especially black darkies, is their is no "average" person.
50 percent of them are way above average status, intelligence, morals etc. This is very commending and rather complimentary. However, the other 50 percent fall far below what is expected of a decent human being. This has nothing to do with "American culture" as the coloured there fall in to the same genetic categories.
A darkie will either embrace you as a brother, give you food warmth and shelter and love you as their own,
OR
pimp out your daughter, shoot you, rape your mother or be a general nuisance.
There is no middle ground at all like whities, asians and the yellow people.
It is a fact. And although I know nothing of genetics or physiology, it is probably something to do with the size of the brain. 50 percent have large ones, 50 percent have underdeveloped and criminal ones.