I know you have some interest in genetics so I will give you the spill. Let me know what you think?
FYI - In the beginning other groups were the slaves and sub saharan africans were the masters.
All Homo sapiens originated in Africa. Since the beginning there was a slave/master relationship with the stronger being the master.
Some of those who were slaves got up the courage to leave. (If you consider those who came to America or those that ventured West, it was usually not those that were in superior positions but those persecuted in some way that migrated.)
These persecuted people when to Europe and Asia. They encountered different/harsh environments. Those with more adaptive skills survived. They passed on the adaptive genes of those who could survive in harsher environments.
If you have ever seen one of those shows about people who live in Alaska - they have to start making plans in June to survive the winter.
Skinny - Outside of Africa. Harsh environment. Those with adaptive skills survived to past on their genes to their children. These skills pertained to deferring immediate gratification and expanding ones planning horizon to (t+1)
Those who stayed in Africa - sub saharan africans - did not have the opportunity to have their genes adapted to more challenging environments. They are more prone to immediate gratification and have a very short planning horizon.
There is a substantial genetic difference between the genes of sub saharan africans and all other groups. That is why on any medical forms they ask if you are sub saharan african or other.
The difference as a % might seem small but it amounts to millions of base pairs.
The skinny - black Americans are genetically different from other groups. black Americans can run fast and jump but are not very good at planning.