This might be a controversial question, so allow me to explain.
As we all know colonists imported slaves from Africa. So initially, we had a pretty small population of a distinctive group of people, who could not breed with people outside of their race due to systematic segregation. So, we had a pretty small population who was isolated in extreme conditions where the easily sick and weak would die leaving only the strongest. So did this intense force of extreme tragedy homogenize genes amongst black people to make them naturally more fit?
More can be written, but you could start with this , in which /u/Elm11 posted three links to other replies by /u/freedmenspatrol and /u/sowser . I would also add this by atomfullerene, which considers practicality.
This is not to discourage discussion. More questions, data, and debate may be posted.