Surprise, there are actually more diverse sets of black people than "African", each with their own biological diversity. African-Americans (that is, blacks in America who can trace their ancestors to the southern slaves) overwhelming come from a specific part of Africa, and those Africans are quite different from Africans elsewhere on the continent. You even have race wars among different ethnic groups of Africans! (See Rwanda for a particularly gruesome example.) So some African subgroups are actually better at different athletic traits -- not all can jump like African-Americans, but then again not all can sprint like another group, or run for very long distances like yet another group -- just as not all White people are actually as intelligent on average as the British. Human biological diversity is pretty rich and varied, it's just unfortunate that the thing that matters most in modern society (intelligence) correlates as well as it does with such general and otherwise not very telling traits like skin color.

Rwanda is a lovely example: an "ethnic conflict" created by Belgian colonialism.