Just by visually comparing African Americans (from West Africa) to whites you can tell they are genetically advantaged when it comes to sprinting:
longer legs, shorter torsos, broader shoulders, narrower hips, longer achilles tendon, more muscular in general, lower body fat…..etc
While the average differences might not seem significant, they mean a lot when you look at the far right side of the bell curve and find that all the elites come from the same place.
Why do they come from the same place? Because for a variety of reasons, evolution over long periods of time in this environment selected for traits ideal for sprinting, whereas in other environments evolution selected for different traits. For example: white athletes generally have more body fat than black athletes because you don't need a lot of insulation when you live in Africa.
The result of this evolution is that every sprinting world record is held by an athlete of West African descent, and every middle-distance and distance event record is held by an athlete of North or East African origin.