If it is purely genetic then Africa would have more sprinters doing well- not just those who leave and learn it elsewhere. Likewise, it is clear that there is a reverse bias against whites in the sprints in America generally. I remember Al Vermiel producing a 4.3 receiver and after the games films were reviewed, and it was clear he was white, his times were rejected as false. The fact that Al had a history of being the S and C coach for the SF49ers when they won the Super Bowl for the first time apparently wasn’t enough to override scepticism.