why isnt there any white male sprinters and no black male swimmers competing in the olympics ?

Have heard but not sure that black people have heavier bone density which is no good for swimming and this is why you don't see them in swimming raceswhy isnt there any white male sprinters and no black male swimmers competing in the olympics ?
I think I heard it mentioned that no white sprinter has managed the 100 metres in under 10 seconds, it does look like there is a slight genetic difference between black/white people which really only shows in the top % of sports. To the average man on the street I bet this difference disappears.
poshman said:why isnt there any white male sprinters and no black male swimmers competing in the olympics
kjacko said:We were told over 70% of Jamaicans can't swim.