> If you look at the top 10 distance runners, they're all from Ethiopia and Kenya. But as you look further down the list into the top 100, you start to see Amer

> If you look at the top 10 distance runners, they're all from Ethiopia and Kenya. But as you look further down the list into the top 100, you start to see Americans and others. Furthermore, the Americans' times are really close to the Ethiopians and Kenyans The Americans still almost certainly have very favourable genetics for distance running, they're just less favourable than the genetics of the Kenyan runners. If you compared the American runners in the top 100 against the average American I would be very surprised if they had similar physical attributes (Lung capacity, muscle fibers, etc).