I do agree that hard work is obviously what drives us to level of fitness and capability we present. However, I remember reading an article in a magazine here at the hospital where I work, which talked about a specific study on muscle tissue from differant ethnic backgrounds.
It mentioned that the Western African tissiues exhibited a cellular strand which would physically move faster with a given amount of electrical impulse, but was not always stronger than others.
Eastern Africans generally exhibited a form of longevity before breaking down, but was not as capable of brute strength.
Cauacasians generally showed a natural capability to have faster mental reaction, but not necessarily muscle reaction. This may explain why caucasians generally still dominate very fast action winter sports which require extremely fast mental reaction and an enormous amount of balance. Although, someone tell that to the Jamaican bobsled team.

I agree that our capabilities are generally a result of our environment, diet, and level of dedication to a specific sport.

But, when if at all, does the long-term effect of being subjected to a specific envirnoment, produce a genetic inheritence, thus allowing a more natural superiority in a specific sport?