A year of running every day :)

[Alan Lucker]

Well that's just plain blinkered. You are suggesting that every being is born as a blank canvass with identical innate ability? Then how do you account for the incredible variety in the world? How do you account for race horses' selective breeding to produce the winners? There is quite a variation in their race times too, and I would suggest they would be less subject to the environmental variations and vagaries that humans bring upon themselves.

Genetic variations (mutations) enabled some humans to survive the plague. Similar variations give some low natural heart rates, high VO2max, low lactate production, etc. (Lance Armstrong is a case in point).

I suspect natural selection has has an effect on the gene pool. It would certainly, neatly, give us the answer as to why all the best sprinters are black. As suggested by the BBC in their Olympic coverage; that slavery of the blacks may have pushed them into a survival of the fittest scenario. Other possibilities are of a more difficult environments to live in. I.e food and water scarce severe heat etc.
It certainly would fit in with Darwins theories.
My opinion is that most are born with a similar ability. But some choose to make the most of it and get very good, and of those some have a slight genetic advantage from birth and become elite, at whatever it is they chose to stick with.
Nurture and nature probably equal elite, but mainly nurture.