This one always tends to go round in circles, but here's a new slant (for me anyway). http://online.wsj.com/article/SB10000872396390443570904577544984097844856.html?mod=wsj_share_tweet (may be paywalled; I'm not sure) key quotes: "With high-level training so ubiquitous, God-given talent and physical advantages become the great differentiators." They go on to consider the huge advantages enjoyed by physical outliers like Usain Bolt, Missy Franklin, Robert Harting, Sebastian Brendel, Mijain Lopez etc. There's also a tennis hook: "Coaches and trainers now look more and more at size when evaluating talent. Patrick McEnroe, the former tennis pro who is now the general manager for player development for the U.S. Tennis Association, said he takes a long look at a promising young player's parents and growth potential when trying to decide whom to recruit. Tennis, he says, has gotten too physical to do it any other way. "I'm not saying everyone has to be 6-2, but if you're 5-9, I'm not sure that's going to work," said Mr. McEnroe, who at 6 feet even is an inch taller than his brother John." So the idea is that with huge strides in training, more rapid diffusion of knowledge etc creating a more level training field, the pendulum swings back towards nature being the big differentiator... Food for thought.