Neither. Many people will try a sport, and those who work incredibly hard will perform exceptionally well. Of those who put in the work, there will be some who are genetically superior to the rest. Those who had the genetics but did not put in the effort will not make it this far anyway because they did not take advantage of them. The genetic specimens who put in the work will be the absolute best at the sport. Therefore, their bodies become the face of the sport. There will be genetic specimens who never tried the sport, and thus, will never make it to the elite level, due to the the fact that they never used their gifts.
For example, if a kid ends up devoting his life to basketball, and becomes really good but turns out short (under 6’1’'), he won’t make it to the elite level. If another kid devotes his life to distance running, and becomes really good but turns out tall (over 6’11"), he won’t make it to the elite level. If a third kid devotes his life to basketball, and becomes really good and turns out tall (over 6’11"), he WILL make it to the elite level.
Elite levels athletes were born genetic specimens and by chance chose the correct sport for there genetic makeup.