I like this topic, David. Also, it is now obvious that genetics (our genetic make up) helps/predisposes us to some sports, activities.
For instance, starting with a higher than normal VO2max (oxidative capacity), or more important, responding well to exercise training like cycling: being able to ramp up all the metabolic adaptations allowing our VO2max to reach very high values (critical in cycling, middle and long distance running, cross country running or skiing, rowing, speed skating).
Some polymorphisms (mutations) in the hemoglobin gene (in some individuals) affect the affinity of hemoglobin (oxygen and CO2 carrier in the blood) for oxygen. A higher affinity helps capture oxygen at high altitudes (where oxygen levels/pressure are low). On the other hand, lower affinity helps oxygen leave the blood and get captured by the (working) muscles (where oxygen is used for oxidation of nutrients to 'produce'/extract energy).
Some athletes may find it 'unfair' that others have genes providing advantages. And they may want to 'compensate' their handicap (which is not allowed by the current World Anti-Doping Code, obviously).
I believe we are all predisposed to something (good at something). People should just choose to do the thing they are good at (sport or other), and be the best at it.