Sorry maydog, you are incorrect. It's physiology, not physics. Sprinter vs Climber is about the bodys natural tendency not the body's actual physical ability. Most of us have never really trained and had their body reach anywhere near it's full potential, hence why, as you say, most people are suited for something in beween.
We all have a genetic disposition to build one type of muscle tissue over the other. It's just like hair color, eye color and so many other of our physical traits. However, as Campy stated, UNLIKE a lot of traits, we can actually change the actual fiber composition in the body through proper training. Easier said than done.