One of the cool things about having smart people to train around is that they make you think. In this case, Master Cape gets the blame, as does Rachel.
"Some people are just natural talents. Others aren't."
The oft quoted Malcolm Gladwell would disagree with you, I think. Not to say I don't get what you're sayin, but I do wonder if there's more to look at. To start with I'll pose a couple questions: can you define what this "natural talent" is? Are there multiple "talents" that could be at work either independently in separate people, or in unison within one to put them even further ahead the curve? You mention genetics. By that do you simply mean physicality and athleticism, or something else?
I suppose a better model would actually be Howard Gardner's Multiple Intelligence's concept (http://en.wikipedia.org/wiki/Theory_of_multiple_intelligences). Gardner's theory, in short, is that intelligence is actually composed of a variety of different intelligences, and some people have a higher intelligence in certain fields than others. One of those intelligences is "bodily-kinesthetic", which correlates learning with physical action. While I think you could reasonably argue that there are other kinds of intelligence that come into play in combat sport, someone with a high bodily-kinesthetic intelligence would probably develop skill faster than someone who did not. On an extremely informal survey, I would guess that Spatial and possibly logical/mathematical intelligences would come into play as well. But I'd have to research a lot more to make that assessment accurately.
RE: Genetics. On the one hand, I think the influence of genetics is often overplayed/used as an excuse. On the other hand, there is no denying the role that genetics play in determining who we are, and what we can do. I could lift weights and take enough steroids turn myself into a friggin' centaur, and I would still never be the size of John Johnston. The weight, maybe. Not the size.
Is there some kind of genetic coding for "fighting well". I have no idea. Fighting, even in the limited context of combat sport, is a pretty complex thing, and involves physical, mental, and emotional factors. Do genetics influence all of those things? I'm inclined to think so, but I have no real proof of that. In any case, they are something totally beyond our control right now, so it's not something that anyone can change, but can only work with.