Nature or nurture?

While at the Mystic 3 convention on Monday, one of the speakers posed a question to the group titled "what is talent" or something like that. I don't know if the question was truly ever answered (or if it can be) but I replied that I felt that passion for something was what drove someone to become talented or to reach their true potential.
So I pose this question to all of you out there.."what is talent and where does it come from"?
I DO believe that everyone was born to be great at something, but only a few lucky ones discover what that is. And then, there are people who are not born with the most natural ability, yet their passion or desire to do well at something takes them to another level. For example, Larry Bird was not born with wonderful athletic ability, but he worked harder than everyone else to overcome his shortcomings and still excel at the highest level.
All of this is not to say that some don't have a "God given" gift to do something well...because some obviously do. But when someone tells me that I am gifted (which is very rare, trust me!)..my response is that the true "gift" is that God allowed me to discover my passion...and that I work very hard to be the best that I can.
So what do you think? Are great musicians born with the natural ability..or did they just work harder at it than most? Maybe it's a combination? Does it go back to the "nature vs. nurture" thing. I am curious to hear your thoughts out there.