There's usually stories behind these "gifted" people though. And a lot of it is down to experience.
Take Amir Khan the boxer for example, he appears to be gifted, way above his peers, but people didn't actually know the amount of fights he had actually had pre Athens 2004. It wasn't like he just appeared from nowhere. When you look at it like that, it seems we only call people gifted when WE OURSELVES ACTUALLY hear of them or see them. Don't get me wrong he has to have some aptitude to be there at such a young age, but athletically there are many more people out there as talented, it's just that they may not have had the experience or opportunity.
How many inner city kids are there with talent, but because they cannot afford to go to Eton and the like they will never realise their true potential?
A lot of these "gifted" people unless they have the determination to break through barriers, often fall by the wayside.
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Also, actually talk to a lot of these "gifted" athletes, i.e. Roger Federer and he will tell you thathe has worked hard to get to where he is now.
PS - Sorry about the sporting examples but I am an athlete myself and I fiind it easier as I don't know anyone who is academically "gifted".
It is my opinion that there's always more to it than meets the eye. I've nevermet anyone who completely defies scientific logic.