Bolt was world champion junior with 15 years¡¡¡¡¡¡¡¡¡¡¡¡
Sub20 in 200 with 17 years¡¡¡¡¡¡¡¡¡¡
It is very sure that he does not appear suddenly
He had several important injuries 18-20 years that got slow very much his progression.
And yes, like jamboy tells, when he got 9.76 with 21 years in kingston was his big step.
And when he got his WR in NY he got a big fame in all world.