But isn't 'moving faster on the growth curve' exactly what it means to be a natural genius? Mozart didn't pick up the violin and instantly compose symphonies, but his talent helped him pick it up at an early age.

And aren't you assuming that everyone's rate of improvement is necessarily going to be fast enough, in the long term, for them to reach 'high echelons' (or even a reasonable level of competence) before they die of old age?