On the other hand, critics of natural talent explanations often point out that too is tautological: someone is talented if they're successful and vice versa. Clearly there aren't proteins for violin bow control, so something happens in between.
Talent doesn't have to be "natural", just uncontrolled factors. Something that is "in the person" at the time of training. This could have come from past experiences, genetic, even things like diet, who knows. The point is, it's still not understood and not controllable.