So, basically, we have the two 'sides' here:
1) There are two significantly different types of people who will score highly on IQ tests: "Ambitious minds" who desire intelligence and knowledge, and "born geniuses" who simply have it as a matter of course.
2) There is no significant difference between these two types of people and/or 'ambitous minds' and 'natural intelligence' are unrelated factors.
I haven't really seen any evidence for one or the other. It's mostly just been anecdote and surly skepticism.
Personally, I think there's a pretty crazy number of factors which will impact adult IQ, so although 'ambition' and 'genetics' may both have significant effects, there's so much more to it than that.