The MCAT is not an intelligence test (and there are criticisms of the inherent validity of "intelligence tests"). Perhaps there is somewhat of an asymptote with regards to the VR section, but in the sciences, the MCAT is about the memorization and practiced application of a finite number of patterns, equations, and relationships. I'm inclined to say that people who can't break a 10 in BS or PS either aren't devoting enough concentrated time to studying, or the don't have good study skills.
I take the MCAT tomorrow and if my past half dozen practice tests are any indication, I'll get around a 13 in each section. I don't think this is because of any superior innate intelligence, but rather because I devoted the past two months to studying and I've become very comfortable with the equations and types of questions on the MCAT.
Anecdotal evidence as an edit: I'm going into my last year of college, and I remember how as a freshman, Intro Biology felt like the hardest class I could imagine. I studied my butt off and did OK in the end. Now I take tougher schedules, with more labs, more upper level science classes, and I do better than I did as a freshman. I recognize this is because I learned how to study, and I'm positive these study skills have helped me on the MCAT.
My sentiments are echoed well by PingPongPro below me, but I think Sahren's logic might have some worth (and s/he at the very least says it very well).