More? If anything, I suspect thinking about quantum physics takes less intelligence; it's just not what we've evolved to do. An abstraction inversion, of sorts.

Hm. I also have this pet theory that some past event (that one near-extinction?) has caused humans to have less variation in intelligence than most other species, thus causing a relatively egalitarian society. Admittedly, this is something I have close to zero evidence for - I'm mostly using it for fiction - but it would be interesting to see, if you've got evidence for or (I guess more likely) against.