Grigori Perelman refused prize because he knows "how to control the universe"

Googling schizophrenia+creativity leads me to suspect that it's more than a cultural expectation. Though I should disclaim the likely bias induced by my personal experience with several creative schizophrenics.

I'd expect it's much more likely that developing intelligence requires an evolutionary trade-off with other useful things

Sure, we can take that for granted seeing how we're not floating superbrains (yet) :D

it's more efficient to have some intelligent people, and that these factors drown out such a putative correlation in the evolutionary calculation.

Efficient to have some intelligent people? Efficient for whom?

Either this is a missunderstanding on my part, or alternatively I would recomment (re?)reading "The Selfish Gene". Because if the answer to who it is efficient for isn't "really, really close kin" I can't think of anything else that could be a valid answer. And how did the reproductive success of brothers and sisters benefit from having a highly intelligent nerd as a sibling?

EDIT: Actually I can think of another answer now that seems more plausible than the kin idea involving an evolutionarily stable strategy. But thinking it through that sounds quite implausible as well.

If we are talking about the evolutionary advantages of intelligence we are almost exclusively talking about the advantages that intelligence could possibly have for the reproductive success of the individual, not the society or the group (s)he's a part of.

The kind of intelligence that was probably most heavily selected for is social intelligence, aka. understanding, navigating and manipulating social relationships. The kind of nerd intelligence you witness in Perelman and around here seems to be an evolutionary by-product of that at best, because let's face it - highly intelligent nerds are weird outliers and rarely seem to posess high attractiveness to the opposite gender in a way that would be able to make their genes outcompete other spunk floating around in the gene-pool. That's why nerds didn't take over the gene-pool in the past, which is why we're still so stupid and overly concerned with all the "wrong" things.

In other words, if we're talking about the evolution of human intelligence, I think we're talking about a very narrow set of (mainly social) intelligence that evolved by being directly selected for, while general intelligence skills like mathematical prowess and rationality are more of a by-product that weren't ever directly selected for. (If anything I'd guess they were rather selected against).