Straightforward intelligence boosting genes are valuable enough that unless they are very recent, they should already have spread everywhere.
It's more likely that developing brains have a huge number of potential tradeoffs to make for what tasks they are good at and how much energy they use. Genetics and epigenetics are merely one of the tools a brain uses to decide what shape it takes, and aren't even close to the whole picture.
It's more likely that developing brains have a huge number of potential tradeoffs to make for what tasks they are good at and how much energy they use. Genetics and epigenetics are merely one of the tools a brain uses to decide what shape it takes, and aren't even close to the whole picture.