>>12271897evolution doesn't pick the best, it picks what's good enough. if you can reproduce, your genes remain. survival of the fittest is a misnomer. it's "reproduction of the fit enough".
if higher intelligence lead to greater chances of survival and reproduction, then given the time, a species would select for that. but the marginal gains of a bigger brain means more caloric intake is required. you can only support so much on a hunter-gatherer lifestyle.
when agriculture was invented, this was bypassed. however, natural selection quit necessarily working on humans at that time too, because the infirm and weak could be kept alive by the labor of others. also, intelligence may be more useful in certain environments, therefore it wouldn't increase uniformly among populations. plus, modern humans haven't been around that long. we still suffer many problems from being previously horizontal animals. stuff like spinal damage, organ prolapse, joint erosion.
tl;dr if intelligence directly correlates with overall survival, given the time, humans would increase in intelligence. there are diminishing returns, also we have broken natural selection, also we are young.
