I think there's a simple explanation for this. Increased head size == greater risk of death in childbirth Female hips have already evolved to be as large as p

I think there's a simple explanation for this. Increased head size == greater risk of death in childbirth Female hips have already evolved to be as large as possible while still being load-bearing. It would be interesting to see what the wide-spread use of Caesarean sections would do to the human brain, if we weren't all going to be transhuman within a few generations anyway As far as whether there are diminishing returns to increased intelligence within one individual, I'd say try taking two people with half of Einstein's IQ and asking them to explain General Relativity