[gwern]

> I'm no evolutionary biologist, but it seems like the increased intelligence (or more accurately, cognitive performance) may not have had all that practical a benefit until just recently in our history anyway.

That's obviously wrong, because the brain is so metabolically expensive that if it was not pulling its weight, it would long ago have shrunk considerably. More intelligence is always better - if the intelligence is not too expensive. (I cover this in the link.)