As it says in the paper, the evolution of hominids doesn't look like this; population genetics says that if hominid brains got larger, the marginal fitness returns on neurons went up.
You've probably read Scott Aaronson's Why Philosophers Should Care About Computational Complexity? [0]. This seems like the perfect area to apply a lot of the questions he brings up. That's what I was looking for as I skimmed through the paper. Maybe that's what idlewords was talking about as well.