If Sapiens were a blog post
What caused our brains to develop? We’re not sure.
It doesn’t seem likely. A larger brain needs more energy and thus reduces the chance you’ll survive. Getting more energy meant hunting more.
One contributing factor was the domestication of fire. Fire paved the way for cooking.
Whereas chimpanzees spend 5 hours a day chewing raw food, a single hour suffices for people eating cooked food. The advent of cooking enabled humans to eat more kinds of food, to devote less time to eating, and to make do with smaller teeth and shorter intestines.