Like Wrangham, the authors also see a feedback loop in the history of feeding. Along with increasing the efficiency of our food intake and eliminating limits on growth, eating cooked food would have increased the time humans could spend around the fire, time spent together. Socializing, along with other "cognitively demanding" activities--like developing speech, social structure and civilization--would have required more brain power. And humans could afford to develop these more powerful brains, thanks to their improved, cooked diet. This positive feedback drove the rapid increase in neurons that took place in human evolution, the authors say.