A group of scientists have revealed a theory which says cooking is what allowed our ancestors to develop efficient brains. The thinking (as it were) goes that after long use, the evolution strategy of getting bigger and bigger brains had run up against physical limitations related to birth. In other words, human heads just couldn't get any bigger and still have women able to walk around. However, by processing our food externally using tools and fire, we greatly reduced the amount of energy required for digestion, freeing it up to be used to power faster metabolic processes in our already quite large brains. In a funny sort of way, it really did amount to "we are what we eat."