The best guesses right now is that our ability to use fire--and eventually create fire--allowed us to evolve the brains that we have now, because cooking food significantly decreases the energy needed to process it, which allows more energy to be used by your brain. And our brain burns a lot of calories. Cooking food is essentially a preliminary digestion process. Without our brain, the modern world as we know it never exists. Hell, we never even evolve past troops of apes.