Chimpanzee brain can only use carbs for energy but human brain can use both fat and crabs. Chimps therefore can not travel far from the equator. How did human evolve our brain to utilize fat and grow our brain size? The trick is the use of fire. We don’t need a strong jaw anymore. That lead to brain size increase. Some fire usage and cooking is still necessary. Human had been using fire to cook our food for about 500 thousand years. We want to eat a lot of fruits and nuts. At the same time, we should use fire to cook certain healthy plant-based whole food to help with our digestion, and complete nutritional requirements.