The human brain went through two enormous evolutionary changes — one in size, followed by an even more important one in cognitive ability. Your brain consumes huge amounts of calories and exhibits incredible prowess. In fact, your brain’s roaring metabolism, possibly stimulated by early man’s invention of cooking, may be the main factor behind our most critical cognitive leap, new research suggests.

About 2 million years ago, the human brain rapidly increased its mass until it was double the size of other primate brains. Some believe this is because humans started to eat better food. But then, about 150,000 years ago, a different type of spurt happened — those big brains suddenly got smart. Humans started innovating, invented many new tools, and started creating art and perhaps religion.

Research suggests that increased access to calories spurred these cognitive advances. The extra calories may have come from the first hearths. Cooking, by breaking down fibers and making nutrients more readily available, is a way of processing food outside the body. Eating cooked meals would have lessened the energy needs of the human digestion system, thereby freeing up calories for the brain.