Hugh Pickens writes "For a long time, humans were pretty dumb, doing little but make 'the same very boring stone tools for almost 2 million years,' says Philipp Khaitovich of the Partner Institute for Computational Biology in Shanghai. Then, 150,000 years ago, our big brains suddenly got smart. We started innovating. We tried different materials. We started creating art and maybe even religion. To understand what caused the cognitive spurt, researchers examined chemical brain processes known to have changed in the past 200,000 years. Comparing apes and humans, they found the most robust differences were for processes involved in energy metabolism. The finding suggests that increased access to calories spurred our cognitive advances, although definitive claims of causation are premature. In most animals, the gut needs a lot of energy to grind out nourishment from food sources. But cooking, by breaking down fibers and making nutrients more readily available, is a way of processing food outside the body. Eating (mostly) cooked meals would have lessened the energy needs of our digestion systems, thereby freeing up calories for our brains. Today, humans have relatively small digestive systems and allocate around 20% of their total energy to the brain, compared to approximately 13% for non-human primates and 2-8% for other vertebrates. While other theories for the brain's cognitive spurt have not been ruled out, the finding sheds light on what made us, as Khaitovich put it, 'so strange compared to other animals.'"