Humans, it turns out, possess much higher metabolic rates than other mammals, including our close relatives, apes and chimpanzees, finds a Harvard study. Having both high resting and active metabolism, researchers say, enabled our hunter-gatherer ancestors to get all the food they needed while also growing bigger brains, living longer, and increasing their rates of reproduction.
This seems to support the theory that it was cooking of foods which led to speciation for early hominids. Cooking releases many more nutrients and calories, or makes inedible foods edible, like bone marrow and root vegetables. More caloric content means less time foraging and eating, and more energy for creativity.