Eating more animal foods is one way of boosting the caloric and nutrient density of the diet, a shift that appears to have been critical in the evolution of the human lineage. But might our ancient forebears have improved dietary quality another way? Richard Wrangham of Harvard University and his colleagues recently examined the importance of cooking in human evolution. They showed that cooking not only makes plant foods softer and easier to chew, it substantially increases their available energy content, particularly for starchy tubers such as potatoes and manioc. In their raw form, starches are not readily broken down by the enzymes in the human body. When heated, however, these complex carbohydrates become more digestible, thereby yielding more calories.

The researchers propose that Homo erectus was probably the first hominid to apply fire to food, starting perhaps 1.8 million years ago. They argue that early cooking of plant foods (especially tubers) enabled this species to evolve smaller teeth and bigger brains than those of their predecessors. Additionally, the extra calories allowed H. erectus to start hunting--an energetically costly activity--more frequently.

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