All known human societies eat cooked foods, among other raw foods. But to what extent had cooking impacted the evolution of the human body and when has the transition from a raw diet to a cooked diet occurred?
We know, for example, that cooked foods are generally softer than raw foods, so humans can eat them with smaller teeth and weaker jaws. Cooking your food also allows you to eat a lot more calories, and therefore more energy. Moreover, up to 50% of women who eat exclusively raw foods develop, amenorrhea, an absence of menstruation sign that the body does not have enough energy to support a pregnancy – a big problem from an evolutionary point of view.
Such evidence suggests that modern humans are biologically dependent on a cooked diet. But at what point in our evolution has this strange new practice been adopted? Some researchers believe that cooking is a relatively “recent” innovation, dating back around 500,000 years. Cooking requires the control of fire, and archaeological evidence suggesting controlled fires before this period are rare.
But over time, the archeological archives are fragile. Others think that fire could have been controlled much earlier. For anthropologist Richard Wrangham, 1.8 million years ago people were already able to control fire. If the custom actually appeared so early, it could explain a defining characteristic of our species: the increase in brain size that occurred at that time.
The link between brain size and cooking
Understanding how and why our brain has become so big is a major puzzle, because such a brain is, at the metabolic level, very expensive. A human brain consumes more energy than any other organ. Having a big brain is therefore a heavy price, and our ancestors may have offset this energy cost by cooking their food.
Like all ideas to explain human evolution, the hypothesis can only be tested indirectly. But there are several convergent proofs that support the culinary hypothesis of Wrangham. For example, fossils show that the teeth and digestive tract of Homo erectus have shrunk at the same time as the brain has grown. This evidence probably means that our ancestors started eating sweeter, higher quality foods – though they were not necessarily cooked. New archaeological research has also pushed back the first known date for fire control. Traces of an intentional fire at the Wonderwerk Cave in South Africa date back more than a million years.
Finally, the work of Alexandra Rosati, Assistant Professor of Psychology and Anthropology at the University of Michigan, showed that chimpanzees have many of the basic cognitive skills needed to start cooking. For example, a preference for cooked foods, the patience to wait for food to be ready, and the ability to plan and transport food to a cooking site. These data mean that ancestral humans probably shared the same abilities, and could have started cooking quickly after gaining the ability to control fire.
This evidence indicates an earlier date for the adoption of a cooked diet. But many questions remain open. To what extent are these changes attributable to the consumption of cooked foods in particular, as opposed to the increased use of other processing techniques such as pounding or cutting of foods? Does the adoption of cooking – a generally community-based process in humans – require changes in our social behavior, given that other monkeys rarely share food? Are there other ways to develop a big brain? The evolution of our species is exciting, and the story is still full of puzzles that we are eager to solve.