All known human societies eat cooked as well as raw food. But to what extent did cooking have an impact on the the evolution of the human body, and when did we move from a raw to a cooked diet?
We know for example that cooked food is generally more tender than raw food, such that humans can eat it with their smaller, weaker jaws than animals. Cooking food also allowed us to take in far more calories, and thus more energy. Additionally, up to 50% of women who eat only raw foods develop amenorrhea -i.e., their periods stop -because their bodies do not have enough fat to support a pregnancy. This would be a huge problem from an evolutionary perspective.
Such proof suggests that modern humans are biologically dependent on a diet of cooked food. But at what point in evolution did this strange new practice take hold? Certain researchers believe that cooking is a relatively “recent” innovation, dating back around 500,000 years. Cooking required the ability to use fire, and archaeological evidence suggests that it was rare for people to have mastered using it before this period.
But the further back we go in time, the weaker the archaeological evidence is. Other people believe that fire was mastered much earlier. For anthropologist Richard Wrangham, it happened 1.8 million years ago. If fire had been used as early as that, it could explain a determining characteristic of our species: the increase in brain size that occurred at this time.
So what is the link between cooking food and brain size? Understanding how our brain got as big as it did is a real puzzle, because metabolically speaking, a brain is very costly. The human brain consumes more energy than any other organ. Having a large brain is thus a costly characteristic, and our ancestors may have compensated for this energy cost by cooking their food.
Like any ideas aiming to explain human evolution, the hypothesis can only be indirectly tested. However, there are several pieces of evidence that come together to support Wrangham’s culinary hypothesis. For example, fossils show that Homo erectus’s teeth and intestines reduced in size at the same time as the brain got bigger. This probably signifies that our ancestors started to eat softer and better quality food, although it need not necessarily have been cooked. New archaeological research has also pushed back the earliest known date for mastery of fire. Evidence of an intentional fire in the Wonderwerk Cave in South Africa in fact dates back over a million years.
Finally, Alexadra Rosati, an assistant professor in psychology and anthropology in the University of Michigan, carried out works showing that chimpanzees have several of the fundamental cognitive prerequisites necessary to start cooking. For example, a preference for cooked food, the patience to wait for food to be ready and the ability to plan and transport food to a cooking area. This data signifies that our ancestral humans probably had the same abilities, and could start to cook shortly after having discovered how to control fire.
This evidence indicates an earlier date for the adoption of a cooked diet. But numerous questions still remain unanswered. To what extent can the changes in humans be attributed to consuming cooked foods in particular, as opposed to the use of a range of other techniques for processing food such as pounding or chopping food? Did starting to cook -generally a community activity in humans -require changes in our social behaviour, given that other monkeys only rarely share food? Are there other ways in which brain size could have rapidly expanded? The evolution of our species is extremely interesting, and history still holds plenty of enigmas that we look forward to solving.