The secret of our big brain is cooking. Our brains are hungry organs. Brain constitutes 2 per cent of our body mass, but consumes 25 per cent of the energy used by the body. Anthropologists say that our body’s biological apparatus for getting energy became smaller over the last few million years and during this period our brains enlarged. The scientists say that the brain of Homo erectus was 50 per cent larger than that of its predecessor, H habilis, and during this time there was a big drop in H erectus’s tooth size. As the hominin body routed more energy to the brain, our biological apparatus (teeth, jaw muscles, stomach, guts) got diminished in effectiveness. They became less and less capable of processing food of all sorts. In spite of the decreased efficiency of jaw and gut, our ancestors managed calorie drought. The choice for them was between ‘better food’ and ‘better food processor’. They chose better food. They preferred to use better techniques to extract more energy with less effort. They invented fire and cooking. Changing the diet decreased the energy requirement of the bigger brain. As biological anthropologist Richard Wrangham, author of Catching Fire: How Cooking Made Us Human, writes, “The steady, accelerating pattern of brain growth was likely supported by shifts in diet as new food-procuring and preparation techniques steadily lifted the energy constraint on the brain’s development.”

Every animal in the animal kingdom would have liked to have bigger brains. But most animals don’t have brains like we have. It is because most animals don’t know how to manage big brains. They don’t know how to meet the energy demands of the big brains. As our brain uses energy it generates heat, and in the process it gets overheated. Fortunately, our hominin ancestors resolved the problem of overheat by developing a system of sweating that is managed by the brain.

Cooking is one of the most important innovations for softening food. This is perhaps the reason why we are called coctivores (those who love to eat cooked food). Food scientist Heribert Watzke says, “Our dental anatomy is actually made, not for tearing down raw meat from bones or chewing fibrous leaves for hours. It is made for a diet which is soft, mushy, which is reduced in fibres, which is very easily chewable and digestible”. If there was no cooking, our ancestors would literally be chewing the gathered food for the rest of the day to get enough calories to survive. Wrangham believes that great apes have helped us a great deal to understand our own behaviour. Life is easier if we understand biological rules. “Recognition of the deep contradictions in humanity binds us to our past, and also lights our future,” believes Wrangham. It is estimated that sometime around 250,000 or 300,000 years ago cooking really got going. There is archeological evidence that shows the presence of earth ovens during that time. Wrangham, however, thinks long before earth ovens came along we must have learned to cook.

Once cooking happened, it showed us completely new ways of utilising our resources. We began to look at the environment with new eyes. We began to see human male-female relationship from a new perspective. Wrangham’s idea is that once females were ready to make a meal by collecting food and cooking it, they became vulnerable to big males (he calls them “scroungers”) who took away their food. Rather than collecting and cooking the food, the easier option for the males was to take it when it is ready. This necessitated the need of females protecting themselves from ‘thieving males’. Perhaps, as Wrangham suggests, this is the origin of human male-female relationships.

(The writer is a biotechnologist and ED, Birla Institute of Scientific Research, Jaipur)