Humans thanks to cooking
What makes us human, beings with superior cognitive abilities to other animals? “Our enormous number of neurons” is the answer we give in my laboratory. Even with a brain smaller than that of elephants and whales, we are probably the beings with the largest number of neurons in the brain, with about 86 billion of them.
And how did we get so many neurons in a single brain? Why is a gorilla three times bigger than us but has a brain three times smaller than ours, with three times fewer neurons?
New work from our lab, published in PNAS in October and featured in newspapers around the world, offered the first answer to both questions: the energy provided by diet limits the body and brain size that primates can sustain—and we are here because we have managed to circumvent this limitation.
With their raw diet, maintaining their bodies and brains already costs gorillas almost eight hours of feeding per day; when the season is not favorable, they lose weight. Doing the math, we show that, for a gorilla, sustaining an even larger brain in addition to their already enormous bodies would not be energetically feasible.
By the same token, given that our brains have three times more neurons than gorillas... we shouldn't be here either. With the same diet as other primates, Homo sapiens is not energetically viable: we would have to spend more than nine hours a day eating to sustain our bodies and brains.
But we are here, and we certainly don't need to spend nine hours a day eating. Why? We agree with primatologist Richard Wrangham: what made our species, with its brain full of neurons, possible was a sensational invention by one of our ancestors, possibly Homo erectus—cooking.
Cooking is a form of pre-digestion that not only more than doubles the energy yield of food but also drastically reduces the time needed to eat it. When it becomes easy to obtain all the calories needed to get through the day in a short time, having a large brain ceases to be a risk and becomes an advantage—and we propose that it was this change that drove the enormous and rapid increase in the size of our ancestors' brains.
Excellent. The problem, however, is that our subsequent inventions, such as agriculture, refrigerators, and supermarkets, have made it too easy to overeat.
Excerpt from Suzana Herculano-Houzel (2025) Neuroscience of Everyday Life, originally published in Folha de São Paulo in October 2010