Did Cooking Make Us Smarter?

What did the advent of cooking bring to human development? Scientific evidence suggests cooking our food may have made us more intelligent.

Olduvai Gorge in Tanzania

B.C. – Before Cooking

If you visited Tanzania’s Olduavi Gorge around two million years ago you would have found a number of small hominid species including Homo habilis walking around a gradually drying landscape. Over the previous million years, these bipedal primates adapted to open grasslands by walking and running. They also extended their food choices by using stone tools to cut meat off animal carcasses, crush nuts and hard fruits, and dig up the region’s abundant tubers. They were a successful but not outstanding animal family.

Two hundred thousand years later (1.8 million years ago), Homo habilis evolved into a hominid powerhouse, Homo erectus. These human-looking primates were different. Nearly six feet tall, they enjoyed a larger brain (62 billion neurons to H. habilis’ 35 billion neurons), a smaller but still efficient digestive system, much less fur, good running skills, and an enhanced social world that included hunting in bands. Indeed, H. erectus proved so capable of adapting to a variety of environments that it was the first hominid species to expand out of Africa into Europe, Central Asia, India, and ultimately China. What caused this evolutionary leap?

Fire and Cooking Expand the Brain

Homo habilis (left) and Homo erectus (right). Reconstruction by W. Schnaubelt & N. Kieser (Atelier Wild Life Art).

Harvard primatologist Richard W. Wrangham argues that control of fire and its immediate consequence—cooking—is the answer. In his 2009 book, Catching Fire: How Cooking Made Us Human, he points out that “cooking gelatinizes starch, denatures protein, and softens everything…. Cooking substantially increases the amount of energy we obtain from our food.”

Wrangham believes that early cooking not only improved the taste of food, but provided the energy needed for the evolutionary advance that led to H. erectus. His theory remains controversial because the archaeological record only supports fire use by Homo erectus dating back one million years.

In 2012, however, two Brazilian neuroscientists, Karina Fonseca-Azevedo and Suzana Herculano-Houzel, produced evidence that Wrangham may be right. In an article published in the PNAS, they investigated why humans have the biggest brain in primates, but not the biggest body. They measured brain vs. body size across 13 primate species and found that gorillas weigh up to three times more than humans, but have brains only with one third of the number of neurons (34 billion neurons in gorillas to 86 billion neurons in humans). The two scientists discovered that there is a limit to the amount of energy any primate can get in a single day of feeding from a low-calorie raw food diet. Given that neural tissue is “energy expensive,” they charted the natural trade-off between body size and brain size. Eating a low caloric diet imposes a size limit on the brain and intelligence of a large primate body.

Cooking Transforms Humans

When the same diet is cooked, that limitation is overcome. The Brazilian study offered direct support for Wrangham’s proposition that humans overcame metabolic limitations when they began to cook their food. Cooking increased the caloric yield of their diet because it allowed easier chewing, digestion and absorption of foods.

In addition, since the majority of the day was no longer needed for eating to obtain minimal raw-food calories, cooking likely increased the time available for social and more cognitively demanding activities. This in turn, as the Brazilian neuroscientists state, “would impose a positive pressure for increased number of neurons, now affordable by the new diet.” The combination of cooking with its higher caloric yield, and increased time for social and cognitive activities, they propose, “drove the rapid increase in the number of neurons encountered in human evolution from H. erectus onward.”

Cooking not only dramatically increased the amount of food energy available for a large body and even larger brain, but gathered everyone around the fire where they could think over the possibilities. So the next time you sit down to dinner, consider that humans may not have invented cooking, rather cooking may have invented humans.

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