Researchers suggest eating cooked food led to larger human brains

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(Medical Xpress)—Brazilian researchers Karina Fonseca-Azevedo and Suzana Herculano-Houzel suggest humans evolved bigger brains because they learned to cook their food. In a paper published in the Proceedings of the National Academy of Sciences, the two outline research they’ve conducted that involved counting the number of neurons in the brains of various primates, the results of which showed that the only way early humans could have evolved bigger brains was to find a way to get more energy from the food they ate, i.e. cooking it.


Cooking food causes it to break down in ways similar to digestion. Thus, animals that eat cooked food don’t have to expend as much energy digesting it as do those that eat their meals raw. Because of this, the researchers in this new study proposed that learning to cook food allowed more time to engage in other pursuits that eventually led to the development of larger brains. To prove their idea sound, they compared the amount and types of food various primates consume and compared it with the amount of energy necessary to fuel their brains which they calculated by counting .

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17 COMMENTS

  1. So is it eating cooked food that enlarged our brains or the fact that eating cooked food gave us more time for other pursuits, or a mixture of both?

    I thought the correlation between eating cooked food and enlarged brains had been made years ago? I am confused.

  2. I know of one male specimen of modern homo sapiens who failed to learn to cook food yet has more leisure time for socialising as a result. He also has failed to learn to clean the bathroom, toilets, vacuum the floors, and get the groceries – each capability failure further contributing to the amount of leisure time available for other pursuits, especially socialising and guitar playing.

    Though there’s some question about actual neural count, plus energy intake from alcohol is relatively high compared to other similar primates.

    One of the side effects of cooking food for early humans is smoke signals from fire. Which changes social dynamics between groups of humans. Smoke can signal that someone nearby has already got something good to eat that might be stolen, or who even might be good to eat themselves and who can easily be located. Much more easily than normal prey. So natural selection would tend to favour the evolution of behaviour that deters sneaking up on neighbours to steal their lunch. Perhaps early aspects of religion?

  3. ? I recall hearing something similar, but cooked food/reduced jaw size seemed to play off each other. A reduced jaw size led to larger brains. It would make sense since our jaw is nowhere near as strong as apes (especially my arthritic temporal mandibular joint.)

  4. I thought that this had already been established years ago? At least this is what i’ve been telling anyone willing to listen for years! … isn’t there also a gene mutation making our jaw muscles much smaller which allowed our brains to grow?

  5. Cooking takes extra time.  Granted, it does let you eat something like grass seeds which don’t run away when you hunt them, giving you time back you would have spent hunting something more agile.

    It also let women take over much of the responsibility for food collecting, something otherwise difficult with a clinging infant.

    I always thought hunter gatherers had plenty of leisure time. We became workaholics only with agriculture.

  6.  I thought this was old news too. From what I recall it might have something to do with switches – genes turning on/off. Anyone? It also makes sense that the someone with a small jaw would need to find a way to compensate and adapt.

  7. I thought that the small jaw and juvenile bone structure (gracile?) was a consequence of not needing to bite other creatures, presumably owing to upright posture freeing the hands for the more effective techniques of punching, clubbing, and slashing with knives. (Or the shooting of handguns in Islamic sectors of Sydney.)

    It seems reasonably to assume that upright posture developed before tool use and fire.

  8. esmith4102,

    I just skimmed through my copy of Wrangham’s book Catching Fire How Cooking Made Us Human. I didn’t find any reference to “counting neurons” specifically.  However, He bases his claims based on brain size and cranial size which I’m going to say is the same thing based on our article above.  What little description that we have of their procedure states that they “counted neurons” and then applied that information to brain size in general to draw some conclusions.  Here is a sample from Wrangham’s book:

    Chapter 5 Brain Foods. Hardcover-page 119

    “Dietary shifts toward roots,meat eating, and meat processing thus can explain the growth in brains from a chimpanzee-like ancestor at six million years to the habilines around two million years ago.  From then on, the increases in brain size were more continuous.  The habiline cranial capacity of 612 cubic centimeters (37 cubic inches) rose by over 40 percent to reach an average of 870 cubic centimeters (53 cubic inches in the earliest measured Homo erectus.  The significance of this rise is complicated by a parallel growth in body weight, from the lowly 32 to 37 kilograms (70 to 81 pounds) of habilines to a substantial 56 to 66 kilograms (123 to 145 pounds) in Homo erectus.  Unfortunately, body weights are hard to estimate accurately from bones and the number of specimens is small, so how much larger relative to body weight the brains of the first Homo erectus were than those of habilines, or whether they were relatively larger at all, is uncertain. However, Homo erectus brains continued to increase in size after 1.8 million years ago, averaging almost 950 cubic centimeters (58 cubic inches) by 1 million years ago.  Given the evidence and arguments I have offered that Homo erectus originated as cooks, the expensive tissue hypothesis suggests their eating cooked food caused their brains to grow.  Once cooking began, gut size could fall and the gut wold be less active, both trends reducing the cost of the digestive system.”

    The expensive tissue hypothesis that Wrangham is talking about here is explained in the same chapter in his book starting on page 109:

    “In 1995 Leslie Aiello and Peter Wheeler proposed that the reason some animals have evolved big brains is that they have small guts, and small guts are made possible by a high-quality diet.  Aiello and Wheeler’s head-spinning idea came from the realization that brains are exceptionally greedy for glucose-in other words, for energy.  
    …Among species that have the same relative basal metabolic rate, such as humans and other primates, extra energy going to the brain must be offset by a reduced amount of energy going elsewhere.  The question is what part of the body is shortchanged.
    ….They (Aiello and Wheeler) discovered that across the primates there is substantial variation in the relative weight of the intestinal system.  Some species have big guts and some have small.  The variation in gut size is linked to the quality of the diet….Aiello and Wheeler estimated the number of calories a species is able to save by having a small gut, and showed that the number matched the extra cost of the species’ larger brains. “

    Very cool stuff. Still, aside from the actual technical lab work of counting the neurons, I still don’t see much that’s new in our article above from the tour de force that Wrangham offers up in his book on the subject of the relationship between food, cooked food, brain size and social evolution of primates. Still, I appreciate the value of this lab work as a supportive structure in this discussion.

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