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Western lowland gorillas forage for raw food in Pointe-Noire, Congo.

Primates (such as these western lowland gorillas in Pointe-Noire, Congo) have smaller brains due to their raw food diet.

Photograph by Michael Nichols, National Geographic

Nicholas Mott

National Geographic News

Published October 26, 2012

Did you eat a hot meal today? It's a smart thing to do, as our ancestors learned.

According to a new study, a surge in human brain size that occurred roughly 1.8 million years ago can be directly linked to the innovation of cooking.

Homo erectus, considered the first modern human species, learned to cook and doubled its brain size over the course of 600,000 years. Similar size primates—gorillas, chimpanzees, and other great apes, all of which subsisted on a diet of raw foods—did not.

"Much more than harnessing fire, what truly allowed us to become human was using fire for cooking," said study co-author Suzana Herculano-Houzel, a neuroscientist at the Institute of Biomedical Sciences at the Federal University of Rio de Janeiro in Brazil.

(Related: "Cooking Gave Humans Edge Over Apes?")

A Diet Unfit for King Kong

Herculano-Houzel and colleague Karina Fonseca-Azevedo measured the body and brain masses of primates and compared them with their caloric intake and hours spent eating. Unsurprisingly, the results showed a direct correlation between calories and body mass. In other words, the bigger you are, the more you have to eat.

But since there are only so many hours in the day, a primate can only become so big. A gorilla, for instance, is the largest primate. Yet it can only eat for ten hours a day, due to limited food supply, the time it takes to find that food, and the lengthy process of chewing through tough fibrous plants.

This results in a maximum weight of around 440 pounds (200 kilograms). On this diet, said Herculano-Houzel, "King Kong could not exist."

Even if he did, his brain would be comparatively small. That's because brain matter "costs" more calories than other body mass, according to the "expensive tissue hypothesis." (See brain pictures.)

And as the team write in their paper, gorillas could never eat enough nutrients to support their enormous size and the expensive tissue of the brain. "Apes can't afford both brain and body," said Herculano-Houzel.

Humans can't either. But when we came to a fork in the evolutionary road—brawn this way, brains that way—we took the cerebral route. This development came to be known as encephalization: We ended up with brains that are much bigger than our body size would indicate.

Cooking was the key, said Herculano-Houzel, whose study appeared this week in the journal Proceedings of the National Academy of Sciences. Heating our food unlocked nutrition: 100 percent of a cooked meal is metabolized by the body, whereas raw foods yield just 30 or 40 percent of their nutrients.

Applying fire to food also softens tough fibers, releases flavors, and speeds up the process of chewing and digesting. The extra nutrition, and the improved eating experience, allowed our prehistoric ancestors to spend less time searching for food—and less time chewing through tough plants for meager caloric reward.

(See "Eating Crocodile Helped Boost Early Human Brains?")

Cooking, therefore, gave us both the nutrition we needed to develop large brains and the time we needed to use them for things more interesting than chewing.

It was at this point, said Herculano-Houzel, that having a large brain stopped being an evolutionary liability—a feature that required a lot of effort to support with nutrients—and became an asset: something that could help us gain those nutrients more easily. We could now spend time thinking of better ways to hunt, to live, to develop culture, art, and early technologies—all the things that made us who we are now.

Evolving or Devolving?

Some today think this was a culinary misstep. They advocate eating prehistoric meals as a way of fighting modern ailments.

Proponents of raw-food diets, for example, don't prepare their meals at all. Like the gorilla, they simply munch away on raw fruits and vegetables.

Why? Some of them believe that heating food over 40 degrees Fahrenheit (4 degrees Celsius) destroys natural enzymes present in plants—molecular structures that help us digest proteins missing in processed foods. Others consider a retrogressive diet more environmentally sound, citing the various problems caused by modern industrial food production and distribution. And some folks simply eat raw foods as a quick way to shed a few pounds.

But "if you're healthy, this is a terrible idea," said Herculano-Houzel. "Sure, you'll lose weight very fast—you'll be eating all day and still feel starved."

That's because the low nutritional yield from raw foods requires massive consumption. In other words, if you want to sustain an active lifestyle, eating raw foods takes time and energy of its own.

Besides, said Herculano-Houzel, cooked food simply tastes better. "Even apes, when offered a choice of raw food or spaghetti and meatballs, will take the meatballs every time."

(See "Human Ancestors Ate Bark—Food in Teeth Hints at Chimplike Origins.")

But too much highly caloric, immediately gratifying foods can be dangerous, too. Diseases like obesity, hypertension, diabetes, and heart disease are all connected to overindulging our taste for refined sugars and processed foods. Humans would do well not to choose the meatballs every time.

Cooking Like a Caveman

"We have not adapted to this modern lifestyle with processed foods and sugars everywhere," said John Durant, author of the blog Hunter-Gatherer.com. "This is why we're seeing lots of major health concerns."

Durant is at the forefront of a different retrogressive movement: the Paleo-diet. Like the raw-foodists, his dietary philosophy entails taking a step back in the evolutionary food chain and eating, literally, like a caveman.

That culinary lifestyle—lots of meat, fresh organic fruits and vegetables, nuts and berries, nothing processed—is at odds with modern meals, which tend to offer thousands of calories, are readily available, and can be eaten quickly.

"In terms of evolutionary biology," said Durant, "we spent far longer as hunter-gatherers than anything else. So what does our metabolism recognize and process well? We're best adapted to eat like our natural ancestors."

Paleo is a relatively new diet, and Durant's claims about dietary evolution have yet to be scientifically verified or denied. Many doctors warn that cutting dairy and grains could lead to a dangerous lack of important nutrients. Cavemen might have been fit, but they did not have a lengthy lifespan.

Yet even Durant, who frequently runs barefoot in Central Park, thinks raw-food-only diets are a bit extreme. "It's not really about nutrition," he said, "just anti-cooking."

Our Next Meal

Eating like our ancestors may prevent modern diseases of overconsumption, but cooking is, after all, what drove our evolution this far.

So what is the next step? And is there still room for us to evolve? (Read about four ways we may, or may not, evolve.)

Herculano-Houzel thinks so.  Human brain size "may not be capped out yet," she said. "Over the last couple of centuries our body size has increased due mainly to changes in our diet, to increased access to better nutrition."

She added that we could continue to evolve bigger and bigger brains—with the right diet. What exactly that is, however, is still a matter of taste.

2 comments
Ronald Grimsson
Ronald Grimsson

How did our ancestors start using fire to prepare food in the first place?


Suggested timeline:


1. Out ancestors were opportunists, scavengers and omnivores. Grassfire was not uncommon on the open savannah, and they would soon learn what a fire meant. Not nearly as destructive as forest fires, fire in open areas can give you a free meal. There are birds who have learned that fire means food, and they pick up small prey running away from the flames, or a looking for dead victims in the ashes after the fire have died or moved on.


When the humanoids saw the smoke, they would have learned that there would probably be some dead animals to be found or exposed nests. Maybe they could also be able to capture some of the smaller prey. And perhaps they discovered that small roasted lizards tasted better than raw ones. Or that certain plants that had not turned into ash had become easier to eat.


2. After getting used to the fire and smoke, they no longer feared it in the same way as other animals. They would eventually learn to take some control of the fire themselves, finding a stick on fire they could use as a torch, or maybe find a branch and stick it into the flames, before carrying it away and spread the flames to new areas nearby, hoping to get an easy meal. Even if they didn't know how to make fire themselves yet, they knew how to use it when they found it. It is also possible they would collect some drye plant matter and use it to make an early "campfire" where they would prepare plants and animals they had found. It is also a chance that it kept predators away, another advantage.


3. Our ancestors were also making stone tools. One such consequence of toolmaking is sparks, and smoke if the sparks lands in dry plant matter. If they were making tools among dry grass or other plants that easily catch fire, it would only be a matter of time before they put together two and two. If they succeeded making fire, it would be a great accomplishment. When chimps can learn how to crack nuts better than inexperienced humans, our ancestors would have been skilled with they hands as well.


Those individuals who could master the skills of how to make fire, would probably have some advantages and produce more offsrping. Making fire could have become a required trait when choosing a partner. They learned which stones and plants that were best suited to make fire with, and they learned how to protected the fire by making it in places protected from the environment and maybe even build shelter over it. And the skills were passed on generation after generation, gradually improving and indirectly changing our ancestors' DNA.


And the ball kept rolling.

Satoshi Nagamoto
Satoshi Nagamoto

Where is this study?

It seems far fetched to me to conclude that we evolved bigger brains AS A RESULT OF cooking.

It seems equally plausible that we started cooking as a result of our development of bigger brains, however that came about.

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