How Cooking Made Humans Smart

Once upon a time, our ancestors ate only raw food. Then, about 2 millions years ago, they learnt how to use the energy of heat. The result: not only did prehistoric humans change their food habits—the new food habits also changed humans.

No one can say when and where the first piece of meat was grilled. However, this much is certain: we began to play with fire over some prehistoric embers, more than 2 million years ago.

And what happened to the wild game—probably slain—must have seemed like a miniature natural disaster to the first observer of this process: the fibres of the meat shrivelled in the heat of the flames within a short time; soon thereafter, the water contained in the muscles seethed, turned to steam, expanding to more than a thousand times its volume, and tore through the fibres to escape.

Hot fat came out of the fissures that had burst open in the meat and dripped with a sizzle into the flame. The pigments deteriorated. Bright red first became a soft pink and then grey.

The blaze was particularly savage and destructive at the edges of the tissue. Within a few minutes, it broke down the proteins and sugars there. Their components subsequently combined to form hundreds of new substances that left a brownish crust full of intensive aromas on the grilled meat.

What might seem banal to our contemporaries and could hardly be any more mundane—barbecuing or cooking food—brought several advantages to the humans in the Stone Age who were the first to master the new technique; they lived longer and produced more offspring.

And it probably played a decisive part in the evolutionary success of Homo sapiens.

Cooking the mild way: While steaming, tiny water droplets form an insulating film on the food being cooked, which retains the heat of the steam. The insides of the vegetable become as hot as 82°C and the water condensed outside 91°C. (Photograph by Ryan Matthew and Nathan Myhrvold)

“After all, the preparation of food is a skill that no other animal possesses,” says British anthropologist Richard Wrangham. “Without it, our brain would probably never have developed so magnificently and we would probably never have evolved as a species.”

To reconstruct the beginnings of cooking, one must first analyse ancient ashes and bones discovered in Africa and carry out anatomical studies. This is the only way to find the evidence required to understand why humans developed in such a different way from their closest relatives, the apes—not only with respect to their brain volume and upright walk, but also in the way in which they consume their food. 

The teeth of Homo sapiens as well as their mouth are almost delicate as compared to those of a chimpanzee, for example. In addition, their jaw muscles and the bones to which these muscles are attached are rather weak. It would be impossible to crush hard-fibred plant stems with such a kit.

Besides, the human large intestine is extraordinarily small when compared to that of a gorilla. This is why humans digest fresh leaves, fruits and vegetables much less effectively than other large primates. The digestive tract also makes them vulnerable—the consumption of raw meat can sometimes even be life-threatening for humans.

But how could a species with so many deficiencies conquer the entire planet? How do the two fit together: weakness and ascent?

Until 2.5 million years ago, the ancestors of Homo sapiens still resembled apes: fossils from that time show that prehistoric humans had long arms and short legs. With an average size of 450cm3, their brains were hardly bigger than those of present-day chimpanzees.

In contrast, they had a prominent ribcage and pelvis, which hints at a spacious gastrointestinal tract. And such a long digestive system was especially suited to processing a plant-based diet, which is why palaeoanthropologists believe that these ape-humans primarily survived on plants.
However, more than 600,000 years later, our ancestors changed enormously: they became more human-like. Their legs became longer and their arms shorter. The thorax and pelvis became smaller—an indication of a reduced gastrointestinal tract. And the chewing surface of the molars shrank by more than 20 per cent, which researchers were able to deduce from the fragments of fossilised teeth. At the same time, the brain gained about 40 per cent volume.

These were radical changes. And according to Richard Wrangham, it was the art of cooking that resulted in these coming about.

According to his theory (which is accepted by several researchers), prehistoric humans had learnt in the course of these 600,000 years how to use stone tools to cut up dead animals and to smash their bones and scrape them out in order to get to the marrow. Incisions in fossilised bones testify to the use of stone blades.

Obviously, our predecessors tapped a rich source of calories—meat—which also led to the brain becoming bigger over several generations.

“However, this alone is not enough to explain the immense increase in cerebral matter,” says Wrangham, “and it does not explain the shortening of the intestine at all.”

Hence, he believes that our ancestors learnt something else in these years: optimising their meat consumption through fire.

It is still unclear exactly when the first barbecue in human history took place. However, the oldest fire pits in Africa are more than 1.9 million years old. It is possible that nature provided an object lesson back then: it could be that roasted big game was left behind after bush fires and it turned out to be delicious.

Heat alters meat: it becomes softer, can be chewed more easily, and acquires a more intensive taste. In addition, the cell walls of microbes in the tissue dissolve and they die away en masse. This is why roasted meat can be eaten even days later without the risk of a microbial contamination.

Braising is physically the most complex form of cooking. The food receives heat from three sources: the hot steam in the pot, the simmering water on the bottom of the pot and the infrared rays emanating from the glowing hot metal. (Photograph by Ryan Matthew and Nathan Myhrvold)

Besides, fire increases the nutritional value of meat, tubers and roots since the nutrients of heated food are much better exploited in the human digestive tract: the human body absorbs only about 65 per cent of the components of raw eggs and more than 90 per cent from boiled eggs.

Even starch, such as in wheat or potatoes, is sometimes twice as valuable when cooked as it is otherwise. It is the heat that makes the tiny starch grains swell and absorb large quantities of water; their strong bonds dissolve in this process. Hence, the enzymes present in the digestive tract can break down the nutritious granules more easily.

Through the use of heat, our predecessors were able to use their foodstuff much better—and also to acquire new sources of nutrition since heating made several plants that are otherwise too hard, too fibrous or full of bitter-tasting compounds softer, sweeter or at least less bitter. Also, numerous plants only lose their toxins through heating—for example, cassava and bamboo (which contain hydrocyanic acid) as well as unpeeled potatoes and string beans.

According to Wrangham, the preparation of food henceforth had an ever stronger influence on the digestive organs of prehistoric humans. Now they could carry out a part of the process of digestion outside the body since they processed their food beforehand, making it softer and more digestible.

Gradually, their lips, mouth, teeth, jaw bones and gastrointestinal tract adapted to the reduced requirements and became smaller.

All these changes facilitated the development of the brain: the shorter the intestine became in the course of evolution, the less energy it required. Thus, the surplus energy benefited other organs, primarily the brain, which was now better supplied, and thus increased in volume. To be more precise, an enormous expansion of the human brain came about.

In addition, our ancestors no longer needed to spend hours chewing stringy meat or fibrous plants any more. Hence, they had more time to prepare their food and to look for new kinds of food, to gather fruits, or lie in wait for animals. And even better: those individuals who got more calories from the food improved their chances of survival, produced healthier offspring and thus ensured the continued existence of their species.

This physical change continued to scale new heights until the anatomically modern version of Homo sapiens developed in Africa about 200,000 years ago. Their intestine was even smaller and consumed 10 per cent less energy than that of the Great apes.

And although the human brain accounted for only about 2 per cent of body mass, it now required up to a quarter of the nutritional energy.

From Africa, Homo sapiens finally conquered the rest of the world. Another 80,000 years later, modern humans were already using elaborate techniques for cooking. They cooked meat in natural vessels, such as tortoise shells. And they probably collected the fat of roasted seals in clam shells. In any case, researchers later observed this technique among the Yamana tribe in Tierra del Fuego, who lived in a very traditional way for a long time.

In addition, sanding marks on stones suggest that Homo sapiens of the Stone Age also pulverised hard grass seeds into flour.

And perhaps the flour congealed into a thick paste one day in the rain and later hardened in the sun: this could be how the first flatbread, which could be preserved for several days,
was produced.

Then, at some point of time, our ancestors discovered another important procedure in using flour: fermentation.

Since the flour sometimes remained moist for several days in the rainy season, fungus and bacteria spread within it and it began fermenting. Some of the microbes produced high-quality proteins that humans could now ingest. During the process of fermentation, carbon dioxide was also produced, which aerated the sticky dough and made it easier to digest.

With the passage of time, humans further developed their cooking methods. They learnt how to cook their food more efficiently with the help of earth ovens, which were discovered 30,000 years ago. The glowing stones in the cooking pit supplied an even heat that enabled them to control the cooking of tubers and meat over a longer time.

Well sealed and filled with water, the pits were probably also where the first soup was cooked.

Then, 16,000 years ago, humans made the first ceramic vessels to cook in. However, it was probably only in ancient times that they learnt how to preserve food for months. They hung up strips of meat or fish in the smoke from a fire or cured them with salt. Thanks to this technique, the tissue acquired more taste, simultaneously losing its juice—which is why bacteria could not multiply in it.

It was another breakthrough, a kind of cooking without heat: smoking made it possible to stock up food, which helped humans to survive in inhospitable regions, or during long sea voyages.

Another culinary revolution occurred at the same time: the cooks discovered the effects of spices. These made all food more delicious and also prevented bacteria from multiplying in the meat. Onions, garlic, oregano or pepper killed several kinds of microbes, and in doing so acted against a variety of diseases and contamination. Pepper was also used to promote digestion.

Since non-refrigerated meat spoilt fast in hotter regions, the people in the tropics started to flavour their food particularly strongly, which enabled them to make it last longer.

Water can be heated up to more than 100°C in a pressure cooker. The method was developed in 1806 to enable Napoleon’s army to sterilise food and make it last longer. (Photograph by Ryan Matthew and Nathan Myhrvold)

Thanks to the development of ever more refined culinary techniques, the human immune system probably also changed besides their anatomy, making them more helpless against plant toxins.

Now, after several generations of surviving on cooked and roasted food, the microbes present in raw meat or eggs are also dangerous for Homo sapiens. Obviously, humans have gradually lost some of the defence mechanisms that once effectively protected them from salmonella or E. coli.

And yet, cooking their food has helped Homo sapiens to emancipate themselves from their direct environment and to inhabit the most barren zones of the planet, the high mountain regions, the rocky deserts, the Arctic Zone. The South American Andes are also an inhospitable habitat. Very few edible plants grow there. One of them is the potato, by far the most important food resource—which, however, would be inedible unless cooked.

It is true that humans have made themselves dependent on their new culinary techniques and become physically vulnerable. However, they have also more than offset these weaknesses with the same culinary art.

Today, there is no society that lives exclusively on uncooked food (people who only eat raw fruits, meat or vegetables almost inevitably lose weight).

And despite all the differences in the food preferences of various human cultures, no other primate today enjoys such a premium-quality, high-energy diet as humans—regardless of whether their diet consists primarily of plant-based or meat-based food.

And another thing: today we need just 5 per cent of our waking time per day on average to nourish ourselves.

Without cooked, softer food we would be spending almost half the day sitting at the dinner table.

A five-volume boxed set, Modernist Cuisine: The Art and Science of Cooking by Nathan Myhrvold, Chris Young and Maxime Bilet is published by Taschen Books.