Nowadays we need fire wherever we are. Survival manuals tell us that if we are lost in the wild, one of our first actions should be to make a fire. In addition to warmth and light, fire gives us hot food, safe water, dry clothes, protection from dangerous animals, a signal to friends, and even a sense of inner comfort. In modern society, fire might be hidden from our view, tidied away in the basement boiler, trapped in the engine block of a car, or confined in the power station that drives the electrical grid, but we still completely depend on it. A similar tie is found in every culture. To the hunting-and-gathering Andaman Islanders of India, fire is “the first thing they think of carrying when they go on a journey,” “the center round which social life moves,” and the possession that distinguishes humans from animals. Animals need food, water, and shelter. We humans need all those things, but we need fire too.
How long have we needed it? Few people have thought about this question. Not even Charles Darwin pursued it, though he had every reason to be interested. During his five-year voyage around the world, Darwin learned what it was like to be hungry in the wild. When camped in harsh places, such as the sodden moors of the Falkland Islands, he made fire by rubbing sticks together. He cooked with hot rocks in an earth oven and called the art of making fire “probably the greatest [discovery], excepting language, ever made by man.” His gritty experiences taught him that “hard and stringy roots can be rendered digestible, and poisonous roots or herbs innocuous.” He understood the value of cooked food.
But Darwin showed no interest in knowing when fire was first controlled. His passion was evolution, and he thought fire was irrelevant to how we evolved. Like most people, he simply assumed that by the time our ancestors first controlled fire they were already human. He cited his fellow evolutionist Alfred Russel Wallace approvingly: “man is enabled through his mental faculties ‘to keep with an unchanged body in harmony with the changing universe.’” The control of fire was just another way for an unchanged body with an adept mental faculty to respond to a natural challenge. “When he migrates into a colder climate he uses clothes, builds sheds, and makes fires; and, by the aid of fire, cooks food otherwise indigestible . . . the lower animals, on the other hand, must have their bodily structure modified in order to survive under greatly changed conditions.”
The notion of prehistoric humans having an “unchanged body” while inventing new ways to make their lives easier is mostly right. Little change has occurred in human anatomy since the time of
Homo erectus
almost two million years ago. Culture is the trump card that enables humans to adapt, and compared to the two-million-year human career, most cultural innovation has indeed been recent. Before two hundred thousand years ago, the main novelties recorded by archaeology were stone tools and spears. Art, fishing tools, personal decoration with necklaces, and stone-tipped weapons all came later. Why should the control of fire be any older? Most anthropologists have followed Darwin’s assumption that cooking has been a late addition to the human skill set, a valuable tradition without any biological or evolutionary significance. We use fire, Darwin seemed to imply, but we could survive without it if we had to. The implication was that cooking has little biological importance.
A century later, cultural anthropologist Claude Lévi-Strauss produced a revolutionary analysis of human cultures that implicitly supported the biological insignificance of cooking. He was an expert on the myths of Brazilian tribes, and he was deeply impressed with the way in which cooking served to symbolize human control over nature. “Cooking establishes the difference between animals and people. . . . Not only does cooking mark the transition from nature to culture,” Lévi-Strauss wrote in his influential 1960s book,
The Raw and the Cooked
, “but through it and by means of it, the human state can be defined with all its attributes.” Lévi-Strauss’s insight that cooking is a defining feature of humanity was perceptive. But strikingly, for him its significance appeared to be entirely psychological. Fellow anthropologist Edmund Leach presented Lévi-Strauss’s views crisply: “[People] do not have to cook their food, they do so for symbolic reasons to show that they are men and not beasts.” Lévi-Strauss was an elite anthropologist, and his implication that cooking had no biological meaning was widely touted. No one challenged this aspect of his analysis.
Despite the predominant skepticism about the role of fire in human evolution, a few contrarians have argued that cooking has been a core influence on human nature. The strongest voices have come from students of food and eating. The celebrated French gastronomist Jean-Anthelme Brillat-Savarin sounded evolutionary even when Charles Darwin was still a teenager. “It is by fire that man has tamed Nature itself,” he wrote in 1825. His experience told him that cooking helps us to eat meat more easily. After our ancestors started cooking, he argued, meat became more desirable and valuable, leading to a new importance for hunting. And since hunting was mainly a male activity, women took on the role of cooking. Brillat-Savarin was prescient in tracing a link from cooking to households, but his ideas were not richly developed. They were throwaway lines hidden in a voluminous output, and they have never been taken seriously.
In the past half century, ideas suggesting how the control of fire might have influenced human behavior or evolution have been proposed by writers in physical anthropology (by Carleton Coon and Loring Brace), archaeology (especially by Catherine Perlès), and sociology (by Joop Goudsblom). But such analyses have been tentative, leaving it to the specialized field of cooking history to provide thoughts as bold as those of Brillat-Savarin. In 1998 cooking historian Michael Symons combined intellectual ingredients from a range of disciplines, and based on the idea that cooking affects many aspects of life from nutrition to society, he made a stronger claim than any before him. Symons concluded, “cooking is the missing link . . . defining the human essence.... I pin our humanity on cooks.” In a 2001 book on the history of food, historian Felipe Fernandez-Armesto likewise declared cooking an “index of the humanity of humankind.” But neither these authors nor any other writer advocating the importance of cooking understood how cooking affects the nutritional quality of food. Critical questions therefore were left untouched, such as whether humans are evolutionarily adapted to cooked food, or how cooking had its supposed effects on making us human, or when cooking evolved. The result was a series of ideas that, however intriguing, were not tied down to biological reality. They suggested that cooking had shaped us, but they did not say why or when or how.
There is a way to find out whether cooking is as biologically insignificant as Darwin implied, or as central to humanity as Symons asserts. We need to know what cooking does. Cooked food does many familiar things. It makes our food safer, creates rich and delicious tastes, and reduces spoilage. Heating can allow us to open, cut, or mash tough foods. But none of these advantages is as important as a little-appreciated aspect: cooking increases the amount of energy our bodies obtain from our food.
The extra energy gave the first cooks biological advantages. They survived and reproduced better than before. Their genes spread. Their bodies responded by biologically adapting to cooked food, shaped by natural selection to take maximum advantage of the new diet. There were changes in anatomy, physiology, ecology, life history, psychology, and society. Fossil evidence indicates that this dependence arose not just some tens of thousands of years ago, or even a few hundred thousand, but right back at the beginning of our time on Earth, at the start of human evolution, by the habiline that became
Homo erectus
. Brillat-Savarin and Symons were right to say that we have tamed nature with fire. We should indeed pin our humanity on cooks.
Those claims constitute the cooking hypothesis. They say humans are adapted to eating cooked food in the same essential way as cows are adapted to eating grass, or fleas to sucking blood, or any other animal to its signature diet. We are tied to our adapted diet of cooked food, and the results pervade our lives, from our bodies to our minds. We humans are the cooking apes, the creatures of the flame.
CHAPTER 1
Quest for Raw-Foodists
“My definition of Man is, a ‘Cooking Animal’. The beasts have memory, judgement, and all the faculties and passions of our mind, in a certain degree; but no beast is a cook. . . . Man alone can dress a good dish; and every man whatever is more or less a cook, in seasoning what he himself eats.”
—JAMES BOSWELL,
Journal of a Tour to the Hebrides with Samuel Johnson
A
nimals thrive on raw diets. Can humans do the same? Conventional wisdom has always assumed so, and the logic seems obvious. Animals live off raw food, and humans are animals, so humans should fare well on raw food. Many foods are perfectly edible raw, from apples, tomatoes, and oysters to steak tartare and various kinds of fish. Tales of raw diets are numerous. According to Marco Polo, Mongol warriors of the thirteenth century supposedly rode for ten days at a time without lighting a fire. The riders’ food was the raw blood of their horses, obtained by piercing a vein. The cavalry saved time by riding without cooking, and they avoided producing the smoke that might reveal their position to hostile forces. The men did not like the liquid diet and looked forward to a cooked meal when speed was not essential, but there is no suggestion that they suffered from it. Such stories make cooking seem like a luxury, unimportant to our biological needs. But consider the Evo Diet experiment.
In 2006 nine volunteers with dangerously high blood pressure spent twelve days eating like apes in an experiment filmed by the British Broadcasting Corporation. They lived in a tented enclosure in England’s Paignton Zoo and ate almost everything raw. Their diet included peppers, melons, cucumbers, tomatoes, carrots, broccoli, grapes, dates, walnuts, bananas, peaches, and so on—more than fifty kinds of fruits, vegetables, and nuts. In the second week they ate some cooked oily fish, and one man sneaked some chocolate. The regime was called the Evo Diet because it was supposed to represent the types of foods our bodies have evolved to eat. Chimpanzees or gorillas would have loved it and would have grown fat on a menu that was certainly of higher quality than they could find in the wild. The participants ate until they were full, taking in up to 5 kilograms (10 pounds) by weight per day. The daily intake was calculated by the experiment’s nutritionist to include an adequate 2,000 calories for women, and 2,300 calories for men.
The aim of the volunteers was to improve their health, and they succeeded. By the end of the experiment their cholesterol levels had fallen by almost a quarter and average blood pressure was down to normal. But while medical hopes were met, an extra result had not been anticipated. The volunteers lost a lot of weight—an average of 4.4 kg (9.7 pounds) each, or 0.37 kg (0.8 pounds) per day.
The question of what kind of diet we need is critical for understanding human adaptation. Are we just an ordinary animal that happens to enjoy the tastes and securities of cooked food without in any way depending on them? Or are we a new kind of species tied to the use of fire by our biological needs, relying on cooked food to supply enough energy to our bodies? No serious scientific tests have been designed to resolve this problem. But whereas the Evo Diet investigation was short-term and informal, a few studies of long-term raw-foodists give us systematic data with a similar result.
Raw-foodists are dedicated to eating 100 percent of their diets raw, or as close to 100 percent as they can manage. There are only three studies of their body weight, and all find that people who eat raw tend to be thin. The most extensive is the Giessen Raw Food study, conducted by nutritionist Corinna Koebnick and her colleagues in Germany, which used questionnaires to study 513 raw-foodists who ate from 70 percent to 100 percent of their diet raw. They chose to eat raw to be healthy, to prevent illness, to have a long life, or to live naturally. Raw food included not only uncooked vegetables and occasional meat, but also cold-pressed oil and honey, and some items that were lightly heated such as dried fruits, dried meat, and dried fish. Body mass index (BMI), which measures weight in relation to the square of the height, was used as a measure of fatness. As the proportion of food eaten raw rose, BMI fell. The average weight loss when shifting from a cooked to a raw diet was 26.5 pounds (12 kilograms) for women and 21.8 pounds (9.9 kilograms) for men. Among those eating a purely raw diet (31 percent), the body weights of almost a third indicated chronic energy deficiency. The scientists’ conclusion was unambiguous: “a strict raw food diet cannot guarantee an adequate energy supply.”
The amount of meat in the Giessen Raw Food diets was not recorded but many raw-foodists eat rather little meat. Could a low meat intake have contributed to their poor energy supply? It is possible. However, among people who eat cooked diets, there is no difference in body weight between vegetarians and meat eaters: when our food is cooked we get as many calories from a vegetarian diet as from a typical American meat-rich diet. It is only when eating raw that we suffer poor weight gain.
The energy consequences of forgoing cooked food lead to a consistent reaction, illustrated by journalist Jodi Mardesich when she became a raw-foodist. “I’m hungry. These days, I’m almost always hungry,” she wrote. A typical day began at 7 A.M. when she cut and juiced two ounces of wheat grass. At 8:30 A.M. she had a bowl of “energy soup,” which she describes as a “room-temperature concoction made of sunflower greens, which are the tiny first shoots of a sunflower plant, and rejuvelac, a fermented wheat drink that tastes a lot like bad lemonade.” She added a couple of spoonfuls of blended papaya for interest. Lunch was a salad of sunflower greens, sprouted fenugreek seeds, sprouted broccoli seeds, fermented cabbage, and a loaf made of sprouted sunflower seeds, dehydrated seaweed, and some vegetables. Dinner was more sprouts, avocado chunks, pineapple, red onion, olive oil, raw vinegar, and sea salt. An hour later she was hungry again. In photographs she looks distinctly thin, but she was happy. She described herself as feeling energized, mentally sharper, and more serene. Nevertheless, after six months, during which she lost 18 pounds (8.2 kilograms), she could not resist slipping out for a pizza. Mardesich was not alone in finding a wholly raw diet a challenge. The Giessen Raw Food study found that 82 percent of long-term raw-foodists included some cooked food in their diets.