Catching Fire: How Cooking Made Us Human (19 page)

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Authors: Richard Wrangham

Tags: #Cooking, #History, #Political Science, #Public Policy, #Cultural Policy, #Science, #Life Sciences, #Evolution, #Social Science, #Anthropology, #General, #Cultural, #Popular Culture, #Agriculture & Food, #Technology & Engineering, #Fire Science

BOOK: Catching Fire: How Cooking Made Us Human
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The idea that cooking led to our pair-bonds suggests a worldwide irony. Cooking brought huge nutritional benefits. But for women, the adoption of cooking has also led to a major increase in their vulnerability to male authority. Men were the greater beneficiaries. Cooking freed women’s time and fed their children, but it also trapped women into a newly subservient role enforced by male-dominated culture. Cooking created and perpetuated a novel system of male cultural superiority. It is not a pretty picture.
CHAPTER 8
The Cook’s Journey
“A great flame follows a little spark.”
—DANTE,
The Divine Comedy
 
 
W
hen Jean Anthelme Brillat-Savarin wrote, “Tell me what you eat and I shall tell you what you are,” he could not have known how right he was. Even nowadays no one knows how deeply the effects of cooking and the control of fire have been burned into our DNA.
Take the pace of our lives. Compared with great apes, we live a few decades longer and reach sexual maturity more slowly. Our long life spans suggest that our ancestors were good at escaping predators. Across species, those who can escape predators more easily tend to live longer. Tortoises, safe in their shells, have lives measured in decades, far longer than most animals their size. Flying species, such as birds or bats, live longer than those confined to the ground, such as mice or shrews. Even in captivity, terrestrial rodents rarely live more than two years, whereas bats of the same size can live for twenty years. Likewise, gliding animals live longer than their nongliding relatives. Bowhead whales stay so far north that killer whales cannot reach them, and they live more than a hundred years. The longevity of early humans is unknown, but their relative safety during evolution must have owed much to the use of fire to deter predators.
Or consider weaning. Cooked food, being soft, enables mothers to wean their young early. During human evolution, early weaning would have allowed a mother to recover her body condition rapidly after birth, promoting a short interval between births. In addition, the higher energy value of cooked food should have promoted a faster rate of growth for the young. The expected early weaning made possible by a human mother’s giving cooked food to her infant would have affected social behavior too. Mothers who weaned their babies early would have larger families than before, an infant and a toddler side by side. The advantages of help given by grandmothers and other kin would have increased. Chimpanzee grandmothers occasionally express interest in their daughters’ offspring through carrying or grooming, but they are normally preoccupied with their own infants. By generating easily donated gifts of cooked food that are useful for the young, the new system of processing food would have favored cooperative tendencies in rearing families.
Cooking also should have reduced the difficulties of finding enough to eat during the poorest seasons, when even now hunter-gatherers routinely find conditions hard. The notion of cooked food making life easier challenges the thrifty-gene hypothesis, which claims that because the environments of our hunter-gatherer ancestors were highly seasonal, we are physiologically adapted to periods of feast and famine. Accordingly, ancestral humans supposedly digested and stored energy in their bodies with exceptional efficiency. The thrifty-gene hypothesis suggests this efficiency was a useful adaptation when starvation was a consistent threat but is responsible for obesity and diabetes in many modern environments. The cooking hypothesis suggests a different idea: during our evolution, our use of cooked food would have left us better protected from food shortages than the great apes are, or than our noncooking ancestors were. It implies that humans easily become obese as a result of eating exceptionally high-energy, calorie-dense food, rather than from ancient adaptation to seasonality. Great apes become obese in captivity on a rich diet of cooked food.
Cooking and the control of fire must have had substantial influences on our ancestors’ digestive physiology. Compared with our close ape relatives, humans regularly experience a higher caloric intake in a short time (e.g., a rapidly ingested evening meal), a more easily digested protein intake, and a higher concentration of the dangerous Maillard compounds that are produced by the combination of sugars and amino acids during cooking. We can therefore expect to find changes in our insulin system compared with those of apes, in the nature of our proteolytic enzymes, and in our systems of defense against a range of carcinogens and inflammatory agents. We might find that we are better protected against Maillard molecules than other primates are, given our uniquely long exposure to ingesting them in high concentrations.
 
 
 
Anthropologists often propose that when fire was first controlled, one of its major contributions was to keep people warm, but that idea wrongly implies that our precooking ancestors would have had difficulty staying warm without fire. Chimpanzees survive nights exposed to long, cold rain-storms. Gorillas sleep uncovered in high, cool mountains. Every species other than humans can maintain adequate body heat without fire. When our ancestors first controlled fire, they would not have needed it for warmth, though fire would have saved them some energy in maintaining body temperature.
But the opportunity to be warmed by fire created new options. Humans are exceptional runners, far better than any other primate at running long distances, and arguably better even than wolves and horses. The problem for most mammals is that they easily become overheated when they run. After a chimpanzee has performed a five-minute charging display, he sits exhausted, panting and visibly hot, beads of sweat glistening among his erect hairs as he uses increased air circulation and sweat production to dissipate his excessive heat. Most mammals cannot evolve a solution to this problem, because they need to retain an insulation system, such as a thick coat of hair. The insulation is needed to maintain body heat during rest or sleep, and of course it cannot be removed after exercise. At best it can be modified, such as by hair being erected to promote air flow.
The best adaptation to losing heat is not to have such an effective insulation system in the first place. As physiologist Peter Wheeler has long argued, this may be why humans are “naked apes”: a reduction in hair would have allowed
Homo erectus
to avoid becoming overheated on the hot savanna. But
Homo erectus
could have lost their hair only if they had an alternative system for maintaining body heat at night. Fire offers that system. Once our ancestors controlled fire, they could keep warm even when they were inactive. The benefit would have been high: by losing their hair, humans would have been better able to travel long distances during hot periods, when most animals are inactive. They could then run for long distances in pursuit of prey or to reach carcasses quickly. By allowing body hair to be lost, the control of fire allowed extended periods of running to evolve, and made humans better able to hunt or steal meat from other predators.
The hair loss that benefited adults would have been a problem for babies because babies spend a lot of time inactive and are therefore at risk of becoming cold unless cuddled or nestled in warm surroundings. Perhaps at first babies retained their body hair even when their older siblings lost theirs. But an infant lying next to a fire would have risked burning his or her body hair. Nowadays, human babies are unique among primate infants in having an especially thick layer of fat close to the skin. Baby fat could well be partly a thermal adaptation to the loss of chimpanzee-like hair.
Even our ancestors’ emotions are likely to have been influenced by a cooked diet. Clustering around a fire to eat and sleep would have required our ancestors to stay close to one another. To avoid lost tempers flaring into disruptive fights, the proximity would have demanded considerable tolerance. The first dogs provide a provocative model for how tolerance might have evolved. According to biologists Raymond and Lorna Coppinger, wolves began their evolution into dogs when they were drawn to human villages in search of food refuse about fifteen thousand years ago. The Coppingers suggest that when wolves were attracted to these potent new food resources, there was intense natural selection in favor of the calmer individuals, because the calmer wolves were able to get closer to the settlements and more easily find the precious new foods. In effect, dogs experienced a form of self-domestication.
The first cooks probably experienced a similar process. Among the eaters of cooked food who were attracted to a fireside meal, the calmer individuals would have more comfortably accepted others’ presence and would have been less likely to irritate their companions. They would have been chased away less often, would have had more access to cooked food, and would have passed on more genes to succeeding generations than the wild-eyed and intemperate bullies who disturbed the peace to the point that they were ostracized by a coalition of the calm. A version of this system had probably already started before cooking, when groups of habilines clustered about a meat carcass.
A process similar to domestication could then have led to an evolutionary advance in ancestral humans’ social skills. In animals, more tolerant individuals cooperate and communicate better. Among chimpanzees, individuals that are more tolerant of each other cooperate better. Again, bonobos are more tolerant than chimpanzees, and they collaborate more readily to obtain food. Experimentally domesticated foxes are likewise more tolerant than their wild ancestors and are better at reading human signals. If the intense attractions of a cooking fire selected for individuals who were more tolerant of one another, an accompanying result should have been a rise in their ability to stay calm as they looked at one another, so they could better assess, understand, and trust one another. Thus the temperamental journey toward relaxed face-to-face communication should have taken an important step forward with
Homo erectus
. As tolerance and communication ability increased, individuals would have become better at reaching a mutual understanding, forming alliances, and excluding the intolerant. Such changes in social temperament would have contributed to a growing ability to communicate, including the evolution of language.
The changes wrought by cooked food would have included family dynamics and their supporting psychological mechanisms. The development of pair-bonds in early humans (or their elaboration, if habilines had already evolved a pair-bonding system) contributed to the importance of romantic attachments. On the other hand, domestic violence would have been promoted by the way in which, thanks to cooking, labor is sexually divided and exchanged. Hunter-gatherers are not the only cultures in which wife-beating can be stimulated by disappointments over cooking. Sociologist Marjorie DeVault studied American households and found that “expectations of men’s entitlement to service from women are powerful in most families, [and] that these expectations often thwart attempts to construct truly equitable relationships and sometimes lead to violence.” Sigmund Freud thought the control of fire led to self-control. Around a hearth, he said, we have to suppress a primal urge to quench the flames with a stream of urine. Freud’s notion is far-fetched, but he was right about one thing: our species must have changed radically when we learned to live with flames.
 
 
 
The changes all depend on the mysterious initial moment. We may never know for sure how cooking started, because the breakthrough happened so long ago and probably rather quickly in a small geographical area. But we can use our growing knowledge of great ape behavior, nutrition, and archaeology to speculate. Consider first the woodland apes, or australopithecines. By the period between three million and two million years ago, several genera and many species of australopithecines had already occupied the African woodlands for perhaps three million years. At that time, the only known species of australopithecines were
Australopithecus afarensis
,
A. garhi,
and
A. africanus
, and then even they disappeared.
Climate change appears responsible for the extinction of australopithecine species. Africa began getting drier about three million years ago, making the woodlands a harsher and less productive place to live. Desertification would have reduced the wetlands where australopithecines would have found underwater roots, such as cattails and water lilies, and they would have found fewer fruits and seeds. The species of
Australopithecus
had to adapt their diet or go extinct. Two lines survived.
One adapted by intensifying its reliance on the underground foods that had provided the backup diet of less preferred foods for australopithecines in times of food scarcity. Their descendants rapidly developed enormous jaws and chewing teeth, and are recognized in the naming of a new genus,
Paranthropus,
or the “robust” australopithecines.
Paranthropus
emerged around three million years ago, possibly descendants of
Australopithecus afarensis
or
A. africanus
. They flourished in some of the same dry woodlands as our human ancestors until a million years ago and still looked like upright-walking chimpanzees. But even more than their
Australopithecus
ancestors
, Paranthropus
relied mainly on a diet of roots and other plant storage organs.
The other line of descendants led to humans, and it began with meat eating. Australopithecines must always have been interested in eating meat when they found fresh kills, just as chimpanzees and almost every other primate are today. They would therefore have readily pirated carcasses from any predator they were willing to confront, such as cheetahs or jackals, both of which had close relatives present in Africa by 2.5 million years ago. Chimpanzees today steal carcasses of young antelope or pigs from baboons. But stealing meat from lions and saber-tooths must normally have been too dangerous for australopithecines. Even lions and hyenas kill each other in competition over food, and australopithecines would have been feeble and slow compared to any of the big carnivores.

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