Catching Fire: How Cooking Made Us Human
By Richard Wrangham
Richard Wrangham's new book is an expansion of a provocative hypothesis about human history that he and his colleagues first published in 1999. Cleverly evoking anthropologist Claude Lévi-Strauss's work The Raw and the Cooked, the article was entitled 'The Raw and the Stolen: Cooking and the Ecology of Human Origins.' Wrangham restates his hypothesis concisely and elegantly at the outset of Catching Fire:
“I believe the transformative moment that gave rise to the genus Homo, one of the great transitions in the history of life, stemmed from the control of fire and the advent of cooked meals. Cooking increased the value of our food. It changed... our social lives. It made us into consumers of external energy and thereby created an organism with a new relationship to nature, dependent on fuel.”
The primary criticism of the cooking hypothesis, as it was first published, centred on the lack of convincing evidence that cooking began about 2 million years ago in Africa. Wrangham, a biological anthropologist at Harvard University, attributes the origin of the large-brained Homo erectus and its geographic expansion out of Africa to the invention of a new mode of preparing tubers that greatly enhanced digestibility and nutritional benefits. The hypothesis was sceptically received in 1999; commentators used the phrases “half-baked” and “Just-so story”. After an additional ten years of research, I hoped Wrangham would present a stronger argument. He does not.
The oldest credible evidence of controlled fire is around 790,000 years old, from a site at Gesher Benot Ya'aqov in Israel. Here, burned flint fragments were clustered, suggesting the use of hearths. But burned seeds and wood, also present, were not clustered near the hearths or one another. So apart from the burned flint, the evidence for controlled fire at this site is equivocal, as is all such evidence before about 250,000 years ago.
The lack of evidence is daunting. If one individual and his descendents made a fire once a week for a million years, they should have left the remains of some 50,000,000 fires. “Evidence of humans controlling fire is hard to recover from early times,” Wrangham says.
The main ingredient of his hypothesis is, succinctly, potatoes. Early hominins used cooked tubers and underground storage organs of plants as an important fall-back food. Tubers were underused by other species because they require digging and cooking for maximum benefit.
But Wrangham runs afoul of the evidence here too. Stone tool assemblages from before 2 million years ago include cores, small sharp flakes for cutting and hammer stones for producing flakes and for pounding. Overwhelming evidence shows that these stone tools were used to cut up dead animals. Cut marks and percussion marks from breaking open long bones to extract marrow occur on hundreds of fossils. In 2002, Eric Hoberg showed that human-specific tapeworms are most closely related to tapeworms that infest the carnivores with which early Homo competed for carcasses nearly 2 million years ago. There is much evidence that early hominins ate meat, but little to show that their tools were used on plants, and none that there were cooking fires or digging sticks at that time.
Wrangham interprets various anatomical traits of humans — small mouths, small gapes, weak jaws, small teeth and a short digestive system — as adaptations to eating soft, high-density food with little fibre in it. Are these truly adaptations to cooked food?
In 1995, Leslie Aiello and Peter Wheeler suggested that increased meat-eating caused the increase in hominin brain size about 2 million years ago. They proposed that a meat-rich diet accessed with stone tools permitted guts to become smaller, freeing up energy for brain growth. Primates with smaller guts consistently have larger brains, and humans are the extreme case of small guts and large brains, they said. Their hypothesis is compelling.
Wrangham argues that lumps of raw meat are difficult to digest and protein intake must be balanced with carbohydrate intake. Carbohydrates can be obtained from fat, marrow, brains, fruits and nuts, and are abundant in foods happily eaten raw by baboons, chimps and warthogs — such as corms, rhizomes and tubers of savannah plants — so Wrangham's dismissal of these sources of carbohydrates is unpersuasive.
Fire has other advantages, Wrangham observes. Sleeping on the ground at night was dangerous for hominins and a fire kept predators away. True, but antelopes sleep on the ground and have not yet invented fire or cooking.
Wrangham's analysis of the effect of cooking on humans is stronger. Cooking may have promoted a division of labour by sex. Large, prized food items hunted by males were taken home and shared, as were large vegetable items, such as tubers, gathered by females. Because females have babies, they often took on the tasks of foraging for staple vegetable foods and cooking.
Pair-bonding is another component of Wrangham's scenario. It ensures that the male hunter will have something to eat if he returns empty-handed, and reassures him that the baby he feeds is his. Pair-bonding assures the female gatherer that someone will contribute high-protein items to her baby. Because fires are visible for long distances, they may draw food thieves, so pair-bonding also gives protection to the cooks.
Wrangham's thinking about the effect of food choices on society is interesting, but his attempt to superimpose his hypothesis on to the early fossil and archaeological record is unconvincing.
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