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Richard Wrangham: Catching Fire: how cooking made us human
(Basic Books: 2009)

“I believe the transformative moment that gave rise to the genus Homo...stemmed from the control of fire, and the advent of cooked meals. Cooking increased the value of our food. It changed our bodies, our brains, our use of time, and our social lives. It also made us consumers of external energy and thereby created an organism with a new relationship to nature, dependent on fuel.... The fossil record shows that before our ancestors came to look like us, they were humanlike in walking upright, but...they were the size of chimpanzees, they climbed well, they had ape-sized bellies, and they had protruding, apelike muzzles...[and brains] barely larger than chimpanzees.... The transition is first signalled at 2.6 million years ago, by...cobblestones deliberately clashed to produce a tool....[and] knife-making suggests planning, patience, cooperation, and organized behavior. Old bones continue the story. By around 2.3 million years ago, the first tentative record emerges of a new species.... Habilines appear to have been about the same small size as australopithecines...yet they are thought to be the knife-makers, and they had brains twice as big as those of living nonhuman apes.... Between 1.9 and 1.8 million years ago, the second critical step was taken: some habilines evolved into Homo erectus...[who] even appear to have grown and matured slowly, in the manner of modern humans...[and] had small jaws and small teeth, that were poorly adapted for eating the tough raw meat of game animals. These weaker mouths cannot be explained by Homo erectus’s becoming better at hunting. Something else must have been going on....  Cooking food does many 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.... Their genes spread, [and] 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.... We humans are the cooking apes, the creatures of the flame.”
(Wrangham, pp.2-14)

While most treatments of human evolution still hew fairly closely to the old hypotheses, across the field a variety of genuinely fresh approaches are making much more sense of the full range of available evidence...from the mimetic culture of Merlin Donald, to Christopher Boehm’s counter-hierarchy, and Jonathan Kingdon’s revolutionary mix of anatomical and biogeographical insight. The latest in this chain of work is also perhaps the best supported - and the easiest to outline - being Richard Wrangham’s Catching Fire (2009)...the first exhaustive treatment of the evidence for cooking as the key which enabled the basic transition from ape to human. For while Kingdon - and a few others - have indeed made this basic claim before, nobody had examined the full implications of such a claim...thereby showing that it is, in fact, remarkably well-supported by a wide variety of evidence.

And the starting point is a remarkably simple one: even in modern sedentary societies, eating high-quality domesticated foodstuffs (w/no dangerous seasonal variability) - frequently ground to a pulp by mechanical food processors (rather than laboriously chewed) - human beings attempting to survive on purely raw foods are 1/- always hungry, 2/- thin to dangerously underweight (about 50% of women cease to menstruate), 3/-  reliant upon oils/fats for calories to a much greater extent than would be possible for virtually all hunter-gatherers. And, before anyone raises the counter-case of traditional  (raw) Eskimo/Inuit diets, this - like their myriad words for snow - is yet another “learned” myth about these isolated peoples. Like every society studied by anthropology, raw food among the Inuit is mainly a snack consumed out of camp...

Unfortunately, simplistic assumptions by early nutritionists - as well as such myths - have tended to obscure the nutritional value of cooking until recently. However, high-quality science is now demonstrating that processing food can have a major impact...

“The mechanisms increasing energy gain in cooked food, compared to raw food, are [now] reasonably well understood. Most important, cooking gelatinizes starch, denatures protein, and softens everything..... Raw starch [for example] is poorly digested, often only half as well as cooked starch.... [Similarly,] denatured proteins are [up to 40%] more digestible because their open structure exposes them to the action of digestive enzymes.... [However,] heat is only one of several factors that promote denaturation. Three others are acidity, sodium chloride, and drying, all of which humans use in different ways.... Although gelatinization and denaturation are largely chemical effects, cooking also has physical effects on the energy food provides...[reducing] the costs of digesting, absorbing, and assimilating [foodstuffs].... Admittedly, cooking can have some negative effects. It leads to energy losses through dripping during the cooking process and by producing indigestible protein compounds, and it often leads to a reduction of vitamins. But, compared to the energetic gains, those processes...[are] relatively unimportant, compared to the impact of more calories.... [For] the result was a new evolutionary opportunity.”
(Wrangham, pp.57-81)

“Evolutionary tradeoffs are common. Compared to chimpanzees, we climb badly but we walk well. Our awkwardness is due partly to our having long legs and flat feet, but those same legs and feet enable us to walk more efficiently than other apes. In a similar way, our limited effectiveness in digesting raw food is due to our having relatively small digestive systems...[that] enable us to process cooked food with exceptional proficiency.... The evolutionary benefits stem from the fact that digestion is a costly process that can account for a high proportion of an individual’s energy budget - often as much as locomotion.... The main differences all involve humans having relatively small features. We have small mouths, weak jaws, small teeth, small stomachs, small colons, and small guts overall...[with] the surface area of the stomach less than one-third the size expected for a typical mammal of our body-weight.... [Interestingly,] in carnivores, meat spends a long time in the stomach, allowing intense muscular contractions of the stomach wall to reduce raw meat to small particles that can be digested quickly...through the small intestine. By contrast, humans resemble other primates in keeping food in our stomachs for a short time...then passing it slowly through the small intestine. Lacking the carnivore system...we humans are inefficient at processing chunks of raw meat....[Furthermore,] evolutionary adaptation to cooking might likewise explain why humans seem less prepared to tolerate toxins than do other apes.”
(Wrangham, pp.38-51)

So...why, precisely, this tradeoff?

Well...primates are predominantly social animals - and there’s a well-attested intelligence arms race in such species, driven by the overwhelming need to monitor shifting group alliances & outwit the opposition. However, brain tissue is very expensive to run - when indolent, every human’s fifth meal is eaten solely to power the brain - and animals can only have the brain they can reliably brain tissue energy consumption is relatively stable across the wake-sleep divide. Therefore, the key lies in the general quality of diet...

As to the archaeology, the earliest well-documented site for fire use (currently) is dated at 790,000 years ago, in Israel, albeit there are many hints that earlier dates/locations are quite tenable. Unfortunately, the best evidence comes from geologically young caves in soft rock - particularly limestone - which have a half-life of around a quarter of a million years...meaning the best is basically unavailable by the time we come to the critical period of erectus evolution. However, as Wrangham explains:

“In response to a major change in diet, species tend to exhibit rapid and obvious changes in their anatomy. Animals are superbly adapted to their diets, and over evolutionary time the tight fit between food and anatomy is driven by food rather than by the animal’s characteristics. Fleas do not suck blood because they happen to have a proboscis well designed for piercing mammalian skin; they have the proboscis because they are adapted to sucking blood.... Therefore, we can identify when cooking began by searching the fossil record...[and] the change must mark when cooking became...a predictable daily occurance...and [it] also marks the time when fire was controlled so effectively that it was never lost again.”
(Wrangham, p.89-90)

Close attention to details here allows Wrangham not only to link the (slight) rise in brainpower of the Australopithecines to newly-regular tuber consumption, and meat to habilines - both now-standard in the literature - but also to note a shortfall between unprocessed raw meat consumption re the purported tradeoff into brain tissue. The parallels  are very interesting here, as are the implications:

“ that meat eating is difficult with ape jaws.... Perhaps because of this hard work and inefficiency, chimpanzees sometimes decline the opportunity to eat meat, despite their usual enormous enthusiasm for it.... When eating muscle, chimpanzees are forced to chew it slowly, taking as much as an hour to chew one-third of a kilogram.... [However,] habilines had access to more advanced techniques. Their bones are found close to stone hammers, fist-size spheres whose shapes provide vivid testimony of their repeated use. Habilines probably used the hammers partly to smash prey bones to extract the marrow. They also doubtless used the hammers to crack open nuts, as West African chimpanzees do. as well as to make other tools...[and] could equally have been used for tenderizing meat.... Even relatively crude hammering would have reduced the costs of digestion...[and] I suspect this was one of the most important cultural innovations in human origins.”
(Wrangham, pp.117-19)

“Reliance on cooked food has...allowed our species to thoroughly restructure the working day. Instead of chewing for (literally) half of their time, as the great apes tend to do,women in subsistence societies tend to spend the active part of their days collecting and preparing food. Men, liberated from the simple biological demands of a long day’s commitment to chewing raw food, engage in productive or unproductive labor as they wish. In fact, I believe cooking has made possible one of the most distinctive features of human society: the modern form of the sexual division of labor.”
(Wrangham, p.130)

“Among hunter-gatherers....women and men spend their time days seeking different kinds of foods, and the foods they obtain are eaten by both sexes.... Although the specific food types varied from place to place, women always tended to provide the staples, whether roots, seeds, or shellfish. These foods normally needed processing, which could involve a lot of time and laborious work.... Men by contrast tended to search for foods that were especially appreciated, but could not be found easily, or predictably.... Human families are unique compared to other species, because each household is a little economy.... The classic explanation in physical anthropology [revolves around] meat...and an unstated assumption was that the food was raw. But if food was raw, the sexual division of labour is unworkable...[as,] conservatively it would [include] just over five hours of chewing in a twelve hour day.... [Moreover,] apes also have to pause between meals.... Therefore, a five hour chewing requirement becomes an eight- or nine-hour commitment to feeding. Eat, rest, eat, rest.”
(Wrangham, pp.133-44)

Which hardly allows any time for hunting.... Although Wrangham doesn’t explore this factor, I think it reinforces the emerging consensus that habilines almost certainly were improved scavengers, rather than reliant upon hunting to any great degree - and that they also probably had some social arrangements unique to their group which made this workable. On the other hand, Wrangham’s made it clear by this point that raw food sharing - according to later models - is simply not on the cards, since physiology/time use are weighed so strongly against it. However, cooking may have solved that problem...but, it also introduced a series of fresh ones to replace it - the “solution” to which was predominantly patriarchy, sexual division of labour, and pair-bonding. And, as Wrangham himself observes: “It’s not a pretty picture.”

“An evening meal cooked by a woman serves her and her children’s needs. It also helps her husband by giving him a predictable source of food, allowing him to spend his day doing whatever activity he chooses. But while the arrangement is comfortable for both sexes, it is particularly convenient for the male. Why should a female cook for him? ...[And] overall, cooking is the most female-biased activity of any.... Even the apparent exceptions the general rule...[as there is] an important distinction between two types of cooking: cooking done for the family, done by women, and cooking for the community, done by men.... The rule that domestic cooking is women’s work is astonishingly convincing.”
(Wrangham, pp.147-51)

“Nonhuman primates mostly pick and eat their food at once. But hunter-gatherers bring food to a camp for processing and cooking, and in the camp, labor can be be offered and exchanged.... [Crucially,] relying on cooking creates foods that can be owned, given, or [easily] stolen.... Cooking takes time, so lone cooks cannot easily guard their wares from determined thieves, such as hungry males without their own food. Pair-bonds solve the problem.... According to this idea, cooking created a simple marriage system...a primitive protection racket in which husbands used their bonds with other men in the community to protect their wives from being robbed, and women returned the favor by preparing their husbands’ meals. The many beneficial aspects of the household, such as provisioning by males, increases in labor efficiency, and creation of a social network for child-rearing, were additions consequent to solving the more basic problem: females needed male protection, specifically because of cooking.”
(Wrangham, pp.152-5)

And the evidence supporting this perspective will be surprising to many...much of it universal across studies of mobile hunter-gatherers. Women’s food is private/domestic...and acceptable forms of begging for it are extremely circumscribed, whereas men’s food is parcelled out across the collective, typically via elaborate formulae.  However, once the men’s food share enters the domestic/female economy, it joins the women’s food in being subject to strong cultural norms, which severely restrict access. Not only must married women cook for their husbands - although they may have help - but (other than her kin) wives do not feed other men, except with the explicit sanction of the husband. This - in direct contrast to many such cultures’ more freewheeling attitudes towards sex, tends to suggest that Wrangham is right...the foundation of monogamy is in the regulation/reduction of competition over food/not sex, as is traditionally assumed. Let’s look at some of the details:

“Under this system, an unmarried woman who offers food to a man is effectively flirting, if not offering betrothal...[and] cofeeding is often the only marriage ceremony.... [Conversely,] among many hunter-gatherers, sexual intercourse is not tightly restricted to marriage. Wives are free to have sexual relations with several men at the same time, and may do so even when their husbands protest.... When an Australian aboriginal wife deserts her husband, wrote Phyllis Kaberry, he can easily replace her role as a sexual partner, but he suffers because he has lost someone tending his hearth. The loss is important because a bachelor is a sorry creature in subsistence societies, particularly if he has no kin....Men need their personal cooks because the guarantee of an evening meal frees them to spend the day doing what they want, and allows them to entertain other men. They can find opportunities for sexual interactions more easily than they can find a food provider.”
(Wrangham, pp.164-8)

“Anthropologists often see marriage as an exchange in which women get resources and men get a guarantee of paternity. In that view, sex is the basis of our mating system; economic considerations are an add-on. animal species, the mating system is adapted to the feeding system, rather than the other way around.... Furthermore, food relationships [among hunter-gatherers] appear more tightly regulated than sexual relationships...[and] when a woman feeds a man, she is immediately recognized as being married to him. Western society is not alone in thinking that the way to a man’s heart is through his stomach.”
(Wrangham, pp.174-5)

“It is impossible to know how rapidly cooking would have ended individual self-sufficiency after it was first practised, but in theory the protective pair-bond system could have evolved quickly.... But, at least we can say that three of the key behavioral elements found in the hunter-gatherer system - male food guards, female food suppliers, and respect for other’s possessions - are found in other animals, suggesting that a primitive version of the modern food-protection regime could have evolved rapidly among early cooks.”
(Wrangham, p.171)

Moreover, fire use/cooking has flow-on effects in other directions...some of which clearly affected our physical and mental evolution. Let Wrangham explain:

“If Homo erectus used fire...they could sleep in the same way as people do nowadays in the savanna. In the bush, people lie close to the fire, and for most or all of the night, someone is awake. When a sleeper awakens, he or she might poke at the fire and chat a while, allowing another to fall asleep. In a twelve-hour [equatorial] night, with no light other than what the fire provides, there is no need to have a continuous eight-hour sleep. An informal system of guarding easily emerges...[and] to judge from records of attacks by jaguars, modern hunter-gatherers are safer in camp at night than they are on the hunt by day.... [In addition,] their new practice of cooking roots and meat meant that food obtained from trees was less important.... [So,] when they no longer needed to climb trees to find food or sleep safely, natural selection rapidly favored the anatomical changes that facilitated long-distance communication, and led to living completely on the ground.”
(Wrangham, pp.101-2)

“[Furthermore,] once our ancestors controlled fire, they could [also] keep warm even when they were inactive. The benefit would have been high: [largely hairless] 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.... [Moreover,] 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...considerable tolerance...[although] a version of this had probably already started before cooking, when groups of habilines clustered about a meat carcass.... 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 each other, so they could better assess, understand, and trust one another.... Such changes in social temperament would have contributed to a growing ability to communicate, including the evolution of language....[And so] the newly delicious cooked diet led to their evolving smaller guts, bigger brains, bigger bodies and reduced body hair; more running; more hunting; longer lives; calmer temperaments; and a new emphasis on bonding between females and males. The softness of their cooked plant foods selected for smaller teeth, the protection fire provided at night enabled them to sleep on the ground and lose their climbing ability, and females likely began cooking for males, whose time was increasingly free to search for more meat and honey.  While other habilines elsewhere in Africa continued for several hundred thousand years to eat their food raw, one lucky group became Homo erectus - and humanity began.”
(Wrangham, p.184-94)

Richard Wrangham’s Catching Fire (2009) is one of the most deceptively clear books I’ve ever read. “Deceptively” because - whether you like it or not - it re-centres the extremely complex matter of human evolution around an extremely compelling and interlocked set of evidence which, quite basically, admits of no other real explanation. This is groundbreaking stuff...

But perhaps the most crucial influence Catching Fire will have lies in its very real potential to enable the synthesis of hitherto disparate - yet important - aspects of human evolution. Clearly, for example, Wrangham’s “hearth politics” provides the crucial context in which Christopher Boehm’s “counter-hierarchies” not only can, but necessarily arise...with the additional input of sexual selective processes - albeit considerably more economic/pragmatic than, say, Geoffrey Miller has envisaged. Similarly, the developmental interaction arguments of Ellen Dissanayake & Sarah Blaffer Hrdy can be expected to come fully into their own once the (partial) taming of the male hierarchy is underway...then leading through to properly mimetic culture/proto-language, and so on... All up, I’m beginning to suspect we now have all the truly critical theoretical ingredients we need to understand to transition to genus Homo...even if that final move to species sapien is still only partially accounted for.

Clearly written & argued, evidentially overwhelming, and entertaining to boot...this one will be enormously influential. And, hopefully soon. I can hardly wait to read mature syntheses to come.

“We once thought of our species as infinitely adaptable, particularly in our diet. Different peoples survive on diets that range from 100 percent plants to 100 percent animals.... Taken to extremes, our species seems to be free to create our own evolutionary ecology. [But] the cooking commitment says otherwise. The human ancestral environment was full of uniform problems: how to get fuel, how to regulate feeding competition, how to organize society around fires. The big problem of diet was once how to get enough cooked food, just as it is still for millions of people living around the world. But, for those of us lucky enough to live with plenty. the challenge has changed. We must find ways to make our ancient dependence on cooked food healthier.”
(Wrangham, pp.206-7)

John Henry Calvinist