This is another excellent book by Richard Wrangham. I loved his book Demon Males. This is just as good. It opens up a new way of looking at old subjects: human evolution, pair bonding, food. His thesis is simple: it wasn't the old story of "fire changed us from apes to humans" or "hunting changed us from apes to humans". Instead he has a more elaborate tale to tell with cooking playing a central role.
His claim is that cooking played a big role in evolution because it allows humans to expand their diet, get more nutrition from what they eat, changed the physiology of humans (shrank the gut and teeth while allowing the brain to get bigger), and created a unique pair-bonding in humans based on an economic unit in which the woman cooks and the male guarantees the security of property for the woman, the children, and the family. Oh, and it created the problem of male dominance and wife beating.
He points out that raw food is not only nutrition poor, but it gobbles up a lot of calories to support digestion. By moving to cooked food, the heating changes the nature of the food, makes it taste better, creates more easily digestible nutrition, and cuts the metabolic costs of digestion. He proposes a change to the story of evolution. For him, the split with chimps/gorillas was because humans took up hunting and became australopithcines. The change from australopithcines to habilines came with the adoption of cooking. The change to sapiens came as habilines fought over food and forced the females to switch from independent members of the troop to a dedicated domestic responsible for cooking while the male took responsibility to enforce the private property of hearth and home. It is an interesting story. It probably has elements of truth in it. It will be interesting to see how critics work this theory over and how it evolves over the next few decades.
Here's the argument that mastering fire transformed australopithcines into habilines:
But when eating muscle, chimpanzees are forced to chew it more slowly, taking as much as an hour to chew one-third of a kilogram (three-quarters of a pound). They can get as many calories per hour by chewing fruits as they can by chewing meat. The habilines would have faced the same challenge. If they had relied on unprocessed meat for as much as half their calories and had eaten their meat as slowly as chimpanzees, with certain cuts of meat they would have to spend several hours a day chewing it. The digestive costs likewise would have been high, since the gut would have been busy digesting for many ours.Here is his argument for cooking as the step that created sapiens:
I have offered that Homo erectus originated as cooks, the expensive tissue hypothesis suggests that eating cooked food caused their brains to grow. Once cooking began, gut size could fall and the gut would be less active, both trends reducing the cost of the digestive system.
The proposal that the human household originzed in competition over food presents a challenge to conventional thinking because it holds economics as primary and sexual relations as secondary. 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. But in support of the primary importance of food in determining mating arrangements, in animal species the mating system is adapted to the feeding system, rather than the other waqy around. A female chimpanzee needs the support of all the males in her community to aid her in defending a large feeding territory, so she does not bond with any particular male. A female gorilla, however, has no need for a defended food territory, so she is free to become a mate for a specific male. Many such examples suggest that the mating system is constrained by the way species are socially adapted to their food supply. The feeding system is not adapted to the mating arrangement. The consequences of a man's economic dependence takes different forms in different societies, but ... his needing a wife to provide food is universal among hunter-gatherers. Food, it seems, routinely drives a man's marriage decision more than the need for a sexual partner.The world of cooking and sitting around a fire had even more profound effects:
Furthermore, food relationships appear to be more tightly regulated than sexual relationships. Among the Bonerif, husbands disapproved of their wives having sex with bachelors, but the bachelors did it anyway. Husbands were relatively tolerant of their wives having ssex with other husbands, perhaps because promiscuous sex involved less threat of losing her economic services than did promiscuous feeding. As in many other hunter-gatherer communities, Bonerif attitudes toward premarital sex are particularly open-minded. One girl had sex with every unmarried male in the community except her brother. But 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.
... 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 vulnerabililty 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.
Even our ancestors' emotions are likely to have been influenced by a cooked diet. ...It is a fascinating book with a distinctly different take on human evolution. It is well worth reading.
... 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 bheen chased away less often, would have had more access to cooked food, and would have passed on more genes to succeeding generations than the wold-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.
... 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.