Cooking: brain development and division of labour
Notes/opinions/learnings from: Catching Fire: How cooking Made Us Human by Richard Wrangham. (Part 4/5) I had written a very in-depth analysis of a huge chunk of the book and it didn’t save so I’m just going to write small paragraphs summarising it.
Cooking was a great discovery not merely because it gave us better food, or even because it made us physically human. It did something even more important: it helped make our brains uniquely large.
The social brain hypothesis explains how animals that live in groups can benefit from being clever by outwitting their rivals in competition over mates, food, allies, and status. It also explains why species with bigger brains tend to have more complex societies, and the hypothesis suggests that if a species has limited brainpower, its social options may be constrained as well: small-brained monkeys may be too dim to handle many social relationships.
A lot of this is because of diet. Our brains use around 20 percent of our basal metabolic rate—our energy budget when we are resting—even though they make up only about 2.5 percent of our body weight. Because human brains are so large, this proportion of energy expenditure is higher than it is in other animal. The high rate of energy flow is vital because our neurons need to keep firing whether we are awake or asleep. Even a brief interruption in the flow of oxygen or glucose causes neuron activity to stop, leading rapidly to death.
There was a steady upward trend in brain size during the lifetimes of the early human species. Brains were notably bigger in late Homo erectus than in early Homo erectus, and in late Homo heidelbergensis than in early Homo heidelbergensis . Major dietary breakthroughs such as meat eating and the invention of cooking cannot account for these smaller changes. The steady rise in brain size between the major jumps is most easily explained by a series of improvements in cooking techniques.
Cooked food can be eaten more quickly than raw food. Reliance on cooked food has therefore allowed our species to thoroughly restructure the working day. The sexual division of labor refers to women and men making different and complementary contributions to the household economy. Though the specific activities of each sex vary by culture, the gendered division of labor is a human universal.
Before our ancestors cooked, then, they had much less free time. Their options for subsistence activities would therefore have been severely constrained. Males could not afford to spend all day hunting, because if they failed to get any prey, they would have had to fill their bellies on plant foods instead, which would take a long time just to chew.
But if food was raw, the sexual division of labor is unworkable. Nowadays a man who has spent most of the day hunting can satisfy his hunger easily when he returns to camp, because his evening meal is cooked. But if the food waiting for him in camp had all been raw, he would have had a major problem. It would be 42 percent of the day, or just over five hours of chewing in a twelve-hour day.
The use of fire solved the problem. It freed hunters from previous time constraints by reducing the time spent chewing. It also allowed eating after dark. The first of our ancestral line to cook their food would have gained several hours of daytime.