June 22, 2009
The 200th anniversary of Charles Darwin‘s birth has prompted a lot of reflection this year on how our understanding of evolution has progressed since the introduction of his theory. One persistent question has been how, and why, humans came to be so different from our primate ancestors. What is it that makes us human?
If Harvard University biological anthropologist Richard Wrangham is correct, the answer has more to do with Julia Child than Albert Einstein. That is, if hominids hadn’t first developed the skills that led to cooks like Julia Child, there could never have been an Albert Einstein.
In his new book, Catching Fire: How Cooking Made Us Human, Wrangham offers a simple hypothesis. In a nutshell, he proposes that it wasn’t our intelligence that allowed us to control fire and cook our food; it was our ancestors’ learning how to control fire and cook food that allowed us to evolve into big-brained humans.
Most anthropologists, from Darwin through recent times, have assumed that cooking was, Wrangham writes, “a late addition to the human skill set; a valuable tradition without any biological or evolutionary significance.” He argues, however, that the anatomical differences between habilines, such as Homo habilis, which evolved about 2.5 million years ago, and the more recent Homo erectus, which arose about 1.8 million years ago, suggest that cooking began long before the dawn of Homo sapiens, which was only 200,000 years ago.
Homo erectus had the greatest reduction in tooth size in the last six million years of human evolution, implying that this species did not need to spend a lot of time chewing bulky raw foods. They had also lost the ability to climb well, meaning they probably slept on the ground—a dangerous thing to do without reliable fire to see at night and scare away predators. Plus, the species had a less-flared rib cage and narrower pelvis than its australopithecine predecessors, indicating a much smaller gut, and a 42 percent increase in cranial capacity. A small gut implies that the animals didn’t have to expend a lot of energy digesting food—so energy could instead go toward powering a big brain, Wrangham explains.
Cooked food is far easier to digest than raw food and therefore, even though nutrients are lost in cooking, those that are left are more readily usable by the body. So cooked food allows us to have small guts (by which he means digestive systems, not beer bellies), and therefore big brains. The first chapter of Catching Fire explains why the current raw food diet fad is a good way to lose weight but would have been a terrible diet for long-term survival. The only reason today’s raw-foodists can survive at all, he says, is that they are eating very high-quality foods that would not have been available to our ancestors.
On the other hand, he concludes, we have gotten so good at procuring high-calorie foods that we no longer have to expend as much energy obtaining them. Our lives are considerably more sedentary, yet we continue to eat as if we were still spending our days tracking prey and doing other physically demanding tasks. Our big brains, which have allowed us to develop societies that make life easier, have also contributed to our expanding waistlines.
Wrangham claims that his theory even explains the relationship between human males and females. He cites cultural anthropology studies showing that women are responsible for domestic cooking in most societies. The marriage system arose, he suggests, as a sort of mutually beneficial arrangement: “Having a husband ensures that a woman’s gathered foods will not be taken by others; having a wife ensures the man will have an evening meal.” To put it in even less-romantic terms, it was “a primitive protection racket.”
On that note, I’d like to offer my warmest wishes to my co-blogger, Amanda, who is about to enter into her own primitive protection-racket arrangement—with a man who cooks more than she does. Happy cooking!
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