It Is the Heat

About two million years ago our ape-ish ancestors experienced a number of rapid physical changes: rib cages shrank, pelvises narrowed, teeth became smaller, stomachs constricted, swinging ability declined and cranial cavities almost doubled. These alterations were by no means haphazard. They collectively drove an evolutionary shift from apelike Habilines to Homo erectus, the precursor to Homo sapiens, which is to say, us.

The fossil record confirms the how of this transition. But the fossil record cannot explain why Homo erectus emerged from its Habiline past. Since the 1950s, scientists have hypothesized that the key factor bringing our ancestors down from the trees was the decision to eat meat. In this persuasively argued book, Richard Wrangham disagrees. Instead, he writes, it was the decision to cook with fire that literally made us human. Meat may have mattered in earlier transitions from one ape-like creature to another, but the critical evolutionary event marking the march toward humanity was cooked food—be it plant or animal. We are, the Harvard anthropologist writes, “creatures of the flame.”

Wrangham initiates his argument with an assault on one of the loonier food trends out there: raw foodism. The inadequacies of uncooked food quickly become apparent through his examination of the nutritional fate of humans who, by choice or force of circumstance, eat food untouched by heat. Raw foodists, he shows, “do not fare well.” They tend to lose too much weight—often to the point that basic biological functionality is hindered. Women experience declines in menstruation and fertility. Men, god forbid, stop thinking about sex. Cooking, on the other hand, “gelatinizes starch, denatures protein, and softens everything”—well, not everything, since sex drive resumes with cooked food. These transformations “increase the amount of energy we obtain from our food.” This added energy changed the rules of the game fundamentally.

Indeed, the relative abundance of energy released by cooking food had a profound evolutionary impact. It basically made our ancestors smarter. Cooking led to bigger brains in our pre-human and early human ancestors as the digestive energy saved by eating cooked plants and animals transferred directly into cranial development. Bigger brains led to more advanced cooking techniques. More advanced cooking techniques led to bigger brains. Knowing this, the invention of the earth oven, the advent of the two-stone griddle, and the use of shells to catch grease dripped from roasting animals become more than gee-whiz anecdotes of culinary history. They’re evolutionary benchmarks, ones we honor every time we heat up dinner.

Wrangham’s attention to the most subtle of behaviors keeps the reader enrapt. The relationships between chewing, hunting, gathering and the division of labor are cases in point. Raw food requires strong jaws. Before the advent of cooking, our ape-ish aunts and uncles had jaw muscles that extended to the middle of their heads—ours end at our ears. These muscles worked hard because Habilines spent about 42 percent of their lives chewing. (Think about those nature shows on television—every time they show an ape, it’s eating.) Chewing time precluded hunting time. Prior to cooking, one could not chew food quickly enough to acquire sufficient energy to leave the village and track game. Cooking, however, enabled our ancestors to spend only four hours a day chewing. Cooked food provided men with an energy-rich diet they could consume quickly. This allowed them to hunt—an activity to which their comparative physical strength over women predisposed them to. Women stayed near home, gathered, and made sure the flame didn’t die. Division of labor was born.

But was it entrenched? Men averse to the kitchen may be tempted to remind their female partners about the advent of hunting and gathering. They should proceed with caution. Wrangham’s analysis of the evolutionary basis of our sociological relationships can be boldly essentialist, perhaps too boldly essentialist. Men hunt, women gather, evolution determines all. Cooking, Wrangham concludes, “perpetuated a novel system of male cultural superiority.” It was, he admits, “not a pretty picture.” Even so, it’s a compelling picture, and one that I now contemplate every time I turn on my stove.

Contributing writer James E. McWilliams is the author of Just Food, due out in August.



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