How cooking helped us to evolve

It is the ultimate domestic cliché: a woman, pinafored and dutiful, tending a stove all day in preparation for her husband’s homecoming. As soon as he walks in, the ritual can begin: family members take their seats around the table (he sits at the head, of course) and dinner is served. Our couple are reliving a scene that has played out billions of times in our history because gender roles — husband at work all day, woman as homebody — have been forged not by relatively recent social conventions but by our distant evolutionary past.

For we are the “cooking ape”, according to Richard Wrangham, a noted British anthropologist and primatologist at Harvard University. The unrivalled success of the human species is down to our mastery of flame and our use of it to transform raw food into cooked. Ours is a species built on hot dinners, not cold plants and berries. The theory is cold comfort for the raw food movement, which believes that it is natural and healthier to eat uncooked food.

“I believe the transformative moment that gave rise to the genus Homo, one of the great transitions in the history of life, stemmed from the control of fire and the advent of cooked meals,” Wrangham explains in his new book Catching Fire: How Cooking Made Us Human. “Cooking increased the (calorific) value of our food. It changed our bodies, our brains, our use of time and our social lives.” He argues, as no one else has done before, that cooking was pivotal in our evolution. “If you feed a chimp cooked food for tens of thousands of years, I find it hard to believe that it would end up looking like the same animal.”

From this, he infers that, for our ancestors, marriages of men and women were ancient pacts built around food, not sex.

It was while lying in front of a fire, preparing a lecture, that Wrangham felt his intellect spark. “I started to wonder how long ago our ancestors had lain at night without fire. It didn’t make sense to me that our ancestors could have existed without fire. I’d spent time watching chimps and even eating their food, which is mainly fruit and a little meat, all raw. This is difficult stuff to eat. It’s like going into the forest and trying to fill up on rosehips — it’s not food. You might find something delicious such as a raspberry, but you usually can’t find many.”

He began to wonder whether our ance — tors could ever have filled their bellies enough on a raw diet to survive, reproduce and evolve into us. Our ancestors, he surmised, must have been cooking — and that meant they needed fire. A mastery of fire would also have allowed them to come down from the trees and sleep on the ground; fire would not only have provided an ancestral security light, but also a weapon against predators.

Cultural, historical and culinary clues point to the plausibility of Wrangham’s intuition. There is no society on Earth that does not cook; not a single people exists on raw food alone. The most remote hunter-gatherer tribes might not have microwaves, but they still pack beans in hot rocks. While the idea of modern humans as carnivores is well-established, our bodies cannot fend off toxins and bacteria found in raw meat, as you would expect if we had evolved to eat it uncooked. It is incredibly hard for us to bite into and digest raw tubers, such as potatoes. And there are no reliable accounts of survivors lasting for more than a couple of months on raw food; even the survivors of the 1972 Andes plane crash are reported to have cooked their fellow passengers before eating them.

Nobody, though, had ever explicitly considered that human beings might owe their spectacular success as a species to their unique propensity to cook. And, to Wrangham’s amazement, the scientific debate about how human beings started using fire had never broached the issue of cooking.

“I couldn’t believe that nobody had thought about the energetic significance of cooked food [cooking releases locked-in calories by breaking down molecular structures in plants and meat; without cooking, some material passes straight through]. As someone who’s been in the bush enough to appreciate a cooked meal, I had a very strong intuition that cooking was crucial to our evolution. I’m now convinced that cooking made us human. It was the biggest improvement in diet in the history of life.”

Cooking would have made a radical difference to the creatures who mastered it: it made plants and meat more calorie-dense; it spared our ancestors from the marathons of mastication required with raw foods (wild chimps spend up to five hours a day gathering food and chewing it); it was easier on the gut. It is utterly within the bounds of belief that the first hominid to put a flame to his food started an extraordinary chain of evolutionary events that culminated in us, the ape in the kitchen.

But Wrangham, who co-wrote Demonic Males, a groundbreaking book on ape violence and its relevance to human violence, strides farther: the advent of cooking led to a restructuring of society and, in particular, liberated men from the chore of chewing but chained women to the stove.

Early human marriages, he suggests, were “primitive protection rackets”, in which men protected women from hungry marauders (attracted by the smoke of the fire) in return for a hot meal at the end of the day and, almost as an afterthought, babies. This is a radical notion — that domestic unions are mainly about food, not sex — but it’s not ridiculous. Anthropolo- gists have noted that many primitive societies will tolerate a married woman sleeping around, but will ostracise her if she feeds any man other than her husband. In the ancestral struggle for survival, it seems, sustenance was more important than sex.

Human beings are unique in that when we cook, we do it to feed others as well as ourselves (other apes, even those who pair-bond, forage for themselves and don’t share). And in almost all societies it’s women who tend the stove. Having a husband ensures that a woman’s gathered food will not be stolen, while having a wife means a man will have an evening meal.

To some, though, this train of thought — that the way to a man’s heart really is through his evolutionarily shrunken stomach — is even more heretical than the idea that we are the cooking ape. “People don’t like it because over the past decades we have understood that our social system comes through the competition for reproductive partners. I’m saying, pair bonds are firstly about food, and that gave a platform to develop those relationships further.”

Wrangham, who is largely vegetarian (“I don’t eat mammals but occasionally I’ll have a bird, but never a parrot”), was thrilled when he came across the work of the anthropologists Jane Collier and Michelle Rosaldo that exposed the marital dynamics around food in different, small-scale societies. “It’s clear that many societies are more tolerant of sexual messing about than they are of a domestic arrangement being upset (such as an intrusion during a family mealtime).”

It is true that we are remarkably fussy about the way we eat: there is a strict table etiquette, a pattern to the handouts (husbands often receive the best meat) and it is regarded as a social sin to interrupt a mealtime, even if it’s sandwiches at a desk.

“It’s hard for us to understand the importance of food because, for us, food is easy,” Wrangham says. “We can buy it and we can get preprepared meals. This is not the case for the majority of the world. In some societies, it really matters to a husband that he can come back to a meal cooked by his wife.

Not that Wrangham’s wife cooks: “We’re housemasters for a Harvard college, so we hardly ever cook. We eat with the students most nights. I’ve often looked at them and wondered whether I should be studying them, as well as the chimpanzees. We’ve come to see food as a way to explore pleasure, as cuisine, to be enjoyed. That’s not how our ancestors saw it. For them, food was a way to survive and have babies.”

His theory that we are the cooking ape, knocks the stuffing out of the raw food movement, which claims uncooked or lightly prepared food to be more natural. But neither history, nor science testifies to the naturalness, for humans, of a raw food diet. Survivors of disasters who get by on raw food invariably show signs of starvation when rescued.

The Giessen Raw Food study, conducted by German nutritionists in 2005, studied more than 500 people who ate a diet that was 70 to 100 per cent raw (vegetables, fruits, cold-pressed oil and honey, plus dried fruits, meat and fish). All the raw-foodists lost weight, sometimes dramatically; the scientists concluded that “a raw diet cannot guarantee an adequate energy supply”. And this in the well-fed West, where the supermarket rather than the forest floor is our larder. Our ancestors would surely have suffered more parlously.

But most damning of all was the finding that many women on the study stopped menstruating. Others saw their cycles become irregular. Conception and pregnancy — that most natural of biological processes — would be a rare feat on an uncooked diet. Wrangham’s message is clear: “I’m impressed by its potential to be a healthy diet but we must be aware of its limitations. I’m amazed at the willpower of some raw foodists but some are deluded; they are wrong about it being natural. If you are cast away on a desert island and you say, ‘I won’t bother cooking’, you will die.”

Our evolutionary history — with one line of descent leading to chimps, and another to us — shows a dramatic change about 1.9 million years ago. If we travelled that far back in time, we would come face to face — or brow to brow — with Homo habilis, or the habilines, our distinctly apelike ancestors that are the closest thing we have to a missing link. These diminutive, chimpanzee-like creatures, who walked upright but were agile climbers, changed abruptly over the course of 100,000 years.

And it is this step-jump in evolution — which led to our forerunner, Homo erectus — that Wrangham credits to cooking. Homo erectus had, as we do, small teeth and weak jaws that would have been ill-suited to ripping raw meat. The smaller gut and slimmer ribcage of erectus also fits with his theory, since cooked food requires less digestive effort. The leftover energy allowed our ancestors’ brains to expand. The result was clever social creatures with large brains (to handle friendships, rivalries and double-dealing that happen in large groups) who cooked; ie, us. While chimps pulverise meat to make it tender, we are the only species that cooks with fire.

There is one snag: anthropologists think that our ability to control fire dates back merely hundreds of thousands of years, not the near two million years that Wrangham’s theory would suggest. Not that this bothers him: “Let’s be clear: there’s no doubt that we are biologically adapted to eat cooked food. Then there’s the separate question of when it happened, about which there is, I admit, a lingering uncertainty. We have circumstantial evidence for 1.9 million years ago: the reduced gut size, smaller teeth, the fact that habilis was a climber and erectus was not.

“But you can light a fire in the bush, and come back months later and find no trace of it. I’m hoping we’ll find genes we can date to a certain period, that are involved in the digestion of cooked food. I’d be amazed if I turned out to be wrong.”

Catching Fire: How Cooking Made Us Human by Richard Wrangham

TimesOnline