Breakfast: fibrous and bitter leaves; fruit. Lunch: bark; fruit; raw monkey meat and brains. Dinner: grubs; leaves; fruit.
No, not the latest food fad from Hollywood, but the diet of our closest living relatives, the chimpanzees. It is not exactly appetising or varied. We, on the other hand, have thousands of foodstuffs to choose from, and also an incredibly versatile range of techniques for altering their chemical composition through the application of heat. In other words, cooking.
Cooking is ubiquitous in humans. All cultures, from the Inuit of the frozen Arctic to the hunter-gatherers of sub-Saharan Africa, are sustained by food that has been chemically and physically transformed by heat. It was an incredible invention. Cooking makes food more digestible and kills off the bacteria that cause food poisoning. But where and when it started is hotly debated. You might call it a food fight.
No food without fire
Cooking cannot happen without fire, so the answer might be found by looking for evidence of the control of flames. This is an incendiary topic, as fire is a tricky thing to identify in the archaeological record. The evidence has literally gone up in smoke, and the remains of a deliberately lit fire are hard to distinguish from those of a natural one caused by lightning. This is why archaeologists look for signs of fire in caves.
Traces of ash found in the Wonderwerk cave in South Africa suggest that hominins were controlling fire at least 1 million years ago, the time of our direct ancestor Homo erectus. Burnt bone fragments also found at this site suggest that Homo erectus was cooking meat. However, the oldest remains of obvious hearths are just 400,000 years old.
“People on a raw vegetarian diet report persistent hunger despite eating frequently and usually have a lower BMI than vegetarians who eat cooked food”
The Neanderthals who evolved from Homo erectus some 250,000 years ago certainly created fires, as hearths have been found at many Neanderthal sites, some containing burnt bones. We also know from analysing their dental plaque that Neanderthals spiced up their diets with herbs. But we don’t know whether they habitually cooked their food.
The earliest firm evidence that our own species was cooking dates back just 20,000 years, when the first pots were made in China. The scorch marks and soot on their outer surfaces point to their use as cooking utensils. But all in all, archaeological evidence doesn’t paint a clear picture. We need to look elsewhere.
Around 1.9 million years ago some major changes occurred in hominin biology. Compared with its ancestors, Homo erectus had very small teeth, a small body and a much larger brain. According to a controversial hypothesis put forward by primatologist Richard Wrangham, these changes were driven by cooked food. In fact, Wrangham believes that cooking drove our lineage’s divergence from more ape-like ancestors and that the bodies of Homo sapiens couldn’t exist without cooked foodSo why are our bodies different to that of apes?
To understand why, imagine eating the same diet as a chimpanzee. To gain enough calories to fuel your energy-guzzling brain, you would have to devote almost all of your daylight hours to searching for food. Chimps forage more or less continuously; gorillas and orangutans eat for nine hours a day.
We’d probably have to eat for even longer. Our brains are more than twice as big, and our intestines are far too small to retain low-quality raw food long enough to digest it properly. In fact, our guts are just 60 per cent of the weight expected if we were a great ape of similar stature.
Our small teeth and jaws tell a similar story. They are too small for the task of grinding down large quantities of tough raw food. Compared with earlier hominins such as Homo habilis, modern humans, Neanderthals and Homo erectus all have small teeth relative to their body size. To Wrangham, these morphological features are adaptations to cooking that arose around 1.9 million years ago.
Why does food turn brown when cooking?
One of the most important processes in cooking is the Maillard reaction, named after the French chemist who described it in 1912. A reaction between sugars and amino acids, it is what creates the brown compounds that make meat, toast, biscuits and fried foods so delicious. Humans generally prefer food that has undergone the Maillard reaction.
From an evolutionary perspective this is hard to explain. The Maillard reaction makes food – especially meat – less digestible, destroys nutrients and produces carcinogenic chemicals. It may be that the other benefits of cooking food massively outweigh these detriments, and so we have evolved to prefer browned food. But that doesn’t explain why it is also preferred by great apes, which can’t cook and won’t cook.
How has cooking improved our lives?
Cooking certainly changed our ancestors’ lives for the better. Heat makes food softer, so less time is needed for chewing. It also releases more calories. Mice fed cooked food get fatter than those fed equivalent raw calories. Heat-treated food is also safer. Scavenged meat has high levels of pathogens. Roasting it on hot coals kills off germs that cause food poisoning. Another benefit of cooking is that it makes otherwise inedible foods, such as tubers, edible. And it frees up time to do more interesting things than just finding food and eating.
Food usually tastes nicer when cooked. We cannot know if our ancestors appreciated the difference, but studies with apes found that they prefer their food cooked, choosing baked potatoes, carrots and sweet potatoes over raw ones most of the time.
Don’t eat it all at once
Cooking requires cognitive skills that go beyond controlling fire, such as the ability to resist the temptation to scoff the ingredients, patience, memory and an understanding of the transformation process. Recent experiments with chimps found that they have many of the cognitive and behavioural skills needed for cooking – and therefore it’s likely that Homo erectus did too.
There are, however, flaws in the cooking hypothesis. Many of the adaptations attributed to cooked food such as large brains could have arisen through an increase in raw meat consumption. The disconnect in time between the biological evidence and the control of fire is another stumbling block.
But whenever cooking was invented, it has evolved into one of the most varied and inventive elements of human culture. We cook thousands of different types of animal, plant, fungus and algae using a dazzling array of techniques. We spend far more hours planning and preparing food than actually eating it, and then sit down to watch programmes about it, hosted by people who have become millionaire household names. We cook, therefore we are.
What about meat?
Cooking causes meat to lose calories due to fat melting out. But it also becomes easier to digest and less likely to cause food poisoning, which probably compensate.
Digesting raw meat is difficult, using up about a third of the energy you have just consumed. In experiments with pythons, cooking meat reduced the cost of digestion by 13 per cent.
Mice fed a 100 per cent meat diet lose weight, but if the meat is cooked they lose it more slowly.