Why We Eat (Too Much) Page 14

  The Chancellor’s Cuts?

  Imagine that the Chancellor of the Exchequer, in his annual budget, had to look after a human body rather than the finances of the British economy. As he held up that battered old briefcase to the press outside Downing Street, how would he go about the strategic planning to turn Homo erectus into Homo sapiens? Instead of budgeting for the different departments – Health, Defence, Environment, Transport, Education – he had to budget for different vital organs: energy for the Heart, Lungs, Intestines, Muscles and the Brain. Instead of making unpopular cuts, for instance in Health and Defence, in order to make the country brighter in the future by expanding Education, how would he find the resources to expand brain size fourfold? Which organ could he afford to trim down to find the spare energy in his constrained budget to run the bigger department of the Brain? Could he afford a cut in Muscle, or Heart or Lungs? Surely this would affect our chances of surviving predators and finding food.

  When some anthropologists looked at the size of human organs and compared them to the size of other similar primates, they noted that humans have a much larger brain and a much smaller gut than similar-sized primates. Their conclusion therefore was that the metabolic room necessary for brain growth and evolution came from a decrease in the size of our guts – to evolve our large brain, our gut was sacrificed.

  Figure 7.1 The density of brain mass in humans is much higher than would be predicted for a primate of our size and the GI tract is much smaller than predicted Source: L. C. Aiello and P. Wheeler (1995). The expensive-tissue hypothesis: the brain and the digestive system in human and primate evolution. Current Anthropology, 36(2), 199–221.

  But how could such a radical cut in the size of our digestive system occur without it affecting our health, or our wellbeing as a species? Would this not cause us to starve or become malnourished? The answer lay in the environment and not within our bodies. Our closest ancestors, Homo erectus, had already begun to develop a brain that was larger than the chimpanzee’s. Archaeological digs have uncovered evidence that they were using knives made from razor-sharp flint to cut up meat. We also know that their natural stamina and increasing cunning made hunting expeditions more successful. Meat was becoming a much more common part of their diet compared to that of chimps that rarely caught small prey. Yet despite eating more meat, Homo erectus were not developing the sharp teeth and powerful jaw muscles that would be expected to cope with this dietary change. How could this be?

  The Million-Year-Old Cooker

  The answer came from South Africa. In the Northern Cape Province, at the foot of a hill, surrounded by scrub, lies a massive cave complex, its entrance obscured by large stones. The Wonderwerk cave has been inhabited by humans, pre-humans and apes for 2 million years. It is one of the oldest known sites of human habitation. In 2012 Dr Francesco Berna from Boston University, USA, discovered that Homo erectus had been using fire to cook food in these caves 1 million years ago.3 This was a full 200,000 years earlier than previously thought and would finally explain Peter Wheeler’s expensive-tissue hypothesis.

  Cephalization, the evolution of our big brain, coincided with the discovery of fire (800,000 years prior to the first humans, i.e. plenty of time for our species to develop from Homo erectus) and with our increasing mobility and improving vision. The discovery of cooking meant that a much wider variety of foods could be eaten.

  If Homo erectus could make and control fire 1 million years ago, then this would explain why, despite the increased consumption of tough meat, their teeth and jaws actually became smaller. The combination of the control and use of fire and the availability of different types of foods, plus much more meat, led the developing humans to start cooking. They cooked their meat to make it easier to chew and swallow. In addition, vegetables were starting to be cooked, meaning that easier digestion of roots and tubers (like sweet potato or cassava) was now possible.

  Our ancestors cleverly used the energy in fire to cook foods, to break them down and make them easier to digest. Raw foods take more energy for our digestive systems to process than cooked foods. This is because the very process of cooking is almost like a pre-digestion. Cooked foods required a less effective intestinal tract to extract the same energy compared to raw foods. The discovery of cooking was the most important factor in conferring a distinct evolutionary advantage for humans over other species. Cooking meant that the quality of our food improved and that we did not need such a long gut to digest it. As the size of our gut decreased, we were left with metabolic capacity in our energy budget to develop a larger brain. We are human only because of this development.

  A Chef, a Chimp and a Gorilla

  As an example, imagine going to the zoo and in one of the enclosures seeing a 65kg man. Imagine a slightly smaller version of chef Gordon Ramsay, or whoever your favourite TV chef is, to make it more vivid – he is standing at a stove frying steak and eggs – and swearing a lot. Next to him stands a 65kg full-grown adult male chimp (eating a mound of nuts and fruits), and on the other side of him is a 65kg growing young male gorilla (eating bamboo and termites). All three of them have the same energy budget per day because they are all mammals and weigh the same. They all need about 2,000kcal per day.

  What is the difference between the three? If you weighed the sizes of their hearts, livers and kidneys, you would find they were similar. However, the reason the chef is able to articulate many swearwords while carrying out complex cooking tasks is because his brain is four times larger than those of the guys next to him making the odd shriek and grunt. The chimp and the gorilla have a much bigger gastrointestinal (GI) tract than the chef – because they eat raw food all day. The chef on the other hand has evolved to have a smaller GI tract because much of the energy that the chimp and gorilla use digesting raw foods he has saved by cooking his food. Not only that but he can take in all his daily nutritional requirements much faster than the chimp, and particularly the gorilla, who spend large parts of the day eating. The release of energy from cooked foods not only enhanced our ability to evolve larger brains but also gave us the time to use that brain while other animals were eating.

  This is an example that I hope you remember because I wanted to demonstrate that when you look at the differences between those three 65kg primates (yes, the chef is classified as a primate – as are you), the difference is the cooker in front of him. Without roasting, frying, boiling or baking our food we would not have been able to evolve a small gut and a large brain. Cooking food is a very big part of us, and is part of what has made us human. This is why we are still fascinated by all things connected to food and cooking – it is as fundamental a part of us as those foreign bacterial furnaces, those mitochondria, squatting in our cells and keeping us warm and alive.

  Figure 7.2 Comparison of size of brain and gut in 65kg man with equivalent weight chimpanzee and adolescent gorilla Source: Adapted from the drawings of Mr Waterhouse Hawkins from specimens in the Museum of the Royal College of Surgeons.

  Could We Survive on Raw Food?

  Now that we have developed a smaller gut, is it possible for us to go back to the days before fire and survive on raw foods only? Are we now reliant on consuming foods that have been cooked and ‘pre-digested’? Can we go back to raw food, or is cooking now a fundamental part of us?

  Devotees of raw food seem to think it is possible to return to pre-fire days. Raw foodists think that by eating raw foods only they will have increased energy and health. Let’s look at the evidence of a study of over 500 raw foodists living in Germany in 1999.4 The study found that when they switched from cooked to raw food they lost a considerable amount of weight. Women lost an average of 12kg and the men lost an average of 10kg. A third of the group had evidence of severely low body weight with chronic energy deficiency. Of the females, 50 per cent reported that they had stopped menstruating and had therefore become temporarily infertile (their low leptin levels caused a shut-down of fertility as a safety mechanism). These quite worrying health outcomes occurred de
spite the raw foodists having all the benefits of living in the twentieth century. The raw foods that they could select from the supermarket or grocer were abundant and wide-ranging and, unlike in the wild, there was no seasonal deficiency of certain foods. The raw foodists of today could even select prime cuts of raw salmon and steak tartare. They consumed high-quality olive oils which gave them 30 per cent of their total energy intake. They were able to use blenders, to finely slice, grind and liquidize their ingredients and make them more digestible. They had all the advantages that modern society gives us. But despite this a third were found to be severely malnourished and half of the women were infertile.

  Without the advantages of the modern world a hunter-gatherer tribe without fire and cooking would fare very badly in comparison. If the raw foodists had been a tribe or community in hunter-gatherer times they would have dwindled to extinction within a few short generations.

  150,000 Years BC

  Let’s take stock of our journey from the primordial sea to The Great British Bake Off show. The time is 150,000 years BC. We have a shorter gut compared to chimps and other monkeys and are reliant on cooking foods for our health and the survival of our species. But as the gut shrank, so our brain size increased, and gradually we evolved fully into what is described by anthropologists as an ‘anatomically modern’ human. What does ‘anatomically modern’ mean?

  Cro-Magnon Man in Regent’s Park

  If you took a Homo sapiens (Cro-Magnon man) cave-dweller from around that time and transported him to the twenty-first century, gave him a wash and dressed him in jeans and a shirt and sat him on a park bench – no one would look at him twice. He would have a dark complexion and blue eyes.5 He might be weather-beaten and have calloused hands and he could be eyeing up the squirrels suspiciously. He would have an encyclopaedic knowledge of nature, the seasons and the stars. He would be a dedicated family man, nurturing and protecting them with his life. He would probably be taller than the average man now. But otherwise, from the outside, he would be just like us. No one would notice any difference. We might think he is a tourist from southern Europe.

  What would amaze us though, if we could look inside this man, would be a complete absence of any type of modern disease. His heart would be pristine, with no signs of atheroma damage,fn4 and his blood pressure would be as low as an athlete’s today. There would be no sign of any type of inflammatory condition such as arthritis and no asthma. He would not be diabetic, and most striking of all there would be very little chance that he would be obese. His body weight would almost certainly be well within the normal healthy range. If he could access our healthcare system for treatment of the conditions that he would have been susceptible to (mainly trauma and infection) he would probably live beyond his ninetieth year.

  Figure 7.3 Forensic facial reconstruction of a Cro-Magnon man, using a cast of the skull Source: This file is licensed under the Creative Commons Attribution-Share Alike 4.0 International License. Used courtesy of Cicero Moraes.

  What did our bushmen ancestors eat to keep so healthy? We know the ‘Paleo diet’ (short for ‘Palaeolithic’, the epoch the cavemen lived in) is supposed to mimic the diet consumed by our ancestors, but what did the real hunter-gatherers live on? We can find this out by studying current hunter-gatherer populations which still remain isolated from modern influences: the Hadza tribe of Tanzania, the Bushmen in Namibia, the Pygmies of the Congo jungle, isolated Amazonian tribes, the Inuit Eskimos in Greenland and the Aborigines in Australia.

  The Hunter-gatherer Supermarket

  Let’s go to the hunter-gatherer supermarket, a vast open-roofed store where all the produce is free, there are no cash tills, but you have to pay in time and energy to fill your bag. There are two sections to this store: one is the greengrocer’s, for fruits, vegetables, nuts, fungi (like mushrooms), eggs, snails (or shellfish), green leaves and herbs; the other one is the butcher’s: for meat. In both sections, there will be small honey areas. Only women and children shop at the greengrocer’s section and only men go to the butcher’s section.

  The supermarket’s greengrocer’s section is quite large – 2 square miles (5.18 square kilometres). The produce is spread out and hidden in bushes or under rocks or soil, meaning that it can take many hours for a woman to find enough food for the evening meal. The most popular carbohydrate of the diet, the food that they rely on the most, is the roots of a plant, the part where all the dormant energy is hidden below ground to keep it safe from leaf-eating, foraging animals. The buried food treasure survives whatever the season; it is available all year round, and is therefore a reliable staple food. The women will have brought special sticks with them to uproot these tubers, roots and bulbs (think sweet potatoes, yam, cassava, ginger and certain flower bulbs – which, when cooked, are safe and nutritious). They will also look for seasonal foods that are found above ground, such as berries, fruits, seeds, mushrooms, nuts, edible flowers and leafy greens and shoots. They will gather bird eggs, snails and, the biggest treat of all, honey.

  Men Only

  Now to the meat section of the hunter-gatherer supermarket: men only allowed. There is twenty-four-hour opening to allow some groups of men to camp out in the middle of the store overnight if they do not find what they want. The size of this section could be as much as 40 square miles (103.6 square kilometres)! It’s interesting to see the techniques for obtaining foods. Groups of five to twelve young and fit men will see an animal from afar. Human males are not as fast as their prey, but they have two advantages. The first is that after learning to stand and balance on two feet, the early humans rapidly became the most efficient animals at moving. They lost their insulating hair as they discovered warming fires and clothes, meaning that they could cool themselves very efficiently by sweating, compared to most animals that rely on panting to cool their bodies when running. Humans take less energy per unit weight than any other mammal to move distances.6 The second advantage that our hunter groups had was their stunning brainpower. They were able to work in teams – communicating, planning and learning how to track down and trap animals. In the early days, before more sophisticated weapons like arrows and spears were used, the hunters would simply go on a marathon trek, keeping the prey in view, and eventually run it down with superior stamina before bludgeoning it with heavy rocks (a technique known as persistence hunting).

  Because the meat section is open 24/7, it also contains a scattering of snack foods to keep the boys going for longer. Tasty insects, fruits and eggs are sometimes available – as well as the honey tree, which requires smoking to unlock the honey from the bees safely.

  Back to the Camp Fire

  Every day in the afternoon the women would return home to their camp with the food they had gathered. Usually the men would return in the evening. It might seem sexist to us that the hunter-gatherer supermarket had separate sections for men and women. This doesn’t happen in any other species. Why are humans so different? Why did early humans organize their male and female tribe members to go looking for different foods? The answer again goes back to cooking. The main staples of their diets were root- or tuber-type carbohydrates (sweet potato, cassava) and wild meat. Both types of food needed to be cooked over a fire. The cooking would be done in the evening, although the cooking fire would be kept alive throughout the day and night. For all other animals, once the food has been killed or foraged, it is eaten raw by the animal that got to the food first (unless it is a mother weaning her young). With humans, the food would not be palatable raw and so had to be taken back to the camp and eaten later. This meant that within family groups food could be shared out among males, females and children.

  In no other animal group is food commonly shared between males and females. The whole concept of cooking together and sharing meant that the members of the tribe who were more likely to be successful hunters could be deployed for this job (young fit men) and those members who would be less successful hunting (women, even if carrying a baby or young child) could use their energy to g
ather plant-based foods. In the evening the families would come together to share food and eat. This was essential for the survival of the tribe. Over the camp fire ideas and stories would be passed on from one generation to the next, so that knowledge acquired could be used by future generations. In this respect, it was not just the chemical energy of the fire to break down food that helped them biologically; it was the social structure around the fire, plus the cooking and the sharing of food among the families, that helped the early humans to continue learning and progressing.

  The hunting party could be away for long periods of time. Once they had killed an animal, quite often they would eat the most prized part of it raw immediately, before carrying the rest back to camp. The most nutritious part of their kill was the liver. One of the characteristics of hunter-gatherer populations (something we have lost) was the consuming of the innards of an animal before moving on to the carcass. Hunter-gatherers would value the liver, kidneys, intestines, bone marrow and brains of an animal above its lean meat, as these organs contain much more nutritional and energy value than muscle tissue.