The Third Chimpanzee: The Evolution and Future of the Human Animal

by Jared Diamond

  Early stages of plant domestication included people harvesting wild plants and throwing out the seeds, which were accidentally “planted.” Those seeds would produce more of the edible plants near places where people lived, ate, or looked for food. in time, people began planting seeds on purpose.

  The Traditional View of Agriculture

  At first, most Americans and europeans would agree with the traditional view that agriculture was a good thing, a milestone of progress. We enjoy the most abundant and varied foods, the best tools and material goods, and the longest and healthiest lives in human history. Who would really trade that for the life of someone who lived ten thousand years ago?

  For most of our history, all humans had to be hunter-gatherers, living by hunting wild animals and gathering wild food plants. According to the traditional view, the hunter-gatherer lifestyle is rugged and short. Because people grow no food and can store only a little, they have no break from the time-consuming struggle to find food and avoid starving, a struggle that starts over again each day. Our escape from this misery came only at the end of the last ice Age, when people in various parts of the world began independently to domesticate plants and animals. The agricultural revolution gradually spread, until today only a few tribes of hunter-gatherers survive.

  In this traditional view of agriculture as progress, no one asks: Why did almost all our hunter-gatherer ancestors adopt agriculture? They adopted it, of course, because it is an efficient way to get more food for less work. Just imagine savage hunters, exhausted from searching for nuts and chasing wild animals, gazing for the first time at a fruit-laden orchard or a pasture full of sheep. How many milliseconds do you think it took those hunters to grasp the advantages of agriculture?

  The traditional, progressive view goes further. it gives agriculture credit for the rise of art. Since crops can be stored, and since it takes less time to grow food in gardens than to find it in the jungle, the idea is that agriculture gave us the free time hunter-gatherers never had. We used this free time to create art—agriculture’s greatest gift to the human race.

  AGRICULTURAL ANTS

  NONE OF OUR PRIMATE RELATIVES DOES ANYTHING remotely like agriculture. The closest forerunner of agriculture in the animal world comes from ants, which have domesticated both plants and animals.

  Several dozen related species of ants in the Americas are farmers. They cultivate special species of yeasts or fungi in gardens within their nests. Leaf-cutter ants, for example, clip off leaves—but not to eat them. The ants slice the leaves into pieces, scrape off foreign fungi and bacteria, and take the leaf pieces into underground nests. There they crush the leaf fragments into pasty pellets, fertilize them with ant saliva and droppings, and seed them with the ants’ preferred species of fungus. This fungus is the ants’ main food, sometimes their only food. When a queen ant goes off to found a new colony, she carries with her a starting culture of the precious fungus, just as human pioneers take along seeds to plant.

  Leaf-cutter ants harvest pieces of leaves that will be used to grow a fungus the ants will eat. The ants are farmers, with leaves as their gardenssoil and fungus as their crop.

  As for animal domestication, ants obtain a sugary secretion called honeydew from various insects, including grasshoppers, aphids, mealybugs, and caterpillars. These insects are like cows for the ants, which “milk” them by stroking them with their antennae to get the honeydew flowing. In return for the honeydew, the ants protect their “cows” from predators and parasites.

  Humans did not, of course, inherit plant and animal domestication directly from ants. Ants evolved it, and later we evolved it separately.

  The Lives of Hunter-Gatherers

  The progressive view tells us that agriculture brought us health, longer lives, security, leisure, and great art. This seems convincing, but it is hard to prove. How do you actually show that the lives of people ten thousand years ago got better when they abandoned hunting for farming?

  One way is to study the spread of agriculture. if it were such a great idea, you’d expect it to have spread quickly. But archaeology shows that agriculture spread across Europe at a snail’s pace— barely a thousand yards per year! From its origins in the Middle east around 8000 BC, agriculture crept northwestward to reach Greece around 6000 BC, and Britain and Scandinavia 2,500 years later. That’s hardly what you’d call a wave of enthusiasm.

  Another approach is to see whether modern hunter-gatherers are really worse off than farmers. Scattered throughout the world, mainly in areas not good for agriculture, groups such as the Bushmen of southern Africa’s Kalahari Desert have continued to live as hunter-gatherers into modern times. Astonishingly, it turns out that these hunter-gatherers generally have leisure time, sleep a lot, and work no harder than their farming neighbors. The average time spent finding food each week, for example, has been reported to be just twelve to nineteen hours for Bushmen. When asked why he had not adopted agriculture, as neighboring tribes had, one Bushman replied, “Why should we plant, when there are so many mongongo nuts in the world?”

  A boy of the Moken people. The Moken, or Morgan, are modern hunter-gatherers and skilled divers. These sea nomads travel along coasts in the indian Ocean and Southeast Asia, living mostly on what they catch and gather, but trading for other goods they need.

  It would be a mistake to swing to the opposite extreme from the traditional, progressive view of agriculture and say that hunter-gatherers lived the life of leisure. Finding food isn’t enough. it also has to be made ready to eat, which can take time. But it would also be a mistake to think that hunter-gatherers worked much harder than farmers.

  Nutrition is another difference. Farmers concentrate on crops such as rice and potatoes, which are high in carbohydrates. The mixture of wild plants and animals in the hunter-gatherer diet provides more protein and a better balance of other nutrients. Hunter-gatherers are healthy and suffer from little disease. They enjoy a varied diet, and they do not experience the food shortages and famines that can happen to farmers who are dependent on just a few crops. it is almost unimaginable for Bushmen, who use 85 edible wild plants, to starve to death. in the 1840 s, however, about a million irish farmers and their families starved when a plant disease attacked potatoes, which they relied on as their staple crop and food.

  Agriculture and Health

  Modern hunter-gatherers have lived close to agricultural societies for thousands of years. But what about hunter-gatherers before the agricultural revolution. Did the lives of people in the distant past get better after they switched to agriculture?

  We can begin to answer that question thanks to paleopathologists, scientists who search for signs of disease in the remains of ancient people. Take the case of historical changes in height. We know that the improved nutrition of modern people has made us taller than people who lived nine or ten centuries ago. We have to stoop, for example, to pass through doorways in medieval castles that were built for a shorter, malnourished population.

  A study of skeletons thousands of years old from Greece and Turkey found a striking parallel. The average height of that region’s hunter-gatherers in the Ice Age was five foot ten for men, five foot six for women. When people adopted agriculture, height crashed. By 4000 BC, men averaged only five foot three, women five foot one. A few thousand years later, heights were slowly on the rise, but modern Greeks and Turks still do not average the height of their healthy hunter-gatherer ancestors.

  Native American hunter-gatherers had skeletons “so healthy it is somewhat discouraging to work with them,” as one paleopathologist said. But once indians began cultivating domestic corn, their skeletons became more interesting. The number of cavities in an average adult’s teeth jumped from less than one to nearly seven. Tooth loss became common. Defective enamel in infants’ teeth suggests that nursing mothers were severely malnourished. Tuberculosis, anemia, and other diseases increased dramatically. Before corn, 5 percent of the indian population lived past the age of fifty. After corn, only
1 percent did, and almost one-fifth of the population died between the ages of one and four.

  Corn, usually considered one of the blessings of the Americas, was actually a public health disaster. Studies of skeletons elsewhere in the world have led to similar conclusions. The transition from hunting-gathering to farming was bad for public health.

  There are at least three explanations for agriculture’s negative effects. First, hunter-gatherers enjoyed a varied diet with enough protein, vitamins, and minerals, while farmers ate mostly starchy crops. Even today, just three high-carbohydrate plants—wheat, rice, and corn—provide more than half the calories eaten by the human species. Second, farmers who depended on just one or a few crops ran a greater risk of malnutrition or starvation if one crop failed, as in the case of the Irish potato famine.

  Finally, most of today’s leading infectious diseases and parasites in humans could not establish themselves until after the switch to agriculture. These killers persist only in societies of crowded, malnourished people who do not move around much and who are constantly reinfected by one another and by their own sewage. Crowd epidemics could not last in small, scattered bands of hunters, who often moved camp. Tuberculosis, leprosy, and cholera had to await the rise of settled farming villages. Smallpox, bubonic plague, and measles appeared only in the last few thousand years, as even denser populations of humans gathered in cities.

  THE NEW SCIENCE OF ANCIENT DISEASES

  THE LATE TWENTIETH CENTURY SAW THE emergence of a new science: paleopathology. The name comes from the Greek root paleo, meaning “ancient,” and the science of pathology, which looks for signs of disease. Paleopathologists study the remains of ancient people to see how healthy or unhealthy those populations were.

  In some lucky cases, the paleopathologist has a lot to work with. Archaeologists in the deserts of Chile have found mummies so well preserved that scientists could determine their causes of death through autopsies, just as with a fresh corpse in a hospital today. Usually, though, the only remains available for paleopathologists are skeletons. Still, experts can make a surprising number of deductions from skeletal remains.

  A skeleton identifies its owner’s sex, height and weight, and approximate age at the time of death. With enough skeletons, researchers can make tables like those used by life insurance companies to calculate a person’s expected life span and the risk of death at any age. This tells researchers how long the people in a particular population typically lived.

  Paleopathologists can calculate growth rates by measuring bones of people at different ages. Slow growth rates may be a sign that people suffered from hunger or poor nutrition. The scientists also examine teeth for cavities (a sign of a high-carbohydrate diet) or for defects in tooth enamel (a sign of poor nutrition in childhood). Finally, experts interpret the scars left on bones by diseases such as anemia, tuberculosis, leprosy, and osteoarthritis. Through paleopathology, our long-dead ancestors are telling us how they lived—and died.

  Class Divisions

  Farming brought another curse to humanity: class divisions. Hunter-gatherers have little or no stored food, and no concentrated food sources such as orchards or herds of cows. They live off wild plants and animals that they obtain each day, and everyone except infants, the sick, and the old joins in the search for food. There are no kings, no fulltime professional experts, and no social parasites who grow fat off the work of others.

  Only a farming population could develop contrasts between the disease-ridden masses and a healthy elite class that is rich or powerful but produces nothing. We see an example of this contrast in skeletons from Greek tombs of around 1500 BC. These remains suggest that royals enjoyed a better diet than commoners. The royal skeletons, for example, were two or three inches taller than those of commoners. Royal mouths contained an average of one cavity or missing tooth, compared with six for the commoners. Something similar shows up in remains from South America. Mummies from three-thousand-year-old cemeteries in Chile show that elites—who were buried with ornaments and gold hair clips—had a rate of bone damage from infectious diseases that was four times lower than the common rate.

  To most American and European readers, the idea that humanity could have been better off as hunter-gatherers than we are today sounds ridiculous, because most people in modern industrial societies enjoy better health than hunter-gatherers. They are the elite in today’s world, however. They depend on oil and other resources imported from countries that have large peasant populations and much lower health standards.

  Some people in industrial and farming societies enjoy more leisure than hunter-gatherers—but this is at the expense of many others who support them and have less leisure. Farming undoubtedly made it possible for societies to support full-time artists and craftspeople, without whom we would not have large-scale art projects such as temples and cathedrals. But great paintings and sculptures on a smaller scale were already being produced by Cro-Magnon hunter-gatherers fifteen thousand years ago, and great art was still produced into modern times by hunter-gatherers such as the Pacific Northwest Indians. And when we think of the specialists whom society became able to support after the shift to agriculture, we should think not just of Shakespeare and Leonardo da Vinci but also of huge armies of professional killers.

  A Prehistoric Crossroads

  Farming could support far more people than hunting—even if it did not always bring more food to each mouth. Population densities of hunter-gatherers are usually one person or fewer per square mile, while densities of farmers are at least ten times that.

  Maybe the main reason we find it hard to shake off the traditional view that agriculture was good for us is that there’s no doubt it meant more tons of food per acre. It also meant, however, more mouths to feed. Farming populations grow more quickly than hunter- gatherer ones because women in settled communities typically had a child every two years. Hunter-gatherer women spaced their children four years apart, because a mother must carry her child until it is old enough to keep up with the group.

  At the end of the Ice Age ten thousand years ago, some bands took the first steps toward agriculture, which let them feed more mouths. In time they outbred and then killed off or drove away the bands that chose to remain hunter-gatherers, because ten malnourished farmers can still outfight one healthy hunter. People who did not adopt agriculture were forced out of all areas except the ones that farmers didn’t want.

  Today, hunter-gatherers linger mainly in places that are useless for agriculture, such as the Arctic and deserts. They are the last people to practice the most successful and long-lasting lifestyle in the history of our species.

  Imagine a twenty-four-hour clock, with each hour of clock time representing one hundred thousand years. If the history of the human race began at midnight, we would now be almost at the end of our first day. We lived as hunter-gatherers for almost all that day, from midnight through dawn, noon, and sunset. Finally, at 11:54 p.m., we adopted agriculture. There is no turning back. But as our second midnight approaches, will we find a way to achieve agriculture’s blessings while limiting its curses?

  CHAPTER 9

  WHY DO WE SMOKE, DRINK, AND

  USE DANGEROUS DRUGS?

  OIL SPILLS, CHEMICAL WASTE DUMPS, smog, contaminated food—every month, it seems, we learn of a new way in which we have been exposed to toxic chemicals because of the careless or harmful actions of others. The public feels outrage toward dangerous elements in our environment. Why, then, do so many of us do the same thing to ourselves?

  Why do so many people deliberately eat, drink, inject, or smoke dangerous or harmful toxic chemicals such as alcohol, cocaine, and the ingredients in tobacco smoke? Various forms of this willful self-damage are found in many societies today, from primitive tribes to high- tech city-dwellers. Chemical abuse also extends as far back into the past as we have written records. How did drug abuse become a hallmark of the human species?

  The Paradox of Self-Destructive Behavior

  When somet
hing goes against logic or common sense, and yet appears to be true, we call it a paradox. Abuse of toxic chemicals, or any other self-destructive behavior, is a paradox. Why would we do something that we know to be harmful or dangerous?

  The mystery isn’t in why people continue to take toxic chemicals once they start. They do so because our drugs of abuse are addictive—once you start, the chemistry of the drug affects the brain, making you want to continue. The real mystery is why we start at all.

  Most of us are familiar with the overwhelming evidence that alcohol, tobacco, and drugs are destructive, even lethal. Only some strong motive could explain why people consume these poisons voluntarily, even eagerly. It’s as if unconscious programs drive us to do something we know to be dangerous. What could those programs be?

  There is no single explanation. Different motives drive different people and societies. Some drink to join friends, others to deaden their feelings or drown their sorrows, still others because they like the taste of alcoholic beverages. In addition, the possibilities for achieving a satisfying life are not the same for human populations and social classes, and this explains some patterns in drug use. For example, self-destructive alcoholism is a bigger problem in parts of Ireland that have high rates of unemployment than it is in southeast England.