The World Until Yesterday: What Can We Learn From Traditional Societies?

by Jared Diamond

  Groups protect themselves by building a network of alliances with other groups, and individuals ally themselves with other individuals. A function of the constant talking that has struck me in New Guinea, and that has struck other visitors to other traditional societies, is to learn as much as possible about each individual in one’s universe of contact, and to monitor people’s activities constantly. Especially good sources of information are women who were born into one’s own group, and who were then sent in marriage to another group, in the common traditional living pattern termed patrilocal residence (i.e., brides moving to join their husband’s group, rather than new husbands moving to join their wife’s group). Such married women often warn their blood relatives in their natal society that their husbands and other relatives by marriage are planning an attack. Finally, just as endless evening campfire conversations about accidents serve not just to entertain but also to educate children (and everyone else) about environmental risks, endless conversations about raids and people alert listeners to dangers arising from people, as well as providing gripping entertainment.

  Diseases

  Depending on the particular traditional society, diseases collectively rank as either the leading danger to human life (e.g., among the Agta and !Kung, where they accounted respectively for an estimated 50%–86% and 70%–80% of all deaths) or as the second most important danger after violence (e.g., among the Ache, among whom “only” one-quarter of deaths under conditions of forest life were due to illness). It must be added, though, that malnourished people become more susceptible to infection, and that food shortage is thus a contributing factor to many deaths whose cause is recorded as infectious disease.

  Among diseases, the relative importance of different categories of disease for traditional peoples varies greatly with lifestyle, geographic location, and age. In general, infectious diseases are most important among infants and young children and remain important at all ages. Parasitic diseases join infectious diseases in importance in childhood. Diseases associated with worm parasites (such as hookworm and tapeworm) and insect-born protozoan parasites (such as malaria and the agent causing sleeping sickness) are more of a problem for peoples of warm tropical climates than for peoples of the Arctic, deserts, and cold mountaintops, where the worms themselves and the protozoa’s insect vectors have difficulty surviving in the environment. Later in life, degenerative diseases of bones, joints, and soft tissue—such as arthritis, osteoarthritis, osteoporosis, bone fractures, and tooth wear—rise in importance. The much more physically demanding lifestyle of traditional peoples than of modern couch potatoes makes the former more susceptible than the latter to such degenerative diseases at a given age. Conspicuously rare or absent among traditional peoples are all of the diseases responsible for most deaths in the First World today: coronary artery disease and other forms of atherosclerosis, stroke and other consequences of hypertension, adult-onset diabetes, and most cancers. I shall discuss the reasons for this striking difference between First World and traditional health patterns in Chapter 11.

  Only within the last two centuries have infectious diseases receded in importance in the First World as causes of human death. The reasons for those recent changes include appreciation of the importance of sanitation; the installation of clean water supplies by state governments, the introduction of vaccination, and other public health measures; the growth of scientific knowledge of microbes as the agents of infectious disease, permitting rational design of effective counter-measures; and the discovery and design of antibiotics. Poor hygiene permitted (and still permits today) the transmission of infectious and parasitic diseases among traditional peoples, who often use the same water supply for drinking, cooking, bathing, and washing, defecate nearby, and do not understand the value of washing one’s hands before handling food.

  Just to mention an example of hygiene and disease that impressed me personally, on a trip to Indonesia during which I spent most of each day bird-watching alone on forest trails radiating from a campsite shared with Indonesian colleagues, I was disconcerted to discover that I was experiencing sudden attacks of diarrhea at an hour varying unpredictably from day to day. I racked my brain to figure out what I was doing wrong, and what could account for the variation of the attacks’ timing. Finally, I made the connection. Each day, a wonderfully kind Indonesian colleague, who felt responsible for my well-being, came out from camp and followed my trail of that day until he encountered me, to make sure that I hadn’t had an accident or gotten lost. He handed me some biscuits that he had thoughtfully brought from camp as a snack, chatted with me for a few minutes to satisfy himself that all was well with me, and returned to camp. One evening, I suddenly realized that my diarrhea attack each day began about half an hour after my kind friend had met me and I had eaten his biscuits on that day: if he met me at 10:00 A.M., my attack came at 10:30, and if he met me at 2:30 P.M., it came at 3:00 P.M. From the next day onwards, I thanked him for his biscuits, disposed of them inconspicuously after he had turned back, and never had any more attacks. The problem had originated with my friend’s handling of the biscuits rather than with the biscuits themselves, of which we kept a supply in their original cellophane packets at our camp, and which never made me ill when I opened the packet myself. Instead, the cause of the attacks must have been intestinal pathogens transmitted from my friend’s fingers to the biscuits.

  The prevalent types of infectious diseases differ strikingly between small populations of nomadic hunter-gatherers and family-level farming societies on the one hand, and large populations of modern and recently Westernized societies plus traditional densely populated Old World farming societies on the other hand. Characteristic diseases of hunter-gatherers are malaria and other arthropod-transmitted fevers, dysentery and other gastrointestinal diseases, respiratory diseases, and skin infections. Lacking among hunter-gatherers, unless they have been recently infected by Western visitors, are the feared infectious diseases of settled populations: diphtheria, flu, measles, mumps, pertussis, rubella, smallpox, and typhoid. Unlike the infectious diseases of hunter-gatherers, which are present chronically or else flare up and down, those diseases of dense populations run in acute epidemics: many people in an area become sick within a short time and quickly either recover or die, then the disease vanishes locally for a year or more.

  The reasons why those epidemic diseases could arise and maintain themselves only in large human populations have emerged from epidemiological and microbiological studies of recent decades. Those reasons are that the diseases are efficiently transmitted, have an acute course, confer lifetime immunity on victims who survive, and are confined to the human species. The diseases become transmitted efficiently from a sick person to nearby healthy people by microbes that a patient excretes onto his skin from oozing pustules, that a patient ejects into the air by coughing and sneezing, or that enter nearby water bodies when a patient defecates. Healthy people become infected by touching a patient or an object handled by the patient, breathing in the patient’s exhaled breath, or drinking contaminated water. The disease’s acute course means that, within a few weeks of infection, a patient either dies or recovers. The combination of efficient transmission and acute course means that, within a short time, everybody in a local population has become exposed to the disease and is now either dead or recovered. The lifetime immunity acquired by survivors means that there is no one else alive in the population who could contract the disease until some future year, when a new crop of unexposed babies has been born. Confinement of the disease to humans means that there is no animal or soil reservoir in which the disease could maintain itself: it dies out locally and cannot come back until an infection spreads again from a distant source. All of those features in combination mean that these infectious diseases are restricted to large human populations, sufficiently numerous that the disease can sustain itself within the population by moving constantly from one area to another, locally dying out but still surviving in a more distant part of the population. For m
easles the minimum necessary population size is known to be a few hundred thousand people. Hence the diseases can be summarized as “acute immunizing crowd epidemic infectious diseases of humans”—or, for short, crowd diseases.

  The crowd diseases could not have existed before the origins of agriculture around 11,000 years ago. Only with the explosive population growth made possible by agriculture did human populations reach the high numbers required to sustain our crowd diseases. The adoption of agriculture enabled formerly nomadic hunter-gatherers to settle down in crowded and unsanitary permanent villages, connected by trade with other villages, and providing ideal conditions for the rapid transmission of microbes. Recent studies by molecular biologists have demonstrated that the microbes responsible for many and probably most of the crowd diseases now confined to humans arose from crowd diseases of our domestic animals such as pigs and cattle, with which we came into regular close contact ideal for animal-to-human microbe transfer only upon the beginnings of animal domestication around 11,000 years ago.

  Of course, the absence of crowd diseases from small populations of hunter-gatherers does not mean that hunter-gatherers are free from infectious diseases. They do have infectious diseases, but their diseases are different from the crowd diseases in four respects. First, the microbes causing their diseases are not confined to the human species but are shared with animals (such as the agent of yellow fever, shared with monkeys) or else capable of surviving in soil (such as the agents causing botulism and tetanus). Second, many of the diseases are not acute but chronic, such as leprosy and yaws. Third, some of the diseases are transmitted inefficiently between people, leprosy and yaws again being examples. Finally, most of the diseases do not confer permanent immunity: a person who has recovered from one bout of a disease can contract the same disease again. These four facts mean that these diseases can maintain themselves in small human populations, infecting and re-infecting victims from animal and soil reservoirs and from chronically sick people.

  Hunter-gatherers and small farming populations are not immune to crowd diseases; they are merely unable to maintain crowd diseases by themselves. In fact, small populations are, tragically, especially susceptible to crowd diseases when they become infected by a visitor from the outside world. Their enhanced susceptibility is due to the fact that at least some of the crowd diseases tend to have higher fatality rates in adults than in children. In dense urban First World populations everyone (until recently) became exposed to measles as a child, but in a small isolated population of hunter-gatherers the adults have not been exposed to measles and are likely to die of it if it arrives. There are many horror stories of Inuit, Native American, and Aboriginal Australian populations being virtually wiped out by epidemic diseases introduced through European contact.

  Responses to diseases

  For traditional societies, diseases differ from the other three major types of dangers as regards people’s understanding of the underlying mechanisms, and hence of effective cures or preventive measures. When someone is injured or dies from an accident, violence, or hunger, the cause and underlying process are clear: the victim was hit by a falling tree, struck by an enemy’s arrow, or starved by insufficient food. The appropriate cure or preventive measure is equally clear: don’t sleep under dead trees, watch out for enemies or kill them first, and ensure a reliable food supply. However, in the case of diseases, sound empirical understanding of causes, and science-based preventive measures and cures, achieved notable success only within the last two centuries. Until then, state societies as well as traditional small-scale societies suffered heavy tolls from disease.

  This is not to say that traditional peoples have been completely helpless at preventing or curing diseases. The Siriono evidently understand that there is a connection between human feces and diseases such as dysentery and hookworm. A Siriono mother promptly cleans up her infant’s feces when it defecates, stores the feces in a basket, and eventually dumps the basket’s contents far away in the forest. But even the Siriono are not rigorous in their hygiene. Anthropologist Allan Holmberg relates watching a Siriono infant unobserved by his mother defecate, lie in his feces, smear them over himself, and put them into his mouth. When his mother finally noticed what was going on, she put her finger into the baby’s mouth, removed the feces, wiped but didn’t bathe the filthy baby, and resumed eating herself without washing her hands. Piraha Indians let their dogs eat off the plates from which they themselves are simultaneously eating: that’s a good way to acquire canine germs and parasites.

  By trial and error, many traditional peoples identify local plants which they believe help cure particular ailments. My New Guinea friends frequently point out to me certain plants which they say that they use to treat malaria, other fevers, or dysentery or to induce miscarriage. Western ethnobotanists have studied this traditional pharmacological knowledge, and Western pharmaceutical companies have extracted drugs from these plants. Nevertheless, the overall effectiveness of traditional medical knowledge, interesting as it is, tends to be limited. Malaria is still one of the commonest causes of illness and death in New Guinea’s lowlands and hills. It was only when scientists established that malaria is caused by a protozoan of genus Plasmodium transmitted by mosquitoes of genus Anopheles, and that it can be cured by various drugs, that the percentage of New Guinea lowlanders suffering malaria attacks could be reduced from around 50% to below 1%.

  Views of disease causes, and resulting attempted preventive measures and cures, differ among traditional peoples. Some but not all peoples have specialized healers, termed “shamans” by Westerners, and given specific epithets by the people involved. The !Kung and the Ache often view illness fatalistically, as something that is due to chance and can’t be helped. In other cases the Ache offer biological explanations: e.g., that fatal intestinal illnesses of children are due to weaning and eating solid food, and that fevers are caused by eating bad meat, too much honey, honey unmixed with water, too many insect larvae, or other dangerous foods, or by exposure to human blood. Each of these explanations may sometimes be correct, but they don’t serve to protect the Ache from a high death rate from disease. The Daribi, Fayu, Kaulong, Yanomamo, and many other peoples blame some illnesses on a curse, magic, or a sorcerer, to be countered by raiding, killing, or paying the responsible sorcerer. The Dani, Daribi, and !Kung attribute other illnesses to ghosts or spirits, with whom !Kung healers attempt to mediate by going into a trance. The Kaulong, Siriono, and many other peoples seek moral and religious explanations for illnesses: i.e., the victim brought the illness on himself by an oversight, committing an offense against nature, or violating a taboo. For instance, the Kaulong attribute respiratory illnesses of men to pollution by women, when a man has made the dangerous mistake of coming into contact with an object polluted by a woman menstruating or giving birth, or when a man has walked under any fallen tree or bridge or has drunk from a river (because a woman might have walked on the tree, over the bridge, or through the river). Before we Westerners look down on those Kaulong theories of male respiratory disease, we should reflect on the frequency with which our own cancer victims seek to identify their moral responsibility or the cause for their cancer, whose specific cause is as obscure to us as is the cause of male respiratory illness to the Kaulong.

  Starvation

  In February 1913, as the British explorer A. F. R. Wollaston was descending in good spirits through New Guinea montane forests after having succeeded in reaching the snow line on New Guinea’s highest mountain, he was horrified to find two recently dead bodies in his path. Over the next two days, which he described as among the most awful of his life, he encountered over 30 more bodies of New Guinea mountain people, mostly women and children, singly or in groups of up to five, lying in rough shelters along the track. One group consisting of a dead woman and two dead children included a still-living small girl about three years old, whom he carried to his camp and fed with milk but who died within a few hours. Into camp came another group of a man, a woman,
and two children, of whom all except one of the children expired. The whole group, already chronically malnourished, had exhausted their supplies of sweet potatoes and pigs and found no wild food to eat in the forest except the hearts of some palm trees, and the weaker ones apparently died of starvation.

  Compared to accidents, violence, and disease, which are frequently recognized and mentioned as causes of death in traditional societies, death due to starvation as witnessed by Wollaston receives much less mention. When it does occur, it is likely to involve mass deaths, because people in small-scale societies share food, so that either no one starves or else many people do simultaneously. But starvation is greatly underappreciated as a contributing cause of death. Under most circumstances, when people become seriously malnourished, something else occurs to kill them before they die purely of starvation and nothing else. Their body resistance fails, they become susceptible to illness, and they are recorded as dying of a disease from which a healthy person would have recovered. As they become physically weak, they become more prone to accidents such as falling from a tree or drowning, or to being killed by healthy enemies. The pre-occupation of small-scale societies with food, and the diverse and elaborate measures to which they resort to ensure their food supply and which I shall explain in the following pages, testify to their omnipresent concern with starvation as a major risk of traditional life.