Guns, Germs, and Steel: The Fates of Human Societies

by Jared Diamond

  AMONG OTHER FACTORS relevant to answering Yali’s question, cultural factors and influences of individual people loom large. To take the former first, human cultural traits vary greatly around the world. Some of that cultural variation is no doubt a product of environmental variation, and I have discussed many examples in this book. But an important question concerns the possible significance of local cultural factors unrelated to the environment. A minor cultural feature may arise for trivial, temporary local reasons, become fixed, and then predispose a society toward more important cultural choices, as is suggested by applications of chaos theory to other fields of science. Such cultural processes are among history’s wild cards that would tend to make history unpredictable.

  As one example, I mentioned in Chapter 13 the QWERTY keyboard for typewriters. It was adopted initially, out of many competing keyboard designs, for trivial specific reasons involving early typewriter construction in America in the 1860s, typewriter salesmanship, a decision in 1882 by a certain Ms. Longley who founded the Shorthand and Typewriter Institute in Cincinnati, and the success of Ms. Longley’s star typing pupil Frank McGurrin, who thrashed Ms. Longley’s non-QWERTY competitor Louis Taub in a widely publicized typing contest in 1888. The decision could have gone to another keyboard at any of numerous stages between the 1860s and the 1880s; nothing about the American environment favored the QWERTY keyboard over its rivals. Once the decision had been made, though, the QWERTY keyboard became so entrenched that it was also adopted for computer keyboard design a century later. Equally trivial specific reasons, now lost in the remote past, may have lain behind the Sumerian adoption of a counting system based on 12 instead of 10 (leading to our modern 60-minute hour, 24-hour day, 12-month year, and 360-degree circle), in contrast to the widespread Mesoamerican counting system based on 20 (leading to its calendar using two concurrent cycles of 260 named days and a 365-day year).

  Those details of typewriter, clock, and calendar design have not affected the competitive success of the societies adopting them. But it is easy to imagine how they could have. For example, if the QWERTY keyboard of the United States had not been adopted elsewhere in the world as well—say, if Japan or Europe had adopted the much more efficient Dvorak keyboard—that trivial decision in the 19th century might have had big consequences for the competitive position of 20th-century American technology.

  Similarly, a study of Chinese children suggested that they learn to write more quickly when taught an alphabetic transcription of Chinese sounds (termed pinyin) than when taught traditional Chinese writing, with its thousands of signs. It has been suggested that the latter arose because of their convenience for distinguishing the large numbers of Chinese words possessing differing meanings but the same sounds (homophones). If so, the abundance of homophones in the Chinese language may have had a large impact on the role of literacy in Chinese society, yet it seems unlikely that there was anything in the Chinese environment selecting for a language rich in homophones. Did a linguistic or cultural factor account for the otherwise puzzling failure of complex Andean civilizations to develop writing? Was there anything about India’s environment predisposing toward rigid socioeconomic castes, with grave consequences for the development of technology in India? Was there anything about the Chinese environment predisposing toward Confucian philosophy and cultural conservatism, which may also have profoundly affected history? Why was proselytizing religion (Christianity and Islam) a driving force for colonization and conquest among Europeans and West Asians but not among Chinese?

  These examples illustrate the broad range of questions concerning cultural idiosyncrasies, unrelated to environment and initially of little significance, that might evolve into influential and long-lasting cultural features. Their significance constitutes an important unanswered question. It can best be approached by concentrating attention on historical patterns that remain puzzling after the effects of major environmental factors have been taken into account.

  WHAT ABOUT THE effects of idiosyncratic individual people? A familiar modern example is the narrow failure, on July 20, 1944, of the assassination attempt against Hitler and of a simultaneous uprising in Berlin. Both had been planned by Germans who were convinced that the war could not be won and who wanted to seek peace then, at a time when the eastern front between the German and Russian armies still lay mostly within Russia’s borders. Hitler was wounded by a time bomb in a briefcase placed under a conference table; he might have been killed if the case had been placed slightly closer to the chair where he was sitting. It is likely that the modern map of Eastern Europe and the Cold War’s course would have been significantly different if Hitler had indeed been killed and if World War II had ended then.

  Less well known but even more fateful was a traffic accident in the summer of 1930, over two years before Hitler’s seizure of power in Germany, when a car in which he was riding in the “death seat” (right front passenger seat) collided with a heavy trailer truck. The truck braked just in time to avoid running over Hitler’s car and crushing him. Because of the degree to which Hitler’s psychopathology determined Nazi policy and success, the form of an eventual World War II would probably have been quite different if the truck driver had braked one second later.

  One can think of other individuals whose idiosyncrasies apparently influenced history as did Hitler’s: Alexander the Great, Augustus, Buddha, Christ, Lenin, Martin Luther, the Inca emperor Pachacuti, Mohammed, William the Conqueror, and the Zulu king Shaka, to name a few. To what extent did each really change events, as opposed to “just” happening to be the right person in the right place at the right time? At the one extreme is the view of the historian Thomas Carlyle: “Universal history, the history of what man [sic] has accomplished in this world, is at bottom the History of the Great Men who have worked here.” At the opposite extreme is the view of the Prussian statesman Otto von Bismarck, who unlike Carlyle had long firsthand experience of politics’ inner workings: “The statesman’s task is to hear God’s footsteps marching through history, and to try to catch on to His coattails as He marches past.”

  Like cultural idiosyncrasies, individual idiosyncrasies throw wild cards into the course of history. They may make history inexplicable in terms of environmental forces, or indeed of any generalizable causes. For the purposes of this book, however, they are scarcely relevant, because even the most ardent proponent of the Great Man theory would find it difficult to interpret history’s broadest pattern in terms of a few Great Men. Perhaps Alexander the Great did nudge the course of western Eurasia’s already literate, food-producing, iron-equipped states, but he had nothing to do with the fact that western Eurasia already supported literate, food-producing, iron-equipped states at a time when Australia still supported only nonliterate hunter-gatherer tribes lacking metal tools. Nevertheless, it remains an open question how wide and lasting the effects of idiosyncratic individuals on history really are.

  THE DISCIPLINE OF history is generally not considered to be a science, but something closer to the humanities. At best, history is classified among the social sciences, of which it rates as the least scientific. While the field of government is often termed “political science” and the Nobel Prize in economics refers to “economic science,” history departments rarely if ever label themselves “Department of Historical Science.” Most historians do not think of themselves as scientists and receive little training in acknowledged sciences and their methodologies. The sense that history is nothing more than a mass of details is captured in numerous aphorisms: “History is just one damn fact after another,” “History is more or less bunk,” “There is no law of history any more than of a kaleidoscope,” and so on.

  One cannot deny that it is more difficult to extract general principles from studying history than from studying planetary orbits. However, the difficulties seem to me not fatal. Similar ones apply to other historical subjects whose place among the natural sciences is nevertheless secure, including astronomy, climatology, ecology, evolutionary
biology, geology, and paleontology. People’s image of science is unfortunately often based on physics and a few other fields with similar methodologies. Scientists in those fields tend to be ignorantly disdainful of fields to which those methodologies are inappropriate and which must therefore seek other methodologies—such as my own research areas of ecology and evolutionary biology. But recall that the word “science” means “knowledge” (from the Latin scire, “to know,” and scientia, “knowledge”), to be obtained by whatever methods are most appropriate to the particular field. Hence I have much empathy with students of human history for the difficulties they face.

  Historical sciences in the broad sense (including astronomy and the like) share many features that set them apart from nonhistorical sciences such as physics, chemistry, and molecular biology. I would single out four: methodology, causation, prediction, and complexity.

  In physics the chief method for gaining knowledge is the laboratory experiment, by which one manipulates the parameter whose effect is in question, executes parallel control experiments with that parameter held constant, holds other parameters constant throughout, replicates both the experimental manipulation and the control experiment, and obtains quantitative data. This strategy, which also works well in chemistry and molecular biology, is so identified with science in the minds of many people that experimentation is often held to be the essence of the scientific method. But laboratory experimentation can obviously play little or no role in many of the historical sciences. One cannot interrupt galaxy formation, start and stop hurricanes and ice ages, experimentally exterminate grizzly bears in a few national parks, or rerun the course of dinosaur evolution. Instead, one must gain knowledge in these historical sciences by other means, such as observation, comparison, and so-called natural experiments (to which I shall return in a moment).

  Historical sciences are concerned with chains of proximate and ultimate causes. In most of physics and chemistry the concepts of “ultimate cause,” “purpose,” and “function” are meaningless, yet they are essential to understanding living systems in general and human activities in particular. For instance, an evolutionary biologist studying Arctic hares whose fur color turns from brown in summer to white in winter is not satisfied with identifying the mundane proximate causes of fur color in terms of the fur pigments’ molecular structures and biosynthetic pathways. The more important questions involve function (camouflage against predators?) and ultimate cause (natural selection starting with an ancestral hare population with seasonally unchanging fur color?). Similarly, a European historian is not satisfied with describing the condition of Europe in both 1815 and 1918 as having just achieved peace after a costly pan-European war. Understanding the contrasting chains of events leading up to the two peace treaties is essential to understanding why an even more costly pan-European war broke out again within a few decades of 1918 but not of 1815. But chemists do not assign a purpose or function to a collision of two gas molecules, nor do they seek an ultimate cause for the collision.

  Still another difference between historical and nonhistorical sciences involves prediction. In chemistry and physics the acid test of one’s understanding of a system is whether one can successfully predict its future behavior. Again, physicists tend to look down on evolutionary biology and history, because those fields appear to fail this test. In historical sciences, one can provide a posteriori explanations (e.g., why an asteroid impact on Earth 66 million years ago may have driven dinosaurs but not many other species to extinction), but a priori predictions are more difficult (we would be uncertain which species would be driven to extinction if we did not have the actual past event to guide us). However, historians and historical scientists do make and test predictions about what future discoveries of data will show us about past events.

  The properties of historical systems that complicate attempts at prediction can be described in several alternative ways. One can point out that human societies and dinosaurs are extremely complex, being characterized by an enormous number of independent variables that feed back on each other. As a result, small changes at a lower level of organization can lead to emergent changes at a higher level. A typical example is the effect of that one truck driver’s braking response, in Hitler’s nearly fatal traffic accident of 1930, on the lives of a hundred million people who were killed or wounded in World War II. Although most biologists agree that biological systems are in the end wholly determined by their physical properties and obey the laws of quantum mechanics, the systems’ complexity means, for practical purposes, that that deterministic causation does not translate into predictability. Knowledge of quantum mechanics does not help one understand why introduced placental predators have exterminated so many Australian marsupial species, or why the Allied Powers rather than the Central Powers won World War I.

  Each glacier, nebula, hurricane, human society, and biological species, and even each individual and cell of a sexually reproducing species, is unique, because it is influenced by so many variables and made up of so many variable parts. In contrast, for any of the physicist’s elementary particles and isotopes and of the chemist’s molecules, all individuals of the entity are identical to each other. Hence physicists and chemists can formulate universal deterministic laws at the macroscopic level, but biologists and historians can formulate only statistical trends. With a very high probability of being correct, I can predict that, of the next 1,000 babies born at the University of California Medical Center, where I work, not fewer than 480 or more than 520 will be boys. But I had no means of knowing in advance that my own two children would be boys. Similarly, historians note that tribal societies may have been more likely to develop into chiefdoms if the local population was sufficiently large and dense and if there was potential for surplus food production than if that was not the case. But each such local population has its own unique features, with the result that chiefdoms did emerge in the highlands of Mexico, Guatemala, Peru, and Madagascar, but not in those of New Guinea or Guadalcanal.

  Still another way of describing the complexity and unpredictability of historical systems, despite their ultimate determinacy, is to note that long chains of causation may separate final effects from ultimate causes lying outside the domain of that field of science. For example, the dinosaurs may have been exterminated by the impact of an asteroid whose orbit was completely determined by the laws of classical mechanics. But if there had been any paleontologists living 67 million years ago, they could not have predicted the dinosaurs’ imminent demise, because asteroids belong to a field of science otherwise remote from dinosaur biology. Similarly, the Little Ice Age of A.D. 1300–1500 contributed to the extinction of the Greenland Norse, but no historian, and probably not even a modern climatologist, could have predicted the Little Ice Age.

  THUS, THE DIFFICULTIES historians face in establishing cause-and-effect relations in the history of human societies are broadly similar to the difficulties facing astronomers, climatologists, ecologists, evolutionary biologists, geologists, and paleontologists. To varying degrees, each of these fields is plagued by the impossibility of performing replicated, controlled experimental interventions, the complexity arising from enormous numbers of variables, the resulting uniqueness of each system, the consequent impossibility of formulating universal laws, and the difficulties of predicting emergent properties and future behavior. Prediction in history, as in other historical sciences, is most feasible on large spatial scales and over long times, when the unique features of millions of small-scale brief events become averaged out. Just as I could predict the sex ratio of the next 1,000 newborns but not the sexes of my own two children, the historian can recognize factors that made inevitable the broad outcome of the collision between American and Eurasian societies after 13,000 years of separate developments, but not the outcome of the 1960 U.S. presidential election. The details of which candidate said what during a single televised debate in October 1960 could have given the electoral victory to Nixon instead of to Kennedy, but no det
ails of who said what could have blocked the European conquest of Native Americans.

  How can students of human history profit from the experience of scientists in other historical sciences? A methodology that has proved useful involves the comparative method and so-called natural experiments. While neither astronomers studying galaxy formation nor human historians can manipulate their systems in controlled laboratory experiments, they both can take advantage of natural experiments, by comparing systems differing in the presence or absence (or in the strong or weak effect) of some putative causative factor. For example, epidemiologists, forbidden to feed large amounts of salt to people experimentally, have still been able to identify effects of high salt intake by comparing groups of humans who already differ greatly in their salt intake; and cultural anthropologists, unable to provide human groups experimentally with varying resource abundances for many centuries, still study long-term effects of resource abundance on human societies by comparing recent Polynesian populations living on islands differing naturally in resource abundance. The student of human history can draw on many more natural experiments than just comparisons among the five inhabited continents. Comparisons can also utilize large islands that have developed complex societies in a considerable degree of isolation (such as Japan, Madagascar, Native American Hispaniola, New Guinea, Hawaii, and many others), as well as societies on hundreds of smaller islands and regional societies within each of the continents.