Still a third type of answer to Yali invokes the supposed importance of lowland river valleys in dry climates, where highly productive agriculture depended on large-scale irrigation systems that in turn required centralized bureaucracies. This explanation was suggested by the undoubted fact that the earliest known empires and writing systems arose in the Tigris and Euphrates Valleys of the Fertile Crescent and in the Nile Valley of Egypt. Water control systems also appear to have been associated with centralized political organization in some other areas of the world, including the Indus Valley of the Indian subcontinent, the Yellow and Yangtze Valleys of China, the Maya lowlands of Mesoamerica, and the coastal desert of Peru.
However, detailed archaeological studies have shown that complex irrigation systems did not accompany the rise of centralized bureaucracies but followed after a considerable lag. That is, political centralization arose for some other reason and then permitted construction of complex irrigation systems. None of the crucial developments preceding political centralization in those same parts of the world were associated with river valleys or with complex irrigation systems. For example, in the Fertile Crescent food production and village life originated in hills and mountains, not in lowland river valleys. The Nile Valley remained a cultural backwater for about 3,000 years after village food production began to flourish in the hills of the Fertile Crescent. River valleys of the southwestern United States eventually came to support irrigation agriculture and complex societies, but only after many of the developments on which those societies rested had been imported from Mexico. The river valleys of southeastern Australia remained occupied by tribal societies without agriculture.
Yet another type of explanation lists the immediate factors that enabled Europeans to kill or conquer other peoples—especially European guns, infectious diseases, steel tools, and manufactured products. Such an explanation is on the right track, as those factors demonstrably were directly responsible for European conquests. However, this hypothesis is incomplete, because it still offers only a proximate (first-stage) explanation identifying immediate causes. It invites a search for ultimate causes: why were Europeans, rather than Africans or Native Americans, the ones to end up with guns, the nastiest germs, and steel?
While some progress has been made in identifying those ultimate causes in the case of Europe’s conquest of the New World, Africa remains a big puzzle. Africa is the continent where protohumans evolved for the longest time, where anatomically modern humans may also have arisen, and where native diseases like malaria and yellow fever killed European explorers. If a long head start counts for anything, why didn’t guns and steel arise first in Africa, permitting Africans and their germs to conquer Europe? And what accounts for the failure of Aboriginal Australians to pass beyond the stage of hunter-gatherers with stone tools?
Questions that emerge from worldwide comparisons of human societies formerly attracted much attention from historians and geographers. The best-known modern example of such an effort was Arnold Toynbee’s 12-volume Study of History. Toynbee was especially interested in the internal dynamics of 23 advanced civilizations, of which 22 were literate and 19 were Eurasian. He was less interested in prehistory and in simpler, nonliterate societies. Yet the roots of inequality in the modern world lie far back in prehistory. Hence Toynbee did not pose Yali’s question, nor did he come to grips with what I see as history’s broadest pattern. Other available books on world history similarly tend to focus on advanced literate Eurasian civilizations of the last 5,000 years; they have a very brief treatment of pre-Columbian Native American civilizations, and an even briefer discussion of the rest of the world except for its recent interactions with Eurasian civilizations. Since Toynbee’s attempt, worldwide syntheses of historical causation have fallen into disfavor among most historians, as posing an apparently intractable problem.
Specialists from several disciplines have provided global syntheses of their subjects. Especially useful contributions have been made by ecological geographers, cultural anthropologists, biologists studying plant and animal domestication, and scholars concerned with the impact of infectious diseases on history. These studies have called attention to parts of the puzzle, but they provide only pieces of the needed broad synthesis that has been missing.
Thus, there is no generally accepted answer to Yali’s question. On the one hand, the proximate explanations are clear: some peoples developed guns, germs, steel, and other factors conferring political and economic power before others did; and some peoples never developed these power factors at all. On the other hand, the ultimate explanations—for example, why bronze tools appeared early in parts of Eurasia, late and only locally in the New World, and never in Aboriginal Australia—remain unclear.
Our present lack of such ultimate explanations leaves a big intellectual gap, since the broadest pattern of history thus remains unexplained. Much more serious, though, is the moral gap left unfilled. It is perfectly obvious to everyone, whether an overt racist or not, that different peoples have fared differently in history. The modern United States is a European-molded society, occupying lands conquered from Native Americans and incorporating the descendants of millions of sub-Saharan black Africans brought to America as slaves. Modern Europe is not a society molded by sub-Saharan black Africans who brought millions of Native Americans as slaves.
These results are completely lopsided: it was not the case that 51 percent of the Americas, Australia, and Africa was conquered by Europeans, while 49 percent of Europe was conquered by Native Americans, Aboriginal Australians, or Africans. The whole modern world has been shaped by lopsided outcomes. Hence they must have inexorable explanations, ones more basic than mere details concerning who happened to win some battle or develop some invention on one occasion a few thousand years ago.
It seems logical to suppose that history’s pattern reflects innate differences among people themselves. Of course, we’re taught that it’s not polite to say so in public. We read of technical studies claiming to demonstrate inborn differences, and we also read rebuttals claiming that those studies suffer from technical flaws. We see in our daily lives that some of the conquered peoples continue to form an underclass, centuries after the conquests or slave imports took place. We’re told that this too is to be attributed not to any biological shortcomings but to social disadvantages and limited opportunities.
Nevertheless, we have to wonder. We keep seeing all those glaring, persistent differences in peoples’ status. We’re assured that the seemingly transparent biological explanation for the world’s inequalities as of A.D. 1500 is wrong, but we’re not told what the correct explanation is. Until we have some convincing, detailed, agreed-upon explanation for the broad pattern of history, most people will continue to suspect that the racist biological explanation is correct after all. That seems to me the strongest argument for writing this book.
AUTHORS ARE REGULARLY asked by journalists to summarize a long book in one sentence. For this book, here is such a sentence: “History followed different courses for different peoples because of differences among peoples’ environments, not because of biological differences among peoples themselves.”
Naturally, the notion that environmental geography and biogeography influenced societal development is an old idea. Nowadays, though, the view is not held in esteem by historians; it is considered wrong or simplistic, or it is caricatured as environmental determinism and dismissed, or else the whole subject of trying to understand worldwide differences is shelved as too difficult. Yet geography obviously has some effect on history; the open question concerns how much effect, and whether geography can account for history’s broad pattern.
The time is now ripe for a fresh look at these questions, because of new information from scientific disciplines seemingly remote from human history. Those disciplines include, above all, genetics, molecular biology, and biogeography as applied to crops and their wild ancestors; the same disciplines plus behavioral ecology, as applied to domestic animals and t
heir wild ancestors; molecular biology of human germs and related germs of animals; epidemiology of human diseases; human genetics; linguistics; archaeological studies on all continents and major islands; and studies of the histories of technology, writing, and political organization.
This diversity of disciplines poses problems for would-be authors of a book aimed at answering Yali’s question. The author must possess a range of expertise spanning the above disciplines, so that relevant advances can be synthesized. The history and prehistory of each continent must be similarly synthesized. The book’s subject matter is history, but the approach is that of science—in particular, that of historical sciences such as evolutionary biology and geology. The author must understand from firsthand experience a range of human societies, from hunter-gatherer societies to modern space-age civilizations.
These requirements seem at first to demand a multi-author work. Yet that approach would be doomed from the outset, because the essence of the problem is to develop a unified synthesis. That consideration dictates single authorship, despite all the difficulties that it poses. Inevitably, that single author will have to sweat copiously in order to assimilate material from many disciplines, and will require guidance from many colleagues.
My background had led me to several of these disciplines even before Yali put his question to me in 1972. My mother is a teacher and linguist; my father, a physician specializing in the genetics of childhood diseases. Because of my father’s example, I went through school expecting to become a physician. I had also become a fanatical bird-watcher by the age of seven. It was thus an easy step, in my last undergraduate year at university, to shift from my initial goal of medicine to the goal of biological research. However, throughout my school and undergraduate years, my training was mainly in languages, history, and writing. Even after deciding to obtain a Ph.D. in physiology, I nearly dropped out of science during my first year of graduate school to become a linguist.
Since completing my Ph.D. in 1961, I have divided my scientific research efforts between two fields: molecular physiology on the one hand, evolutionary biology and biogeography on the other hand. As an unforeseen bonus for the purposes of this book, evolutionary biology is a historical science forced to use methods different from those of the laboratory sciences. That experience has made the difficulties in devising a scientific approach to human history familiar to me. Living in Europe from 1958 to 1962, among European friends whose lives had been brutally traumatized by 20th-century European history, made me start to think more seriously about how chains of causes operate in history’s unfolding.
For the last 33 years my fieldwork as an evolutionary biologist has brought me into close contact with a wide range of human societies. My specialty is bird evolution, which I have studied in South America, southern Africa, Indonesia, Australia, and especially New Guinea. Through living with native peoples of these areas, I have become familiar with many technologically primitive human societies, from those of hunter-gatherers to those of tribal farmers and fishing peoples who depended until recently on stone tools. Thus, what most literate people would consider strange lifestyles of remote prehistory are for me the most vivid part of my life. New Guinea, though it accounts for only a small fraction of the world’s land area, encompasses a disproportionate fraction of its human diversity. Of the modern world’s 6,000 languages. 1,000 are confined to New Guinea. In the course of my work on New Guinea birds, my interests in language were rekindled, by the need to elicit lists of local names of bird species in nearly 100 of those New Guinea languages.
Out of all those interests grew my most recent book, a nontechnical account of human evolution entitled The Third Chimpanzee. Its Chapter 14, called “Accidental Conquerors,” sought to understand the outcome of the encounter between Europeans and Native Americans. After I had completed that book, I realized that other modern, as well as prehistoric, encounters between peoples raised similar questions. I saw that the question with which I had wrestled in that Chapter 14 was in essence the question Yali had asked me in 1972, merely transferred to a different part of the world. And so at last, with the help of many friends, I shall attempt to satisfy Yali’s curiosity—and my own.
THIS BOOK’S CHAPTERS are divided into four parts. Part 1, entitled “From Eden to Cajamarca,” consists of three chapters. Chapter 1 provides a whirlwind tour of human evolution and history, extending from our divergence from apes, around 7 million years ago, until the end of the last Ice Age, around 13,000 years ago. We shall trace the spread of ancestral humans, from our origins in Africa to the other continents, in order to understand the state of the world just before the events often lumped into the term “rise of civilization” began. It turns out that human development on some continents got a head start in time over developments on others.
Chapter 2 prepares us for exploring effects of continental environments on history over the past 13,000 years, by briefly examining effects of island environments on history over smaller time scales and areas. When ancestral Polynesians spread into the Pacific around 3,200 years ago, they encountered islands differing greatly in their environments. Within a few millennia that single ancestral Polynesian society had spawned on those diverse islands a range of diverse daughter societies, from hunter-gatherer tribes to proto-empires. That radiation can serve as a model for the longer, larger-scale, and less understood radiation of societies on different continents since the end of the last Ice Age, to become variously hunter-gatherer tribes and empires.
The third chapter introduces us to collisions between peoples from different continents, by retelling through contemporary eyewitness accounts the most dramatic such encounter in history: the capture of the last independent Inca emperor, Atahuallpa, in the presence of his whole army, by Francisco Pizarro and his tiny band of conquistadores, at the Peruvian city of Cajamarca. We can identify the chain of proximate factors that enabled Pizarro to capture Atahuallpa, and that operated in European conquests of other Native American societies as well. Those factors included Spanish germs, horses, literacy, political organization, and technology (especially ships and weapons). That analysis of proximate causes is the easy part of this book; the hard part is to identify the ultimate causes leading to them and to the actual outcome, rather than to the opposite possible outcome of Atahuallpa’s coming to Madrid and capturing King Charles I of Spain.
Part 2, entitled “The Rise and Spread of Food Production” and consisting of Chapters 4–10, is devoted to what I believe to be the most important constellation of ultimate causes. Chapter 4 sketches how food production—that is, the growing of food by agriculture or herding, instead of the hunting and gathering of wild foods—ultimately led to the immediate factors permitting Pizarro’s triumph. But the rise of food production varied around the globe. As we shall see in Chapter 5, peoples in some parts of the world developed food production by themselves; some other peoples acquired it in prehistoric times from those independent centers; and still others neither developed nor acquired food production prehistorically but remained hunter-gatherers until modern times. Chapter 6 explores the numerous factors driving the shift from the hunter-gatherer lifestyle toward food production, in some areas but not in others.
Chapters 7, 8, and 9 then show how crops and livestock came in prehistoric times to be domesticated from ancestral wild plants and animals, by incipient farmers and herders who could have had no vision of the outcome. Geographic differences in the local suites of wild plants and animals available for domestication go a long way toward explaining why only a few areas became independent centers of food production, and why it arose earlier in some of those areas than in others. From those few centers of origin, food production spread much more rapidly to some areas than to others. A major factor contributing to those differing rates of spread turns out to have been the orientation of the continents’ axes: predominantly west-east for Eurasia, predominantly north-south for the Americas and Africa (Chapter 10).
Thus, Chapter 3 sketched the immediate fact
ors behind Europe’s conquest of Native Americans, and Chapter 4 the development of those factors from the ultimate cause of food production. In Part 3 (“From Food to Guns, Germs, and Steel,” Chapters 11–14), the connections from ultimate to proximate causes are traced in detail, beginning with the evolution of germs characteristic of dense human populations (Chapter 11). Far more Native Americans and other non-Eurasian peoples were killed by Eurasian germs than by Eurasian guns or steel weapons. Conversely, few or no distinctive lethal germs awaited would-be European conquerors in the New World. Why was the germ exchange so unequal? Here, the results of recent molecular biological studies are illuminating in linking germs to the rise of food production, in Eurasia much more than in the Americas.
Another chain of causation led from food production to writing, possibly the most important single invention of the last few thousand years (Chapter 12). Writing has evolved de novo only a few times in human history, in areas that had been the earliest sites of the rise of food production in their respective regions. All other societies that have become literate did so by the diffusion of writing systems or of the idea of writing from one of those few primary centers. Hence, for the student of world history, the phenomenon of writing is particularly useful for exploring another important constellation of causes: geography’s effect on the ease with which ideas and inventions spread.
What holds for writing also holds for technology (Chapter 13). A crucial question is whether technological innovation is so dependent on rare inventor-geniuses, and on many idiosyncratic cultural factors, as to defy an understanding of world patterns. In fact, we shall see that, paradoxically, this large number of cultural factors makes it easier, not harder, to understand world patterns of technology. By enabling farmers to generate food surpluses, food production permitted farming societies to support full-time craft specialists who did not grow their own food and who developed technologies.
Guns, Germs, and Steel Page 3