Diamond now returns to the question Yali asked (the question brought up at the beginning of the book): “Why is it that you white people developed so much cargo … but we black people had little cargo of our own?” the answer to Yali’s question is this: “The differences between the long-term histories of peoples of the different continents have been due not to innate differences in the peoples themselves but to differences in their environments.”
In particular, there are four underlying environment factors that determine the course of human history: 1) availability of wild plants and animals for domestication, 2) barriers to diffusion and migration within a continent, 3) barriers to diffusion and migration between continents, and 4) population size and density. Factor 1 is especially critical in determining a society’s nutritional intake and health, its immunity to disease, and its amount of social specialization. Factors 2 and 3 are especially important in determining a society’s “stockpile” of technology, including a written alphabet. Finally, Factor 4 is important in determining a society’s level of political centralization, as well as its immunity to disease.
The four factors Diamond discusses here are geographic in nature, although factor 4, population size, is itself subject to the influences of factors 1, 2, and 3, as Diamond discusses in Chapter 14. Put together, the four factors play a large part in determining a society’s technology, organization, and immunity to disease—in short, its capacity to colonize and “engulf” other societies.
There are some notable caveats to Diamond’s conclusions. Most basically, Diamond’s book is too short to account for all of human history—it’s simply not possible for any one book to talk about 13,000 years of history.
Diamond has taken some criticism from academics who feel that his knowledge of his subject matter is sometimes superficial. But, to state the obvious, Guns, Germs, and Steel isn’t long enough to address all the (potentially infinite) data. While Diamond focused on a few notable cases of geographic determinism in Part Four, there are many others he has no time to address.
Another important caveat to Diamond’s conclusions is the supremacy of Europe over China and the Fertile Crescent. Why, exactly, did Europe overtake China and the Middle East as a world leader, given that all three regions had comparable advantages in the four geographic factors Diamond lists above? Specifically, why was it Europe, not China or the Middle East, that developed mercantile and capitalist economies, which allowed for world exploration and technological research?
One common criticism of Diamond’s book is that, while he shows how agricultural societies have an advantage over hunter-gatherer societies, he doesn’t show fully why some agricultural societies triumph over others. As he admits here, he hadn’t shown fully why Europe overtook China and Mesopotamia in the early modern era.
A partial answer to this question is that the Fertile Crescent lost its geographic advantages over time. As it entered the modern era, Mesopotamia became drier, the soil became less fertile, and the region as a whole ceased to be a major producer of food. Most of northern and western Europe has continued to produce crops and livestock for thousands of years.
Diamond doesn’t have time to answer the question he’s just posed in full detail—however, the change in climate in the Middle East, which paralleled the Middle East’s decline in global power, would suggest that geographic factors can explain why Europe overtook the Middle East after 1492.
Why was it Europe, not China, that became a world leader in the late 15th century? One would think that China’s huge technological innovations (the compass, printing, gunpowder) and sophisticated navy would have made its global influence and domination inevitable. Yet China mostly gave up its maritime expeditions in the middle of the 15th century. China was a politically unified country at the time; the dynastic powers ruled that China would no longer explore the rest of the world with its ships. Because of the stability of Chinese society, one dynastic decision determined the course of Chinese foreign policy for the next 400 years, thereby allowing Europe to seize power in the New World without any Chinese competition.
Often, historians have pointed to a single, unusually straightforward reason for China’s failure to overtake Europe in the early modern era: the dynastic powers mandated that there would be no more maritime exploration. Diamond’s challenge is to show the geographic factors underlying this decision. He begins by arguing for the political unification of China that led one political decision to carry such weight for so long—a phenomenon that he already explained largely in geographic terms in Chapter 16.
In Europe, there was much less political unification than in China. One reason for this is that Europe itself is a more geographically fragmented region than China. China is one solid landmass with long rivers and a relatively few islands; Europe has large islands, mountains, and small rivers that don’t connect together the entire continent. So it’s possible that China, because of its geographic unity, became more politically unified than Europe. As a result, there were power squabbles in Europe, resulting in death and destruction, but also more competition between nation-states. Competition inspired Western European nation-states to invest large sums in exploring the New World—the states were worried that their rivals would overtake them. This analysis, perhaps, begins to explain why Europe, not China or the Fertile Crescent, came to dominate world exploration after the 15th century.
Diamond acknowledges that it would take an entire other book to explain why Europe overtook China after 1492 A.D. But he suggests that China’s geographic unity—that is, its network of unusually long rivers connecting together different regions of the country—allowed for unusually strong political unification, which in turn allowed one dynasty’s decision to forego maritime exploration to influence Chinese development for hundreds of years.
Another important caveat to Diamond’s argument is the role of culture in history. By and large, the book avoids talking about cultural differences between different peoples of the world, preferring to frame its conclusions in terms of geography. Yet there are undeniable differences between different cultures, which may be the product of environmental factors. This is an important topic, but beyond the scope of Diamond’s book.
Diamond does not deny that there are major differences between cultures—that is, major differences between different societies’ values and behaviors. Diamond believes, however, that geographic causes explain many of these cultural differences—differences which, he admits, have been important to history. But, as with many of the questions raised in the Epilogue, culture will have to be a subject for another book.
Similarly, Diamond’s conclusions don’t account for individual people. Sometimes, a single, unpredictable person, like Lee Harvey Oswald (who assassinated President John F. Kennedy) can change the course of human history; Oswald’s actions (or the actions of any other single, historically important person) don’t seem reducible to geographic causes. Diamond concludes, “it remains an open question how wide and lasting the effects of idiosyncratic individuals on history really are.”
Diamond has deliberately avoided discussions of influential individuals, because such discussions might imply that historical changes largely result from individual people’s talent and intelligence—a hypothesis that Diamond has tried to replace with the theory of geographic determinism. Diamond doesn’t deny that individual people can be important to history; nevertheless, he maintains that geography plays a far greater historical role.
During the book, Diamond has aimed for a scientific approach to the study of history, while respecting the basic differences between science and history. Science is a study of causes and effects; using experiments, scientists aim to isolate which causes are linked to certain effects. In history, it’s often difficult to isolate the causes of historical events—there’s no “experiment” that historians can use to identify an independent variable’s effect on a dependent variable. Nevertheless, there are certain approaches that historians can take to studying their data that make their approach more scientific. For example, historians can compare civilizations that are environmentally similar, thereby doing a better job of isolating the relationship between causes and effects. (Diamond has spent most of his book trying to isolate the various causes of differences between civilizations.) In general, history is a complex field—in a way, much more complex than any of the sciences, because there are so many different causes to analyze. Nevertheless, it’s important to study history scientifically so that we can understand how the modern world came to be the way it is.
Diamond contrasts the scientific approach to history with the more traditional, humanities-based approach. Essentially, Diamond defines “scientific” as the strategy of trying to isolate independent and dependent variables; that is, trying to determine the precise causes of different phenomena. It is extremely difficult to bring a scientific approach to history, because, unlike in most scientific fields, it’s almost impossible to perform an experiment (there’s no way to artificially isolate a historical event’s causes, and everything being studied has already occurred). Because of the difficulty of the scientific approach, many historians have abandoned scientific methods altogether, but Diamond argues that it’s still worthwhile to study history scientifically. He’s attempted to show how certain specific causes, such as latitude, climate, presence of large mammals, etc., cause specific societal effects, such as immunity to disease and presence of complex technology.