Guns, Germs, and Steel

Guns, Germs, and Steel Summary and Analysis of Part 3: From Food to Guns, Germs, and Steel


In the second section, Diamond explained the ways in which food production contributed to differences in ancient societies. However, food production is not a proximate cause. It is only an ultimate cause, or a basic prerequisite for certain other factors that directly determined modern differences. If a farmer and a hunter-gatherer fought each other one-on-one and naked, for example, neither one would have a large advantage over the other. The advantages that do distinguish these men come from factors related to their differing strategies for food production: societies with agriculture have denser populations, breathe out nastier germs, own better weapons, and live in centralized governments with elites who can wage war. This third section will explore how the ultimate cause, food production, led to more proximate causes such as germs, literacy, technology, and centralized government.

Diseases were a crucial proximate cause of domination by one society over another; in the majority of wars, most deaths were caused not by warfare itself but by the exchange of diseases. This leads to a key question: why was the exchange of nasty germs between Europe and the Americas so unequal? To answer this, Diamond considers why some microbes make us sick and others don’t, why many diseases run in epidemics, and how diseases pass from humans to animals. Germs make us “sick” in order to pass themselves from one host to another; for example, coughing is a strategy by which a germ can transfer through the air to a new host. Germs have a vested interest in passing from one person to another, and in making sure that they have enough available hosts to stay alive. In an epidemic, germs are particularly quick and deadly, and can kill otherwise healthy individuals. Over time, human populations exposed to a given germ came to have a high proportion of people with genes for resistance, since they were selected for survival of such epidemics. This kind of “crowd disease” can only be sustained in large populations, where there are enough people to spread amongst that the germs can continue to pass themselves along; otherwise, the germs would quickly die out as all people in the society died out. In small hunter-gatherer societies, of course, such diseases would very quickly kill everyone and thus die out themselves. For this reason, new crowd diseases do not develop in small societies—hunter-gatherer tribes do not have enough population density to beget their own deadly diseases that they could pass to larger sedentary societies.

Moreover, human proximity to domesticated livestock is what caused certain deadly germs to develop in sedentary, food-producing societies instead of hunter-gatherer communities. Animals carry a number of germs that were first passed on to humans in a variety of ways. In fact, many deadly diseases such as smallpox and AIDS first originated with animals, and then spread to humans, in a new form, through human contact with these animals. Of course, these germs were most likely to be passed along to humans who kept domesticated animals and lived closely together with them. These conditions were most common in food-producing societies with a sedentary lifestyle. Overall, then, it was populations higher in density and with greater contact with domesticated animals that developed the deadliest diseases and were able to spread them to societies that couldn’t cope with them. This was how Europeans developed the smallpox that would decimate Native Americans. It also explains why Native Americans did not develop diseases of the same scale that could decimate European populations in turn.

Writing was also first developed in some societies and not others, and brought these communities a number of important advantages. Writing made it possible to transmit knowledge accurately, in greater quantity and detail, across space and time. But why did no traditional hunter-gatherers adopt writing? Actually, very few people invented writing entirely on their own throughout history: the Sumerians in Mesopotamia, Mexican Indians, Egyptians, and the Chinese. Whether or not a given society developed or adopted writing depended on whether they would find it useful, and whether they could support specialists who acted as scribes. These conditions only existed in societies that had complex and centralized political institutions. As established earlier, this kind of political institution was supported by the ultimate cause of food production. Food production was a necessary condition for the adoption of writing, but not a sufficient condition; some societies that were very isolated because of their geographic barriers also failed to adopt writing because the invention had trouble reaching them. The history of writing reinforces the importance of geography and ecology to the spread of human inventions.

The spread of technology can be equally baffling to historians. Archeologists in Crete recently discovered an implement called the “Phaistos Disk,” dating from 1700 B.C. The disc seemed to be used as a stamp for producing written documents, and anticipated humanity’s invention of printing. But we know this technology was not widely adopted in Crete or nearby for many more years. Why was this disc not immediately influential? Why did it take so much longer for these societies to adopt printing technology? Such questions suggest how unpredictable the spread of technology can seem. In fact, most inventions were developed not in response to a demand for a new product, but simply out of idle experimentation or curiosity. Invention, Diamond argues, is “the mother of necessity,” as opposed to vice versa. For example, Thomas Edison’s phonograph was first meant to preserve last words, record books for blind people, etc; none of these uses seemed to have commercial value. But once he started to offer them, other people found a popular use for them: recording and playing music. Technology finds most of its uses after it has been invented, rather than being invented to meet a foreseen need.

Technology develops cumulatively, meaning it requires contributions from several people and organizations, instead of in isolated heroic acts. Lone geniuses are thus not particularly important; it is how a society responds to a new product that determines the importance of any invention. Also, most inventions we attribute to a single person actually followed the previous work of other inventors who had developed earlier prototypes or aspects of the resulting technology. No one really worked alone to change an entire society. Even though we hear mainly about the many genius inventors of Europe, Europe did not actually have more individual geniuses than other societies. It simply had more inventions we hear about today, because societies recognized their uses and spurred their popularity. Four factors influence whether a given invention is accepted: relative economic advantage compared with existing technology, social value and prestige, compatibility with existing companies’ vested interests, and how obvious its advantages are.

But how do different societies become more or less receptive to innovation? Historians of technology have proposed many factors. These include life expectancy, which gives potential inventors more time to work on their products. Five factors relate to the organization of society: the availability of slave labor that freed up time for others to focus on technology, patents and property laws that rewarded innovation, opportunities for technical training, a capitalistic model that rewarded investment in technological development, and the individualism of a society that let inventors profit from their own work. Four other factors are ideological: risk-taking behavior, a scientific outlook, tolerance of diverse views, and religions that encourage innovation. But none of these factors relate to geography, or address ultimate factors. Perhaps the diversity of factors helps to explain the patterns of the spread of technology. In fact, the development and reception of inventions varied enormously from society to society on the same continent, and over time within the same society. It is thus impossible to claim that any group of people has simply “always” been more backwards. We must look to broad patterns instead of specific examples in order to understand the spread of inventions.

So what are the most important factors driving the adoption of a new technology in a given society? New inventions tend to crop up when, either: other societies learn of inventions elsewhere, are receptive to it, and adopt it, or a society lacks an invention that exists nearby and finds itself at a disadvantage. For example, the Maori tribes that adopted muskets were able to subjugate the tribes that did not take on this new technology. Societies that are geographically isolated can even adopt and then abandon a technology. For example, Japan briefly adopted guns before abandoning them shortly after, which was possible only because it was an isolated island that could not easily be overwhelmed by neighbors who did have guns. If a location is thus isolated, it is less likely to acquire and keep technologies. Technology also spreads by “diffusion,” meaning that one small invention can lead to a host of later inventions that build on this original model. This means that those societies that adopted new technologies very early had an advantage when it came to inventing more and more complex technologies later. Sedentary societies were better able to do this because they could hold on to possessions, develop specialized roles, and had more people who could potentially contribute new inventions. In conclusion, it was Eurasia’s distinctive geography that led it to develop more inventions, which enabled it to overwhelm other, more isolated, hunter-gatherer societies.

Government and religion are two other factors that often go hand in hand, and can determine the structure and power of a society. Human societies have generally progressed in order from bands—small groups consisting of 5 to 80 people—to tribes—hundreds of people living in fixed settlements—to chiefdoms—several thousands of people with established hierarchies—to states, which had an even more complex political structure. In these larger and more complex societies where power was typically concentrated in a single leader, societal organization was more complex. A crucial challenge also emerged: how did leaders, like chiefs or kings, motivate their followers to keep them in power and obey them? They could either disarm the populace and arm the elites, or redistribute tribute in ways that kept the masses happy, use their monopoly of force to maintain order and curb violence, or construct an ideology or religion that justified their rule. This last option explains why so many complex societies also developed a religion. Religion also brings two other important benefits to centralized societies: it helps unrelated individuals to live together without killing one another by giving them a bond not based in kinship, and it gives people a motivation to sacrifice their lives on behalf of others. Both of these benefits help these religious societies to work together and to subjugate other, less religious or centralized communities. Size is the greatest predictor of the kind of complexity that also leads societies to develop religion, technology, writing, or diseases.


This section begins with a particularly comical and graphic illustration of the problem it is considering: how animals can pass germs to humans. Diamond describes a friend’s story about treating a patient who was reluctant to mention how he may have caught the unusual infection he was dealing with. Eventually, the patient admits that he had had sex with the sheep at his family’s farm, to the shock and rage of his wife. Similarly, Diamond uses another colorful example at the beginning of chapter 13, when he is introducing the dilemma of how technology spread in certain areas faster than others. He builds suspense, beginning by noting that, “archeologists…chanced upon one of the most remarkable objects in the history of technology” before going on to reveal that this was the Phaistos disk. In both of these examples, Diamond gives readers a reference point for the topic at hand; he uses a memorable, surprising example in order to get readers engaged in the issue and help them to grasp its relevance.

Diamond also makes his argument more relatable and easier to follow by alluding to modern historical examples or common sayings. Although he is discussing very ancient history in this section, which covers the origins of early human societies, he uses more modern examples to help illustrate his points. For example, he points out that historians today debate whether Russian development of the atomic bomb can be attributed to blueprint copying, or to idea diffusion. He relates this more contemporary example of a historical dilemma to the question of how writing first developed: was it through the spread of ideas in general, or through simple copying? The example of the atomic bomb invention in Russia allows readers to better grasp the significance of the dilemma. Today, we wonder whether idea diffusion or blueprint copying was to blame because it could help to explain the course of the Cold War, the capabilities of Russian intelligence, and the potential of the atomic bomb. Similarly, Diamond wants readers to understand that we need to determine what caused the spread of writing in order to better understand how the invention of writing worked in the first place, how different societies responded to its invention, and how the course of history changed as a result.

He also offers readers key images to keep in mind for the major points he makes throughout the section. For example, when he is discussing the spread of technology, Diamond points out four key factors that influenced whether an invention was adopted: relative economic advantage compared with existing technology, social value and prestige, compatibility with existing companies’ vested interests, and how obvious its advantages are. He associates the first three factors with a particular image: wheels, which were only used for transportation in societies where this was economically advantageous; designer jeans, which were developed not for practicality but because of social prestige; and QWERTY keyboards, which demonstrate how a more practical innovation may be blocked if existing companies have a vested interest in keeping the older, less practical model around. Because he associates each of these ideas with an image, Diamond emphasizes their importance and helps his readers to keep them in mind. By staying attuned to those aspects of the argument that are paired with a key image, readers can build a mental map of the course of Diamond’s argument.

Throughout the section, Diamond is also careful to explore a number of different theories before zeroing in on the one he thinks is the best. When he is addressing the issue of technology, he cites a number of different possible explanations for why technology developed in certain areas and not in others. Perhaps it developed in countries that were culturally superior? Maybe it is due primarily to the influence of lone geniuses? Or maybe it depends on societal receptivity to new inventions? By doing this, Diamond gives readers a crash course in the history of theories pertaining to this topic. He is careful to update them on what previous theorists believed, before offering his new explanation for the issue at hand. In this case, his exploration of these other theories leads him to a key question that remains open for his book to answer: “the question of why technology did evolve at such different rates on different continents.”

Diamond also continuously reminds readers of the central pattern of the book: how differences in geography influence everything relating to human development. When he discusses technology, he comes back to this idea by noting, “For the purposes of this book, the key question about the laundry list is whether such factors differed systematically from continent to continent and thereby led to continental differences in technological development.” In other words, the central issue in his exploration of technology’s development is how this development varied geographically. He is careful to remind readers that this lies at the bottom of every topic he explores, whether that be the spread of disease, the diffusion of technologies, the invention of language, or the domestication of plants and animals.

This section also emphasizes the scope and key focus of the book. Scope is particularly important in this text, which ranges from very broad discussions of general historical patterns, to specific analyses of particular examples in history. When discussing the differences across tribes that adopted technology in varying ways, Diamond notes that, “to the student of broad historical patterns, though, it makes no difference what the specific reasons were in each of those cases.” Readers of this book are trained to be such students of “broad historical patterns,” since the aim of the text is to answer the very broad question: why did some societies end up with far fewer resources than others? It is important to keep this scope in mind, even when Diamond includes some more specific examples; readers should consider how these specific examples may fit into the broader patterns he is establishing.