Guns, Germs, & Steel by Jared Diamond: Overview

This article is an excerpt from the Shortform book guide to "Guns, Germs, and Steel" by Jared Diamond. Shortform has the world's best summaries and analyses of books you should be reading.

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What is Guns, Germs, and Steel by Jared Diamond about? What are the key takeaways from the book?

Guns, Germs, and Steel is Jared Diamond’s attempt to determine why societies historically took different paths. It was named one of TIME’s best non-fiction books of all time, awarded the Pulitzer Prize in 1998, and turned into a PBS documentary released in 2005. 

Keep reading for an overview of Diamond’s award-winning book.

Guns, Germs, and Steel: Book Overview

After completing his doctorate at Cambridge University, Diamond did research among the remote tribes of New Guinea. It was there that he became interested in figuring out why the local tribespeople—whom he saw as every bit as intelligent and capable as he—never developed writing, steel tools, centralized governments, or a complex society like that of the British colonists who annexed New Guinea in the 19th century. 

He became convinced that differences between such societies were caused by environmental factors that affected their historical development, not biological differences between the people of the societies. These differences led Eurasians—people living in Asia, Europe, and North Africa, by Diamond’s account—to historically have strategic advantages over non-Eurasians. 

According to Diamond, these Eurasian advantages included: 

• Advanced knowledge that led to written language, durable weapons, oceangoing vessels, and other sophisticated technologies
• Centralized governments that supported complex infrastructure and the efficient management of resources
• Infectious diseases to which they were largely immune 

With these advantages, Eurasian colonists came to dominate much of the world. Diamond believes that each advantage was made possible by incidental geographic and environmental conditions that led to the rise of bountiful food production first in Eurasia. 

(Shortform note: While we’ve described knowledge, governments, and diseases as advantages, Diamond isn’t arguing that humanity is better off for having developed in this way. In fact, he has suggested elsewhere that each of these advantages has ultimately left us worse off. For instance, he believes food production may have been humanity’s worst mistake.) 

In our overview, we’ll see how Diamond draws the link between food production and these advantages.

It Started With Adequate Food Production  

In Guns, Germs, and Steel, Jared Diamond argues that the development of advanced civilizations depended first on the development of varied, abundant, and dependable food sources. This food production was achieved through the invention of agriculture, which gave rise to the strategic advantages listed above and which we’ll detail in the following sections. 

(Shortform note: Some scholars claim that Diamond places too much stock in the idea that agriculture revolutionized the lifestyle of early humans. They feel there’s little evidence to distinguish foragers from farmers: Early civilizations practiced foraging while they farmed for millennia—so it’s not clear that farming should be seen as a starting point from which different societies diverged. Nevertheless, Diamond’s argument is supported by a population boom found in the archaeological record which suggests that the widespread adoption of farming did have significant effects on societies.) 

Diamond says Eurasia could develop such food sources because it had geographic and environmental advantages over other regions of the world, so food production took off more readily in Eurasia than it did elsewhere. These advantages were: 

• Domesticable plants 
• Domesticable animals
• Geography favorable to food production 

We’ll take a closer look at each of these. 

Eurasia Had Plants Well-Suited to Domestication 

Diamond explains that wild plants are generally good prospects for domestication if they have some of the following attributes: 

1. They show natural traits that are useful to humans, such as being sweet, oily, fibrous, or easy to gather.

2. They have successful germination attributes (such as producing many seeds that can stay dormant for years at a time) that enable them to survive bouts of bad weather.

3. They reproduce by means that allow humans to control and predict the usefulness of the plant’s offspring. 

The Fertile Crescent (the modern-day Middle East) was the first place where plant domestication occurred independently in the world because the plants of that region were well suited to it. Diamond offers several potential reasons why domestication was so successful there. 

First, the climate of that region—mild, wet winters and long, hot, dry summers—resulted in many annuals that lived for one growing season and put most of their energy into producing large seeds capable of surviving the hot, dry season to sprout when the weather turned mild and wet again. This survival strategy resulted in more edible material (seeds) per plant than is common with perennial plants. Perennial plants such as trees often put more energy into growing long-lived, inedible material (such as woody stems) than into producing seeds that can survive for the next growing season. Thus, in places where perennial plants dominated, food production was slower to take off. 

Second, the abundant edible wild plants in the Fertile Crescent produced huge quantities of comestible seeds that hunter-gatherers could easily store. The sheer volume of useful, storable seeds encouraged tribal bands to establish settlements rather than stay on the move seeking other food sources. This kick-started the practice of maintaining crops. In places where plants produced less abundant edible and storable material, hunter-gatherers were slower to settle down. 

Finally, according to Diamond, many of the edible wild annual plants in the Fertile Crescent tended to reproduce by self-pollination: They’d fertilize themselves and produce identical offspring. This was valuable because it ensured future generations would maintain the desirable traits of their parents. Importantly, however, many of these plants could also reproduce by cross-pollination. This meant two parent plants could be bred with each other to produce a daughter plant with a combination of the parent traits. This was helpful because occasionally, plants that reproduced this way resulted in daughter plants with better traits than the parents. 

Early Fertile Crescent settlers, therefore, had good, abundant plant stock to work with. Because of this, they had an easier time domesticating their local wild plants than settlers in many other regions of the world. 

Eurasia Had More Domesticable Animals 

In addition to having good plants to work with, Eurasia had many wild animal candidates that were suitable for domestication. Diamond identifies seven attributes that wild animals must have to be good candidates for domestication, including the following four: 

1. They must have a diet that’s sustainable under domestic conditions: That is, they must eat a type and amount of food that early farmers could provide. Non-picky herbivores or omnivores were better candidates than picky eaters or carnivores.   

2. They must grow quickly. Animals that don’t reach maturity or reproduce for years are unsuitable for domestication.    

3. They must have a relatively tolerant disposition. If they’re too aggressive, they won’t be suitable for domestication. 

4. They must be relatively calm and not quick to spook and run. Otherwise, they’d be completely unmanageable.  

Only 14 ancient animals in the world had all the attributes Diamond describes. Eurasia was the continent with the greatest number of candidates: It had 13. No other continent had nearly as many. For this reason, Eurasia had the most potential for developing animal domestication. 

Diamond suggests three reasons Eurasia had so many animals that met these qualifications, while other continents didn’t. 

First, Eurasia simply had more animals that were potentially good for domestication before humans even began living on the continent. This was mainly due to its extremely large land area and favorable ecological conditions, which together supported a diverse array of animals. 

Second, it didn’t lose as many animal candidates to prehistoric extinctions as other continents, such as Australia and the Americas. Diamond suggests this is because the animals on those continents were first exposed to humans later in human history, when we were more developed as hunters. Because those animals were unafraid of humans (having never encountered them before), the hunters could hunt them to extinction. In Eurasia, by contrast, animals and humans interacted throughout the long process of human evolution, so animals became more accustomed to the danger humans posed and developed successful survival strategies.  

Finally, more of the surviving Eurasian animals were good for domestication than were the surviving animals of other continents. Diamond observes that 18% of the surviving animal candidates in Eurasia were suitable for domestication—in the Americas, only 4% were, and there were no native animal candidates in Australia or Sub-Saharan Africa. 

Eurasia’s Geographic Conditions Supported the Rise and Spread of Food Production

In addition to having domesticable plants and animals, Diamond contends that Eurasia benefited from having geographical features that supported the rise and spread of food production. 

A Favorable Axis Orientation

His main argument on this point is that Eurasia’s average north-south distance across the continent is shorter than the average east-west distance across the continent. He describes this as the continent’s axis orientation: Eurasia (including present-day Asia, Europe, and North Africa) has a predominantly east-west orientation. In contrast, the orientation of the Americas is north-south, as is the remaining portion of Africa. 

Diamond contends that an east-west axis facilitates the development and spread of food production more easily than a north-south axis because plants adapt to grow within similar latitudes: Plants suited to a certain seasonal day length can’t easily spread to another latitude where the seasonal day length differs. By contrast, continents with a north-south axis encompass more latitudes. If humans on these continents tried to spread crops to other latitudes, those crops wouldn’t thrive. Regions that face these geographic limitations to the spread of crops, therefore, face limitations to the spread of food production, which is largely based on maintaining crops. 

In addition, animals adapt to thrive within certain latitudes and climates. It would have been harder, therefore, for domesticated animals to spread along a north-south axis with its drastically different climates than to spread along an east-west axis. 

Fewer Topographic or Ecological Obstacles

A second factor affecting the spread of food production is the presence of topographic or ecological obstacles. It’s not quite enough to have an east-west axis, according to Diamond—over time, humans had to be able to spread crops and animals along that axis without encountering obstacles that threatened the survival of the plants, animals, or humans.

In Eurasia, there were historically few obstacles to the spread of domesticated plants and animals from the Fertile Crescent westward. Archaeologists find that food production spread quickly in that direction. However, the Fertile Crescent plants and animals weren’t well adapted to the different rainfall conditions of eastern India, so they were delayed in their spread eastward. Nevertheless, Fertile Crescent crops spread over the majority of Eurasia earlier and faster than crops on other continents. 

In North America, for instance, early domesticated crops spread extremely slowly from the US Southeast to the US Southwest—which share the same latitude—because infertile desert conditions barred the way. Ecological barriers therefore affected the spread of food production across North America more than the spread of food production across Eurasia.  

For these reasons—an abundance of domesticable plants and animals, and favorable geographic conditions—Eurasia got a head start on food production compared to the rest of the continents. 

Diamond argues that this head start, combined with the favorable conditions that enabled it, led to the three strategic advantages we mentioned at the start of the guide. We’ll now take a look at each of these below.  

The Advantage of Knowledge

Eurasians developed advanced knowledge leading to innovations that gave them advantages over societies whose knowledge was more limited, writes Diamond. 

Some of these key innovations were: durable metal weapons, armor, and tools; efficient means of transport such as the wheel and oceangoing ships; navigational equipment; and written language. When Eurasians traveled across the ocean to the Americas, their metal armor and guns were superior to the wood, bone, leather, and stone weapons and armor of the indigenous peoples. Moreover, the written languages of the Eurasians facilitated clear communication, which both inspired and coordinated expeditions and conquest. For these and other reasons, the invaders quickly subdued the Native Americans despite their having been established on the continent for millennia. 

Diamond argues that Eurasians didn’t develop this advanced knowledge because of some unique set of special abilities. Let’s look at the factors he believes led to this knowledge. 

Factors That Contributed to the Rise and Spread of Knowledge

Diamond identifies three factors that contributed to the rise and spread of knowledge in Eurasia: 

1. Early onset of food production: Food production led to the development and spread of knowledge because it created food surpluses and increased population density. Because Eurasia had a head start on food production, it had a head start on creating these conditions. 

Having extra food meant that a society could support non-farming specialists—such as craftspeople and bureaucrats—who could focus their time and energy on advancing their specialized knowledge. Craftspeople who may initially have developed specialized tools for farming, for example, could in time develop specialized weapons for warfare. Likewise, bureaucrats responsible for organizing harvests and building projects had to keep records and collect and transfer information: According to Diamond, this was a necessary condition for the invention of written language. 

In hunter-gatherer societies, by contrast, all members of the society had to spend most of their time and energy on collecting enough food to survive, so they weren’t free to advance their knowledge in other areas, and they had little use for innovations such as written language. 

2. Large area and population size: We’ve already seen that Eurasia had earlier and better food production than other continents, but it also happened to be the largest continent by far, and larger continents could support larger populations. Having more people provided more opportunities for ideas to arise and spread. 

Diamond explains that Eurasia (including North Africa) is nearly eight million square miles (21 million km²) larger than the next largest continent group: North and South America. Similarly, the current population of Eurasia is many times larger than any other continent. While the ancient population size isn’t known, Diamond contends that Eurasia likely had the largest population in the past, also. 

3. Ease of diffusion: The same reasons that gave Eurasia advantages in the spread of food production gave it the upper hand in the diffusion of knowledge: a dominant east-west axis and fewer geographic obstructions. 

A dominant east-west axis free of major obstructions facilitated the spread of knowledge because knowledge moved with people. As groups crossed Eurasia and set up farms and villages, they brought ideas and skills with them. Once new ideas emerged, they replaced or corrected old ideas and stimulated more new ideas, which led to more innovation. 

Because of these factors, Diamond believes Eurasia had an advantage over other regions of the world for advancing knowledge since any idea that arose was more likely to spread and develop across a large network of people.

The Advantage of Centralized Government

In addition to having more advanced knowledge, Eurasia benefitted from having more centralized governments, contends Diamond. Societies that had centralized governments, organized with hierarchies of authority and specialized roles, came to dominate societies that didn’t organize themselves this way. 

Centralized societies were better able to initiate and coordinate complex activities such as construction projects and wars of conquest. Rulers could give unilateral commands and mobilize armies through numerous subordinate leaders. They could justify wars and individual sacrifice by appealing to religious authority and the spirit of social unity. By contrast, egalitarian societies that viewed everyone as basically equal couldn’t easily unite around a single authority, so they were less able to coordinate large-scale cooperation and encourage self-sacrifice for a common good. 

Factors That Contributed to the Rise of Centralized Government

Why did Eurasian societies develop centralized government more than other societies? The two main reasons are related, writes Diamond: food production and population size.

As we’ve discussed, Eurasia’s population could grow due to its head start in food production. Diamond believes the size and density of the regional population was the biggest factor in determining how complex and organized societies became. He says there are several reasons for this.

First, larger and denser populations experienced more conflicts between strangers. These conflicts required more sophisticated mediation than family feuds or conflicts between people who knew each other. Sophisticated mediation, though, required more organized governance. 

Next, larger societies needed more efficient and productive means of food production. Often this included large-scale projects such as irrigation systems or public buildings suitable for crop storage. These projects required a great deal of coordination, which created the need for management, planning, and even record keeping. 

In addition, accomplishing large-scale projects also required a great deal of labor—this created a need for slaves. Because of this, victors in battle enslaved the losers and thereby grew their societies. Larger societies led to larger, more complex governments as the need to control and organize vast groups of people became more demanding. 

Finally, if victors didn’t absorb societies around them, they often left them in place to extract tribute. Extracting tribute further increased societal complexity because facilitating the collection of tribute and the stratification of different classes of people (for example, slaves and citizens) created a need for complex organizational systems and specialized bureaucratic roles. 

According to Diamond, of all the continents, Eurasia had the largest head start and the most favorable conditions for developing highly populated and complex societies with centrally organized governments.

The Advantage of Epidemic Diseases

Diamond claims the final advantage Eurasian societies had over other continents was a blessing in disguise: epidemic diseases. 

For those encountering epidemic microbes for the first time, the results are often deadly. However, if a person has survived previous exposure, they typically have some level of immunity to the disease. Therefore, societies that had the chance to develop immunities to epidemic diseases had a significant advantage over those that didn’t. 

Such societies could unwittingly wipe out a population of previously unexposed people without ever wielding a weapon, thereby clearing the way for new settlements on once-occupied land. For example, according to Diamond, archaeologists estimate that the population of the Americas declined by as much as 95% in the years following Columbus’s arrival—much of this was due to the spread of diseases such as smallpox. 

Factors That Contributed to the Development and Spread of Infectious Diseases

Why did societies in Eurasia harbor so many infectious diseases that worked to their advantage? Diamond suggests that the reasons are again linked to food production—namely, living close to domesticated animals and other humans. 

As Eurasian societies incorporated more animals into their growing, sedentary, food-producing towns and cities, they spent more time in close contact with those animals and with each other. This was the perfect breeding ground for disease. 

According to Diamond, scientists discovered that the major infectious diseases of recent history—including smallpox, tuberculosis, malaria, plague, measles, and cholera—have microbial ancestors that still infect common farm animals, such as pigs and cows. At some point in history, they believe, these microbial ancestors transferred from animals to humans, allowing humans to contract diseases that were previously exclusive to livestock. 

Once a microbe transfers from an animal host to a human host, it can begin to spread among the human population. When people live in relatively close proximity, this is easy. Diamond argues that Eurasian towns and cities, organized as they were around agriculture, provided numerous opportunities for diseases to spread among the population. Not only did people live and work close to one another, but they also used animal and human waste as fertilizers for their crops. 

Eurasians, therefore, had many opportunities to be infected by these microbes, says Diamond—epidemics were common throughout their history. After an epidemic wiped out a large portion of a society, people that survived tended to have genetic features that made them immune to the microbes that caused the epidemic. Thus, the Eurasian survivors and their children were largely protected from these deadly infections by the time they encountered the inhabitants of other continents, though they would still get sick from the microbes periodically. 

In this way, Eurasians acted as vectors, carrying with them microbes that could no longer kill them but could easily kill those without immunities. Eurasians’ germs went ahead of them, hitching a ride on explorers’ ships and landing on the shores of the Americas and isolated islands, wiping out entire civilizations without any armed conflict. 

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• An in-depth look into why societies historically took different paths
• The environmental factors that affected the historical development of those societies
• Why Eurasians had strategic advantages over non-Eurasians

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