In Guns, Germs, and Steel, Jared Diamond outlines the theory of geographic determinism, the idea that the differences between societies and societal development arise primarily from geographical causes. The book is framed as a response to a question that Diamond heard from Yali, a charismatic New Guinean politician. Yali wanted to know, “Why is it that you white people developed so much cargo … but we black people had little cargo of our own?”—in other words, why have European societies been so militarily, economically, and technologically successful in the last 500 years, while other societies have not approached such a level of achievement?
In Part One of the book, Diamond sketches out the course of recent human history, emphasizing the differences between civilizations. Beginning about half a million years ago, the first human beings emerged in Africa, and eventually migrated around the rest of the world in search of game and other sources of food. About 11,000 years ago, certain human beings developed agriculture—a major milestone in human history. By the 15th century A.D., enormous differences had arisen between civilizations. For example, when Francisco Pizarro led a Spanish expedition to the Inca Empire in the early 16th century, he was able to defeat the Incan Emperor, Atahuallpa, easily. Why did the Europeans colonize the New World, and not the other way around?
In Part Two, Diamond talks about the dawn of agriculture and explains why it arose in certain parts of the world, but not others. Using carbon-dating technology, archaeologists have determined that the first sites of agriculture were Mesopotamia (in the Middle East), followed by Mesoamerica and China. Agriculture arose in those areas for a few reasons. Most of the human beings on the planet at the time were hunter-gatherers, meaning that they hunted game and picked nuts and berries for their food. But in the parts of the world that first developed agriculture, game and fruit were becoming scarcer, motivating experimentation with new forms of food production. In Mesopotamia, ancient humans used trial and error to learn how to plant certain large seeds in the earth, resulting in crops that could be harvested and converted into highly nutritious foods. These early peoples also learned how to domesticate wild animals, breeding familiar modern animals like dogs, cows, and horses. Humans used their domesticated animals to assist with agricultural work, while also learning how to domesticate certain wild crops, breeding most of the world’s familiar modern crops.
Agriculture arose in Mesoamerica and China. Due to environmental qualities like soil fertility, availability of domesticable animals, and availability of edible crops, however, it took a longer time for agriculture to supplant hunter-gatherer culture in most other regions. Once agriculture had arisen around the world, it spread or diffused to neighboring regions. By and large, Diamond argues, it is easier for ideas, goods, and foods to spread from east to west than it is for them to spread north and south—this is because the Earth spins east-west, meaning that areas with the same latitude share a similar climate and environment. Archaeological data indicates that agricultural innovations diffused east and west far sooner than they diffused north and south.
In Part Three, Diamond shows how basic agricultural differences between early societies magnified over time, leading to vast differences between societies’ health, technology, and social structure. First, he shows that agricultural societies developed immunities to deadly diseases like smallpox. Constant proximity to domesticated animals, combined with increased population density, meant that new germs were constantly circulating in agricultural societies. As a result, these societies became resistant to many epidemics—those who couldn’t survive died off, while those with immunities survived and passed on their immunities to their offspring.
Another important development in the history of agricultural societies was the invention of written language. While it’s difficult to show exactly why writing emerged in certain agricultural societies but not others, it’s clear that the structure of agriculture society (which requires lots of record-keeping for crops) put a high premium on a writing system. Furthermore, east-west diffusion patterns ensured that, once one society developed language, it diffused, along with agriculture itself, to surrounding areas, particularly those with similar latitude.
The history of language acts as a case study for the history of technology in general. While it’s again difficult to explain why certain inventors develop certain inventions, the structure of agricultural societies favored the invention of new technologies. This is true for a number of reasons. Agricultural societies lead to the creation of leisure time, since crops can be stored for long periods—in their leisure time, citizens of early agricultural societies experimented with the resources and raw materials around them. Additionally, agricultural societies were denser than hunter-gatherer societies, increasing the velocity with which people exchanged ideas. As a result, agricultural societies developed more new technologies than hunter-gatherer societies, and passed on their innovations to neighboring agricultural societies.
Ancient agricultural societies tend to develop into large, complex states. While the earliest agricultural societies were “bands” and small tribes, these small tribes gradually merged into larger and larger societies, either through conquering or mutual agreement. As societies became larger and denser, they tended to develop centralized structures of power—in other words, a central leadership that commanded a set of subordinate leaders, who in turn commanded local groups of people. States ruled through a balance of kleptocracy—i.e., leaders ordering their subjects to give up a portion of their possessions—and religion or patriotic fervor. By the 16th century—not coincidentally, the time when Europe was beginning its conquest of the New World—the state had become the dominant mode of society.
In Part Four, Diamond looks at a series of case studies that support his theory. In the first, he demonstrates that the New Guineans developed agriculture, sophisticated technology, and political centralization while the neighboring aborigines of Australia did not, due to geographic distances and factors like the ones sketched out in Part Two. He also argues that China was able to become the world’s first large, centralized state for environmental reasons—the temperate climate and homogeneous geography enabled easy communication and political unification between the states of China. The New Guineans were more successful than their neighbors, the peoples of Java and Borneo, in staving off European colonization and massacre in the 18th and 19th centuries, largely because their agricultural practices made them resistant to malaria, preventing colonists from staying for too long on their island. In the New World, agriculture arose in certain regions, but did not diffuse to neighboring regions due to the presence of geographic barriers like deserts and mountains. Finally, Diamond studies the history of Africa and argues that the Bantu peoples of North Africa were more militarily successful than their sub-Saharan neighbors because they developed some limited forms of agriculture. In the sub-Saharan environment, however, peoples didn’t have any way of developing agriculture, so their societies never had the time or organization to develop complex technologies.
In conclusion, Diamond argues, the differences between different peoples and societies of the world are largely attributable to geographic differences between different regions of the world. In certain parts of the world, humans began pursuing agriculture because the fertile soil and temperate climate made agriculture a good use of time and resources. Agricultural societies then gained tremendous advantages over non-agricultural societies, because the increase in leisure time enabled people to develop technologies and centralized political structures, and the proximity to animals gave people immunities to deadly diseases. As a result, some societies were able to conquer others.