Guns, Germs and Steel summary

Food surpluses make complex human societies possible. Civilization is calorific – it’s what happens when you grow enough food to feed people who don’t work the land. 

In other words, it all starts with a warehouse full of grain. That’s how you feed an urban settlement – the civitas as it’s called in Latin, a language in which the word for “city” is etymologically related to “civilization.” Crowding lots of people together in cities is a recipe for disease, but that’s a good thing (evolutionarily speaking, anyway). Exposing populations to germs is how they develop immunity against diseases like smallpox. The city is also a hothouse for innovation. For one, it’s home to artisans and tinkerers as well as the wealthy patrons who sponsor their work. Then there’s the political factor. Cities compete with one another, and few things drive technological development like an arms race with a geopolitical rival. 

Add all that together and you get a technologically advanced, disease-resistant society that’s armed to the teeth. It’s a lethal combination – and a good description of the Spanish conquistadors who colonized the Americas. Guns and steel gave them an advantage on the battlefield; the diseases they brought with them decimated indigenous societies off it. 

Why, though, did Europeans like the Spanish have guns, germs, and steel while, say, the Incas of Peru didn’t? To answer that question, we need to turn to the origins of agriculture. 

The heartland of human agriculture is the Fertile Crescent – a curve of valleys and floodplains that arcs through eastern Turkey into the Levant and down the Euphrates river into Iraq. 

Some 12,000 years ago, foragers in this area began deliberately planting wild grasses with large, nutritious seed heads – the ancestors of wheat and barley. Without knowing it, they had sown humanity’s first crops. Lentils, olives, figs, almonds, and chickpeas followed. Next up were animals. Wild cattle, sheep, pigs, and goats were all domesticated in the Fertile Crescent. When the first cities began popping up after 7,500 BCE, their inhabitants relied on these foods. 

There were other centers of agricultural innovation and other bases for cuisines and cultures. China, for example, had rice and soy; Mexico had maize, beans, tomatoes, and squash. Other parts of the world weren’t blessed with such abundance. Sub-Saharan Africa had millet, sorghum, yams, and groundnuts – but these plants didn’t grow in the same places. Large African mammals, meanwhile, resisted domestication. The real problem, though, were geographical barriers preventing the diffusion of crops. Let’s break that down.

The Eurasian landmass falls along an east-west axis. Pretty much every fertile region lies at roughly the same latitude, meaning there are few seasonal differences and the days are similarly long or short. The upshot is that crops which thrive in one region tend to also do well in others. Buckwheat, for instance, grows just as happily on the Breton coast as it does in the Alpine foothills of northern Italy and on the plains of Ukraine or the islands of Japan. This geographical quirk meant that Eurasian societies could rapidly exchange crops, enlarge their food supplies, and accelerate the growth of large and complex civilizations.

The Americas and Africa, by contrast, fall on north-south axes that cover many different degrees of latitude. Exchanging crops between fertile regions in, say, Mexico and Peru is tricky since these areas have significantly different day lengths and seasonal patterns. The diffusion of agricultural practices along this axis is thus much slower than it is along the east-west axis. A plant that thrives in Mexico – maize is a good historical example – has to undergo a huge amount of genetic adaptation before it’s of any use to farmers in the Andes. 

The speed at which societies developed toward ever greater complexity was largely determined by agricultural capacities. The emergence of farming in Eurasia around 8,000 BCE led to a series of breakthroughs that other societies simply didn’t have the food surpluses to support. Metal tools, centralized states, and writing were well established in the Fertile Crescent by 2,500 BCE. In Africa and the Americas, such developments came much, much later. 

So Eurasia had a multi-millennium head start on other regions, and that advantage compounded down the centuries. By the time agricultural revolutions were reshaping societies in Africa and the Americas, Eurasian states had already developed ships capable of circumnavigating continents – not to mention muskets and cannons. That’s ultimately why Eurasians were able to conquer Australians, Americans, and Africans.