A book that tries to answer the question of why human societies developed on different continents at different rates, by Jared Diamond.

Summary

The central question that the book tries to answer is: why did human development on different continents happen at such different rates? The author rejects the idea that the divergence of the human development rates was due to racial intelligence differences. The answer that it was due to the superior intellect of the European people was popular many years ago, but has fallen out of the academic consensus in recent times. Instead, the author’s answer, and the core thesis of the book, is that history evolved differently for different peoples because of environmental differences, not biological differences.

The book’s analysis begins at around 11,000 BC (i.e. about 13,000 years ago), and notes that it was a good starting point as the people on most continents were at about the same point in development at that time, with nobody having an obvious “head start”. In fact, if we were to point out some small advantages at this time, Africa had the biological and evolutionary advantage, while the Americas had the geological advantage. So how come Eurasia got ahead in the end? Here are the arguments of the book summarized as a series of “why” questions, going backwards in time.

Why did people on the Eurasian continent (and Europe specifically) come to dominate the world by the time that the New World was discovered?

Because they had guns, germs, and steel, while the others, such as the indigenous people on the American continents, did not. Let’s start with the guns and steel.

Why did the Eurasians have guns and steel when many others did not?

Because they were able to develop and diffuse languages, which are then used to much more effectively communicate and pass down ideas and thoughts, as well as more effectively organize larger number of people in more complex social structures. The people on other continents (e.g. New Guinea) were mostly stuck in much smaller groups, each with their own unique language, and extremely limited exchange of information between groups.

Why were the Eurasians able to develop and diffuse languages much better than people on other continents?

Because they were able to form significantly larger groups that were much more capable of accruing incremental gains from discoveries and inventions, and had the necessity for common shared languages to help govern social dynamics. Higher population density, increased life expectancy, and better quality of life all contributed to the increased development and diffusion of language.

Why were the Eurasians able to form much larger groups and societies than people on other continents?

Because they were able to develop and diffuse food production techniques, i.e. agriculture. It is extremely difficult for hunter-gatherer groups to get too big, due to their mobile nature. With agriculture, people can be more sedentary, and with a much more stable source of food, population grew dramatically faster, and larger groups became sustainable.

Why were the Eurasians able to develop and diffuse agriculture, while many people on other continents weren’t?

Because of the geography, climate, and fauna of the Eurasian continent. For agriculture to emerge as a superior strategy to displace hunter-gatherer, one would need a minimum set of crops, termed the “founder crops”, that is energy-dense, can provide the necessary nutrients of humans, and is relatively easy to cultivate (from the wild) and store. So the availability of local wild plant species that satisfy these requirements is critical, and the Fertile Crescent, commonly known as the cradle of civilization on Eurasia, was almost the perfect region for this. It began with 8 “founder crops” that formed a powerful agricultural package, which then spread to other places. In contrast, New Guinea is on the other extreme: the available plants there are not suited for the development of agriculture at all.

In addition, Eurasia was also much better suited for the diffusion, or spread of agriculture, because it is much larger along its west-east axis than its north-south axis. Since it is so difficult for an agricultural package of founder crops to emerge, it is even more difficult for different areas to independently develop their own packages. It is much easier to spread one that was created elsewhere. Because crops are heavily climate dependent, agriculture can spread much easier along the same latitude, because the climate variation is much lower. The Americas are much larger along their north-south axis, and this is not conducive to the diffusion of agriculture. Crops that can grow in Mexico cannot survive further up north in Minnesota. The domestication of animals also contributed greatly to the diffusion of agriculture, as well as language and technology, which we’ll get to soon.

That’s the end of the line for guns and steel. What about germs?

Why are germs even important?

Germs, or diseases in general, are very important because they not only served as an effective means of extermination (of many indigenous people), they also limit the movement and colonization of settlers. New Guinea, for example, was not colonized by the Europeans in part because of the presence of malaria there, which was new for the Europeans and made them sick. Continental Australia, on the other hand, was different, because most of southern Australia does not have malaria, and as a result was colonized by Europeans.

Why did the Eurasians have so many more deadly germs and diseases, such as smallpox, compared to people on other continents?

Because they had first domesticated animals on a large scale. The vastly increased human interactions with animals at close proximities contributed to the much greater spread of diseases. The people that did encounter these diseases have their immune system gradually adapted to better survive them.

Why were the Eurasians able to domesticate animals, while people on other continents had such a difficult time?

Again, just like the development of agriculture, it came down to the environment. There are five major large mammals, the domestication of which had large impacts on human development: sheep, goat, cow, pig, horse, and Eurasia had them all and then some (Eurasia had 14 minor mammals as well, such as donkeys). Only animals that make sense to be domesticated (e.g. grows fast, provides good “energy fed” to “energy provided” ratio, etc…), and can be domesticated (e.g. not too dangerous, survives well in captivity, can be selectively bred, etc…), could’ve been domesticated. This severely limited large mammal domestication by geographical region. The Americas famously had no native horses until the Europeans brought them over.

This concludes the Eurasia vs. other continents analysis. Lastly, there is the question to be asked within Eurasia.

Why were the Europeans the dominant force in recent centuries, and not the Middle East or the Far East?

This is a much more complex question, and not really the focus of the book. But the author does touch on the subject, speculating that receptivity of the cultures to external systems and ideas probably plays a large role.

Commentary

The continental axis thesis presented in the book seems a bit far-fetched. The author claims that Eurasia, being much wider (i.e. west-east axis) than taller, is much more conducive to the diffusion of both food production and other technologies. But the continents are so vast for the relative small size of people, that which axis is technically larger shouldn’t really make that big of a difference. However, it does make sense that the spread of food production is easier along the west-east axis.

The animal domestication analysis is a weaker argument compared to the one about the spread of agriculture. Why couldn’t Africans domesticate zebras? Why couldn’t Americans domesticate bisons? The author does point out various attributes that make certain animals on other continents difficult to domesticate, but makes no mention of how hard (or easy) it was for the Eurasians to domesticate the large domesticated mammals that we take for granted today, such as horses, cows. The truth might simply be that we don’t know how hard it was, because there were no written records back then, and this type of information is difficult to acquire archaeologically. The author’s analysis may be correct, but to me, it is also entirely possible that Eurasians managed to domesticate these large mammals not because they were inherently easy to be domesticated, but because of some other reason.

Overall the book does a great analysis on an extremely complex and difficult question. I would like to see more evidence and more rigor (as would the author, I believe), but the reality of the subject matter is that it will probably never be possible to have that level of analysis on this topic.

One interesting tidbit: the indigenous people in the American continents never adopted the wheel as a tool, but they did have them in the form of toys for children! This is most likely due to the lack of domesticable large mammals that can pull carts in the Americas. The mechanical advantages of the wheel is minimal when one still has to rely on human power, and it is only when utilizing animal power that their true advantage is realized. And without such animals being domesticated in the Americas, wheels never developed into a critical tool in transportation.