One of the books that influenced my decision to switch from biology to history was Guns, Germs, and Steel. There are lots of good ideas there, and our subsequent empirical analyses with historical databases (a comprehensive summary in The Great Holocene Transformation, GHT) supported some of them, but not all. An example of what Jared Diamond got wrong is, actually, in the title of his book. His list, guns, germs, and steel, omits a much more important, even pivotal factor that explains “the fates of human societies” — horses and, especially, horse-riding.
Horseman on a Pazyryk felt carpet in the Hermitage Museum (St. Petersburg). Photo by the author
Using the Seshat data, my research team has analyzed the “fates” (well, evolution and dynamics) of hundreds of past societies spanning the globe and last 10,000 years. The most powerful and consistent factor that explains transitions from small-scale societies to large-scale societies organized as states turns out to be the sophistication of military technologies. And the most important of these was cavalry, the use of horse-riding in warfare.
Other factors, such as iron metallurgy (or Diamond’s steel), are also important, but they are trumped by the ability to ride horses. We show that when cavalry spreads to a region, it intensifies military competition between societies there. And then, 300-400 years later we start seeing unprecedentedly large empires. See the table below.
Source: from Table 7.1 in the Great Holocene Transformation
And those empires need sophisticated institutions that prevent them from splitting up. Even major advances in religion and philosophy, it turns out, were driven by horse-based warfare (see Table 8.2 in the GHT). It is not by chance that the Axial Age (c.800-200 BCE) followed shortly after cavalry spread from the Great Eurasian Steppe to the Imperial Belt below it. Each of the regions in the table above developed a major Axial Age ideology: Monotheism (Central), Buddhism (Southern), Confucianism (Eastern), and Greco-Roman philosophy (Western).
Of course, in history one must work hard to establish causality, because we cannot resort to experiments. But we can use “natural experiments.” As an example, horses were introduced into the Americas in 1492. By 1600 they spread into North America, and were eagerly adopted by Native Americans. And sure enough, by the 18th century we see the first imperial confederation of horse-riders in the Southern Great Plains — a polity very similar in nature to the empires of the Central Asians (such as the Scythians, the Turks, and the Mongols).
This was the “Comanche Empire”, or Comancheria (see the map below).
None of the Diamond’s trifecta help us understand the rise of the Comanche Empire. They had no steel, nor guns. Germs were a huge negative factor, a brake on Comanche development, because Eurasian diseases kept decimating the Comanche population, and they could only maintain their numbers by aggressively recruiting from other Native American populations. But they had horses, and that was enough.
But how did humans learn to ride horses? Horses are big, powerful, and — let’s be honest — mean creatures. I remember how I got on a horse for the first time in my life, more than 50 years ago. As soon as the animal realized that I was not an experienced rider, he headed for the nearest fence and attempted to smash my left knee against it. How did first riders solve this problem?
Four years ago I published an article stressing the role of horse bit and bridle in enabling horse riding. This insight is still valid, but new developments in archaeogenetics have substantially added to this story. These results were recently published in Science (see Selection at the GSDMC locus in horses and its implications for human mobility). As this article is behind the paywall, you may instead read a popular article in Science News, Horses may have become rideable with the help of a genetic mutation.
It turns out that there were two mutations that enabled humans to ride horses. The first one (ZFPM1) made horses less mean, while the second one (GSDMC) enabled them to better bear weight. Both gene variants were very rare at the beginning of the third millennium BCE, but became common by the end of the millennium. Clearly, there was very strong (artificial) selection that drove this genetic shift.
These two mutations, and especially ZFPM1, which yielded tame horses, thus, were a historical accident with huge consequences for human history. It would not be much exaggeration to say that it was thanks to ZFPM1 that mega-empires and mega-religions appeared during the Axial Age. A closely related species, the zebra, has no comparable mutation and countless attempts to domesticate them all failed.
By the way, the senior author of the Science article, Ludovic Orlando, recently published a book, Horses: A 4,000-Year Genetic Journey Across the World, which I heartily recommend (full disclosure: I also wrote an endorsement for it).
I see that quite a number of comments below disagreed with the main message of this post, that it was invention and adoption of horse riding that transformed past societies. Naturally, I did not have space in this post to develop this argument in detail, so you will have to go to my books, if interested.
The statistical pattern is very strong and is covered in detail in the Great Holocene Transformation.
In my other writings I also explain the causal mechanism underlying this statistical pattern. There was interesting variation in how causality flowed, depending on the proximity of the region in question to the Great Steppe and its suitability for rising horses. Thus, in the Central Eurasian Region (Iran-Mesopotamia) cavalry was adopted fairly rapidly and became the main striking force, increasing in importance from Assyria to the Achaemenids to the Parthians.
In the Western and Eastern regions, early empires struggled to secure plentiful supply of horses, and thus had to rely on infantry to counter the threat from cavalry armies. Because infantry is much less mobile, they had to compensate by recruiting huge numbers of them. This is what we see in China and Rome. For details, see chapter 9 of Ultrasociety.
Thus, causality could work in direct or indirect ways.
Finally, Eurasian regions very distant from the Steppe, such as Southeast Asia and Northwest Europe, did not develop megaempires before 1500, because they were insulated from cavalry armies. The rise of Europe was due to the next military revolution (gunpowder and sailing ships).
How do the pre 1492 South American empires fit into this picture? And horses played very little role in empire building in South East Asia too. While horses may have played a significant role in empire building in certain regions, they do not seem to have been essential requirement for empires to arise given the number of contrary cases.