Cultural Evolution of Pants II

Peter Turchin


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Part I here

While classical Greece and Rome produced excellent heavy infantry (hoplites), their cavalry was really pathetic. Yes, some of them (usually, the wealthy) rode horses. Among the Romans the upper class was even called ‘knights’ – equites, from equus, the Latin word for horse, but these ‘knights’ served mostly as officers and perhaps messengers. They never played a decisive role in battle. On the other hand, the greatest enemy of the Romans, Hannibal, knew how to use cavalry. As long as the Numidian horse riders fought on the side of Carthaginians, they trounced Romans, again and again. The Romans only won one major battle in that war, the Battle of Zama, which ended the war. Interestingly enough, the Numidians switched sides just prior to the battle…

The Romans eventually realized that they had to acquire reasonably efficient cavalry. At first, cavalry was an auxiliary force, manned by non-Roman citizens. During the Empire (from the first century AD on), the Romans began to employ cavalry more effectively. But riding a horse while wearing a tunic is not very comfortable. So Roman cavalrymen started wearing pants, or braccae as they called them (borrowing a Celtic term; this word eventually became ‘breeches’). After the collapse of the Roman Empire, Europe fell under the rule of warriors who fought from the horseback – the knights (this transition actually occurred during the Carolingian times, roughly eighth century AD). So wearing pants became associated with high-status men, and gradually spread to other males. By the way, I am talking here about the Mediterranean cultures. In northern Europe, of course, pants were worn by both Celtic and Germanic people at least from the Iron Age on.

The argument, then, is that the switch from the tunic to trousers in the civilized Europe followed the replacement of the hoplite by the knight. Historically there is a very strong correlation between horse-riding and pants. In Japan, for example, the traditional dress is kimono, but the warrior class (samurai) wore baggy pants (sometimes characterized as a divided skirt), hakama. Before the introduction of horses by Europeans (actually, re-introduction – horses were native to North America, but were hunted to extinction when humans first arrived there), civilized Amerindians wore kilts:

An elite Cahokian

But when the Plains Indians started riding horses they also adopted pants. Another correlation is that typically only men wear pants (or men are first to switch to wearing pants). One striking exception to this rule is the Amazons, who are, of course, famous for their horse-riding and archery skills:

An Amazon wearing pants

All these examples together amount to a strong, but circumstantial case for the association between horse-riding and wearing of pants. In one case, however, we have direct evidence for this connection.

The fifth through third centuries BC in China are known as the Warring States period. This period preceded the unification of China by the Qin emperor Shi Huangdi in 221 BC. It was also the time when a new type of Central Asian ‘barbarians’ arrived on the Chinese steppe frontier. These barbarians, the Hunnu (also referred to as Hu, Xiongnu, Hsiung-nu), were horse archers – and they, naturally, wore pants. The Chinese at the time wore robes.

Very soon the Hunnu demonstrated the superiority of cavalry over foot soldiers, and the rulers of Chinese states realized that they needed to acquire this military technology, both as a defense against the nomads, and in order to prevail in their struggle against other civilized states. King Wuling, who was the ruler of one of these states, Zhao, was keen on building up cavalry as an important element in the Zhao armies. However, he noticed that his commanders, continued to wear the normal court dress even on horseback, which made them very inefficient riders. He tried to order them to wear ‘barbarian’ clothing (that is, pants), but they refused.

Wuling then determined to lead by example. But it was a very difficult decision. To give you an idea, imagine that there is a compelling reason why we need to switch from wearing trousers to wearing a sarong, and it falls to President Obama to lead by example. Would he be re-elected?!

According to a Chinese chronicle of the Warring States period (Zhan Guo Ce), King Wuling confessed to an advisor, “Now I am about to adopt the Hu [Hunnu] costume and mounted archery … , and the world will certainly criticize me.” The advisor then urged the King to be resolute in his decision, but Wuling lamented, “It is not that I have any doubt concerning the dress of the Hu. I am afraid that everybody will laugh at me.” After musing that “The laughter of the stupid man is an affliction to the man of worth,” Wuling, nevertheless, decided that in the long run adopting the ‘barbarian’ dress will pay a dividend in an increased military efficiency and better prospects of expanding the state territory: “Even though it drives this generation to laugh at me, I shall undoubtedly possess the lands of the Hu and Ching-Shan.”

Fortified by this argument, Wuling started wearing pants in court. But this innovation was met with an enormous amount of resistance from the more conservative elements of Wuling’s government, starting from his own uncle and including many of his ministers. The resulting debate is covered in Zhan Guo Ce. Here’s an example of the argument against Wuling’s innovations:

“Now Your Majesty is changing what has been the practice from the beginning and is not according with the established customs. You are adopting the dress of the Hu and have no regard for the age. That is not how to instruct the people and perfect the rules of propriety. Moreover he who puts strange attire has a dissolute will. He who goes perversely against the established customs disorders the people. That is why he who presides over the state does not clothe himself in strange and perverse attire.” (quoted from a translation of Zhan Guo Ce by B.S. Bonsall)

I have quoted this chronicle at length because it gives us a wonderful insight into how difficult it is to go against the cultural inertia. As I said in the previous blog, social factors trump the considerations of mere comfort. Just imagine President Obama giving the State of the Union in a sarong, with the Republicans accusing him of undermining the very foundations of the American democracy…

In the end, pants won in China by the process of cultural group selection. Those states that did not adopt cavalry (and pants), or adopted them too slowly, lost to the states that did so early. In the end, it was the semi-barbarian state of Qin, located in the northwest and under the greatest pressure from the Central Asian horse archers, that evolved fastest into a highly efficient military machine and unified China by overrunning other Warring States.

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Steve Ehrstein

Wow, this is great. I have been using this exact example for years when teaching World History to high school students. As per the young, they always ask “Why study history? It’s just a bunch of old stories that have no relevance to now.” So I pose the question, “Why do you wear pants?” And the ball rolls from there. In the end we get to the conclusion that everything that happened in the past drives every single detail of their lives now; history is their map of time.

Peter Turchin

So when you ask them why we wear pants, and before you expose them to history, what are their typical responses?

By the way, I’ve been using the same approach with the students in my cultural evolution class at UConn.

Steve Ehrstein

Usually it is “to keep warm” or “to cover up” to which the reply is “So why not a tunic, sarong, or kilt? More comfortable for the menfolk.” It moves around to the idea of clothing as protection. Then “why protect the insides of our legs?” I then ask if anyone owns, cares for or has ridden horses – in our area that gets quite a few of them thinking. Then we move on to where horses are from. Eventually I tie it all back in with a quick geography and cultural diffusion lesson using maps and timelines. Then full circle back to “why study history?”

Yasha Hartberg

I’d like sometime, Peter, to read a followup to this series of blogs entitled why do we STILL wear pants. This is a great evolutionary story, of course, but it only explains the genesis of pants wearing. The far more intriguing question to my mind is not the origins, but rather the persistence of this practice in modern society where, after all, very few people ride horses and where cavalry (in the original sense of the word) no longer plays any role at all on the modern battlefield. Yet not only do we continue to wear pants, the practice has spread, both within our own societies (to women) and to cultures we’ve come into contact with.

Peter Turchin

Yasha, cultural persistence is a very general process. It’s basically the null model. Culture is inertial, it is transmitted from the previous generation to the next. In other words, we tend to do things the way our ancestors did. So what needs to be explained is change.

In genetic evolution, it is also change that needs to be explained, not persistence.

The question how women started wearing pants is an interesting one. I know a little about it, but not enough to write a blog.

Yasha Hartberg

Although your position is a common one, Peter, I couldn’t disagree more. To keep our examples within the realm of clothing, your position suggests that we require an evolutionary explanation for why some fashions change on a yearly basis while we need no evolutionary explanation for why blue jeans have remained a staple of American clothing for 150 years or so. I find that problematic. Why should we tend to wear some clothes that our ancestors did yet not others? What makes one article of clothing relatively impervious to change while others seem almost incapable of persistence? Sometimes persistence is undoubtedly the result of simple inertia, but often deeper processes are at work.

Yes, change is an important aspect of evolutionary theory, but so is robustness which is, itself, an evolved property that is not only adaptive in many contexts, but also a necessary component for evolvability. Assuming that it is simply a null model misses extremely important evolutionary processes that not only constrain change but also that make change possible.

Peter Turchin

No, it doesn’t. The null model is dp/dt = 0, where p is the frequency of the trait, and dp/dt it’s rate of change. If there is change, then
dp/dt = c, or dp/dt = cp, depending on the details of how the trait changes. In any case, the greater the rate parameter, c, the faster the trait will change. So if c is high enough you will have yearly changes of fashion, if c is small enough, then it will take decades or even centuries.

Of course, we need theory to tell us something useful about the magnitude of c.

Yasha Hartberg

I would invite you, Peter, to review the literature regarding the evolution of robustness and evolvability. In particular, you might start with concepts such as pleiotropy and canalization. These are general evolutionary processes and there is absolutely no reason to believe they are not also important in cultural evolution.

Yasha Hartberg

Peter, I’ve written a more detailed response than space here would allow. If you’re interested, it can be found at


Stasis itself is fairly widely considered to be an important evolutionary phenomenon. The case for that was made long ago – in Eldredge, Niles and S. J. Gould (1972). “Punctuated equilibria: an alternative to phyletic gradualism”.

Matt Zimmerman

Hi Peter, This question of persistence of pants may be partially explained by something like the Boyd and Richerson: “punishment stabilizes any norm – especially not very costly ones.”

Juan Alfonso del Busto

The persistence can also be explained by sensory bias or social biases like Boyd and Richerson´s prestige bias. Along with these biases, conformity bias and conformity enforcement can also play important roles here. Inertia can be viewed mainly in terms of conformity bias, whereas change can be viewed in terms of (cultural) drift, migration and mutation (random or designed).
The yearly changes in fashion are not “natural”, they are deliberately fostered by the clothing industry which survives by creating an extremely fast programmed psychological obsolescence for its products. This industry introduces and increases the frequency of non-random mutations through prestige bias (famous people wearing Nike shoes or slim-fit levi´s), which often undergo runaway processes analogous to those driven by sexual selection as status markers or fitness indicators. Remember Zahavi´s Handicap principle.
By the way Peter, this is how, I think, the tie evolved.


Is there a strong record of men initiating social change for the sake of aesthetic expression? Men and women may seek power, or position but male culuture doesn’t often seek to “express itself” visually and without a compelling social need why would people move away from pants? The only social force seeking these changes are, as outlined in the kilt’s discussion off this blog, are transgender or “freestylers” who, as that blog indicates, have limited social power.

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