If you are in North America or Western Europe and look around, on any particular day, you will find most people wearing pants. But why is it the standard item of clothing for people, especially men belonging to the Western civilization. Why not a kilt, a robe, a tunic, a sarong, or a toga?
I asked this question here two days ago and got a variety of replies. As you will see, my preferred explanation will use several of the reasons people brought up. However, the most common theme in the discussion was utility or convenience. Here’s where I disagree: comfort provides (at most) 10 percent of the explanation. Just think of that ridiculous contraption, the tie, that you have to wear if you want to be elected to public office, or to become CEO. No, the much more important factors are the social ones: conforming to social norms and signaling social identity or status.
To convince you of the primacy of social factors I urge you to check out this extremely funny site, Bravehearts in Kilts Against Trouser Tyranny:
This site is hilarious not because the Bravehearts in Kilts are stupid, but precisely for the opposite reason. Once you have read their passionate defense of the kilt, you (at least if you are a male) will realize that it is us, pant-wearers, who are stupid. In warm climates or during summers in the temperate zone the kilt is much more comfortable to wear than the jeans.
Male’s testes hang outside the body for a reason: the optimum temperature for spermatogenesis is a couple of degrees less than the body temperature. So wearing tight pants kinda defeats that purpose.
A skirt is more comfortable in summer than pants (image from kiltmen.com)
But I am not switching to the kilt any time soon. Let’s face it, men in skirts look funny. The social factors trump convenience. Take a look at this web page (Confronting the Objections of Trouser Tyrants – Wives and Parents), just to see the kind of uphill battle the Bravehearts face:
Good luck to them.
In the Arctic and during the temperate winter pants are very convenient, there is not question about it (although let’s not forget that in places like Russia or Sweden winters are pretty cold, yet until recently half of the population wore skirts even in winter). But plenty of people living in warm climates wear pants. How did this social convention get started?
If we go back to the ‘Cradle of the Western Civilization,’ the Mediterranean region two thousand years ago, we will find that none of the civilized people there (notably the Greeks and the Romans, but also Phoenicians and Egyptians) wore pants.
Clothing worn by the Classical Romans belonging to different classes. A toga, by the way, was not particularly convenient type of clothing to wear. You couldn’t even wrap yourself in it without help. So it probably started as a status statement (“I am rich, I have slaves”). During the Classical period, only Roman citizens were allowed to wear a toga. You had to wear it if you wanted to be elected to office (so it was the Roman equivalent of suit and tie). (image from http://www.vroma.org/~bmcmanus/clothing_sources.html)
The only people you would see wearing pants were the visiting ‘barbarians,’ like the Scythians (see image), or Medes and Persians (the latter were, of course, a highly civilized people, but the Greeks still considered them ‘barbarians’).
In Iron Age Europe only ‘barbarians,’ like these two Scythian warriors, wore pants (image from http://www.german-hosiery-museum.de)
Just as a sight of a man in a skirt causes uncontrollable laughter in a typical Westerner today (unless you are a Scot), we know from the their literature that wearing pants seemed weird and even ridiculous to the Greeks. The Classical Greek did not even have a word for ‘trousers.’ There are two famous passages referring to trousers. One is from The Wasps by Aristophanes about a battle in which the Persians were defeated: “Then we pursued them, harpooning them through their baggy trousers.” Another is from Euripides’ Cyclops about the seduction of Helen by Paris: “The sight of a man with embroidered breeches on his legs and a golden chain about his neck so fluttered her, that she left Menelaus, her excellent little husband.”
Apparently the actual word used in both passages is ‘sack,’ translated in these two passages as ‘baggy trousers’ or ‘breeches.’ So, according to the Greeks, the Persians were running away with bags flapping around their legs…
The basic garment worn by the Greeks was the chiton (basically, same as the Roman tunic). And wearing ‘sacks’ around their legs was something that only barbarians did. The Romans of the Classical Age felt the same way. Citizens were required to wear togas for any official functions, and at other times (e.g., for war) they wore tunics.
A Greek charioteer in a chiton (from Wikipedia)
So if you go back to Italy of the Classical Age, nobody (apart from barbarians) is wearing trousers. Fast forward a thousand years to medieval Italy and all men are wearing a kind of trousers (hose).
During the Middle Ages Italian men wore tight pants, a hose (image from Google)
Why did the Italians switch from tunics to pants? The answer is the horse. Not only are the horses responsible for why we live in complex, large-scale societies (or, at least, how such large-scale societies first evolved), they are also the reason why males have to swelter in pants in summer, instead of wearing the cool kilt. As I will discuss in my next blog, there is an exceedingly close historical correlation between the adoption of cavalry and switching to wearing pants.
Some readers of this blog may be getting a bit tired of the group selection debate, which can get rather abstruse. So let’s shift gears on this holiday, when Americans celebrate their national independence, and consider a lighter topic.
Why do we wear pants? More specifically, why are trousers (breeches, jeans, slacks, pantaloons) a standard item of clothing worn by men in Western societies? Why shouldn’t it be a kilt, a robe, a chiton, or a toga? Clearly, I have my own answer, but I first want to hear what others think. Please write your suggestions as comments on the blog, or send them to me by e-mail. I will compile your answers and include them in the blog that I am writing on cultural evolution of pants, and post it in a day or two.
If CMLS (cultural multilevel selection) doesn’t help to explain human social evolution, how did human ultrasociality (ability to cooperate in huge groups of unrelated individuals) evolve? Steven Pinker falls back on the ‘usual suspects,’ kin selection and reciprocal altruism: “The huge literature on the evolution of cooperation in humans has done quite well by applying the two gene-level explanations for altruism from evolutionary biology, nepotism and reciprocity, each with a few twists entailed by the complexity of human cognition. … A vast amount of human altruism can be explained in this way.”
The problem with these two theories is that they cannot explain the evolution of human ultrasociality. Even in bands of hunter-gatherers the majority (three-quarters, according to recent estimates; Hill et al. 2011) are unrelated to ‘ego,’ and of course the average relatedness among huge societies of hundreds of millions of individuals is indistinguishable from zero. As to reciprocity, models show that it can work in small groups of few individuals, but it breaks down completely once the group size exceeds ten. This was clear to such eighteenth century thinkers as David Hume:
Two neighbors agree to drain a meadow, which they possess in common; because ’tis easy for them to know each other’s mind; and each must perceive, that the immediate consequence of his failing in his part is abandoning of the whole project. But ’tis very difficult and indeed impossible, that a thousand persons shou’d agree in any such action; it being difficult for them to concert so complicated a design, and still more difficult for them to execute; while each seeks a pretext to free himself of the trouble and expense, and wou’d lay the whole burden on others.
Although Pinker does not explicitly acknowledge this point, he seems aware that straightforward “nepotism and reciprocity” cannot explain extensive cooperation in groups of millions of people. Here’s where he brings in “cognitive twists.” The basic idea is that human propensities for cooperation with kin and in reciprocal settings are manipulated by other humans.
This is a version of the ‘big mistake’ hypothesis (as Boyd and Richerson have characterized this current in the Evolutionary Psychology theorizing), according to which people are somehow ‘fooled’ to cooperate with millions of other members of their society because they mistakenly consider them as relatives.
The version advocated by Pinker can be called the ‘Great Deception’ hypothesis. He uses this to explain away suicide terrorism. But what about volunteering for military service in times of war? Pinker writes, “Even in historical instances in which men enthusiastically volunteered for military service (as they did in World War I), they were usually victims of positive illusions which led them to expect a quick victory and a low risk of dying in combat.” But that does not describe the actual historical cases, e.g., volunteering by the British men during WWI. The British continued to volunteer long after it became abundantly clear that there will be no quick victory and that the war was a slaughterhouse. The British authorities did not need to implement the draft until 1916 (for a more nuanced discussion of this case, see my War and Peace and War).
Furthermore, a big part of Pinker’s argument is that it is “other humans” (presumably, political elites) who fool common people to fight and die to advance their nefarious ends. But there are many counterexamples. To give just one, the ruling elites of the Roman Republic (the senatorial class) bore their fair share (and perhaps even more) of the burden of Rome’s continuous warfare. The senatorial class fought and died on the front lines during the battles of the Second Punic War. Proportionately, the Senate lost more members than common citizens in such defeats as Lake Trasimene and Cannae. So who was fooling Roman patricians to sacrifice their lives for the sake of Patria?
There are many other examples in cultural evolution in which political elites (that is, the segment of the society that concentrates power in their hands) end up sacrificing their fitness. In a recent paper, Joe Henrich and coauthors analyze the spread of monogamy using the framework of cultural group selection. Without such a perspective it is very difficult to understand why would male elites agree to limit themselves to a single wife. Since the number of offspring left by a human male is determined primarily by the number of wives he has, one would expect that polygamy would greatly benefit wealthy and powerful males. Yet monogamy spread, and Henrich et al. make a credible case that it did so by the process of cultural group selection.
In the final analysis, research programs (sensu Lakatos) are judged by how productive they were. The CMLS framework has motivated a vibrant program of model development and empirical tests. The ‘Big Mistake’ and ‘Great Deception’ hypotheses of the Evolutionary Psychology have failed to lead to similar developments. It is not even clear to me how we could test Great Deception explanations empirically (can it be falsified?). In contrast, the young discipline of CMLS has already shown that it can generate testable (and empirically tested) predictions. In the end, I will not be surprised if the CMLS theory ends up completely transforming our understanding of human history.
A recurrent idea in Steven Pinker’s essay is that group selection “adds little to what we have always called ‘history’.” I argue, on the contrary, that cultural multi-level selection (CMLS) provides a highly productive theoretical framework for the study of human history, including (and integrating over) both modeling and empirical approaches. Notable examples developed during the last decade include the evolution of religion (e.g., in the work of David Sloan Wilson and Richard Bellah), the evolution of monogamy (e.g., the work of Joseph Henrich), and my own work on the evolution of social complexity. It is worth noting that I came to CMLS indirectly. My own research has focused on the mechanisms that underlie the rise – and recurrent demise – of historical large-scale societies (‘megaempires’), and so far I found no other framework that could even approach the utility of CMLS.
Large-scale human societies are not simply undifferentiated ensembles of individuals. They are ‘segmentary’ in the anthropological jargon, that is, their internal structure can be represented as groups nested within groups nested within groups … and so on. In other words, human societies are truly multilevel entities and evolution of large-scale sociality in humans was not just one major evolutionary transition, but a whole cascade of them. In order for societies to exist without fragmenting, forces holding together groups at various levels must overcome centrifugal tendencies (and when they fail to do so, the result is a failed state). A major theoretical result in MLS is the Price equation, which specifies the conditions under which the balance shifts either toward integration, or disintegration.
Cultural traits of central interest are prosocial norms and institutions (for more on this, see recent articles by Peter Richerson, Sam Bowles, and others). They are critical for the stability and functioning of large-scale societies, but have very significant costs at lower levels of social organization. Thus, we have a typical multilevel situation, in which traits are under divergent selective pressures acting at different levels of organization.
CMLS is much more than a metaphor, it yields quantitative predictions that can be (and have been) tested with historical data. The Price equation includes not only coefficients of selective pressures (working against each other at lower vs. higher levels), but also cultural variances at two (or more) levels. Incidentally, the critical importance of variances is a new insight for most social scientists, not steeped in evolutionary theory. But we can go beyond such conceptual insights to empirical applications. In particular, the Price equation suggests that large states should arise in regions where culturally very different people are in contact, and where interpolity competition – warfare – is particularly intense.
In a recent article, I tested this prediction for the period of human history between 500 BCE and 1500 CE, and found a very good match between predictions and data. A further development of this approach is the current collaborative project with Tom Currie, Edward Turner, and Sergey Gavrilets. We have developed an agent-based model of cultural evolution of prosocial institutions on a realistic landscape (Afroeurasia between 1500 BCE and 1500 CE). We also quantified the spatiotemporal distribution of historical large-scale societies by counting how frequently each 100 × 100 km square found itself within a large territorial polity. Our results indicate that the model predicts over 60 percent of variance in the data, a level of precision practically unheard of in historical applications.
Thus, the theoretical framework of CMLS provides not only new conceptual insights into the study of human history, but it also guides empirical research and, most notably, yields predictions that exhibit an excellent match with data.
This is a draft of a commentary that I intend to submit to The Edge, where Steven Pinker’s essay was published. I would really appreciate any comments. The commentary is a bit too long (600 instead of 500 words), so suggestions on which pieces are not critical would also be very welcome.
An additional note:
After posting the commentary I discovered the “Editorial Marching Orders” for publishing comments at the Edge, which specifically prohibits ‘self-promotion’. As my counter-example to Pinker’s claim that group selection adds little to the study of human history relies on my own work, this disqualifies my comment for the Edge. So I will have to either rethink my commentary, or simply not bother submitting it to the Edge. In any case, I remain very interested in comments from all.
A (hopefully) final note:
I have now heard that the restriction against referring to own works has been relaxed, so from this point of view, my commentary should be OK after additional editing.
Social norms and institutions have been the subject of several blogs by me and others on the Social Evolution Forum. Understanding how social norms are maintained and, especially, how they change (see, e.g., the post by Bernard Winograd) is a central issue of social evolution.
I have been thinking about this issue during my sojourns in Frankfurt and Moscow, with norms governing interactions between drivers and pedestrians as a specific example. These norms vary dramatically between countries, and even regions within countries. In New York City, for example, pedestrians pay no attention to traffic lights – you check the traffic and cross the street. In Seattle, on the other hand, you are not supposed to do that, and cops will actually write you a ticket for jaywalking (at least, they did in the 1980s, when I did my post-doc there).
In Germany pedestrians are very disciplined and will wait to cross the street until they get the green light – even if there is no traffic. For somebody raised in New York (and many other places outside of Germanic countries), this feels really weird, and even unnatural. I noticed that many tourists crossed illegally, with natives looking upon such ‘antisocial behavior’ disapprovingly. Frankfurt is not a big tourist destination, but I wonder whether the norm prohibiting jaywalking is sustainable in cities where the majority of pedestrians are foreigners. Theoretically, if enough people disregard a norm, it should collapse.
Then there are norms regulating when drivers should yield to pedestrians. In many countries, including Russia, pedestrians have the right of way on zebra-crossings. But, as we all know well, just having a law on the books doesn’t mean that it is actually followed. When I again started visiting Russia regularly in the 1990s, I noticed with dismay that drivers paid no attention to pedestrians trying to cross a street. Using zebra crossings became a deadly game of the Russian roulette (sorry about the cliché).
When asked, my friends offered several explanations. One obvious possibility was that the behavior of drivers simply reflected the general unraveling of cooperative norms that accompanied the civilizational and societal collapse of the Soviet Union. Another explanation was that the 1990s were the first decade when the Russians began using automobiles massively, and the norms of civilized behavior simply had not had a chance to spread though the population of new drivers. The third one pointed to the influx of drivers from the North- and Trans-Caucasian republics (then, as now, most taxi drivers in Moscow came from that region), who brought a different set of norms with them.
A more general (ultimate, rather than proximate) explanation is suggested by recent theoretical research on the evolution of cooperation. Cooperative equilibria tend to be fragile, and can collapse in no time at all. A more interesting and difficult question is how we can go from a noncooperative equilibrium to a cooperative equilibrium. This is where the story gets interesting.
During the early 2000s, drivers gradually started treating pedestrians more considerately. This trend became very noticeable last time I was in Moscow, a week ago. Now when you come to a zebra crossing drivers routinely stop for you (a major exception, however, is zebra crossings across very busy roads with four or more lanes). This seems to be a true equilibrium, because all players expect drivers to stop for pedestrians. This includes other drivers, which is important because previously a major worry was that if you stop at a zebra, you could be hit from behind by another car that did not expect you to do it. Pedestrians now start crossing fairly confidently, whereas during the 1990s they behaved like deer during the hunting season. And even cops started enforcing the law, which is probably the most amazing development, given how notoriously corrupt the road police are in Russia.
It’s interesting to speculate how this positive change came about. A part of the explanation is that there were several well-publicized cases of drivers killing pedestrians on zebra walks. Two years ago a law was passed that required drivers to stop when a pedestrian approached a zebra crossing (previously they were required to stop only when someone was already crossing). But while this is undoubtedly part of the story, I feel that laws by themselves are insufficient; there must also be a cultural change that enables laws to become effective.
I queried my local informants and I heard a similar story from three independent sources. Basically, the claim is that this is a case of cultural diffusion of social norms from European countries, carried by Russians who visit them as tourists and businessmen. One of my friends related to me the story of how he was driving in Germany several years ago, and habitually did not stop for pedestrians at a zebra crossing. He particularly noted how those people looked at him as he was whizzing by.
Humans are very good both at conveying the information that a norm is being violated, and are also very sensitive to receiving such signals. Maintaining cooperative norms is much easier if signals are sent to norm violators by third parties. In Moscow now pedestrians expect cars to stop for them, and they will look pointedly at those who don’t do so. This bodes well for the stability of the new cooperative equilibrium. Additionally, while cops should fine violators, my guess is that it is more important that society at large clearly expresses its disapproval of norm violators. We have a legal speed limit of 65 mph on highways in the United States, yet despite millions of tickets handed out, the majority in the state where I live drives at around 80 mph. There is simply no social stigma associated with driving above the speed limit.
The observation that sometimes cooperative norms spread is heartening, but in reality we don’t have a general understanding of how we can flip the society to a cooperative equilibrium. Perhaps the new science of cultural evolution will eventually help us to answer this question!
I am writing this in Frankfurt, where we have just concluded a week-long meeting on cultural evolution. I was hoping to write about it earlier, but this meeting has been so intense that I literally could not find a couple of hours to put my impressions on paper (or computer screen). The meeting was organized by Strüngmann Forum. There are no talks. Instead some participants write position papers that serve as a basis for discussions (mine was on the evolutionary transition from small-scale to large-scale societies, naturally). During a typical conference there are always talks that are less interesting, and that gives one the opportunity to write something, but not in this one.
Most discussions were within four subgroups, meeting separately, although there also was plenty of opportunity to attend other groups. My group focused on the evolution of small-scale and large-scale societies in humans. We had a developmental psychologist, primatologists, anthropologists, and modelers in the group. A really interesting and novel aspect for me was our focus on psychological predispositions (that are genetically determined), which made the transition from very small-scale societies of our putative ape ancestors to small-scale societies of humans (which are huge by comparison with other mammals, such as chimps or wolves). And then what role these psychological mechanisms played in the transition to large-scale societies. Basically, these predispositions were the building blocks that evolution used in constructing our societies
As an example, humans are primed to recognize norms (socially transmitted rules of behavior) by extracting the relevant information from observations of how other people behave. This ability appears very early in infants, but great apes don’t have it. And, of course, the norms and institutions are at the core of human sociality, both in small-scale and in large-scale societies. But not all of our behavioral predispositions played the same role at different phases of human evolution. For example, inequity aversion was a key enabler of cooperation in small-scale societies. On the other hand, it was a barrier for the transition to large-scale societies that evolution had to overcome. This is a very interesting subject, on which I have already touched earlier, and will need to return to it again.
Group 2 addressed the evolution of technology and science. Technology is a great case study of cultural evolution because it is relatively easy to trace how it develops (usually, in small increments and as a result of much blind variation). Group 3 discussed the evolution of language, our best example of gene-culture coevolution. As our ancestors began using vocalizations for communication, there was a very strong genetic evolution that remodeled our ability to produce sounds very precisely, and also our ability to distinguish speech patterns (for example, humans are extremely good at detecting accents). The evolution pressure was very strong, because those who could not express themselves well (and understand others well) would not get mates, lose out in negotiations, etc. Just think of the fact that in English the word ‘dumb’ is often used as a synonym for ‘stupid.’
Group 4 was devoted to the evolution of religion. This is the one I spent the most time with because I am very fascinated by the question of how religion, especially Axial religions, enabled the rise of really large societies. In fact, I am involved in a collaboration where we plan to add religious variables to our historical database of cultural evolution, which will enable us to test a variety of theories on the interrelations of organized religion and social complexity.
One thing that really struck me at this meeting is how far cultural evolution has progressed in the last decade or so. In particular, there was a great degree of consensus among the participants that cultural group selection is the only general mechanism for explaining how human sociality evolved that really has the logical coherence and empirical support. I already had this experience during our NIMBioS workshop in Knoxville, and there was very little overlap between the NIMBioS group and the Frankfurt group (about 45 people were in attendance here). There is really some kind of sea change occurring right now. It looks like cultural evolution is in phase transition from a marginal new discipline to a field that will establish the next paradigm of how we think about human nature and the nature of human societies.
I’ll have to deal with these fascinating issues in later blogs, because now I have to rush to the airport for my flight to Moscow, where I will probably not have a good e-mail connection. So I will resume blogging after I get back from Europe two weeks from now.
The central question of social evolution is how we can understand the rise of complex societies with extensive cooperation among millions (and more) of people. In less technical terms, what are the origins of civilizations and empires? I couldn’t help but think about this question during my visit to the Cahokia Mounds. Why was the largest-scale society in North America located in southern Illinois? Why did it arise around 1000 CE?
As readers of my books know, my favored explanation for the evolution of social complexity is the theory of cultural group (better, multilevel) selection. Since throughout most of human history competition between societies usually took the form of warfare, we need to look to the patterns of warfare to understand the rise of civilizations.
Take the case of the Sinic (Chinese) civilization. Over the last three thousand years the cradle of the Chinese civilization, the Yellow River Basin, has been unified by one empire after another. There is no other region on Earth that could rival the Yellow River Basin in the intensity of ‘imperiogenesis’ (proportion of time that it found itself within a large empire). In a series of publications (for example, this one) I have argued that the explanation of this remarkable pattern has to do with the very intensive warfare between nomadic pastoralists (Hunnu, Turks, Mongols, etc) and the agrarian Chinese. This is why China was typically unified from the North (and most frequently from the Northwest) – it was the military pressure from the Great Eurasian Steppe that selected for unusually cohesive North Chinese societies, which then would go on to build huge empires by conquering the rest of East Asia.
Steppe frontiers are crucibles of empires; you add a major river and you are practically guaranteed to have an imperiogenesis hotspot. Examples are numerous: the Nile, the Tigris-Euphrates, and the Indus are the usual suspects. But the first empires in sub-Saharan Africa (Ghana, Mali, and Songhai) arose on the Niger River where it flows through the Sahel. This correlation has been long noted. Karl Wittfogel attempted to explain this observation with his theory of ‘hydraulic empires’, based on the control of irrigation by state bureaucracy, but this theory has been empirically disproved. For example, the major river of eastern Europe, the Volga, was the cradle of a number of empires (Bulghar, the Kazan Khanate, and, most notably, Muscovy-Russia), none of which relied on intensive irrigation. Nor did the Chinese along the Yellow River. In other civilizations irrigation was typically a local, rather than an imperial concern. Most likely, the river effect is due to a combination of good environment for intensive agriculture on alluvial soils and the ease of communications (because transporting goods on water was an order of magnitude cheaper than carting them on land).
Whatever the causal factors, let’s go back to the empirical generalization, that there is something special about a major river flowing though a steppe frontier that predisposes such places to engender complex societies. If you were to look within the American landmass north of Mexico for a spot that would fit this description best, where would it be? Incredibly, southern Illinois.
First, the mightiest river in North America is indisputably the Mississippi. Second, as the Mississippi flows South along the boundary of Missouri and Illinois, it leaves the steppe region (known in North America as the Prairie) just North of modern St. Louis/ancient Cahokia. This can be seen on the map of Gross Primary Productivity, where the Prairie is colored in browns and yellows:
or even more clearly on the map of major biomes from the Cahokia Mounds Interpretive Center:
Note also that Cahokia is located in the far northwest corner of the Mississippian Cultural Area:
This is eerily similar to China, which was invariably unified from the North, and most usually from the Northwest. As a result, Chinese capitals were always located on the Northwestern frontier with the steppe, not in the Yangzi River valley, which is much more centrally located and has much more productive agriculture. In the Mississippian culture, similarly, the greatest plant productivity is in the Southeast (see the map of Gross Primary Production above), yet the first and the largest urban center, Cahokia, is located in the Northwest, on the steppe frontier.
So there are several remarkable similarities between the Chinese and Mississippian civilizations. However, I do not want to push the analogy too far. The population of urban Cahokia was perhaps 30,000 people, whereas populations of Chinese capitals, both in Ancient and Medieval times, easily topped one million. The scale of the Cahokian polity was an order (or two) of magnitude less than that of ancient Chinese empires.
A closer Chinese analog of Cahokia is not the later Imperial period, but the Erlitou Culture (early II millennium BCE), which has been tentatively identified with the shadowy Xia Dynasty (which preceded a better known Shang period). Like Cahokia, the Erlitou Culture was also in the same ambiguous position of being either a very complex chiefdom, or an archaic state (recent excavations suggest that it has achieved the statehood). And we know very little about the territorial extent of the Erlitou/Xia state, just as we are unsure about how far the rule of Cahokia extended. Other such ambiguous cultures include Uruk in Mesopotamia (IV millennium BCE), Egypt under the Dynasty 0 (late IV millennium BCE), and the Indus Valley Civilization (III millennium BCE). Archaeologists still argue whether Uruk, or Mohenjo-Daro, were city-states, or capitals of extensive territorial states.
So Cahokia seems similar to the very first urbanized societies of the Old World. Had not the Europeans arrived in the New World around 1500 CE, perhaps the Mississippian culture would also rise again – and fall again, and so on – in a typical sequence of rise and demise that was the historical pattern in Egypt, Mesopotamia, India, and China. However, the urbanized Mississippian culture arose much later than its Old World analogs. Why couldn’t a complex society evolve in North America before c.1000 CE?
I think there are two factors that determined the timing of the rise of the Mississippian civilization. First, it was only during the first millennium of the Common Era that intensive maize agriculture developed in the Mississippian region. As we know well, a productive agrarian base is a necessary condition for large-scale, complex societies. This is the standard explanation that you will see in archaeological books and articles. But intensive agriculture is only a necessary condition, not a sufficient one. Many regions on Earth had agriculture, but did not develop states until they were colonized by European Great Powers.
The second factor, I would argue, was the diffusion of bow-and-arrows into the Mississippian region from the northwest during the second half of the first millennium. The introduction of this novel military technology must have led to more destructive warfare in the Mississippian region, leading to more intense cultural group selection, and then on to larger-scale societies. Perhaps people of the Oneota Culture, who lived in the Prairies to the northwest of Cahokia, were the functional equivalent of the steppe nomads northwest of the Chinese?
Of course, archers on foot in the American Great Plains are a far cry from the mounted archers of the Great Eurasian Steppe. They were probably a much lesser threat to agrarian societies. But the Mississippian polities were also of a much lesser scale than the Chinese empires. It is a reasonable proposition that similar evolutionary mechanisms were operating, but on a much reduced scale in North America, compared to the Old World.
During the Spring semester I teach a class in Cultural Evolution for about 150 students. We use a ‘clicker’ technology that allows me to poll all students in the class electronically. Every year I ask them, in what state was the most complex, largest-scale pre-Columbian society in North America located? Most students choose New Mexico, because they have heard about the Anasazi. But the Ancient Pueblo People lived in small-scale, uncentralized societies. It is remarkable, but almost none of my students choose the correct answer – Southern Illinois, just across the Mississippi River from St. Louis.
I had wanted to visit Cahokia Mounds for years, and finally my chance came during the trip to St. Louis two weeks ago. What follows is my photo reportage of the visit to the site.
The site itself is not particularly impressive. Here’s the view of the largest mound, known as the Monks Mound:
The staircase that leads to the top of the mound is, of course, a modern addition:
From the top of the Monks Mound one can look across what used to be a huge public space to the Fox Mound:
The folks at the Cahokia Mounds State Historic Museum Society have done a great job of reconstruction of what the Mississippian culture might have looked. Naturally, there is a lot of guesswork involved, but as our archaeological knowledge gets better, many of the errors of interpretation will be corrected.
Here’s an artist’s reconstruction of central Cahokia (by the way, obviously, we don’t know what the natives called their great city; unfortunately the Mississippian society had no writing):
The large mound in the back is the Monks Mound, and the partially visible mound on the right in the forefront is the Fox Mound (compare to my photographs above).
The depicted activities of people are, as far as I know, a pure fantasy on the part of the artist (this is not a criticism – he or she had to somehow fill the landscape; just take it with a large helping of salt). One thing that is almost certainly wrong is the grassy green slopes of mounds. My colleague and co-author David Anderson told me that the mounds were probably covered with red, black, and white clays laid out in horizontal layers, which must have made for a visually striking image back in the thirteenth century.
There is probably a lot wrong with this reconstruction, but one thing seems certain – there was a huge public space in the middle of this pre-Columbian city. It was probably used for public rituals, and its extent is suggestive of huge crowds that must have participated in these rituals.
The scale of social organization is also indicated by the amount of labor that was necessary to mobilize in order to build the monumental mounds:
According to the calculation at the Center, the amount of labor that was required just to move earth to create the Monks Mound (the largest mound, but one of many) was c.5,000 people-years.
The central plaza was surrounded by houses, and there was a palisade that protected the center of Cahokia from attack:
Note that many buildings were placed outside the defensive walls. Cahokia was a center of trade, and imported exotic materials from far away:
Here’s a very nice Caddoan water bottle that came from another culture to the southwest of Cahokia:
The Mississippian society was a complex, centralized polity. It was either a complex chiefdom, or even an archaic state, as recently argued by some archaeologists such as Tim Pauketat:
This social structure is reconstructed based on historically attested Mississippian chiefdoms after the European contact (which, however, were of much lesser scale than Cahokia).
The paramount ruler of Mississippian polities was called ‘Great Sun’ in later chiefdoms:
We actually have a pretty good idea of the kind of dress and ornamentation the Cahokian elites wore, from the burials:
A live elite individual could have looked like this:
Note the kilt decoration, hair pins, and copper ear spools.
The Mississippian art was quite sophisticated. Here’s a figurine that may represent the “earth mother” or an agricultural deity:
The Mississippian culture was Neolithic. A flintknapper:
Women preparing food:
and cooking it:
Agricultural diets (in particular, over-reliance on corn) imposed heavy costs on the health of ancient Cahokians, as indicated by tooth decay:
So why did the complex society, centered on Cahokia, collapse? The Interpretive Center lists four possible explanations:
1. Over-exploitation of land
2. Climatic change
3. Failure of leadership
4. Cultural change
Clearly, these folks need to learn about cliodynamics 🙂
As readers of my books know, the explanation of societal collapse that I have argued for (at least, for societies inhabiting non-marginal environments, including most certainly Cahokia) is internal warfare brought on by a structural-demographic crisis. What is remarkable, is that the Center does not ever mention warfare. When I realized it, I specifically went on the second circuit and checked all exhibits. The only indirect mention of warfare I found was the identification of this individual as a high-status warrior:
That was it. This is yet another example of what has been called “the pacification of the past.”
Despite this caveat, I thought that the exhibition was really well done. Naturally, much of it is speculative, and the reconstructors surely got many things wrong. But I still feel very grateful to them for making this attempt of bringing the lost culture of pre-Columbian Mississippians to life. I enjoyed my Cahokia trip enormously.
Cultural evolution is what created the – in many ways – wonderful societies that we live in. It created the potential to free our lives from hunger and early death, and made possible the pursuit of science and art. But cultural evolution also has a dark side, in fact, many ‘dark sides.’
Clearly domestication of plants and animals is what made our civilization possible. All sufficiently complex societies are possible only on the basis of agriculture. But we have paid, and continue paying a huge price for this advance of human knowledge and technology. This idea was brought home to me as a result of several conversations I had with Michael Rose during the Consilience Conference at St. Louis, which I talked about in my previous blog. Michael is an evolutionary biologist at the university of California at Irvine, who studies aging from the evolutionary perspective. I actually read his book Evolutionary Biology of Aging some twenty years ago, but never met him until two weeks ago.
One way people talk about the price of civilization is in terms of evolutionary mismatch (which is one of the focus areas at the Evolution Institute). The idea is that our bodies and minds evolved during the Pleistocene, when we lived in small groups of hunter-gatherers. Now we live in a dramatically different environment, and that causes all kinds of problems. The psychological aspect of the problem was recently discussed by Robin Dunbar and commentators on his Focus Article. The physiological problems include rampant obesity, heart disease, and diabetes.
There is currently no consensus on the role of changing diet and other aspects of lifestyle, most notably exercise, in causing modern-day health problems. Some people argue that our Plestocene bodies are not adapted to high-calorie diets and sedentary life-styles of today. On the other hand, agriculture was invented roughly 10,000 years ago. 400 generations is not an insignificant length of time for evolution to do its thing. Some anthropologists (including another participant of the Consilience conference, Henry Harpending) argue that humans evolved very intensively during this period. One famous example is the evolution of lactose tolerance, that is, ability to digest milk.
Michael Rose develops a more subtle and sophisticated argument, which is explained at length in his 55 theses – a New Context for Health. There is a sophisticated mathematical model underlying his argument, but the basic logic of it is actually quite simple.
We think of people having ‘traits,’ but actually we change quite dramatically as we age. The key ‘trick’ is to realize that people have a suite of traits, and they can be quite different, depending on what stage in life we are talking about. As an extreme example, consider reproductive ability, something of great interest to evolution. Humans do not reproduce until they reach a fairly advanced age of maturation (puberty). Young adults are not very good mothers or fathers, but they improve with age during their twenties. After that reproductive ability declines and eventually disappears. So reproductive ability is actually a trait that varies quite a lot with age.
Another example is hair color. One man can have red hair and another blond hair. However, this will be true only while they are relatively young. Older men become grey, and many become bald. So by the time our two men turned 60, they may have the same hair color (grey), or no hair at all (bald). By the way, it is likely that the reason is not simple ‘degradation,’ reduced function due to aging, but that greyness and baldness evolved to signal maturity and wisdom. To really describe the phenotype of an individual we need to specify at what age it is expressed.
Ability to digest certain foods can also be age-dependent. I have already mentioned the ability to digest lactose, the sugar present in milk. Before we domesticated animals such as cows and sheep, only very young humans had this ability. Natural selection turned this ability off in adults because they never needed it (and it would be wasteful to continue producing the enzyme lactase that aids in the digestion of milk sugar).
Now clearly traits expressed at different ages are not completely independent of each other. An ability to digest milk sugar as an adult depends on the presence of an enzyme that evolved in order for babies to digest their mother’s milk. So traits at different ages can be correlated, either positively, or negatively. An example of negative correlation is the reproductive ability – in many animals, putting a lot of effort in reproducing early reduces the reproductive ability later in life. So the sophisticated mathematical framework for dealing with age-dependent traits has to take into account all kinds of possible correlations, both between the same trait at different ages and between different traits. For example, most individuals have dark eye and dark hair color, or light eye and light hair color, with dark/light and light/dark combinations a relative rarity.
We can now get to the crux of the matter. Because abilities to do something at the age of 10, 30, 50, etc. are separate (even if correlated) traits, they evolve relatively independently of each other. When grains became a large part of the diet, the ability of children to digest them (and detoxify the chemical compounds plants put into seeds to protect them against predators such as us) became critical. If you don’t have genes to help you deal with this new diet, you don’t survive to adulthood and don’t leave descendants. In other words, evolution worked very hard to adapt the young to the new diet. On the other hand, the intensity of selection on the old (e.g., 55 years old) was much less – in large part, because most people did not live to the age of 55 until very recently. Additionally, once an animal gets past its reproductive age, the evolution largely ceases to have an effect (in humans, presence of older individuals was somewhat important for the survival of their genes in their children and grandchildren, so evolution did not entirely cease, but was greatly slowed down).
What this means is that evolution caused rapid proliferation of genes that enabled children and young adults to easily digest novel foods and detoxify whatever harmful substances were in them. Genes and gene combinations that did the same for older people also increased, but at a much, much slower rate. This may sound puzzling – if we have the detoxifying genes that work for young adults, why shouldn’t they work for older adults? The reason is that one gene-one action model is wrong; it’s not how our bodies work. Most functions are regulated not by a single gene, but by whole networks of them. As we age, some genes come on, and others go off, and the network changes, often in very subtle and nonlinear ways. That’s why we need the ‘trick’ with which I started, to consider functions at different ages as separate traits. During the last 10,000 years evolution worked very hard to optimize the gene network operating during earlier ages to deal with novel foods. But the gene network during later ages was under much less selection to become optimized in this way.
The striking conclusion from this argument is that older people, even those coming from populations that have practiced agriculture for millennia, may suffer adverse health effects from the agricultural diet, despite having no problems when they were younger. The immediate corollary is that one thing they can do to improve their health is to shift to something known as the ‘Paleolithic diet,’ or paleo diet, for short. In the simplest form, this means eliminating from your diet any cereals (wheat, rice, etc), legumes such as beans and peas, and any dairy products (e.g., cheese). It is striking that this is almost precisely the opposite of the popular Mediterranean diet, which emphasizes wheat products (bread, pasta), cheese, and legumes (as in the Italian bean soup, in pasta fagioli, and in hummus).
We are now getting to something I have a personal (rather than a scientific) interest in. I am about to turn 55, and although I am generally in good health, various worrying indicators – cholesterol, sugar – have been inexorably inching up. A couple of years ago I read Ray Kurzweil Fantastic Voyage, but I was unpersuaded by his prescriptions to better health and longevity. Kurzweil’s prescription is, at basis, a calorie-restricted diet. Like the great majority of human beings, I find it extremely difficult to starve myself. More generally, his approach to human health and longevity is that of an engineer – you turn that dial down, another one up, and get the result you want (according to his book, he spends one day a week connected to a machine that removes bad things from his blood and adds good things). I am very doubtful that such an approach will work on an evolved system with multiple nonlinear feedbacks, which is the human body. So changing one variable (e.g., reducing the cholesterol level in the blood) may have unintended – and usually negative – consequences elsewhere (perhaps increasing the risk of cancer).
To conclude, the paleo diet is the first diet, of the ones I heard of, that has a sound evolutionary basis going for it. This was a deciding factor in persuading me to try it out, which I did, starting about two weeks ago. It apparently takes about six months to see its full effects, so stay tuned for progress reports.
Follow Peter Turchin on an epic journey through time. From stone-age assassins to the orbiting cathedrals of the space age, from bloodthirsty god-kings to India’s first vegetarian emperor, discover the secret history of our species—and the evolutionary logic that governed it all.
200 years ago Alexis de Tocqueville wrote about the exceptional ability of Americans to cooperate in solving problems that required concerted collective action. This capacity for cooperation apparently lasted into the post-World War II era, but numerous indicators suggest that during the last 3-4 decades it has been unraveling.
Pants are the standard item of clothing for people, especially men belonging to the Western civilization. Why not a kilt, a robe, a tunic, a sarong, or a toga?