So what kind of theory may replace the standard ‘bottom-up’ theory, when, or if, it collapses under the accumulated weight of anomalies? In the previous blog I found the alternative explanation, described in the National Geographic, unsatisfactory.

Actually, the bottom-up theory also has a huge logical gap. It assumes that when foragers discovered how to cultivate plants, they gladly switched to this more productive way of making a living.

Comic by David Steinlicht

But this makes sense only from the point of view of a person who came from a culture with long-established farming practices (such as academic anthropologists). Real foragers, on the other hand, are very resistant to abandoning their ways of life, and they have good reasons for such reluctance.

If you think about it, why humans switched from hunting and gathering to agriculture is a big, big puzzle. This has been most effectively argued by Sam Bowles (most recently in a PNAS paper co-authored with Jung-Kyoo Choi).

The first problem is that farming involves a lot of back-breaking labor. Early agriculture was not particularly productive, and it required many more hours of work, compared to foraging.

Second, hunter-gatherer societies share the food; hoarding marks you as an anti-social deviant. What this means is that you could put all that work into growing plants (clearing the field, planting, weeding), but others would think nothing of harvesting the plants when they ripen. Or you could get to the point of harvesting and storing the crop, but then everybody else in your community would expect you to share it.

Third, agriculture has its dark side – it’s negative effect on human health. Evidence is overwhelming that after switching to agriculture human heights decreased, and that is a very reliable indicator of a decline in biological well-being. People fell sick more often because of higher population density and because pathogens jumped from domesticated animals to humans. The quality of nutrition declined, as is abundantly documented in ancient bones and teeth.

A skull fragment from a teen buried at Rome’s Casal Bertone necropolis. The teen ate a millet-heavy diet in childhood but switched to wheat in the years before death. Pores in the bone of the eye socket known as cribra orbitalia suggest the teen was anemic. CREDIT: Kristina Killgrove Source

But the switch to agriculture did occur, and farming did spread, so there had to be a compelling reason why. Let me sketch a possible explanation, which fits the various data pretty well (or so it seems to me). Long-time readers of this blog will not be surprised to discover that the explanation focuses on warfare, or more properly cultural multi-level selection.

Consider a landscape inhabited by many local groups, each with a territory that they use for hunting and gathering. These groups (typically around 50 individuals) are in turn grouped into larger ‘tribes’ – ethno-linguistic communities (typical size = 1-3 thousand individuals) who cooperate in warfare against other ethno-linguistic communities.

Now suppose that something happens that leads to more intense warfare. In historical times, the most likely trigger has been the invention or spread of a new military technology — bows and arrows, cavalry, gunpowder. (We have a paper in review modeling this process, and it predicts the rise of large-scale states and empires in history remarkably well.)

But the most likely trigger at the dawn of agriculture was climate change. When climate became dryer and cooler during the period, known as the Younger Dryas, the productivity of plant communities declined, which caused a decrease in the carrying capacity for humans who depended on these resources (game animals also decreased because their food base shrank).

Lower overall resources led to a spike in conflict between ‘tribes’ (ethno-linguistic groups) because each group attempted to expand its territory to compensate for lower carrying capacity. A possible example of this dynamic is the intensification of warfare among the Anasazi after climatic conditions in the American Southwest deteriorated.

Most likely humans who lived in the Fertile Crescent had already known about techniques needed to intensify plant production, but for reasons we have discussed, did not deploy them. The new conditions of widespread warfare, however, imposed an intense selection regime for larger group size, because the best way to ensure tribal survival was to have more warriors. Growing their own food enabled human groups to raise more warriors and concentrate them within larger war bands. Such groups then expanded at the expense of groups that didn’t have agriculture. So we have a typical process of evolution by cultural group selection.

Why was the cultural group selection necessary? Because you cannot switch to farming when everybody else in your group is foraging. The whole group needs to shift to farming together and to acquire a new set of cultural norms, most notably, private property rights. Bowles and Choi in their paper model how this dual switch can occur.

However, more is needed. Switching to farming makes evolutionary sense only if it leads to a larger tribe size, which is key for surviving under conditions of intense intertribal warfare. But it is not easy to keep a large group of people internally cohesive. You need a new type of social glue.

In his recent articles, including one on the Social Evolution Forum, Harvey Whitehouse argues that large-scale human societies can build up cohesion by inventing and conducting regular symbolic, or ‘doctrinal’ rituals that bring together large numbers of people. Everything we know about Göbekli Tepe suggests that it was used precisely for such rituals, and that it served a very large ritual community. It took many hundreds of people to build the monument, so there had to be a large community numbering in many thousands, since somebody had to provide the food. And it brought together population from a large area.

The cultural group selection logic also explains why agriculture was adopted despite its huge health costs. Groups of poorly nourished and perhaps even chronically sick, but numerous farmers exterminated healthy and tall foragers because of the group size advantage. So individual fitness (both in the evolutionary sense, and in the common sense of physical fitness) declined, but the evolutionary fitness of the group increased, and that is what drove the whole process.

Notes on the Margin: I will be away from the Internet during the next week; when I come back I will continue with this series. Next is a discussion of Poverty Point.

THE BIRTH OF RELIGION: The World’s First Temple

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The article was authored by Charles C. Mann, of the 1491 (and now 1493) fame:

and it describes excavations at Göbekli Tepe in southern Turkey led by Klaus Schmidt.

It’s likely no one lived at Göbekli Tepe, a religious sanctuary built by hunter-gatherers. Scientists have excavated less than a tenth of the site—enough to convey the awe it must have inspired 7,000 years before Stonehenge. (National Geographic, June 2011)

There was a series of monumental structures built one after another at this site

There is no question that Göbekli Tepe is a spectacular site. But it also presents an enormous challenge to the standard archaeological theory of how complex large-scale societies evolved.

For most of our evolutionary history we, anatomically modern humans, lived in small-scale societies. And I mean, really, small-scale. Paleolithic humans interacted, on a daily basis, with at most a few dozens of other people, each of whom they knew intimately. These closely-knit local communities were embedded within ‘tribes’ – ethno-linguistic groups numbering many hundreds, or perhaps even two-three thousand people, who spoke the same language, shared same sacred beliefs, used distinctive ethnic markers (dress, tattoos, artifact styles) to distinguish ‘us’ versus ‘them’, and tended to cooperate with each other (especially when attacked by other ethno-linguistic tribes).

Beginning about 10,000 years ago this started changing, and now the vast majority of humans live in large-scale societies. And I mean really large scale – tens and hundreds of millions instead of hundreds/few thousands 10,000 years ago. In some cases (China, India) over a billion of individuals are encompassed by the same political community. If you think about it, this is truly an astronomic change – 6 freaking orders of magnitude! So how did it come about?

The standard archaeological model (which is so standard that it is rarely formulated in explicit terms) explains it this way. Around 10,000 years ago humans began domesticating plants and animals. This allowed them to dramatically increase production of food, which in turn enabled greater population densities, sedentary way of life, villages – and then cities, complex societies, states, writing, etc. – in short, civilization.

The adoption of agriculture, thus, created a resource base capable of sustaining high population densities and an extensive division of labor. It also generated the capacity to produce ‘surplus’ to support craftsmen, priests, and rulers. At this point, the standard theory branches out into several different models, with some emphasizing the need to manage economy, others focusing on warfare, and yet others stressing the role of ideological specialists (priests and religion). Details vary, but the common denominator is that a rich resource base is not only a necessary condition, but also a sufficient one. I call this the ‘bottom-up’ theory of the evolution of social complexity, because it treats social complexity as a sort of ‘superstructure’ on the material resource base.

In other words, you stir in enough resources into your evolutionary pot, and social complexity will inevitably ‘bubble up’, although different theories evoke different mechanisms explaining exactly how and why this happens.

The problem for the bottom-up theory is that Göbekli Tepe flatly contradicts the sequence of events postulated by this theory. Göbekli Tepe was a major religious and ritual center. It periodically gathered together people from a fairly large-scale society. Constructing the monument and carving the pillars required hundreds of workers and artisans laboring together, so the supporting society had to number in the thousands, at the very least. Probably tens of thousands, given that it couldn’t have a high capacity to generate the surplus needed to support the workers.

Building Göbekli Tepe (National Geographic, June 2011)

Its capacity for generating surplus had to be limited, because the society that built Göbekli Tepe subsisted by hunting and gathering. The earliest complex at Göbekli Tepe was built roughly at 9600 BCE, while the first evidence of agriculture in the area dates to at least one thousand years later. The workers at the site ate game – gazelles and aurochs – probably supplemented by gathered plant foods. They did not eat any cultivated grains.

So here we have an inverted sequence of events. First, a fairly large-scale society arises, with quite sophisticated ritual activities and buildings requiring mobilization of large numbers of workers. Next comes agriculture. This sequence suggests that the standard theory inverses the cause and effect. The National Geographic article suggests an alternative causation:

“Over time, Schmidt believes, the need to acquire sufficient food for those who worked and gathered for ceremonies at Göbekli Tepe may have led to the intensive cultivation of wild cereals and the creation of some of the first domestic strains. Indeed, scientists now believe that one center of agriculture arose in southern Turkey—well within trekking distance of Göbekli Tepe—at exactly the time the temple was at its height.”

The two rival models are illustrated in this diagram:

Exciting! Are we witnessing a scientific revolution in process?

Before we jump on this bandwagon, however, let’s ask two questions.

Question 1. Is Göbekli Tepe a freakish outlier, an unusual data point that should be discounted? Perhaps there is some problem with dating that, when corrected, will show that agriculture actually was adopted earlier than thought. In any case, a scientific theory cannot be rejected on the basis of a single example. However, as I will discuss in subsequent blogs we now have multiple examples in which an increase in the social scale precedes agriculture. But what we clearly need is a systematic study.

Question 2. Is the alternative explanation logically consistent? Here I am bothered by the key step, described in the diagram as follows: “Wonderment at changes in the world leads to organized religion”.

??! This reminds me of one of my favorite math cartoons:

(to be continued)

There are good practical reasons for banning ideology from the SEF. During the early days of the Internet I have followed a number of discussion boards and on-line forums. With depressing regularity, they all foundered when the discussion turned from issues to politics, and then to increasingly bitter ad hominem attacks.

More generally, there are equally good practical reasons to keep ideology out of science as much as possible. Empirically, once ideology sneaks in, the quality of resulting science quickly deteriorates.

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But we also want our science to be relevant. In fact, we scientists owe it to the society that ultimately supports us. It doesn’t mean that every scientific project needs to justify itself by promising to produce an immediate benefit to the society. Readers of this blog know that I think such an attitude is counterproductive (and, not to put too fine a point on it, stupid).

But ultimately – in the long run – science should be a force for good. Most scientists, a few ivory tower inmates excepted, agree on it.

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This question has lately been much on my mind, because I am currently writing a critique of a scholarly book that boldly mixes up ideology and science (with predictable results). In general, history is a discipline that is particularly prone to be misused and abused for ideological purposes.

Incidentally, this is why the Soviet Union produced so few famous historians and social scientists, and so many fine mathematicians and chess players. Fortunately for the latter, dialectical materialism says nothing about how to prove theorems, or how to move figures on the chessboard.

If you know your history well enough, you can always find multiple historical examples to support any theory that you like – and a different set to support its logical opposite. This doesn’t mean that history is hopeless; it just means that we have to be careful about how we test our theories about the past. In particular, no cherry-picking is allowed. You must include all cases within a certain, objectively specified sampling set. Also, you have to worry about biases that may affect your data, including political agendas of chroniclers (and their bosses) and physical processes that may make some artifacts more persistent in the archaeological record than others. It’s technical, requires a lot of thought and work, but quite doable.

Saint Nestor the Chronicler

All of this is fairly obvious (which does not stop politicians and their academic shills from continuing to routinely abuse history). But consider another example. Suppose a small, but proud country teaches its youth about its glorious national past, its celebrated victories over external enemies, and the important contributions it made to the world’s cultural heritage. In reality, the surrounding empires never bothered conquering it, because it was too poor and had no strategic value; none of its writers are read outside the country, and none of its scientists ever got a Nobel Prize.

Would you insist that they bring their school curriculum in line with our best and objective historical scholarship? I am not sure I would. After all, nations need their ‘mythomoteurs’ (using the felicitous term of Anthony D. Smith and John Armstrong). Who knows, if you were to destroy their pride in their glorious past, it might degrade the ability of people inhabiting the country to cooperate within national institutions; it could increase cynicism and corruption, and ultimately lower their quality of life.

In other words, history curriculum in schools is not about science. It has much to do with social glue, but it is orthogonal to cliodynamics.

Of course, the sense of national pride and self-importance can get out of hand, as happened with Georgia in 2008. By attacking South Ossetia and Russian peace-keepers therein, the Georgians triggered the war with Russia, which led to a speedy and humiliating defeat, and a painful blow to national pride.

Not-so-small and proud nations are also prone to nationalistic hubris, with disastrous consequences for the surrounding countries and, often, for themselves. The example of the Nazi Germany is, of course, paradigmatic, but one can think of many others.

I am not sure if I can come up with any earth-shattering conclusions. Still, I believe that keeping science as ideology free as possible is a good idea. It’s very important not to mix ‘what is’ with ‘what should be.’ If we want to change the world for the better, we first need to be clear-headed about why societies work the way they are. Good science can yield politically incorrect and, sometimes, difficult to swallow results. But if we shy away from such unpalatable conclusions, we simply sweep the deep causes of social ills under the rug. That’s not the most effective way of changing our societies for the better.

So, in order to be the most efficient about achieving ‘what should be,’ we first need to ignore it in the pursuit of ‘what is.’ Only after we have figured out how societies function and evolve we can start designing ways of nudging them in the right direction.

What it also means is that any explicit (or even strongly implicit) ideological or partisan comments will continue to be ruthlessly expurgated!

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I was unable to find a good estimate of how much breadfruit is grown globally, but another FAO study guesstimated the quantity as 1-2 million tons at most.

In my previous blog I related how I discovered that breadfruit is at least as tasty as wheat. At the same time, it lacks all the harmful chemical compounds (lectins etc.) that make wheat a source of much misery and ill-health today. Why we eat bread instead of breadfruit is a very interesting question, for which I hope to have an answer one day (and it’s not obvious, if you think about it). Another question is why we persist in eating wheaten bread, and how long it will take us to switch to healthier foods (well I personally have not eaten any wheat in more than a year).

But another, and even more important question is why Pacific Islanders, as well as folks inhabiting many other tropical islands, eat bread. Many tropical countries import the majority of their food – wheat, corn, rice, soybeans – from the US and other temperate countries. This is absolutely crazy.

Now ancestral Polynesians were much smarter. When they got to New Guinea c.1500 BC they brought with them rice cultivation.

Source: Wikimedia

But when they saw that bread grew on trees, they must have said, oh my God! Why devote innumerable hours of backbreaking labor to grow grass seeds, when you can simply pick bread from trees? So they abandoned rice cultivation, and switched to eating breadfruit. Together with such root crops as sweet potato and taro, which are also healthy sources of carbohydrates and many other nutrients. Actually, rice is not even the worst cereal, as I will discuss below. Nevertheless, this switch worked for them – when first Europeans arrived at Pacific islands, they could only marvel at the great health, tall stature, and natural beauty of Polynesians.

Tragically, that all is in the past. A year ago the premier medical journal Lancet published the latest data on the prevalence of obesity among different countries in the world. Although we tend to think of Americans as the fattest nation on Earth, that is actually not the case. The fattest nations today cluster in the Pacific region:

In Samoa and Tonga the proportion of adult women who are obese (BMI > 30) is around 70 percent. In American Samoa, where the local population switched from traditional Polynesian diet to American one virtually overnight, 80 percent of women are obese.

This empirical observation is actually one of the most striking examples of gene-culture coevolution. Polynesians, who did not experience many generations of selection for ability to detoxify gluten, gliadin, and other ‘secondary compounds’ that grasses load their seeds with, were really clobbered when they become exposed to such evolutionary novel foods. Of course, cereals (and legumes and dairy) are only part of the story. Novel industrial foods clearly also play a role (they are probably a big part of the explanation for the current obesity epidemic in the United States, as well as in many Middle-Eastern countries, such as Egypt).

Furthermore, it looks like not all grass seeds are equally bad. Take a note of the least obese countries in the graph above. OK, Ethiopia is at the bottom of the list because they’ve had a multi-year famine. But prosperous rice-eating countries, like Japan and Hong Kong, also have a very low prevalence of obesity. Paul and Shou-Ching Jaminets consider rice a “safe carbohydrate,” and these data suggest that they may be right. Additional support for the idea comes from the observation of very different health outcomes between wheat-eating and rice-eating regions within China (populations eating rice have much lower prevalence of heart disease and diabetes).

So we have this ironic situation, if ironic is the right word (tragic may be a better one), when poor tropical countries import wheat-based products, at great expense, from the rich North. And suffer a variety of health-related problems because of it.

An obvious solution for improving health, and wealth of people living in the Global South is for them to start growing, and consuming locally grown foods, including breadfruit. In fact, there are several current initiatives that aim to do just that. As an example, Diane Ragone, Director of the Breadfruit Institute at National Tropical Botanical Garden in Hawaii, argues that breadfruit cultivation can be the solution to hunger in the Tropics.

But it can also be a solution to ill-health, at least in the Pacific tropics, where native populations have not evolved the ability to detoxify harmful compounds within grass seeds.

Furthermore, why think small? Can we imagine the situation where all wheat-, corn-, and soybean-producing agricultural conglomerates in the Global North have gone out of business, and instead everybody is buying breadfruit flour and other healthful tropical products from the (formerly poor, and now rich) Global South? Sounds like science-fiction?

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*As well as pastry, cake, and as food additives into many processed foods. For example, most soy sauce is made with wheat as an additive

But later I learned it was true! There is a real plant that is called breadfruit tree.

Ever since I switched to paleo diet a year ago, I have been dreaming of tasting breadfruit. It sounds like a perfect substitute for bread because it is a real fruit, whereas bread is made from grass seeds. Evolutionary reasoning suggests that plants, who don’t want their seeds to be eaten, should protect them as best as they can – for example, by loading them up with poisons. And that is what grasses do (read about lectins on Paleo Mom’s blog).

Fruits, on the other hand, are something that plants want us to eat (typically, seeds are ingested with the fruit, but not digested, and when they are defecated out, the plant gets to disperse and a little bonus in the form of natural fertilizer, to boot). Breadfruit trees, thus, should be putting all kinds of wholesome and yummy nutrients in their fruits. And they do.

Yesterday, finally, my dream has come true. The Indian food store, patronized by my daughter-in-law got a shipment of breadfruits, and we have acquired one. I checked the Web for recipes, and it turns out breadfruit can be cooked in a variety of ways. I decided to follow the basic recipe of Helene Dsouza, except I omitted all spice apart from salt and a dash of vinegar, because I wanted to find out what the breadfruit itself tastes like. So, I started with the fruit:

peeled and quartered it

removed the core, cut it into chips, and soaked/marinated it in salted, vinegary water for about 30 minutes

and, finally, fried them in olive oil

Here’s what the final results looked like

As a result of my inexperience the chips are a bit too well done, so next time I will finish cooking as soon as they get to the golden brown stage.

I tasted the result with some trepidation. Over the last year I have tried a variety of tuber and root vegetables (cassava, taro, jicama), but I don’t see making any of them a staple (so I stick with potato, while occasionaly eating yams, carrots, and parsnips for variety). All of those exotic tubers had tastes that I found slightly unpleasant (if I grew up eating them I would probably feel otherwise, but I come from a potato-eating culture).

My experience with breadfruit was very different. It tastes great! It is like potato in that it is bland enough to serve as a base for a meal, when combined with a variety of other ingredients and spices. But it also has a distinctive and pleasant taste, so it is a true alternative to potato. If I only can find a reliable supply around here, I am going to make it a staple.

Now that I have tasted breadfruit, I find it highly ironic that the humanity consumes so much wheat bread, while eating so little breadfruit. How did we end up making poisonous grass seeds our most important food source, when we have so many alternative, much more healthful foods to choose from?!

Even more poignantly, why do pacific islanders eat bread, rather than breadfruit? In the next blog I will discuss such broader implications.

to be continued

All fotographs in this blog ©Peter Turchin

Let’s start by acknowledging that there are no departments of cliodynamics – and it is quite likely that there never will be. In fact, I would prefer it to stay that way. Academic science is already fragmented along many artificial lines, and the last thing we need is yet another department of social science. The way of the future is doing interdisciplinary – indeed, transdisciplinary – research. We need to take steps to overcome the balkanization of science, not add to it.

Thus, my advice to a budding cliodynamicist is to first decide on a disciplinary home, and then build a career within it. Only after you have tenure, can you truly pursue cliodynamics. You have to think long term.

In principle, any social science department can serve as a decent disciplinary home (a bit later I discuss which ones I would choose if I were starting my scientific career). You can even be based in a natural science department. For example, my primary department is Ecology and Evolutionary Biology, and I have cliodynamic colleagues who were trained as physicists and engineers. Still, while my biological background was a great help in training me for my current research in social evolution and cliodynamics, if I were starting my career now, I’d go into one of the social science disciplines. The problem is that I have a large baggage of completely useless – for cliodynamics! – information (to give an example, I still remember a lot about how juvenile hormones regulate insect physiology – don’t ask).

So which discipline would I choose? My first choice is anthropology/archaeology (in fact, I am adjunct in my university’s anthropology department, as well as in mathematics). History is pretty much out, at least as it is practiced in the United States, where it is considered to be one of the humanities, rather than sciences. It may be a viable option outside of the US (in fact, I know of several highly promising young scientists who have, or are getting Ph.D.s in history outside the US). Archaeology is the closest thing to scientific history we currently have. Graduate students in archaeology can get rigorous training in substantive disciplines that require knowledge of natural sciences (geology, ecology, evolution, etc.). Statistical and mathematical skills are not frowned upon (towards the end I will discuss the mathematical curriculum that is useful for cliodynamics). Archaeologists deal with both general theories and the nitty-gritty of getting the data to test theories.

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If I were an aspiring cliodynamicist, I would actually do a largely empirical Ph.D. – participate in the excavations, and do the laborious, often boring, and at times mind-numbing stuff that is necessary to force the uncooperative universe to yield ‘data’. I did this as a Ph.D. student and a post-doc in ecology, so I know intimately how data are obtained. All theoreticians should design their own field studies and do all the donkey work, at least once in their career, to understand where scientific ‘facts’ come from.

So archaeology/anthropology would be my first choice. Another good choice is sociology, because it is fairly strong on general theory. Problems with sociology, however, are two-fold. First, there is too much emphasis on reading and re-reading the great ‘dead white men’, Weber, Durkheim, Marx, etc. Most evolutionary biologists never read Darwin, even though they are Darwinians. When sociology becomes a ‘rapid discovery science’ (using the terminology of Randall Collins, although he is somewhat pessimistic on whether social sciences are capable of making this transition), sociologists similarly will be too busy churning out new results, to read and re-interpret Weber, Durkheim, and Marx.

The second problem with sociology is that only a relatively small proportion of sociologists address big questions in historical or macro sociology. Most of the rest do microscopic science of great value to specific societal problems, not doubt, but of little relevance to big questions.

Political science is also not a bad choice. It is very quantitative, with many practitioners being quite comfortable with statistical methods and analyzing large data sets. Its theory tends to lean towards what I would call ‘phenomenological models’, that is, a reliance on regression, rather than arguing from first principles (a mature science needs both). Also, political science tends to be, for obvious reasons, heavily politicized/ideologized, which is a drag.

Finally, there is economics. Paul Krugman, as a young man, read Isaac Azimov’s Foundation series, and wanted to become a psychohistorian. He went into economics because it was the closest thing, at the time, to psychohistory. Today, however, there are some disadvantages to choosing economics as your disciplinary home, if you want to do cliodynamics. The problem is that economics was the first social science to become mathematized, and it did so before the complexity science and nonlinear dynamics revolution of the 1970s–1980s. So traditional economic theory is heavily reliant on equilibrium methods. This is changing – many economists are embracing non-equilibrium approaches, and there is now a strong current of evolutionary thinking in economics (‘evonomics’). However, because of its initial success, economics seems to be somewhat isolated from other social sciences, which is a problem for transdisciplinary research. Still, most economic historians are housed within economics departments and, as I said, many economists are now pursuing explicitly historical questions, as well as evolutionary thinking and dynamical methods. So one of such nontraditional economics departments could also be a good place to get a Ph.D. which would lead, eventually, to cliodynamic research.

OK, so choosing a disciplinary home is the most important decision. Also, doing a Ph.D. project that is not entirely theoretical or, even better, mostly empirical or experimental, is what I would suggest. The goal is to become embedded in a supporting network of colleagues, both senior and peers. Getting a job in academia these days is not easy, and one must be very strategic about it.

But let’s not forget that the goal is not just to get a tenure-track job, but to do cliodynamics. This means that you need to acquire the necessary quantitative tools.

What are they? Here’s my list of suggestions. First, you need a solid grounding in mathematics and dynamical systems. This means taking the following courses:

Calculus
Ordinary differential equations
Qualitative theory of differential equations (stability analyses)
Partial differential equations
Stochastic Processes

Next, you need several statistics courses:

Introduction to Statistics
Regressions
Time-series Analysis
Bayesian Statistics
Numerical Methods

Finally, you need good programming skills, because most of the models that are realistic enough will have to be solved numerically, or simulated using the computer. My personal take is that you don’t need to take formal courses in programming; you can simply learn it by doing. But it wouldn’t hurt taking a general course in good programming practices.

So there you have it. You’ve got to become ‘numerate.’

It’s quite a lot, so if you are still in college, you should start taking math and statistics now. It will be much more difficult once you are in a graduate school and need to concentrate on your Ph.D. research. But although acquiring quantitative skills takes a lot of work (you will have to do innumerable homework, because that’s the only way to learn math), it will pay, and continue paying for years and decades. I am still living off the mathematical capital I acquired in the first 25 years of my life.

One of the earliest known examples of math homework

Also, while my strategy suggests doing a mainly empirical project for Ph.D., having theoretical and quantitative skills is a very important competitive advantage in the job market. Once you have established solid disciplinary credentials, theoretical skills indicate additional breadth that most departments will value (and want to get).

And there you have it. It’s a lot of work, but it will pay for itself in the long run. As the famous Russian general Alexander Suvorov liked to say, “Hard in training, easy in battle.”

Kinky Boots: Billy Porter as Lola, a drag performer, in this musical at the Al Hirschfeld Theater. Sara Krulwich/The New York Times

Ironically, three hundred years ago it would be equally scandalous for a woman to be seen wearing high-heel boots. Unless you were a Russian Empress, who didn’t have anything to lose after she led a coup-d’etat against her husband, deposed him, and (most probably) had him murdered:

Catherine the Great wearing the uniform of her Preobrazhenskii regiment, by Vigilius Eriksen, 1762. Source

High-heel boots were, most definitely, part of male attire. In fact, it was the most masculine and martial of men who wore them:

Musketeers in their kinky high-heel, over the knee boots (Source)

High-heel boots, however, were a relatively new fashion in the early modern Europe (‘early modern’ refers roughly to the seventeenth and eighteenth centuries). During the Middle Ages and Renaissance well-dressed men wore low-heeled shoes and boots (although they sometimes made up for this deficiency by wearing shoes with extravagantly long toes, called poulaines).

Source

What was worse, they even made armored  boots with long, pointy tips:

A suit of armor with poulaines (c.1480) Source

Now there are all kinds of problems with wearing long, pointy and heal-less shoes, when you ride a horse. And, if you want to get anywhere while wearing this suit of armor, which probably doubled the weight of the guy it protected (especially when you add a sword and a shield), you have to ride.

To see why such shoes are a poor design, consider the beautiful functionality of a cowboy boot, the result of 1500 years of cumulative cultural evolution.

Cowboys sitting on the fence during a rodeo in Texas (source)

The starting point of this evolution was the invention the stirrup, probably by the Mongolian nomadic people called Xianbei around 300 AD. This was such a useful invention that by the sixth century it spread through all of Eurasia, from Japan to Europe. By providing the rider with unprecedented stability, the stirrup made heavy cavalry (actually, any kind of cavalry) much more effective. Some historians even argued that the stirrup gave rise to feudalism in medieval Europe, and something very similar in Japan (take this with a grain of salt).

The problem with the stirrup is that when you fall off the horse (and if you ride horses a lot, especially under the chaotic conditions of war, you will inevitably do so once in a while), there is a danger of your foot being caught in the stirrup. Countless riders have been dragged to their deaths by panicking horses.

And here is where a properly designed stirrup/boot combination comes in. An iron stirrup with large enough opening for the boot allows you to kick it off as you fall. A high heel, on the other hand, gives you the stability by preventing the foot from slipping through the stirrup. It helps to have a very slick, slippery sole for ease of foot extraction in case of mishap.

High heels and slippery soles make for rather uncomfortable walking (I would not recommend wearing true cowboy boots in New England’s winter!). But for riding it’s just right.

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What is interesting is that it took a lot of time for the Europeans to catch on to the utility of high heels. In fact, according to a recent BBC article, Europeans never figured it out on their own – this invention came to Europe from Iran.

Source

The fashion for high heels went all the way to the top.

Louis XIV wearing his trademark heels in a 1701 portrait by Hyacinthe Rigaud (source)

In the early-modern Europe high-heeled footwear also served an important function of distinguishing the nobility from the peasants. Then came the Age of Revolutions (from the French Revolution of 1789 to the Paris Commune of 1870), which introduced a new era that stressed equality and blurred class lines. At the same time, the horses gradually lost their function as the means of land transport, being replaced by railroads and the automobile. And so high heels lost their functionality, and became just a fashion fad. Or nostalgia.

Clint Eastwood, the Man with No Name (source)

Although the model is very simple, this simplicity is somewhat deceptive. The model, in fact, combines a number of factors, which have been proposed as explanations for the wage slump, in a very frugal way. Thus, immigration (both legal and illegal) enters the equation by making the labor supply increase faster. Trade deficit, on the other hand, subtracts from the GDP, and thus decreases the demand for labor. Real minimum wage moved in parallel with a number of other indicators reflecting the action of non-market forces. The model, thus, can be used as a common framework within which different explanations can be compared to each other quantitatively.

A disbalance between labor supply and demand clearly played a very important role in driving real wages down. As Harvard economist George J. Borjas recently wrote, “The best empirical research that tries to examine what has actually happened in the U.S. labor market aligns well with economy theory: An increase in the number of workers leads to lower wages.”

Between 1977 and 2012 demand for labor increased only by 31 percent, while supply grew by 56 percent. A big chunk of the increase in the labor supply was simply the overall population growth. Between 1977 and 2012 the population of the United States increased by roughly 42 percent (without immigration it would be less).

But the supply of labor increased much faster. One big factor is immigration. In 2011 the total American work force was 153 million, of which 24.4 million workers (15.9 percent) were foreign-born (this number includes both legal and illegal immigrants).

So immigration had a big effect. But consider the second factor, an increased proportion of women who enter the labor force. Back in the 1970 only 40 percent of women were in the labor force, today it is close to 60 percent. If labor participation rate of native women (so that we don’t double count foreign-born women in the labor force) stayed at its 1970s level, today there would be 20 million fewer workers – an effect of the same magnitude as that of immigration.

Before the turning point of the 1970s the American work force was predominantly male and native-born. In the last decades, the oversupply of labor drove down the wages of males, both for the lowest paid 10 percent and for typical (median) workers:

Source of data: State of Working America

If median wages of men declined, why did the median household incomes continue to rise after 1979, even if much slower than the growth in GDP per capita? The answer is: an increasingly greater proportion of married women working and women earning more, as a result of their wages gradually converging to those of men. As men’s real wages declined, an increasing number of families switched to two-earner households, which allowed them to increase their combined income.

The supply of labor is affected by additional factors, such as changing age composition of the population, but these factors are of much lesser magnitude, so let’s not worry about them. But there are other important factors on the demand side that we need to look at next (in a future blog).

Valentina Kulagina, “International Working Women’s Day is the day of judging of socialist competition,” 1930. Source

You are an heir of a Noble House. Your enemies, who include the emperor and a powerful noble, have assassinated your father and destroyed your House. You have escaped, but you have no loyal retainers, no troops, no allies, and no money.

You want revenge! But you also want to rebuild your House. In practical terms, this means that you need to destroy the evil baron and overthrow the emperor.

How can you do it?

Avid consumers of science fiction (like myself) will probably recognize this predicament as that of Paul Atreides (Muad’Dib), the protagonist of Frank Herbert’s great novel DUNE.

DUNE is a complex, multilayered work. It has everything – a complex and dynamic main hero, great villains, neat ecology (planetology!), philosophical and religious insights, and (what is particularly fascinating to me) a well-structured social world.

But how well did Frank Herbert construct the social reality of DUNE? For an answer to this question I turn to the new science of Cliodynamics, and to centuries-old ideas of the great medieval Arab sociologist Ibn Khladun (whose main ideas have been validated by recent research).

Consider the balance of forces that young Paul Atreides needs to contend with.

His assets are, first, himself. And this is a pretty strong asset. He is extremely intelligent and has been trained in ‘Mentat’ techniques, which means that his brain can operate as a computer. He has been trained by his mother in Bene Gesserit techniques of body and mind control. He is an accomplished fighter. In short, Paul is an awesome human being. His second asset is his mother, Jessica the Bene Gesserit witch, who is also a pretty awesome person.

But the forces arrayed against Paul and Jessica are enormous. First, it’s the Padishah emperor, Shaddam IV and his Sardaukar. The Sardaukar are tough, loyal, and extremely capable shock troops, unrivaled by any other fighting force in the known universe. Second, it’s the evil Baron Harkonnen and his house. Harkonnens are also filthy rich.

Paul’s enemies are enormously powerful and wealthy. He can’t defeat them by himself (even helped by his mother). His individual power is not enough; he needs others – thousands, ultimately millions of others – to succeed in his quest. In short, he has to acquire social power.

The first decision fork he comes to is right after the disaster strikes, and the House Atreides is all but destroyed. Should he become an urban guerilla, by organizing and leading an uprising in Arrakeen and Cartag? There are a lot of advantages to this course of action. It is extremely difficult to winkle out urban guerillas from the population that supports them, even if passively.

The other route is to become a desert warrior, which means recruiting the Fremen to your cause. So, which road to take?

Ibn Khaldun says that you should put your money on the Fremen, and Cliodynamics concurs.

Statue of Ibn Khaldun in Tunis

Who is, or rather was, Ibn Khladun? This great Arab historian and sociologist was born in Tunis in 1332 and died in Egypt in 1406. He served as ambassador, prime minister, and supreme justice in various North African states, and traveled from Spain to Middle East. He was imprisoned by rulers, and he led an uprising of desert Fremen against those rulers.

Oops, I mean, Berbers, not Fremen. But it’s the same thing, so we should listen closely to his advice.

One of the most important concepts in Ibn Khaldun’s theory of history was asabiya, the social glue that binds individuals into cohesive social groups. Groups wielding greater asabiya impose their will on (if not defeat outright) groups possessing lesser asabiya. But how do groups acquire asabiya and why do they lose it?

Ibn Khaldun argued that the Desert was the crucible of asabiya. Only groups that have high asabiya can survive and thrive in this harsh environment. In contrast, in the urban civilization asabiya is gradually degraded, until they lose their ability for concerted collective action.

Satellite view of Northwest Africa: if you wrap this landscape around a ball, you will get Arrakis

This is why Ibn Khaldun says, go to the desert. (This is what he himself did – when he decided to rebel against one of the rulers of North African states, he went into the desert and organized a Berber uprising.)

The Fremen live in a very harsh environment. What’s most important is not the harsh physical environment, but the harsh social environment. Before the Atreides acquired Arrakis, it was brutally governed by the Harkonnens, who “hunted the Fremen like animals.” The Harkonnen goal was to exterminate the Fremen. Instead what happened was that they imposed a selection regime under which only the toughest, most capable, and most cohesive Fremen tribes survived. The Harkonnens also inadvertently imposed a regime of shared pain and suffering that, as recent research shows, leads to social ‘fusion.’

To cut the long story short, the Fremen on Arrakis evolved into tough, even fanatical warriors. Given some additional training they are quite capable of matching, and even surpassing the dreaded Sardaukar. The Fremen have a lot of asabiya.

But there is a problem for Paul. While tribal-level asabiya is a great social glue, making each tribe an effective war machine, Paul needs to unify all desert tribes to defeat Shaddam and the Harkonnens. In order to bind the Fremen into a single force, tribal asabiya is not enough. Another kind of social glue is necessary.

Ibn Khaldun says (and Cliodynamics concurs) that Paul Muad’Dib needs religion. It is religion that has the potential to weld disparate tribes (and more generally, ethnic groups) into a cohesive force. Perhaps the most famous example is the rise of Islam, when Prophet Muhammad united the tribes of Arab Bedouins, which his successors lead to conquests from Spain in the West to what is now western China in the East.

Fortunately for Paul, the Bene Gesserit missionaries have already prepared the ground by planting among the Fremen prophecies of a messiah to come. Somewhat reluctantly, Paul assumes the role of the Mahdi (the prophet) in the new religion, which unleashes the Fremen Jihad across the universe.

The final ingredient that’s needed is a charismatic leader. This is the easiest, because he is, as I said before, a pretty awesome human being. Interestingly enough, although Frank Herbert devotes a lot of attention to how wonderful Paul is as a fighter, historically speaking, a great martial capability is not a particularly important requirement for a successful leader. Muhammad, for example, was not an accomplished martial artist.

What is more important is charisma, ability to fire up followers. Equally important is just plain luck. It is critical for the potential leader to win the first two or three engagements. Especially if he is a religious leader. Victory validates his claim to divine support.

Stilgar: a great sietch leader, but he can’t unify all Fremen

It is also important that the leader comes from outside the social system. It is extremely difficult for one of the tribal leaders to unify the tribes by imposing himself as an overarching authority. The other tribal leaders are liable to say: why you and not me? This quickly leads to bickering and things falling apart. This is why great unifiers, such as Muhammad, Chinggis Khan, and Paul Muad’Dib, were relative outsiders (but at the same time, they were attuned to the culture of the people they ended up leading).

To conclude. Paul Atreides has all the tools to engineer a comeback. He has two kinds of social glue – tribal-level asabiya that produces fanatical, highly effective warriors, and religion, asabiya that glues together tribes. He is just the right kind of a leader. He still needs luck, but otherwise the defeat of his enemies is all but inevitable. So yes, Frank Herbert did a pretty good job of social engineering.

Also sprach Ibn Khaldun (and Cliodynamics concurs).

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A Note: The preceding is the text of my presentation at the Science at the Movies before we watched David Lynch’s screen adaptation of DUNE. You can watch the video here (warning: the quality of sound is not great)

What I will do now is called the stepwise analysis: I will build the model in a series of steps, adding a single explanatory variable in each step. This approach allows us to understand whether any of the explanatory factors are necessary to explain the dynamics of the response variable (which is, in our case, the real wage from 1927 to 2012). We will also be able to see which features of the data each explanatory variable helps us to understand.

The first step is to look into the effect of growth in GDP per capita:

What we see is that the growth of GDP per capita explains why real wages in 2012 are higher than in 1927, but not much of anything else. Over the last 85 years GDP per capita grew fairly steadily, although sometimes at a faster, and at other times at a slower rate. There is not a hint of a break in the GDP curve during the late 1970s, when the real wage abruptly shifted from the fast growth regime into that of stagnation and decline. Why did the growth rate of real wages outpace that of GDP per capita before 1970s? Why did the growth rate of GDP per capita outpace that of real wages after the 1970s? We need to look to other factors for possible explanations.

The model that takes into account both GDP (per capita) and labor supply/demand ratio yields the following results:

Statistical analysis says that this model explains data substantially better than the model with just GDP. The predicted curve hints that demand/supply ratio may be responsible for some of the trend reversals in the data, but overall, the model is not particularly satisfactory.

The next step is to add the proxy for non-market forces (“culture”):

Adding this variable results in a dramatic improvement of the model-generated trajectory. But we are not done yet. Notice that the break point in the model curve, when it shifts from the growth to the stagnation regime, occurs several years before the break point in the data. As I discussed in a previous installment, this is precisely the expected pattern. As economic conditions change (for example, supply begins to overtake demand for labor), wages do not adjust to the new situation immediately. Contracts need to run their course and be renegotiated, and both employers and employees don’t yet know whether this year’s conditions are part of the long trend, or just a temporary spike. This means that real wage this year actually reflects the social and economic conjuncture that obtained several years ago.

It looks like the lag time involved in the response by wages is at least five years. Re-analyzing the model by regressing real wages on the values of explanatory variables lagged by five years, yields the following result:

We now see that the model now accurately predicts the break point, which is not surprising, because I introduced the delay parameter to account for this feature. What is surprising is that the model now predicts the wage dynamics during the stagnation phase: down during the 1980s, up until the early 2000s, and then down again. Such fine-scale correspondence between the model trajectory and data is entirely unexpected, and serves to further strengthen our confidence in the ability of the model to capture the forces driving the dynamics of real wages.

Additional exploration of various combinations of explanatory variables confirms that all three components are needed to replicate the data pattern. The conclusion is that real wages grow faster, or slower than “per capita income” (GDP per capita) due to an interplay between market forces (captured by the labor demand/supply ratio) and cultural influences (proxied by the real minimum wage).

What’s new here is the use of the real minimum wage as a proxy for ‘cultural’ forces (remember, that this is my shorthand notation for such non-market factors as social norms and values, political and legislative landscape, and the balance of power between employers and employees). As far as I know, nobody has attempted to include ‘culture’ in a quantitative analysis of forces affecting real wages. But once we do so, we find  that culture is of paramount importance (quantitatively, its effect is greater than that of the demand/supply ratio).

What else?

It would be desirable to do two other things. First, the model is very simple, which is definitely a virtue. It folds a number of factors that have been discussed by economists and reporters (immigration, trade deficit, labor productivity, etc.) into a single measure, demand/supply ratio (and similarly with the cultural influences). I need to ‘unpack’ this aspect of the model so that we can weigh the relative contributions of such factors to the overall outcome (whether wages grow or stagnate). This looks like a good topic for the next blog.

Second, the model does not incorporate (at least explicitly) the effect of technological evolution. Some of it is folded into the growth of the GDP, which I take as given, but it would be extremely interesting to look at its effect as a separate explanatory variable. Does anybody know of a good proxy for this very important factor?

Technical note

As I promised in a previous blog, I plan to post a document that provides technical details of the statistical analysis that generated the results I discuss above. This has been delayed due to heavy teaching and demands on my time last week, but I will get to it as soon as I can. For those who can’t wait, the regression model looks like this:

where W is the real wage, G/N is GDP per capita, D/S is the labor demand/supply ratio, and C is the real minimum wage; τ is the time lag. The predictor variables were smoothed by kernel regression with bandwidth = 4 y (the response variable, naturally, is not smoothed).