Sunday, January 17, 2010

A model of the history of human misery   posted by Razib @ 1/17/2010 08:24:00 PM

In the comments below I was outlining a simple model which really is easiest to communicate with a chart. I removed the labels on the Y and X axes because the details don't matter, the X axis is simply "time," and the Y axis simply reflects the magnitudes of the three trendlines. The key is to focus on the relationship between the three. I've labeled for clarity, but more verbal exposition below....

For most of the human history we've been hunter-gatherers. But over the past 10,000 years there was a switch in lifestyle, farming has emerged independently in several locations, and filled in all the territory in between. One truism of modern cultural anthropology is that this was a big mistake, that hunter-gatherer lifestyles were superior to those of peasant farmers, less miserable with much more free time. I think this is somewhat unsubtle, which is ironic since cultural anthropologists really love to deconstruct the errors of others which they themselves are guilty of (i.e., in this case, the normative aspect immediately jumps out in the scholarship. There's little doubt as to who they're "rooting" for).

I am willing to grant that the median hunter-gatherer exhibits somewhat less morbidity than the median farmer. They're taller and have better teeth than farmers. Compared to modern people living in developed countries though the differences will seem trivial, so remember that we're talking on the margins here. So why did societies transition from hunter-gathering to farming? I doubt there's one simple answer, but there are some general facts which are obvious.

There's plenty of evidence that farming supports many more people per unit of land, so in pure demographic terms hunter-gathering was bound to be doomed. They didn't have the weight of numbers. But why did the initial farmers transition from being hunter-gatherers to farmers in the first place? Because I think that farming was initially the rational individual choice, and led to more potential wealth and reproductive fitness. Remember, there's a big difference between existing in a state of land surplus and one of labor surplus. American farmers were among the healthiest and most fertile human populations which had ever lived before the modern era. Pioneers had huge families, and continued to push out to the frontier. This was not the lot of Russian serfs or Irish potato farmers. But eventually frontiers close, and Malthusian logic kicks in. The population eventually has nowhere to go, and the surplus of land disappears. At this point you reach a "stationary state," where a peasant society oscillates around its equilibrium population.

I suspect that new farming populations which slam up against the Malthusian limit suffered even more misery than their descendants. This is because I believe that their demographic explosion had outrun their biological and cultural capacity to respond to the consequences of the changes wrought upon their environment. First and foremost, disease. During the expansionary phase densities would have risen, and infectious diseases would have begun to take hold. But only during the stationary state would they become truly endemic as populations become less physiologically fit due to nutritional deficiencies. The initial generations of farmers who reached the stationary state would have been ravaged by epidemics, to which they'd only slowly develop immunological responses (slowly on a human historical scale, though fast on a evolutionary one). This is even evident in relatively recent historical period; Italians developed biological and cultural adaptations to the emergence of malaria after the fall of Rome (in terms of culture, there was a shift toward settlement in higher locations).

But there would be more to adapt to than disease. Diet would be a major issue. During the expansionary phase it seems plausible that farmers could supplement their cereal based diet with wild game. But once they hit the stationary phase they would face the trade-off between quantity and quality in terms of their foodstuffs. Hunter-gathering is relatively inefficient, and can't extract as many calories per unit out of an acre (at least an order of magnitude less), but the diet tends to be relatively balanced, rich in micronutrients, and often fats and protein as well. The initial shock to the physiology would be great, but over time adaptations would emerge to buffer farmers somewhat from the ill effects of their deficiencies. This is one hypothesis for the emergence of light skin, as a way to synthesize vitamin D endogenously, as well as greater production of enzymes such as amylase and persistence of lactase, which break down nutrients which dominate the diet of agriculturalists.

Once societies reached a stationary state it would take great shocks to push them to a position where becoming hunter-gatherers again might be an option. A population drop of 50%, not uncommon due to plague or political collapse, would still not be low enough so that the remaining individuals would be able to subsist upon game and non-cultivated plant material. Additionally the ecology would surely have been radically altered so that many of the large game animals which might have been the ideal sources of sustenance in the past would be locally extinct. The collapse of the Western Roman Empire and the highland Maya city-states seems to have resulted in lower population densities and reduced social complexity, but in both regions agriculture remained dominant. On the other hand, there is some evidence that the Mississippian societies might have experienced die offs on the order of 90% due to contact with Spanish explorers, and later ethnography by European settlers suggests much simpler tribal societies than what the Spaniards had encountered. Though these tribal groupings, such as the Creeks, still knew how to farm, it seems that judging from the conflicts which emerged due to European encroachment on hunting grounds that this population drop was great enough to allow for a greater reversion to the pre-agricultural lifestyle than was able to occur elsewhere. But then the pre-Columbian exchange and the exposure of native populations to the 10,000 years of Eurasian pathogen evolution was to some extent a sui generis event.

The model I highlight above is very stylized, and I am aware that most societies go through multiple cycles of cultural, and possibly biological, adaptation. The putative massive die off of native populations of the New World may have resulted in a reversion to simpler hunter-gatherer cultural forms in many regions (North America, the Amazon), and also reduced morbidity as diets once more became diversified and indigenous infectious diseases abated due to increased physiological health and decreased population density. In China between 1400 and 1800 there was a massive expansion of population beyond the equilibrium established between the Han and Song dynasties. The reasons for this are manifold, but one was perhaps the introduction of New World crops. Clearly in Ireland the introduction of the potato initially resulted in greater health for the population of that island, as in the 18th century the Irish were taller than the English because of their enthusiastic adoption of the new crop.

Over the long term, at least from the perspective of contemporary humans, agriculture was not a disaster. Dense populations of farmers eventually gave rise to social complexity and specialization, and so greater productivity. Up until the 19th century productivity gains were invariably absorbed by population growth or abolished by natural responses (e.g., in the latter case Sumerian irrigation techniques resulted in gains in productivity, but these were eventually diminished by salinization which entailed a shift from wheat to barley, and eventually an abandonment of many fields). Additionally, the rise of mass society almost immediately birthed kleptocratic rentier classes, as well as rigid social forms which constrained human individual choice and possibilities for self-actualization. The noble savage who lives in poverty but has freedom may look ludicrous to us today, but from the perspective of an 18th century peasant who lives in poverty but has no freedom it may seem a much more appealing model (though these sorts of ideas were in any case the purview of leisure classes).* But 10,000 years of crooks who innovate so that they could continue to steal more efficiently eventually gave rise to what we call modern capitalism, which broke out of the zero-sum mentality and banished Malthusian logic, at least temporarily (remember that it is critical to note that population growth leveled off after the demographic transition, which allowed us to experience the gains in productivity as wealth and not more humans).

I should qualify this though by noting that we can't know if the emergence of modern capitalism was inevitable in a historical sense. It happened once in Western Europe, and has spread through the rest of the world through emulation (Japan) or demographic expansion (the United States). The only possible "close call" was Song China, which had many of the institutional and technological preconditions, but never made the leap (whether that was because of the nature of the Chinese bureaucratic state or the disruption of the Song path toward capitalism by the Mongol conquest, we'll never know). By contrast, the spread of agriculture was likely inevitable.** Agricultural emerged at least twice, in the Old and New World, and likely multiple times in the Old World. Kings, armies and literacy, and many of the accoutrements of what we would term "civilization" arose both in the Old and New World after the last Ice Age. In all likelihood a confluence of biological, cultural and ecological conditions which were necessary for the rise of agricultural civilization were all in place ten thousand years ago. This also suggests that certain biological adaptations (e.g., lactase persistence) were also inevitable.

* Though from what I have read hunter-gatherers are strongly constrained by their own mores in a manner which rivals that of traditional peasant societies; only they have no priests who have written the customs down and serve as interpreters. Rather, it is the band (mob?) which arbitrates.

** We have data on independent shifts toward agricultural lifestyles. We don't have data on independent shifts toward modern capitalist economies. I suspect that the shift toward capitalism is probably inevitable over the long term because I don't think pre-modern agricultural civilizations would ever have been exploitative enough of the natural resource base that they would have been subject to worldwide collapse in any normal timescale. So there would always be potential civilizations from which modern post-Malthusian technological civilization could have emerged.