When I was a teenager I read William H. McNeill's Plagues and Peoples, an attempt to sketch out a brief history of the world shaped by the parameter of disease (I also recommend The Human Web: A Bird's-Eye View of World History, where the same author takes a broader view of events). Though I enjoyed it, I was a different person then, and since I know quite a bit more evolution, history and basic biology now, I thought I'd check it out again. And I am glad for it, Plagues and Peoples was published in the 1970s, but it prefigures many of the points brought up in recent works such as 1491 and A Farewell to Alms. McNeill makes grand, and occasionally preposterous, connections; but the overall effect of his incredible synthesis of the details of textual history, the empirical record of disease and evolutionary theory is highly illuminating.
Consider the case of Sumer, often termed the "Cradle of Civilization." Though less famous than Egypt, it was in Mesopotamia that the first hallmarks of higher culture flowered; from literacy to city-states. The people who we term Sumerians were ascendant between 3000 and 2000 B.C.E, after which they were succeeded by the Amorites who founded the Babylonian culture. The Babylonians inherited and transmitted much of Sumerian civilization; and the language of the Sumerians became a religious and ritual language, much like Latin. But there is a difference: the languages of Western Europe are by and large genetic descendants of Latin, while Sumerian was a linguistic isolate unrelated to any other language then or now. Ancient Mesopotamia seemed to be a polyglot region, and our knowledge of linguistic geography is likely constrained by the fact that we view it through the lens of literacy. But one thing that does seem to be clear is that speakers of Semitic languages were extant across Mesopotamia from a very early period. Though Sumerian speakers were dominant in the city-states, Semitic names for potentates exist from the very beginning of the history of the region, implying that non-Sumerians were not necessarily marginal outcastes or necessarily subordinate. Over time these Semitic elements came to become more prominent, until Sumerian went extinct as a spoken language during the period between 2000 and 1750 BCE, as classical Babylonian civilization crystallized, exemplified by Hammurabi.So what happened to the Sumerians? I point out that the post-Sumerian languages of Mesopotamia were Semitic, and not lineal descendants of Sumerian, to emphasize that one can not make an argument here that there was a linguistic evolution. The question of when Latin ended and Italian began is somewhat academic, and it was many centuries after the fall of Rome that the people of the Mediterranean realized that they no longer lived in the Classical World and that no restoration of the old order would occur. In contrast, though the post-Sumerian peoples perpetuated a host of Sumerian cultural forms and motifs, using their script, translating their gods and continuing the evolution of architectural styles, it seems that the fact that the dominant class spoke languages which were as similar to Sumerian as Chinese or English (aside from borrowings of vocabulary) counts for something. The end of the Sumerian ascendancy was marked by invasions of a people termed the Guti, but this was not the first nor would it be the last incursion into Mesopotamia by barbarians. The period of chaos brought about by the Guti invasions does not seem sufficient probable grounds for a cultural break of the order of a language shift among the Mesopotamian elites. Another phenomenon which must be noted is that Semitic peoples from the desert were constantly moving into rural areas; so one could posit simple population replacement through migration as being the primary driver of change. But there seems to be an ecological consideration which makes wholesale replacement implausible: the density of human populations in deserts is generally far lower than in arable lands. I can not imagine that former nomads were more than a tiny fraction of the number of farmers during any given period. Likely there were already large numbers of Semitic speaking peoples who were already farmers and of long residence, so the influx of outsiders who spoke affinal dialects might have had a quantitative affect, but it does not seem to be a likely cause for the collapse of Sumerian city culture and the switch to Semitic as the dominant identity.McNeill offers a simple point in Plagues and Peoples which I think is possibly part of the answer, and may along with other necessary conditions be one of the main pillars for the disappearance of the Sumerians: pre-modern cities were unhealthful places and have traditionally been population sinks because of their disease burden. In other words, by the act of moving to the city a farmer may increase their short-term prosperity (I would assume that many peasants migrated to urban areas due to dislocation or dispossession as opposed to positive opportunities), but sharply reduces their long-term fitness because mortality rates for their offspring and offspring's offspring will be so high. Cities maintained, or increased, resident populations through absorbing the excess from rural areas. Mesopotamia for the one thousand years during which Sumerians were ascendant was the most urbanized region of the world, and McNeill points to historical evidence which suggests it was one of the earliest plague loci because of the density of living as well as trade contacts. As I note above it was a culturally diverse region, but for most of that period Sumerian identity intersected predominantly with the political elites who were resident in the cities (both temporal and sacral). Though most Sumerians might not have lived in cities, most city-dwellers were Sumerian. In contrast, it seems likely that Semitic peoples would be more dominant, if not always a majority, across great swaths of the rural areas, especially those somewhat marginal as farmland and so given over to some level of nomadism. For any given peasant one could posit a model where a Sumerian speaker was more likely to change status and move to the cities because their cultural identity was an easier fit in an urban milieu. Concomitantly there was always a flow of Semitic nomads into rural areas. Over time one could imagine that the proportion of Semitic speakers slowly increases in the countryside. In the cities Sumerian remains dominant in part due to acculturation of non-Sumerian speakers and the emigration of Sumerian speakers from rural areas to cities. So long as the shocks to this dynamic were modest enough one could imagine this system existing at a level of metastability for long periods. In other words, despite the decrease in the proportion of the Sumerian speaking peasantry, the cities remain redoubts of that language because it is the lingua franca perpetuated through cultural transmission asnon-Sumerian speaking become converted to Sumerians language shift. But one could foresee at some point that socio-political disruptions combined with a particular sharp increase in the number of immigrants could overthrow this structure; and once Sumerian speakers were thrown down from their cultural heights without a rural reserve to replenish them they might quickly diminish in numbers in just a few generations!This is possibly not the whole story, or even part of the real story. But, it is I think an important consideration. An acquaintance of mine, a physicist, asked me recently if I believed cultural anthropology could become a science like geology, with robust generalizable insights. I offered a qualified yes, but, I did stipulate that cultural anthropologists have to integrate the findings of lower complexity disciplines (psychology, economics) in the construction of their models, as well as use formal quantitative frameworks to scaffold their hypotheses. Biology is part of history. The Black Death in medieval Europe, the plague during the reign of Justinian and the pandemics with swept the New World during the 16th to 18th centuries have all had important historical consequences. The concentration of persons of indigenous ancestry in highlands and those of African origin around continental littorals across the tropical Americas has causal parameters of a biological nature. McNeill's conjectures are perhaps a bit too ambitious, and the trend of always finding nails for his hammer certainly is present in Plagues and Peoples, but overall I judge the arguments to be far more fruitful in generating inferences than vague assertions about the omnipresent role of "power relations" in human history or an overly narrow and historically contingent argument about class struggle.1 - The period before 3000 is murky in part because literacy does not push much further before that point.2 - The northern city of Kish, which for many centuries was the most powerful hegemonic power among the city-states of Sumer, seemed to have had a dominant Semitic element.3 - A parallel process occurred in the Ottoman provinces of Iraq in the past few centuries with the reopening of lands due to modern irrigation techniques. Whole clans of Arab nomads settled down to become farmers, and during this period they converted from Sunnism to Shiism under the influence of the nearby Shia holy cities.4 - Not only are person of African ancestry more resistant to diseases introduced during the period of the slave trade, but in the case of the peoples of the Andes they themselves had biological advantages at high altitude. Some literature suggests that women of European ancestry suffered higher miscarriage rates at the upper elevations.
