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divide into movements affecting the unskilledprimarily peasants or ex-peasants — and movements of elites.
4)First, consider mass migration patterns. My hypothesis rests on the idea that differential patterns of
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mortality were created by the conditions of city life. This in turn permanently drew migrants from their
places of birth — into cities, on the one hand, and off towards the frontiers of settlement, on the other. How
epidemiology could create and sustain such a double pattern of die-off and compensatory migration
40
requires a little explanation. When comparatively large numbers of human beings began to live in cities,
many different infections became more common because proximity multiplied opportunities for parasitic
organisms to pass from one human host to another. Not only this: when human numbers attained a critical
45
threshold (sometimes in the hundreds of thousands), entirely new
forms of infection that passed directly
from human to human with no intermediate host or dormant form of the infectious organism became
viable. These infections constitute the array of familiar childhood diseases of the recent past: smallpox,
50
measles,
mumps, and the like. Such diseases could survive only within civilized societies, since only there
were human numbers and frequency of contact sufficient to allow the infectious organism to find an
unceasing succession of new hosts.
5)This class of infections provokes antibody formation in infected humans so that one exposure to the
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disease will create immunity for many years, usually for a lifetime. In a disease-experienced population,
therefore, only children are suitable hosts for these infections. But among inexperienced populations this is
not the case. In such societies adults are just as vulnerable as children to infection and death. Thus the
60 impact of these civilized disease's upon disease-experienced populations is entirely different from their
impact upon virgin populations: a fact of enormous import for human history.
6) A result of the intensification of infection that urban conditions of life induced was that until the
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latter part of the nineteenth century cities were population sumps. Eighteenth-century London, for instance,
required an in-migration of an average of 6,000 persons per annum simply to maintain itself — a sum of
600,000 for the entire century, which was more than the entire population of the city in 1700. No
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comparably reliable figures exist for earlier ages; but I believe this necessity for recruiting urban
population from the countryside — what we can perhaps call the Dick Whittington syndrome — is about as
old as cities themselves.
7)The reasons for saying this are twofold. Early (ca. 2000 B.C.) Mesopotamian texts such as the Epic of
Gilgamesh refer casually to lethal epidemic infection as an evidence of divine power. This shows that
conspicuous and demographically significant epidemic infections had become routine aspects of
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urbanism by 2000 B.C., i.e., within the Hrst millennium of city living. Secondly, the language of
administration and record-keeping in the cities of southern Mesopotamia shifted during the third
millennium from Sumerian to Akkadian. I believe that this shift registered the result of in-migration to the
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(initially) Sumerian-speaking cities from the Akkadian-speaking countryside — a pattern of migration that
at some point must have assumed such velocity as to make it unnecessary for the in-migrants to learn the
language of the established managers of the city. A modem parallel from European history is the way in
90
which Prague and Budapest ceased to be German-speaking cities when the pace of in-migration from the
Czech — and Magyar-speaking countryside assumed an increased velocity in the course of the nineteenth
century, partly in response to industrial expansion, and partly as an aftermath of cholera (and other
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epidemic) die-off of German-speaking urban dwellers. It seems possible, therefore, that the linguistic shift
in ancient Mesopotamia (which had no apparent political or military base) attests the existence in remote
antiquity of the same rural to urban migration current that played such a prominent role in eighteenth
100 century London and nineteenth-century Prague and Budapest.
8) Armies constituted another significant population sump for civilized societies. They assumed
demographically significant roles about a thousand years after cities first came into existence. It is, indeed,
105 useful to think of armies as mobile cities, exercising power over the countryside from a movable focus in
much the same way that cities were accustomed to exercise power over their rural hinterlands from a fixed
location. And like cities, the human density of armies (and of people fleeing before their ravages) induced
110 intensified infections that were far more lethal than weapons. In modem times, when figures become more
or less accurate, soldiers' deaths from disease far outranked deaths in action until after the Boer War,
1901-3.
115 9) Rural emigrants had, accordingly, two alternative paths of migration available to them: either moving
into the city to make their fortunes as chance and aptitude and places opened by die-off of older urban
populations might permit, or serving in an army-voluntarily or by conscription — and pursuing a
120 career under arms, where life expectancy was even shorter than in town and the pattern whereby fresh