The rhythms of population recovery offer yet another parallel between East and West. By the latter part of the tenth century, Chinese populations, like those of northwestern Europe, seem to have achieved a successful biological accommodation to whatever new infections had assailed their forefathers in the preceding centuries. Human numbers began to grow at a pace to produce a population for the entire country of about 100 million by A.D. 1200.85 To achieve such mass, two things were needed: a suitable microparasitic accommodation to the ecological conditions of the Yangtze Valley and regions farther south, and a regulated macroparasitism that left enough of their product with the Chinese peasants so that they could sustain a substantial rate of natural increase over several generations. Only then could the teeming millions of rice paddy farmers fill up the relatively vast spaces of central and southern China.
The biological adjustments required for survival in southern China probably took a long time. Signs of really dense populations in the Yangtze Valley and farther south do not become very noticeable until the eighth century; and only under the Sung Dynasty (960–1279) does anything like the population density familiar from ancient times in the Yellow River valley begin to exist in the Yangtze and other southern areas. As we saw in Chapter II, malaria, bilharzia, and dengue fever were probably among the major obstacles to Chinese penetration southward. Variations of inherited human resistance to these infections, together with very delicate balances between different species of mosquitoes, the prevalence of different kinds of warm-blooded animals (humanity being only one possible supplier of blood for mosquitoes, after all), and the virulence of the infectious organism itself, undoubtedly controlled the incidence and seriousness of these diseases. But we cannot expect to recover details of how Chinese peasants learned to survive and flourish in the South with the densities their style of rice paddy cultivation allowed. It is enough to realize that this adjustment was probably not perfected until after A.D. 700, and full occupancy was not attained until about 1100.
As for the macroparasitic side: with the establishment of the Sung Dynasty in A.D. 960 a relatively successful bureaucratic system spread throughout most of China (the northern tier of provinces remained under barbarian masters), and a remarkably rational pattern for training and selecting high officials became normal. While no one supposes that official oppression ceased, its scope may have been less under the Sung than in earlier times, since systematic supervision of the official class tended to check at least the more flamboyant form of corruption. The massive expansion of population into the South proves that traditional rents and taxes were set at a level that allowed the peasantry to thrive on hard work in the fields, at least as long as sufficient new land could be brought under cultivation to absorb surplus offspring.
Thus China apparently paralleled Europe’s disease experience fairly closely in the centuries with which we are here concerned, arriving at a balance between micro- and macroparasitism that was, in the short run at least, more successful than that of the West. In Europe, after all, local self-defense by formidable arrays of knights did not guarantee peace, since knights and their feudal superiors frequently fell to fighting among themselves, thereby damaging peasant life and production. China’s bureaucratic imperial administration was clearly superior from this point of view, as long as it continued to be able to ward off attack from the warlike barbarian peoples of the North and West. From the microparasitic side, too, one can rightfully say that the Chinese achievement was superior in the sense that Chinese populations moved up a disease gradient in learning to live successfully in warmer, wetter lands; whereas the shift of European populations toward the North was a movement down a disease gradient into lands where exposure to infestation was naturally less, thanks to cooler temperatures and longer periods of freezing winter weather.
China’s superior success in accommodating to altered conditions of micro- and macroparasitism was reflected in the country’s religious and cultural history. For after 845, Buddhism was replaced as a religion of state by a revived and elaborated Confucianism. It was as if Charlemagne, in reviving the title of Roman Emperor, had also restored paganism as the court religion. Buddhism, of course, continued to exist in China, appealing mainly to peasants and other uneducated classes. But victorious Confucianism absorbed and made its own some of the metaphysical doctrines that had helped to attract the court to Buddhism in the first place. Thus the antibodies that imported diseases provoked and sustained in Chinese bloodstreams had their analogues in the Buddhist themes engrafted into official Confucianism. For the new doctrines received into official Confucianism constituted moral and intellectual antibodies against the charms which Buddhist (and other alien) paths to salvation continued to exert among the lowly and uneducated classes.
Japan’s geographical position obviously tended to insulate the archipelago from disease contacts with the world beyond. This was, however, a mixed blessing, for insulation allowed relatively dense populations to develop which were then vulnerable to unusually severe epidemic seizure when some new infection did succeed in leaping across the water barrier and penetrating the Japanese islands. Japanese rural populations remained much sparser than was the case in China, at least until rice paddy farming established itself also in Japan (a process still under way in the seventeenth century); and Japanese cities remained much smaller than those of China until quite recent times. This meant that a number of important and lethal diseases that became chronic in China could not establish themselves lastingly among the Japanese until about the thirteenth century. Consequently, for more than six hundred years, before Japan’s population density surpassed the critical threshold that allowed these epidemics to subside into endemic infections, the islands suffered a long series of severe disease invasions.
The first recorded contacts with the mainland came in A.D. 552, when Buddhist missionaries from Korea first set foot on Japanese soil. The newcomers brought with them a new and lethal disease—perhaps smallpox.86 A similar severe outbreak occurred again a generation later, in 585, by which time immunities arising from the epidemic of 552 would have worn themselves out. A far more sustained epidemic experience began in 698 and ricocheted through the islands during the following fifteen years; the disease returned again in 735–37; yet again in 763–64; and twenty-six years later, in 790, “all males and females under the age of thirty were afflicted.” Periodic records of the return of this disease continue until the thirteenth century. Then it became a children’s disease (first so described in 1243), having at last achieved permanent lodgment within the Japanese islands.87
Dates for the introduction and eventual lasting establishment of other infectious diseases in Japan are not so clear. A new disease from which “over half the population perished” arrived in 808. By analogy from the evidence of the probable spread of plague along the China coast between 762 and 806, it seems at least possible that this was an irruption of bubonic plague into Japan, although absence of clinical description makes the identification merely a guess. In 861–62 yet another new disease—the “coughing violence”—hit the islands, and recurred again in 872, and in 920–23, with heavy loss of life. Mumps (whose distinctive swelling makes it a disease easy to recognize in ancient texts) appeared in Japan in 959; and recurred in 1029. In 994–95 another disease struck in which “over half the population died.” If such a statistic is anywhere near the truth, such a heavy mortality must also have been the result of an unfamiliar infection encountering a virgin population. The measles record is also of interest. The modern term used for measles appears for the first time in 756, but serious and repeated epidemics so named began only in the eleventh century (1025, 1077, 1093–94, 1113, 1127). It was first mentioned as a childhood disease in 1224—thus anticipating the date at which “smallpox” achieved a similar status by a mere nineteen years.
Such records show that the Japanese islands pretty well came abreast of the disease patterns of China (and the rest of the civilized world) during the thirteenth century. For more
than six hundred years prior to that time, however, Japan probably suffered more from epidemics than other, more populous, and less remote parts of the civilized world. As long as the island populations were not sufficient to enable such formidable killers as smallpox and measles to become endemic childhood diseases, epidemics of these (and other similar) infections coming approximately a generation apart must have cut repeatedly and heavily into Japanese population, and held back the economic and cultural development of the islands in drastic fashion.
Precisely the same considerations apply also to the British Isles. The surprisingly low level of British population in medieval times as compared to that of France, Italy, or Germany, may owe far more to the vulnerability of an islanded population to epidemic attrition than to any other factors. Without a lifetime of research, however, it is unfortunately not possible to compare the epidemic experience of Britain with that of the continent of Europe, since there is no continental equivalent to Charles Creighton’s classic, A History of Epidemics in Britain. Yet the very fact that Creighton could assemble so much data for the British Isles may itself reflect the fact that epidemics mattered more in Great Britain than on the main- land of Europe, where the shift to endemicity presumably occurred earlier because populations were larger and had more nearly uninterrupted contact with urban (initially, Mediterranean) sources of infection.
Moreover, in both Great Britain and Japan a critical threshold was eventually crossed when earlier vulnerability to epidemic disaster ceased to manifest itself. In Japan the transition took place in the thirteenth century; in Britain the catastrophic intervention of the Black Death in the mid-fourteenth century delayed matters, so that sustained population growth only set in after 1430. But once they had crossed the critical epidemiological threshold, Japanese and British populations both exhibited more dynamic growth than occurred on the adjacent mainlands. The effect in Japan was dramatic. A plausible estimate of Japanese total population runs as follows88:
Period Millions
ca. 823 3.69
859–922 3.76
990–1080 4.41
1185–1333 9.75
As for Great Britain, comparable estimates are only available for England89:
Period Millions
1086 1.1
1348 3.7
13 77 2.2
1430 2.1
1603 3.8
1690 4.1
Here the downturn resulting from the Black Death is dramatically apparent; and a doubling of population, such as probably occurred in Japan in the 250 years from 1080 to 1333, had its analogue in England only between 1430 and 1690, when population also almost doubled.
The laggard adjustment to infections that thus becomes evident in Britain and Japan can be clearly related to the political and military history of the two islanded peoples. England’s record of moving into and subduing the Celtic fringe within the British Isles is well known; the further effort to conquer France, beginning in 1337, illustrates an even more ambitious scheme for utilizing the strength inherent in a growing population. Once the Black Death struck, of course, the force went out of both movements. English expansion was resumed only under Elizabeth in the second half of the sixteenth century. In Japan’s case the pace of expansion within the archipelago itself (at the expense of the Ainu) and overseas (at the expense of Koreans and Chinese) also assumed noticeably greater speed and force from the thirteenth century onward. A big factor in this phenomenon must surely have been the achievement of a new disease balance within Japanese society, as once damaging epidemics coming from outside transformed themselves into less costly endemic infections.
Unfortunately, nothing in available scholarly writing allows any similar reconstruction of the disease history of the rest of the world. Very possibly, most of the new diseases to which European and Far Eastern populations had to accustom themselves in the centuries between A.D. 1 and A.D. 1200 had evolved previously in India and the Middle East. Plague, at any rate, seems pretty surely to have diffused east and west via the shipping lanes of the Indian Ocean; and the rash and fever afflictions that visited both the Roman and the Chinese worlds arrived by land routes, i.e., proximately, if not necessarily ultimately, from Middle Eastern lands.
Plague, when it came to Rome, came also to Mesopotamia and Iran, and may have been quite as devastating in those regions as it was in the Mediterranean.90 Since maintenance of canals required massive annual effort, any decay of population in Mesopotamia was sensitively registered by the abandonment of canals formerly in use. Modern surveys discover such a retreat in generations just before the Arab conquest in 651. Decay continued after the conquest as well.91 There is no reason to suppose that the Moslem newcomers wreaked any very significant damage to the irrigation system, since the Arabs were already familiar with irrigation and had no interest in destroying potential taxpayers. It therefore seems probable that something else upset the population balance of Mesopotamia. Although salting and other technical difficulties may have already made the irrigation system precarious, recurrent exposure to plague offers a plausible explanation of the precipitous decay of Mesopotamian population that accompanied and followed the Arab conquests of the seventh century A.D.
As for India, the existence of temples for worship of a deity of smallpox shows that the disease (or something closely akin thereto) was of considerable significance in Hindu India from time immemorial—however long that may be historically. Unfortunately, absence of records permits no account whatever of Indian encounters with infectious disease before 1200.
Because smallpox and measles are especially spectacular when they attack virgin populations, and because plague remained spectacular in its incidence always, these diseases almost monopolize literary references in those cases when it is possible to surmise what infection caused some sudden and large-scale die-off. But the same changes in human patterns of communication that propagated these infections in new regions obviously allowed other diseases also to circulate beyond earlier limits. This seems to have been the case with the disease modern doctors call leprosy, for a special study of more than 18,000 skeletons showed no signs of the disease until the sixth century A.D., when it appeared in Egypt, France, and Britain.92 On the other hand, skin ailments that fell under the Old Testament ban on leprosy must have been much older. The establishment of special houses for lepers is attested in Europe as early as the fourth century A.D., but this should not be interpreted as evidence of the arrival of a new disease. Rather, it was probably the result of the Roman government becoming Christian and taking seriously biblical injunctions about how to treat persons with disfiguring skin diseases.93
Other diseases must also have found new geographic range in the early Christian centuries. Some of them, tuberculosis, for example, or diphtheria and influenza, together with various forms of dysentery, may have exerted demographic effects comparable to the effects of smallpox, measles, and plague. Moreover, formerly formidable local diseases may have disappeared when forced to compete with some invading infection; at least, as we shall see in the next chapter, there is some reason to think that this happened in later times when new and drastic epidemics afflicted Europeans.
Uniformity of infectious patterns was never attained; but despite innumerable local variations, defined by climatic and other ecological factors, it seems reasonable to conclude that within the circle of Old World civilizations, a far more nearly uniform disease pool was created as a by-product of the opening of regular trade contacts in the first century A.D. By the tenth century, the biological adjustments provoked by this reshuffle of infectious patterns had had time to work themselves out both in Europe and in China, with the result that population began again to rise in each of these civilized areas. Correspondingly, the relative weight and mass of China and of Europe vis-à-vis the Middle East and India began to grow. Subsequent world history could in fact be written around this fact.
In addition, we may reasonably believe that a fringe of peoples all across Asia, and extending into both easte
rn and western Africa, entered at least marginally into the disease circulation centering in the older civilized lands. Moslem and Christian traders and missionaries penetrated far into the Eurasian steppe and northern forest lands; other pioneers of civilization infiltrated Africa. Everywhere they must have carried with them the possibility of exposure to civilized diseases, at least on a sporadic, occasional, once-a-generation or once-a-century basis.
Occasional heavy die-offs of some hitherto isolated population must often have occurred. Among the survivors, however, adjustment to the new epidemiological patterns of the Old World seems to have proceeded among the steppe peoples about as rapidly as it did in northwestern Europe. The reason for saying this is that Turks and other nomads, when they penetrated civilized landscapes, whether in Asia or in Europe, do not seem to have suffered any very sharp disease consequences. If they had been completely inexperienced with civilized diseases in their steppe homelands, these nomad invaders would have died off very quickly.
Plagues and Peoples Page 16