Plagues and Peoples

by William H. McNeill

  Clearly, whatever intensification of infection and infestation occurred when Chinese farmers began to spend a significant part of their working time in shallow standing water—and there must have been striking consequences of such a change from the semi-arid conditions of loess farming—the new patterns of disease did not forestall a steady increase in human numbers. Otherwise manpower for building and maintaining an ever-expanding network of dikes and water channels, not to mention the manpower for increasingly massive armies, would simply not have been available. When, however, engineering techniques along with the administrative and moral bases for stable imperial government had been achieved by the end of the third century B.C., nothing remained to inhibit the rapid development of central and southern China except the disease barrier. The power of that barrier is attested by the five to six additional centuries that elapsed before massive occupation of the Yangtze Valley by Chinese settlers became an accomplished fact. Put very simply, too many immigrants from the cooler, drier North died to permit a more rapid buildup.

  All these assertions remain uncomfortably abstract and a priori. As in the case of the Middle East, there is little hope of discovering from ancient texts exactly what the humanly dangerous parasites may have been. Still, ancient writers often betray keen awareness of the disease risks of the South. Thus, Ssu-ma Ch’ien, the founder of Chinese historiography, who lived from about 145 to 87 B.C., tells us: “In the area south of the Yangtse the land is low and the climate humid; adult males die young.”14 He also comments on the abundance of land suitable for cultivation and the sparsity of population in the region. This is authoritative testimony, for Ssu-ma Ch’ien made a personal tour of the country to prepare himself for writing his history. In later literature, the unhealthiness of the South was taken for granted. Special handbooks for southern travelers prescribed suitably exotic regimens and medicines for the malignant diseases encountered there.15 These did not help very much, as the remarkably short tenure of office and high mortality recorded for officials sent to the South attests.

  Modern disease distributions, so far as they can be plotted on the map of China, also confirm the expectation that a richer variety of infection and infestation flourishes in the warmer and wetter South. A number of modern disease boundaries fall between the Yellow River and the Yangtze, and climatic patterns certainly suggest that such a disease gradient is age-old.16 The form in which ancient Chinese medical texts have come down to us, however, tends to hide regional differentiations, for the long list of distinct diseases Chinese medical writers recognized were organized around the seasons at which they were most prevalent. Some, such as malaria, can be confidently recognized today; for many others such identification with modern classifications of infection is as difficult as it is to translate Galen’s language into twentieth-century medical terminology.17

  Malaria, although occurring occasionally in the North, is a modern health problem only in the South.18 In fact it may have constituted the principal obstacle to early Chinese expansion southward. Another mosquito-borne disease, dengue fever, which is closely related to yellow fever though not as lethal in modern times, also affects southern parts of China. Like malaria, dengue fever may have been present from time immemorial, lying in wait for immigrants from more northerly climes among whom prior exposure had not built up any sort of natural resistance. Fevers, including regularly recurring fevers that must have been malarial, figure very prominently in ancient Chinese medical writings, a fact that supports the notion that such afflictions mattered a good deal in the early centuries of Chinese expansion.19 Chinese materia medica of the nineteenth century also embraced several effective febrifuges—so much so that imported quinine scarcely seemed superior, even in the eyes of European doctors.20

  Schistosomiasis is another major health problem of southern and central China in modern times. It, too, has probably always conformed to climatically defined boundaries. The recent discovery of a corpse from the second century B.C. SO well preserved that evidence of chronic schistosomiasis could be positively discerned proves that this affliction had established itself in China before Chinese pioneers were able to develop the Yangtze Valley to anything like the levels familiar in the North.21

  All in all, one may say that the Chinese met with striking success—technical and political as well as epidemiological—in penetrating the difficult environment of the Yellow River flood plain in the centuries about 600 B.C. They achieved a no less striking success after about 200 B.C. in arriving at a tolerable and unusually stable macroparasitic balance between food producers and those who lived off peasant harvests. At the microparasitic level, however, far-reaching adjustments within the vast regions to the South were still under way during the pre- and post-Christian centuries. The Yangtze Valley and other territories under Chinese political domination from 211 B.C. (or earlier) could not be fully incorporated into the Chinese body social because of disease barriers until after the fall of the Han Dynasty (A.D. 221), when, as we shall presently see, other drastic and far-reaching disease adjustments also occurred.

  In India, information about the early agricultural development of the middle Ganges Valley and of adjacent regions closer to the Bay of Bengal is practically nil. Rice cultivation became important at an early time—but just when seems impossible to tell. Nor is it even clear how important irrigation was. In the Ganges Valley monsoon rains were fully adequate for most agricultural purposes without bothering to tap the Ganges’ waters. Irrigation was, however, essential for multiple cropping in a single year, since in summer and fall monsoon rains cease, and artificial means for bringing water to the fields became necessary if the land were not to lie idle until the rains returned. Multiple cropping has been widespread in recent centuries; how ancient it may be has never been satisfactorily established.

  What is known is that powerful and extensive kingdoms developed in the Ganges Valley beginning about 600 B.C. Soon after Alexander’s invasion (327–325 B.C.), one such state, ruled by Chandragupta Maurya (ca. 321–297 B.C.), united the entire region into a single imperial structure, and his successors extended their authority throughout most of the Indian subcontinent. Early in this political development, Prince Gautama, the Buddha (traditional dates: 563–483 B.C.), played a role strikingly parallel to that of his Chinese contemporary, Confucius. For like Confucius in China, Buddha in India articulated a world view and exemplified a style of life that became widely influential.

  As compared to China, however, both the political and the intellectual structures that arose in the Ganges region before and after 500 B.C. remained unstable, and never were consolidated into an enduring whole. One of the reasons—and perhaps a very pervasive factor in all Indian history—was the heavy microparasitism characteristic of a climate as warm and wet as that of the Ganges Valley and of the rest of India’s best agricultural lands.

  The cities and states around which subsequent Indian civilization crystallized were located in an environment very different from the semi-desert in which the earlier Indus civilization had been based. That civilization, indeed, occupied a region of India where the climate resembled that of Mesopotamia or Egypt. In the Indus Valley rain was scant and agriculture depended on irrigation. In the Ganges Valley, on the other hand, the monsoons brought abundant rain for part of the year, and the shelter of the Himalayas meant that temperatures practically never approached freezing. Such a climate is, in fact, wetter and warmer than the climate of the Yangtze Valley that Chinese farmers had such difficulty in penetrating because of the intensified risks of infection. Classical Indian civilization thus took form under climatic and (presumed) disease conditions that the early Chinese found too much to bear.

  Today the Ganges region sustains cholera, malaria, and dengue fever together with a great variety of multicelled parasites, as well as the more universal diseases of cities and civilization that are familiar in cooler climes. What disease organisms may have circulated in ancient times cannot be said for sure, but the climate of the Ganges Val
ley certainly must have permitted a rich array of parasites to arise as soon as dense human populations came into existence.

  Adjustment to survival in such a land had its advantages, of course. For people accustomed to the Ganges environment, other similarly situated river valleys of southeastern Asia—the Brahmaputra, Salween, and Mekong in particular—lay open to pioneer exploration and development. Accordingly, a “Greater India” arose overseas between about 100 B.C. and A.D. 500 through the efforts of Indian merchants and missionaries, who provided models of civilized living to the indigenous rulers and peoples of those parts. Some of the islands of Indonesia also shared in this development. The geographic range and cultural significance of Indian expansion overseas in these centuries is hard for heirs of a civilization that scarcely extended beyond the narrow confines of the Mediterranean to appreciate. We are, after all, accustomed to view Asia through maps of a far different scale from those of ancient Greece, whose “Magna Graecia” in Sicily and southern Italy was of trifling size in comparison to the Greater India of southeastern Asia and Indonesia.

  On the other hand, a heavy load of infestation and infection must have reduced individual vigor and capacity for physical labor to a significant degree. Insofar as this was so, peasant families were less able to produce a surplus of food for the support of kings, landlords, armies, and administrators. From a distance India looked wealthy, since its exports were gems and spices, but in spite of that reputation it seems likely that the subcontinent as a whole was always comparatively poor inasmuch as a rather slender margin existed in most times and places between what an average peasant family could produce and what it needed for survival.

  The matter can be thought of as a sort of energy balance. Food extracted from peasants for the support of rulers, soldiers, and city folk, as well as food consumed by microparasites within their own bodies, represents a net withdrawal of energy available to the food producers themselves. More going to one kind of parasite leaves less for others, and if it was true that Indian peasants carried more microparasites than was the case north of the Himalayas, then Indian cities and rulers simply had less surplus energy available to them—whether stored in the form of taxable grain or other food, or simply as peasant muscle power that could be conscripted for war or public works.

  This was probably an important reason why Indian empires were fragile, evanescent structures. India’s political and military weakness made invasion and conquest relatively easy for a long succession of foreigners who came from the Northwest, where the protecting mountain barrier was most easily penetrable. Indian diseases were, in fact, a more reliable protection against such intruders than organized human defenses, since troops from beyond the Himalayas were liable to very heavy die-off when they met the microparasites of the northern Indian plains for the first time. The military and political history of the subcontinent, from the time of Aryan invasions of the fifteenth to twelfth centuries B.C. until the eighteenth century A.D., turned very largely upon the balance between invaders’ military prowess and the ravages unfamiliar diseases brought to their ranks.

  Two other leading traits of Indian civilization can also be connected with the prevalence of disease. As suggested above in Chapter II, the caste organization of Indian society may have partly been a response to the kind of epidemiological standoff that arose when intrusive Aryans, who had probably learned to live with some acute “civilized” diseases—e.g., perhaps smallpox—encountered various “forest folk” who had acquired tolerances for formidable local infections that flourished in the warmth and moisture of southern and eastern India. And, of course, insofar as the caste principle of personal identity became normative, it tended to weaken the power of the state. Political loyalty scarcely extended across caste lines. Rulers became just another, particularly bothersome, caste from whom prudent men of different caste withdrew as much as possible.

  In addition, the transcendentalism that became characteristic of Indian religions accorded well with the circumstances of poverty-stricken, disease-ridden peasants. Unlike Confucianism, which supported and modulated the Chinese imperial structure, the two great Indian religions of Buddhism and Hinduism were fundamentally apolitical. Both, at least in theory, rejected worldly pomp, wealth, and power as mere illusion, along with everything else perceptible to the senses. Confucius had tried to regulate and control the macroparasitism of the upper classes by defining a decorum that would restrain the exercise of power; Indian teachers, on the other hand, turned their backs on politics and society—in a sense despairing of it—and enjoined upon their followers a penurious way of life, minimizing their material demands on the environment in order to invite a liberating mystic vision more effectually. Starving holy men who sought systematically to repress their senses and bodily processes so as better to attain transcendent bliss surely constituted a cultural elite optimally compatible with the slender capacity of a hard-pressed peasantry to support those who did not themselves produce food.

  An ideal of escape from the suffering of existence, such as Buddha preached, and the renunciation of worldly goods and attachments that he recommended, obviously also weakened political identities and diminished the significance and scope of politics. But no calculus seems possible of the roles played in weakening Indian states by otherworldly attitudes and values, by the autonomy of castes, or by technical limitations of Indian agriculture. A fortiori, the significance of disease in shaping each of these aspects of Indian civilization cannot be measured or exactly defined. The point rather is that everything fitted together in mutually supportive fashion to constitute a very effective and enduring adjustment to the special conditions of civilized life in the Indian subcontinent.

  If we compare Indian with Chinese circumstances, then, the material demands of Indian political and cultural elites upon the peasantry seem to have been significantly less than comparable classes in China could safely extract from a less heavily diseased peasant population. Fragile and evanescent state structures and ascetic otherworldly ideals of life may, therefore, have been necessary adaptations to the narrower range of material surplus attainable in a society where microparasitism was more pervasive than in climates where freezing winter weather inhibited various forms of infection and infestation.

  Indian civilization, in fact, arose in a climate analogous to that of the African savanna lands, where rains prevail for only part of the year but where warm temperatures are uninterrupted. Such a climate had in all probability been humankind’s cradleland, and across the millennia of anthropoid evolution toward humanity, African parasites had also been able to evolve, keeping pace with any and every increase in the prevalence of their protohuman and fully human hosts. A more nearly stable ecological balance therefore prevailed in regions of the world suited to human nakedness than was the case farther north. Risk of the fulminating sort of macroparasitism we call civilization was correspondingly reduced. But since some of Africa’s more serious biological obstacles to the multiplication of human numbers—sleeping sickness, for instance—did not extend into India, the possibility of sustaining the macroparasitic social classes needed for civilization did exist there, at least marginally.

  Yet despite all the drains upon the energy at their disposal, whether micro- or macroparasitic, a small surplus must have remained at the disposal of both the Indian and Chinese peasantries during the first millennium B.C. This allowed their multiplication, which in turn led to colonization of new regions, and to the elaboration of economic as well as of political and cultural structures near the major centers of population. Without such a growth of peasant numbers the two civilizations could not have developed as they did, and as long as the peasant base continued to expand without meeting insurmountable and lasting checks, the ecological disbalance favoring the rise of civilization continued to exist both in India and China.

  A similar disbalance existed during the first millennium B.C. in the Aegean basin, and more generally throughout the Mediterranean coastlands. As in China and India, farmer
s in the most active Aegean centers of cultural development were also exploring the potentialities of a new sort of cultivation. The Aegean system was, however, more complicated in the sense that it required exchange of products between economically differentiated regions; and this, in turn, rested upon the availability of cheap transport, i.e., large-scale movement of goods by ship. This exchange pattern affected farming fundamentally. By planting ground with vines and olive trees, and waiting a few years for them to mature, wine and oil could be produced and then exchanged for grain and other less highly valued commodities on very advantageous terms. That is, an acre of land put under vines or olives could in most seasons produce a quantity of wine or oil exchangeable for an amount of grain that needed far more land for its production.

  The organization of “barbarian” societies to provide a steady surplus of grain and some other key supplies—metals, timber, slaves—was just as necessary for the emergence of Greek civilization as the Aegean venture toward more and more specialized production of wine and oil. How suitably large-scale grain production was managed escapes written record; but it is clear enough that as they became aware of the charms of wine and oil (and of a few other civilized products), chieftains and men of power located at diverse spots around the Mediterranean and Black Sea coastlands found it advantageous to collect grain and other commodities from their subordinates in order to be able to barter what they had collected for the goods of civilization, brought from afar by Greek ships.