Plagues and Peoples (20 page)

Historic evidence, indeed, suggests that the plagues of the sixth and seventh centuries had an importance for Mediterranean peoples fully analogous to that of the more famous Black Death of the fourteenth century. The disease certainly provoked an initial die-off of a large proportion of the urban dwellers in affected regions, and the over-all diminution of population took centuries to repair. Precision is, of course, quite impossible; but Procopius reports that at the peak of its first visitation the plague killed 10,000 persons daily in Constantinople, where it raged for four months.
⁷²

As in the case of the earlier great pestilences of 165–180 and of 251–266, the political effects of this plague were far-reaching. Indeed, the failure of Justinian’s efforts to restore imperial unity to the Mediterranean can be attributed in good part to the diminution of imperial resources stemming from the plague. Equally, the failure of Roman and Persian forces to offer more than token resistance to the Moslem armies that swarmed out of Arabia so suddenly in 634 becomes easier to understand in the light of the demographic disasters that repeatedly visited the Mediterranean coastlands from 542 onward, and accompanied the Moslems in the first critical stages of their imperial expansion.
⁷³
More generally, the perceptible shift away from the Mediterranean as the preeminent center of European civilization and the increase in importance of
more northerly lands—a shift Henri Pirenne noticed and made famous years ago—was powerfully assisted by the long series of plagues, which confined their ravages almost entirely to territories within easy reach of Mediterranean ports.
⁷⁴

To be sure, epidemics were not absent from northern Europe in these centuries. A severe disease raged in the British Isles after the Synod of Whitby (664) had brought together churchmen from Ireland, Wales, and England, for instance; though whether it was plague, smallpox, measles, influenza, or something else is hotly disputed.
⁷⁵
This was the most important but by no means the only such visitation; indeed, Anglo-Saxon records mention no fewer than forty-nine outbreaks of epidemic between
A.D
. 526 and 1087.
⁷⁶
Many of these were relatively minor; and indeed, a pattern of increasing frequency but declining virulence of infectious disease is exactly what a population learning to live with a new infection experiences as the accommodation between hosts and parasites moves toward a more stable, chronic state.

What is not clear is whether the ravages of disease were heavier in urbanized Mediterranean lands than in the rural Germanic and Slavic portions of Europe. Some diseases needed urban crowding (or equivalent military concentrations of personnel into armies and fleeing hordes) to attain epidemic intensity. This was generally the case for diseases communicated through drinking water—typhoid, dysentery, and the like. Some, like the plague, seem to have been confined to Mediterranean lands, simply because Indian black rats had not yet established themselves in Atlantic seaports. But other diseases, including both measles and smallpox, were capable of spreading far and wide amid rural communities; and previous isolation tended always to make the arrival of such an infection more lethal among rural folk than was likely in disease-experienced cities. Thus
a priori
considerations work in opposite directions, and one must remain content with uncertainty as to whether urbanized Mediterranean populations suffered more or less from epidemic diseases than rural northern peoples did.

What is certain is this: until after
A.D
. 900 the Germanic and Slavic peoples of Europe did not suffer anything like the macroparasitic drain on their resources that the continued existence of the Roman imperial state and of Mediterranean urban populations imposed on the peasantries of the South. Differential population growth, which does indeed seem to have favored the more northerly peoples, probably reflected this fact as much as any microparasitic advantage that may have arisen from the rural and dispersed patterns of settlement characteristic of the North. The chief evidence for population growth in the North between the fifth and eighth centuries
A.D
. is the colonization of the Balkan peninsula by Slavs and of Britain, together with the Rhine and Danube frontier lands, by Germanic settlers. Behind the Viking raids, 800–1000, must also lie a substantial swarming of population in remote Scandinavian fjords and coastlands.

To be sure, factors other than the balance between micro- and macroparasitism affected Europe’s population. In particular, food production increased in northwestern Europe between the fifth and eleventh centuries, thanks to important improvements in agricultural methods resulting from the spread of moldboard plows. This in turn sustained the beginnings of what in some essentials was a new style of civilization—organized states, hierarchical churches, and expanded movement of goods by sea and land, whether for raiding or trading—all brought about intensified contacts with the Mediterranean lands to the south. Within limits set by climatic gradients and population densities, therefore, the tendency clearly was for European populations as a whole to become sharers in a single disease pool, even in such formerly remote lands as Scandinavia and Ireland.

As this process worked itself out, diseases that on their initial appearance in Europe had been highly lethal, settled toward endemicity, at least in those places where sufficiently dense populations existed to sustain a chain of infection indefinitely. In fringe areas, where population was not dense enough to sustain a stable pattern of endemic infection, demographically
costly epidemics continued to break out from time to time. Such pestilences sallied forth from regions of endemicity along the routes of trade and communication connecting scattered populations with the urban centers. This situation persisted in rural and remote parts, especially islands, until the nineteenth century.
⁷⁷

As encounters with such epidemics increased, however, death tolls decreased. Shortened periods of time between successive exposures meant an increase in the proportion of persons with effective immunities created by earlier disease invasions of the community in question. When a given disease returned at intervals of a decade or so, only those who had survived exposure to that particular infection could have children. This quickly created human populations with heightened resistances. The upshot, therefore, was relatively rapid evolution toward a fairly stable pattern of co-existence between host and parasite.

An infectious disease which immunizes those who survive, and which returns to a given community at intervals of five to ten years, automatically becomes a childhood disease. And since children, especially small children, are comparatively easy to replace, infectious disease that affects only the young has a much lighter demographic impact on exposed communities than is the case when a disease strikes a virgin community, so that old and young die indiscriminately. This process of epidemiological adjustment was energetically under way in Europe as a whole during the so-called Dark Ages. As a result, the crippling demographic consequences of exposure to unfamiliar diseases disappeared within a few centuries.

In western Europe adjustment to intensified microparasitism seems to have taken place long before containment of excessive macroparasitism proved feasible. It was only after about
A.D
. 950 that a class of knights, suitably armed and trained, and supported locally by peasant villages, became numerous enough on the ground and formidable enough in the field to repel Viking sea raiders from the most fertile regions of northwestern Europe. From that time forward, despite
continued local disorders and sporadic renewal of depredation, the population of that part of the continent entered a new period of dramatic growth.

By that time, the biological as well as the political and psychological consequences of the interpenetration of civilized disease pools that commenced in the second century
A.D
. had been fully absorbed; and western Europe was in a position to cash in on technical and institutional innovations that had been propagated throughout Latin Christendom during the troubled centuries when that part of the earth came fully and finally into the circle of civilized lands.

No comparably circumstantial history of gradual accommodation to new diseases can be written for any other part of the world. It is probable that if scholars with appropriate linguistic skills were to comb Chinese sources for information about diseases in the Far East, similar patterns of initial disaster and subsequent epidemiological adjustment to new diseases would become apparent. Chinese medical literature is ancient and abundant; and references to unusual outbreaks of disease occur frequently in official dynastic histories, as well as in other sorts of records. But there are difficult problems of interpretation, and the scholars who have paid any attention at all to disease in ancient China and Japan approached the problem without asking the questions that are most important for this inquiry. Until expert and careful work has been done, therefore, answers which may be buried in the vast array of Chinese and Japanese texts remain inaccessible.

A few points do deserve our notice nonetheless. For China two compilations of recorded epidemics exist: one the work of a scholar of the Sung Dynasty (960–1279) named Ssu-ma Kuang, and a second compiled in 1726 as part of an imperial encyclopedia. The published versions of these two lists contain inaccuracies of transcription and calendrical translation; but it is possible to conflate the two and correct at least some of their errors by checking the sources they cite. The result is the list of recorded epidemics in China reproduced in the Appendix.
⁷⁸

By charting epidemic outbreaks thus recorded on a time line, two major clusters appear in the early Christian centuries, and two particularly severe die-offs stand out: one in
A.D
. 161–62, the second in 310–12. According to the list, in 162 a pestilence broke out in the Chinese army serving on the northwestern frontier against the nomads. Three or four out of ten men died. In 310–12, another great pestilence, preceded by locusts and famine, left only one or two out of a hundred persons alive in the northwestern provinces of China; and this was followed ten years later, in 322, by another epidemic in which two or three out of ten died over a wider region of the country.

Obviously the first of these might and the second must—if the recorded statistics are even approximately correct—represent the arrival in China of some hitherto unknown infection, else such rates of mortality could not have occurred. In the second case, a disease involving rash and fever may well have been responsible, since the earliest description of such an illness traceable in Chinese medical writing comes from the hand of a doctor who lived
A.D
. 281–361, named Ho Kung. The relevant passage of his book has been translated as follows:

This seems like a clear description of smallpox (or measles), but there are difficulties, since the passage continues:

Reference to an event three hundred years after Ho Kung’s lifetime certainly confuses the question of when this description of smallpox was first composed. Inasmuch as it was a common practice for Chinese scholars to attribute their own words to ancients, since antiquity made a text more respectable, one cannot be sure that Ho Kung wrote this part of the text ascribed to him, or that smallpox came into China in the early fourth century
A.D
. Nevertheless, the likelihood remains fairly high.

What one can conclude, even from this fragmentary and imperfect data, is that some time between
A.D
. 37 and
A.D
. 653 diseases like smallpox and measles arrived in China. Coming overland from the northwest, they acted like new infections, breaking in upon a virgin population. Demographic consequences must have been similar to those the Roman world was experiencing at the same time.

As for bubonic plague, the earliest Chinese description of this disease dates from
A.D
. 610. In 642 another writer again mentioned it and observed, significantly, that plague was common in Kwangtung (i.e., the province in which Canton is located) but rare in the interior provinces.
⁸¹
On the strength of these references it seems reasonable to believe that bubonic plague came to China via the seaways, arriving early in the seventh century, i.e., about two generations after the disease had penetrated the Mediterranean in 542.