Plagues and Peoples

by William H. McNeill

  As in the case of the Antonine plague, there is nothing in existing records upon which to base an exact identification of the disease (or diseases) that ravaged Roman populations in the third century. Nevertheless, there are some suggestive circumstances that make it tempting to believe that these two demographic disasters may signalize the arrival among Mediterranean populations on an ongoing basis of the two most formidable of our familiar childhood diseases, i.e., measles and smallpox. As we have seen, the evidence of Hippocrates seems to show that no such diseases were known in his time. But by the ninth century A.D. when the Arabic physician al-Razi (850–923), who worked in Baghdad, gave the first unambiguous clinical description of these afflictions, epidemic diseases involving skin rashes were of immemorial familiarity in Near Eastern lands.59

  If one looks for earlier mentions of fevers with skin eruplions, the most notable passage occurs in Gregory of Tours, who mentions an epidemic in southern France in the year 580 that involved skin rashes of some sort.60 Before that, texts are vaguer, though various other references can be interpreted as referring to skin eruptions in connection with epidemic outbreaks. The great doctor and influential medical writer, Galen, actually lived through the Antonine “plague,” but he is not very helpful. Galen classified the disease ás an abscess of the lungs, because spitting blood seemed a far more important symptom to him than mere spots on the skin. Still, in several passages he refers incidentally to epidemic outbreaks of fever together with pustules, but his humoral theory of disease made such symptoms insignificant. His phrases therefore remain tantalizingly imprecise and resistant to conclusive modern diagnosis.61

  By the sixteenth century, when European medical writers finally recognized that measles and smallpox were distinct diseases, there is no doubt that both had become standard childhood afflictions, familiar in all parts of the continent, and of considerable demographic significance, inasmuch as many children died of one or the other, with or without additional infectious complications. The literary record therefore points to the second to third centuries A.D. as the most probable time for these two diseases to have established themselves among Mediterranean populations. The sequence of two devastating pestilences, the first coming between A.D. 165 and 180, and the second raging from A.D. 251 to 266, is exactly what one would expect—indeed what was required—if, one after the other, these two highly infectious diseases broke in upon the comparatively massive but previously unexposed populations of the Mediterranean world.

  No satisfactory estimate of over-all population loss can be made. It must have been very high, though, for disease was not the sole factor attacking Mediterranean populations. Beginning in 235, civil disorders and barbarian invasions spread destruction far and wide within Roman frontiers, and famine not infrequently followed. Agreements allowing barbarian tribesmen to settle within Roman frontiers in return for some sort of agreed military service began in the second century and multiplied in later times. This in itself is indication of empty or near-empty land that could be assigned to immigrants without displacing Roman taxpayers and potential recruits. Even more telling was the series of laws, beginning in the time of Diocletian (reigned 285–305), that prohibited cultivators from leaving the land and made a number of other occupations hereditary and obligatory. The object of such laws was to compel the population to provide services required for maintenance of the imperial administration. Obviously, the only reason for such legislation was persistent shortage of persons able to perform the required functions voluntarily.

  One must, then, imagine prolonged population decay resulting from intensified micro- and macroparasitism within the Mediterranean lands. Even in the first century A.D. after the Augustan peace had ended the destructive civil wars, there were some parts of the empire—Greece and Italy particularly—that failed to prosper. The Roman imperial system collected tax moneys from lands close to the sea and transferred spare cash to the armies stationed at the frontiers. This remained a viable arrangement (though Augustus and other emperors often found it difficult to meet the military payroll) until the heavy blow of unfamiliar disease seriously eroded the wealth of the Mediterranean heartlands between A.D. 165 and 266. Thereupon, rapid die-off of large proportions of the urban populations at the most active centers of Mediterranean commerce diminished the flow of cash to the imperial fisc. As a result, pay for the soldiers at accustomed rates could no longer be found, and mutinous troops turned upon civil society to extract what they could by main force from the undefended landscapes which the Roman peace had created throughout the empire’s Mediterranean heartlands. Further economic decay, depopulation, and human disaster resulted.

  Military uprisings and civil wars of the third century A.D. quickly destroyed one set of landlords—the curiales—whose rents had sustained the outward trappings of Greco-Roman high culture in the empire’s provincial towns, but a new and more rural landlord class, often enjoying partial immunity from imperial taxes, arose almost at once. Insofar as this arrangement prevailed, the hard-pressed peasant population of the empire, by submitting to a local landlord’s demands for goods and services, escaped the older jeopardy of owing rents and taxes to different authorities, but it is doubtful whether the over-all pressure upon cultivators was significantly reduced. Rather, by channeling more into the hands of local potentates, resources at the command of the central administration diminished, and the empire became more vulnerable to external attack. The upshot, as is well known, was the breakup of the imperial fabric in the western provinces and its precarious survival in the more populated east.

  Historians have traditionally emphasized the macroparasitic side of this balance. This accords with the tenor of surviving sources, which allow a reasonably exact reconstruction of the wars, migrations and flights that resulted in the fall of the Roman empire in the west. Yet, the ravages of armies, and the ruthlessness of rent and tax collectors—great though these certainly were—probably did not damage Mediterranean populations as much as the recurrent outbreaks of disease, for, as usual, disease found fresh scope in the wake of marching armies and fleeing populations.

  What seems to have occurred in the Mediterranean lands was that a tolerable macroparasitic system—the imperial armies and bureaucracy of the first century A.D. superimposed upon a diverse muster of local landlords who generally aspired to an urban, Greco-Roman style of life—became unbearably top-heavy after the first disastrous ravages of epidemic disease hit home in the second and third centuries. Thereafter the macroparasitic elements in Roman society became agents of further destruction to population and production, and the resultant disorders, famines, migrations, concentrations and dispersals of human flotsam and jetsam, in turn, created fresh opportunities for epidemic diseases to diminish population still more. A vicious circle thus arose that lasted throughout several centuries, despite some periods of partial stabilization and local population recovery.62

  The importance of disease in the entire process has long been recognized by historians; but because they have not been aware of the unusual force of a fresh infection arriving amid a population lacking any sort of established immunities or resistances, they have systematically underestimated the significance of the two initial epidemics in triggering the entire devolution. There is, however, ample historical evidence of the catastrophic nature of epidemic invasions of virgin populations. In particular, as we shall see in Chapter V, the devastating effect of exposure to new infectious diseases was repeatedly demonstrated by what happened to islanded populations (Amerindians most conspicuously of all) when they encountered European diseases after 1500.

  Political, economic, and cultural consequences of the intensification of micro- and macroparasitism in the Mediterranean lands are too familiar to need much emphasis here. Repeated waves of barbarian invasion accompanied by the decay of cities, migration of artisans to the countryside, loss of skills (including literacy) and the breakup of imperial administration are the familiar hallmarks of the so-called Dark Ages in the West.

&
nbsp; Simultaneously, the rise and consolidation of Christianity altered older world views fundamentally. One advantage Christians had over their pagan contemporaries was that care of the sick, even in time of pestilence, was for them a recognized religious duty. When all normal services break down, quite elementary nursing will greatly reduce mortality. Simple provision of food and water, for instance, will allow persons who are temporarily too weak to cope for themselves to recover instead of perishing miserably. Moreover, those who survived with the help of such nursing were likely to feel gratitude and a warm sense of solidarity with those who had saved their lives. The effect of disastrous epidemic, therefore, was to strengthen Christian churches at a time when most other institutions were being discredited. Christian writers were well aware of this source of strength, and sometimes boasted of the way in which Christians offered each other mutual help in time of pestilence whereas pagans fled from the sick and heartlessly abandoned them.63

  Another advantage Christians enjoyed over pagans was that the teachings of their faith made life meaningful even amid sudden and surprising death. Release from suffering was, after all, much to be desired, in principle if not always in practice. Moreover, even a shattered remnant of survivors who had somehow made it through war or pestilence or both could find warm, immediate and healing consolation in the vision of a heavenly existence for those missing relatives and friends who had died as good Christians. God’s omnipotence made life meaningful in time of disaster as well as in time of prosperity; indeed untoward and unexpected disaster, shattering pagan pride and undermining secular institutions, made God’s hand more evident than it was in quiet times. Christianity was, therefore, a system of thought and feeling thoroughly adapted to a time of troubles in which hardship, disease, and violent death commonly prevailed.

  Christian writers recognized this fact too. Cyprian, bishop of Carthage in 251, wrote in a tract celebrating the plague that was raging at the time:

  Many of us are dying in this mortality, that is many of us are being freed from the world. This mortality is a bane to the Jews and pagans and enemies of Christ; to the servants of God it is a salutary departure. As to the fact that without any discrimination in the human race the just are dying with the unjust, it is not for you to think that the destruction is a common one for both the evil and the good. The just are called to refreshment, the unjust are carried off to torture; protection is more quickly given to the faithful; punishment to the faithless.… How suitable, how necessary it is that this plague and pestilence, which seems horrible and deadly, searches out the justice of each and every one and examines the minds of the human race.…64 Such sublime capacity to cope with the horrors and psychic shock of unexampled epidemic was a significant part of the attractiveness of Christian doctrine for the hard-pressed populations of the Roman empire. By comparison, Stoic and other systems of pagan philosophy, with their emphasis on impersonal process and natural law, were ineffectual in explaining the apparent randomness with which death descended suddenly on old and young, rich and poor, good and bad. In any case, it seems quite certain that the altered incidence of microparasitism upon the Roman populations after A.D. 165 had a good deal to do with the religious and cultural history of the empire as well as with its social and political development.

  Such speculation cannot really be proven, even if it seems intrinsically persuasive. We move to firmer ground by returning to the history of disease in the Mediterranean coastlands, and noting that the next conspicuously significant pestilence arrived in A.D. 542 and raged intermittently until 750. On the strength of a lengthy and exact description by Procopius, the so-called plague of Justinian (542–43) can confidently be identified as bubonic, although all of the subsequent infections that ricocheted through the Mediterranean coastlands in the following two centuries were not necessarily also bubonic.65, 66 The disease (or something very like it) had appeared previously in Egypt and Libya in the third century B.C., if a casual remark by a medical writer named Rufus of Ephesus (ca. 200 B.C.) is to be believed. Thereafter it disappeared until Justinian’s time.67

  In the case of bubonic plague the significance of extended contacts with distant lands is unusually clear, for the disease must have penetrated the Mediterranean from an original focus either in northeastern India or in central Africa. The plague spread within the Mediterranean by ship; the pattern of infection and details of its incidence as described by Procopius make this unmistakable. Presumably other ships, traversing the waterways of the Indian Ocean and Red Sea, allowed the infection to reach the Mediterranean in the first place.

  A good reason for believing Procopius is that his account fits perfectly with modern patterns of bubonic plague dissemination among human populations. Medical research in the nineteenth and twentieth centuries proved that in some circumstances, the infection can pass directly from human host to human host when droplets put into the air by a sick person’s coughing or sneezing enter another’s lungs. In the absence of modern antibiotics, this pneumonic form of the plague is uniformly fatal; its extreme effects also mean that pneumonic outbreaks are short-lived. The more usual route of contagion is via the bite of an infected flea that acquires the disease from a sick rat (or some other rodent), and then, when the rat or other infected rodent dies, abandons its natural host in favor of a human being. In the absence of a reservoir of infected rats, the pneumonic form of the plague cannot long endure; hence human liability to plague is limited to regions where rats or some other rodent population also exists in sufficient numbers to act as carriers for the infection.

  The species of “black rats” that carried the plague in Europe appear to have lived originally in India. Rats of this species survive in a wild state in parts of that subcontinent, and they probably existed there long before learning to live as a “weed species” in and around human houses. But as weeds, rats were able to enter a new ecological niche that permitted them to spread far beyond their original homeland.68 The most convenient way to travel, for rats as much as for men, was by ship. The black rat is a skilled climber, and therefore found it easy to board ships by ascending mooring ropes. Going ashore in a strange port was equally easy. In all probability, therefore, the arrival of black rats in the Mediterranean was an early result of the opening of sea communications between Egypt and India, and in subsequent centuries the invader presumably extended its range inland from the ports. But as late as the time of Justinian, the black rat had probably not reached northern Europe, thus confining the plague of that era to Mediterranean coastlands within relatively easy reach of navigation.69

  The plague is, however, not a stable infection among black rats. Indeed their relation to the disease is precisely parallel to that of humankind, for it constitutes a lethal epidemic among rats as well as among humans. Rats pick up the infection not only by an exchange of fleas with one another but also from contacts with wild rodents whose burrows harbor the bacillus of plague, Pasteur ella pestis, on a steady, ongoing basis. In modern times, all regions of the world where large populations of burrowing rodents live in underground “cities” are infected with Pasteurella pestis Most of these foci of infection are very recent—an affair of the twentieth century—but three of them are much older: one in the foothills of the Himalayas between India and China; one in central Africa in the region of the Great Lakes; and one scattered across the entire length of the Eurasian steppe from Manchuria to the Ukraine.70 As I will argue in the next chapter, it is highly unlikely that the steppe reservoir of this infection is older than the fourteenth century A.D. This means that either in central Africa or in northeastern India at some perhaps geologically ancient time, Pasteurella pestis and the community of ground-burrowing rodents set up housekeeping together in a fashion that has endured to the present.

  There appears to be no basis for deciding which of these two natural reservoirs is the oldest. What matters, for human plague, was the development of a susceptible rodent population that could expose human beings to bubonic infection. This was the work of t
he black rat and that rat’s fleas. Perhaps what happened was that as the Indian black rats began to expand their range by becoming dependent on food supplies concentrated for them by human activity, they somewhere encountered the plague bacillus (perhaps in Africa). Then, via a network of rats and ships that already extended around the shores of the Indian Ocean, they may in turn have transferred the infection to communities of burrowing rodents in the Hi- malayas, among whom it became a stable, ongoing form of infection. Alternatively, the accommodation between the plague bacillus and the community of ground-burrowing rodents may have evolved in situ in the Himalayan region. In that case, Pasteurella pestis presumably spread with the black rat, and at some time in the past found a new group of congenial hosts among the burrowing rodents of central Africa. The twentieth-century spread of the infection to communities of burrowing rodents in North and South America, Australia, and South Africa, proceeded in this fashion, as we will see in the next chapter.

  Wherever Pasteurella pestis may have had its original home, the Himalayan (and probably also the central African) focus of the disease almost certainly date back at least to the beginning of the Christian era. This takes us back to a time before plague manifested itself in any part of the world where surviving records allow modern experts to identify the infection, though absence of records does not prove that bubonic infections did not occur among the human populations of India and Africa long before anything of the kind broke into the Mediterranean.

  Learned discussion of plague has, unfortunately, been clouded by uncritical acceptance of biblical references to epidemics as cases of plague. The term “plague” came naturally to the translators of the King James Bible, since in their day the only epidemic disease that retained its terrors was bubonic plague. Thereafter, the word “plague” became enshrined in English sensibilities; and the same thing happened in other European lands. Hence Georg Sticker and other nineteenth-century scholars accepted the idea that the “plague of the Philistines” referred to in I Samuel 5:6–6:18 was bubonic, though the Hebrew word used to describe the affliction has no assignable meaning whatever. Yet the idea that bubonic plague was very ancient lingers on, despite scholarly efforts to challenge the biblical equivalency of epidemic with bubonic plague.71