Plagues and Peoples
Page 24
Contemporary evidence therefore amply attests that syphilis was new in the Old World, at least in the sense that the venereal mode of transmission and the symptoms that resulted therefrom were new. But as we saw in the last chapter, this may have arisen independently of contacts with America, if a strain of the spirochete causing yaws found a means of short-circuiting the increasingly ineffective path of skin-to-skin infection by instead moving from host to host via the mucous membranes of the sex organs.
Yet medical opinion is not unanimous. Some competent experts continue to believe that syphilis came to Europe from America, and was therefore exactly what contemporaries thought it was—a new disease against which Eurasian populations had no established immunities. The timing of the first outbreak of syphilis in Europe and the place where it occurred certainly seems to fit what one would expect if the disease had been imported from America by Columbus’ returning sailors. This theory, once it had been promulgated in 1539, became almost universally accepted among Europe’s learned until very recently, when the inability to distinguish between the spirochete causing yaws and that of syphilis in laboratory tests led a school of medical historians to reject the Columbian theory entirely. Proof, one way or the other, awaits the development of precise and reliable methods whereby the organisms causing lesions in ancient bones can be identified. If this proves permanently beyond the reach of biochemical techniques, it seems unlikely that any adequate basis for choice between the rival theories as to the origin of syphilis will be attainable.35
However conspicuous and distressful syphilis may have been for those who contracted it, its demographic impact does not seem to have been very great. Royal houses often suffered and the political decline of Valois France (1559–589) and of Ottoman Turkey (after 1566) may have been related to the prevalence of syphilis in the respective reigning families of the two states. Many aristocrats suffered similarly. But the inability of royal and aristocratic families to give birth to healthy children merely accelerated social mobility, making more room at the top of society than there would otherwise have been. Lower down the social scale syphilis had less devastating effects, for the fact seems to be that European populations continued to increase throughout the sixteenth century when the disease was at its height. By the end of the century, syphilis began to recede. The more fulminant forms of infection were dying out, as the normal sorts of adjustment between host and parasite asserted themselves, i.e., as milder strains of the spirochete displaced those that killed off their hosts too rapidly, and as the resistance of European populations to the organism increased. Even though data seem lacking, the same pattern of relatively speedy adjustment without significant demographic loss along the way presumably also prevailed in the other parts of the Old World.
The same must also be said of typhus. As a recognizable and distinct disease, typhus made its debut on European soil in 1490, when it was brought to Spain by soldiers who had been fighting in Cyprus. Thence it came into Italy with the wars between Spaniards and French for dominion over that peninsula. Typhus achieved a new notoriety in 1526 when a French army besieging Naples was compelled to withdraw in disarray due to the ravages of the disease. Thereafter, outbreaks of typhus continued to be sporadically important in disrupting armies and depopulating jails, poorhouses, and other—in the literal sense—lousy institutions, down to World War I, when two or three million died of this infection.36
Yet the occasional military and political importance of typhus fever was not matched by any notable demographic significance for the peoples of Europe or anywhere else, so far, at least, as the very sketchy indications of population trends allow one to judge. Typhus was, after all, a disease of crowding and of poverty. For most of the poor who died of typhus, statistical probability assures us that if infected lice had not assisted their demise, some other disease would soon have carried them off. Particularly in urban slums, or anywhere else that undernourished people huddled miserably together, there were plenty of other infections—tuberculosis, dysentery, pneumonia—competing for victims. The fact that typhus brought death quicker than most of the other infections therefore perhaps made less difference demographically than the number of typhus deaths might suggest at first glance.
The third new, or apparently new, infection, the “English sweats,” is of interest on two counts. It exhibited an opposite social impact from typhus, preferring to attack the upper classes much as poliomyelitis did in more recent times. Secondly, it disappeared after 1551 as mysteriously as it had come in 1485. The disease broke out first in England as the name implies, soon after Henry VII had won his crown at the battle of Bosworth Field. Then it spread to the Continent and created considerable furor because of the high mortality it caused among upper classes. Symptoms resembled scarlet fever, but such an Identification has not won general acceptance among medical historians. The fact that it was believed to be a new disease does not prove that it had not existed in some endemic form as a modest childhood affliction elsewhere, perhaps in France whence Henry VII recruited some of the soldiers who won him his crown.37 But even more clearly than in the cases of syphilis and typhus, the sweats did not affect enough people to have any noticeable over-all demographic effect.
On the other hand, it is the case that an outbreak of the dreaded “sweats” in 1529 led Luther and Zwingli to break off their colloquy in Marburg, without achieving agreement on a definition of the eucharist.38 Whether a longer conference would have led to agreement between these two headstrong paladins of ecclesiastical reformation may well be doubted. Nevertheless, the fact remains that it was their precipitate flight from risk of infection that sealed the split between Lutheran and Swiss (soon to become Calvinist) reform along lines that deeply affected subsequent European history, and have endured to the present.
Such events involve the interaction of sharply different determinants of human action: the one ideological and conscious, the other epidemiological and independent of human intention. Historians have never been comfortable when trying to deal with such “accidents,” and it is partly for that reason that the history of disease had been so little attended to by my predecessors. Infection and fear of infection, indeed, as manifest at Marburg in 1529, resemble for us today the unpredictable and incomprehensible intervention of Divine Providence which our ancestors invoked to explain epidemics. Heirs as we are to the Enlightenment, which sought to banish the inexplicable, if necessary by neglecting it, historians of the twentieth century have also usually preferred to overlook such events. Anything else spoiled the web of interpretation and explanation through which their art sought to make human experience intelligible.
Though it is the aim of this book to correct such oversight and bring the role of infectious disease in shaping human history into a juster perspective than others have allowed, it remains the case that accidental events like this, however pervasive the results which may be thought to have flowed from them, seem somehow too trifling to be credited with vast consequences. There is, alas, simply no way to decide whether the division between the two main branches of the Protestant movement in Europe would have taken place anyway, or whether that important phenomenon did take a decisive turn when Luther and Zwingli bade one another a hasty adieu in 1529 in order to escape the “sweats.”
It is, paradoxically, far easier for historians to talk about statistical results and longer-range demographic phenomena, even when hard data are absent and guesswork has to provide a substitute. Thus one may be comfortable in asserting that population in Europe, or those parts of it where reasonable estimates can be made, seems to have increased uninterruptedly and relatively rapidly from the mid-fifteenth century (when recovery from plague losses set in) until about 1600.39 Yet it was during these decades that the oceanic discoveries took place, and European sailors had the opportunity to import new infections into their homelands from the ports of all the earth. Even so, the new disease risks such transport patterns permitted did not prove very serious for European populations, presumably becaus
e most infections that could flourish in the European climate and under the conditions then prevailing in European cities and villages had already penetrated the Continent as a result of older circulation of infections within the Old World.
For Europe, as for other civilized lands, infections by familiar epidemic disease surely became more frequent, at least in the major ports and at other foci of communication; but infections that returned at more and more frequent intervals became, by necessity, childhood diseases. Older persons would have acquired suitably high and repeatedly reinforced levels of immunity through prior exposures. Thus by a paradox that is only apparent, the more diseased a community, the less destructive its epidemics become. Even very high rates of infant mortality were relatively easily borne. The costs of giving birth and rearing another child to replace one that had died were slight compared to the losses involved in massive adult mortality of the sort that epidemics attacking a population at infrequent intervals inevitably produce.
Consequently, the tighter the communications net binding each part of Europe to the rest of the world, the smaller became the likelihood of really devastating disease encounter. Only genetic mutation of a disease-causing organism, or a new transfer of parasites from some other host to human beings offered the possibility of devastating epidemic when world transport and communications had attained a sufficient intimacy to assure frequent circulation of all established human diseases among the civilized populations of the world. Between 1500 and about 1700 this is what seems in fact to have occurred. Devastating epidemics of the sort that had raged so dramatically in Europe’s cities between 1346 and the mid-seventeenth century tapered off toward the status of childhood diseases, or else, as in the case of both plague and malaria, notably reduced the geographic range of their incidence.40
The result of such systematic lightening of the microparasitic drain upon European populations (especially in northwestern Europe where both plague and malaria had about disappeared by the close of the seventeenth century) was, of course, to unleash the possibility of systematic growth. This was, however, only a possibility, since any substantial local growth quickly brought on new problems: in particular, problems of food supply, water supply, and intensification of other infections in cities that had outgrown older systems of waste disposal. After 1600 these factors began to affect European populations significantly, and their effective solution did not come before the eighteenth century—or later.
All the same, the changing pattern of epidemic infection was and remains a fundamental landmark in human ecology that deserves more attention than it has ordinarily received. On the time scale of world history, indeed we should view the “domestication” of epidemic disease that occurred between 1300 and 1700 as a fundamental breakthrough, directly resulting from the two great transportation revolutions of that age—one by land, initiated by the Mongols, and one by sea, initiated by Europeans.
Civilized forms of person-to-person infection had entered the scene with the rise of cities and the development of intercommunicating human herds of half a million or so. Initially this could only occur at selected spots on the globe, where agriculture was especially productive and local transport nets made concentration of resources into urban and imperial centers relatively easy. For millennia thereafter, these civilized infections played a double role. On the one hand, they cut down formerly isolated populations that came into contact with disease-bearers from one or another of the civilized centers, and thereby facilitated the process of “digestion” of small, primitive groups into the body politic of persistently expanding civilized communities. On the other hand, these same diseases enjoyed an imperfect circulation within civilized communities themselves, and could often therefore invade a particular city or rural community with almost the same lethal force they regularly exerted vis-à-vis isolated populations.
Particularly when it came to disease relations across civilizational boundaries, this possibility remained demographically important for civilized humankind, as the disease die-offs of early Christian centuries attest. After 1300, contacts between the major civilizations of the Old World became closer and closer. Disease exchanges intensified correspondingly, with frequent disastrous but never quite paralyzing consequences. In the sixteenth and seventeenth centuries, when the Amerindian die-off was at its peak, the homogenization of civilized infectious disease throughout the world gradually attained such a level that the old forms of sporadic epidemic that could carry off up to half the population of a particular community in a single season could no longer occur in those parts of the world where long exposure to the multiplicity of infectious organisms created suitably complex patterns of immunity among all but young children.
Thus there emerged a new relation between humankind and parasitic micro-organisms. It was a more stable pattern of parasitism, less destructive to human hosts, and correspondingly more secure for the parasites. The infectious organisms could count on a fresh supply of susceptible children, whose numbers and availability were subject to far smaller statistical variation than had been the case when epidemic patterns of disease produced alternate feast and famine for the organisms infecting humanity. Both sides were therefore more secure, and in that sense better off. As endemicity set in at one port city after another, filtering inland along main routes of movement and seeping more slowly into the countryside, a new ecological era dawned. Massive growth of civilized populations, and correspondingly accelerated destruction of the remaining isolated human groups was the first and most obvious consequence of the new disease regime, a disease regime we can appropriately call “modern.” Imminent collision with limits on food supply, as well as other strains upon human adaptation to the environment, was the other side of this modern microparasitic regime.
The shift from epidemic to endemic forms of infection was, of course, not complete; the next chapter will have something to say about smallpox and cholera and some other notable encounters with epidemics that humanity has experienced in recent centuries. Nonetheless, the force of the modern pattern of infection was clearly evident by 1700, or by 1750 at the latest—and not only in Europe, but throughout the world.41
Before turning briefly to consider what little can be said of disease and population histories of Asia and Africa, however, another point about Europe’s disease experience should be made. The fundamental character of the changing incidence of epidemic disease was obscured in early modern times by the onset of particularly severe weather conditions that created frequent crop failures and famines in northern Europe.42 Simultaneously, the Mediterranean lands underwent a general crisis owing to mounting shortages of food and fuel.43 Parts of Europe were also devastated by war—e.g., Italy between 1494 and 1559, and Germany between 1618 and 1648. These wars were waged with more than customary brutality, owing to difficulties regularly constituted governments faced in supplying mercenary troops. Armies tended, therefore, to plunder friend and foe almost indiscriminately.44
Moreover, urban growth in northern Europe often put strains on pre-existing sanitary arrangements, so that death rates in thriving cities like London or Amsterdam may well have edged upward.45 Yet on the whole it seems safe to say that intensified efforts at public sanitation forestalled major disaster. These were largely initiated in times of plague, stimulated in the North by the example of Italian cities whose public sanitation and health services were more highly developed than elsewhere in Europe.46 The result, therefore, was that the tendency toward systematic population growth inherent in the changing pattern of disease incidence was partially masked for two centuries by factors that acted in a contrary sense. Yet the fundamental fact remains: European population did continue a slight increase despite local setbacks and temporary crises; and did so despite adverse weather and war.
Europe’s expansion is such a central fact of modern history that we are likely to take it almost for granted and fail to recognize the quite exceptional ecological circumstances that provided sufficient numbers of exportable (and often expendable)
human beings needed to undertake such multifarious, risky, and demographically costly ventures. The fact was that Europe found itself in a position to capitalize handsomely on the new capacity for demographic growth which the altered disease pattern conferred on all civilized peoples of the Old World.47 Lands emptying of Amerindians were supplemented by lands emptying of Pacific islanders and Australians, of Siberian tribesmen, and of Hottentots.48, 49, 50 In all these disparate regions, Europeans were uniquely in a position to move in, thanks to their control of transoceanic shipping and other means of transport, and to the possession of other technological skills superior to those which disease-decimated local peoples could command. In all of this vast process, bacteriology was at least as important as technology. The decay of native numbers and the availability of European populations to occupy such vast and varied emptied spaces both derived from the distinctive modern pattern of epidemiology.
The key significance of the altered pattern of infectious disease in the complex of factors sustaining Europe’s expansion is confirmed if we turn attention to what happened among other civilized peoples of the Old World. For there, too, the opening of the oceans to regular shipping and the intensification of contacts resulting from circulation of ships and crews had noticeable effects on populations and disease.
The only new disease known to have come to India, China, Japan, and the Middle East was syphilis; and its demographic impact in these lands seems no different from that in Europe. That is to say, initial dismay and extended comment ebbed away as the infection became less florid in its symptoms and subsided toward chronic endemicity.51
Familiar infections continued to manifest themselves as epidemics, in Asia as much as in Europe; and there is reason to think that the frequency of epidemics may have increased. Certainly, Chinese records show a sharp upsurge in epidemic outbreaks, as the following table, based on the researches of Dr. Joseph Cha, makes obvious52: