Plagues and Peoples (31 page)

The long and lethal series of European diseases was not all that Amerindians had to face. For in tropical regions of the New World climatic conditions were suitable for the establishment of at least some of the African infections that made that continent so dangerous to the health of strangers. The two most significant African diseases to establish themselves in the New World were malaria and yellow fever. Both of them became important in determining human patterns of settlement and survival in tropical and subtropical parts of the New World.

Fevers, leading to heavy die-off, often afflicted early European settlements in the New World. Columbus, for example, had to shift his headquarters in Hispaniola to a more healthful
location in 1496. This and other disasters met by early expeditions of explorers and colonists have been adduced as proof that malarial fevers and/or yellow fever existed in the New World before European ships began crossing the ocean. But extremes of malnutrition arising from inadequate provisioning of expeditions that counted on somehow living off the land explain most such cases; and there are a number of contrary evidences that make it practically certain that neither malaria nor yellow fever existed in the Americas before Columbus.
²²

As far as malaria is concerned, the most telling argument rests on studies of the distribution of human genetic traits associated with tolerance of malarial infection. These appear to have been entirely absent from Amerindian populations. Similarly, malarial parasites that infect wild monkeys of the New World appear to be identical with those of the Old—transfers, in fact, from human bloodstreams. Nothing like the extraordinary specialization of malarial parasites that occurs in Africa, whereby different forms of the plasmodium infect different host species and prefer different mosquitoes as alternate hosts, can be found in the Americas. Such facts make it almost certain that malaria is a newcomer to the American scene, and that neither man nor monkey harbored the parasites in pre-Columbian times.
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Literary evidence from the early years of Spanish invasion supports this idea. Thus, for example, a Spanish expedition traveled down the Amazon in 1542, losing three men from Indian attack and seven from starvation; but the report makes no mention of fever. A century later another party ascended the Amazon and arrived at Quito on the other side of the Andes. The very detailed report of this voyage made no mention of fevers en route, and described the native populations along the river as vigorous, healthy, and numerous. No one today would describe the Amerindians of the Amazon basin as numerous, and those tribes that have entered into contact with outsiders are neither healthy nor vigorous either. Nor could any European expect to preserve his health during such a voyage today or at any time in the nineteenth century with-
out a copious supply of anti-malarial drugs. The inference seems irresistible: malaria must have arrived in the Amazon some time after 1650.
²⁴

The establishment of malaria was not so long delayed in other, more traversed regions of the New World, although no clear time and place for the debut of the plasmodium in the New World can be discovered. Almost certainly, the infection was introduced many times, since Europeans as well as Africans suffered chronically from malaria. Before it could take root and spread in the American environment, suitable species of mosquitoes had to adjust to the plasmodium; and in some regions of the Americas this may have required the establishment of Old World types of mosquito on new terrain. The factors governing distribution of differing species of mosquitoes are not well understood, but studies in Europe show that small differences of widely discrepant factors affect the prevalence and absence of one as against another mosquito species.
²⁵
Suitable anopheline species probably already existed in the New World, tinder for infection with the malarial plasmodium in much the same way that the burrowing rodent populations of North and South America were ready for infection with the plague bacillus in the twentieth century. Only so is the rapid development of malaria as a major disease factor in the New World credible. Yet malaria appears to have completed the destruction of Amerindians in the tropical lowlands, so as to empty formerly well-populated regions almost completely.
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Yellow fever announced its successful transfer from West Africa to the Caribbean for the first time in 1648, when epidemics broke out in both Yucatan and Havana. What delayed its establishment until this comparatively late date was probably the fact that before it could become epidemic in the New World, a specialized species of mosquito, known as
Aedes aegypti
, had to find and occupy a niche in the New World environment. This mosquito, in fact, is highly domesticated, preferring as its breeding places small bodies of still water. Indeed, it is said never to breed in water with a natural bot-
torn of mud or sand, but to require a manufactured container—water cask, cistern, calabash, or the like, for laying its eggs.
²⁷

Until this specialized mosquito
crossed the
ocean aboard ship (riding, no doubt, in water casks) and established itself ashore in places where the temperature always stayed above 72 degrees Fahrenheit, yellow fever could not propagate itself in the New World. But when these conditions had been met, the situation became ripe for yellow fever to assume epidemic proportions among men and monkeys alike. Europeans were as vulnerable as Amerindians to this infection; and its sudden onset and frequently lethal outcome made it more feared among whites than malaria. Nonetheless, malaria was far more widespread and undoubtedly accounted for a larger number of deaths than its dreaded African cousin, whom English sailors nicknamed “Yellow Jack.”

The peculiar affinity of
Aedes aegypti
for water casks meant that mosquitoes carrying yellow fever from sailor to sailor could remain on shipboard for weeks and months at a time. This distinguished it from practically every other infectious disease, most of which, if they did break out on shipboard would speedily burn themselves out. Either almost everyone got sick and recovered simultaneously, as when influenza struck; or else only a few individuals, who happened to lack previously acquired immunities, fell ill. But since death from yellow fever was the usual outcome when a European met the infection as an adult, few sailors had any immunity to the disease. Consequently, a voyage lasting for months could be haunted by an unending chain of fatal attacks of yellow fever; and no one understood or could know who would get sick next and die in his turn. No wonder that the “Yellow Jack” was so dreaded by the sailors of the Caribbean and other tropical seas where the temperature-sensitive
Aedes aegypti
could flourish!

In regions of the New World where tropical infections from Africa could establish themselves freely—coming as they did on top of crushing exposure to European infections—the re-
suit was almost total destruction of the pre-existing Amerindian population. On the other hand, in regions where tropical infections could not penetrate, like the Mexican interior plateau and the Peruvian altiplano, the destruction of pre-Columbian populations was less complete, though drastic enough even there.
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African slaves took the place of the vanished Amerindians along the Caribbean coast and in most of the islands of the Caribbean where plantation enterprises called for heavy input of human labor. Since many Africans were already attuned to survival in the presence of malaria and yellow fever, losses from these diseases were relatively small, although other unfamiliar infections—gastrointestinal in particular—led to a high mortality among the slaves. In addition, a heavy preponderance of males, unfavorable conditions for raising infants, and continual disturbance of local disease patterns as a result of the arrival of new human cargoes from Africa meant that the black population of the Caribbean area did not grow very rapidly until the nineteenth century. Then, when the flow of newcomers was cut off, and the noisome slave ships that for two and a half centuries had propagated disease on both sides of the ocean, ceased to ply the seas, black numbers began to surge upward in most of the Caribbean islands, whereas whites diminished proportionately and sometimes absolutely. Economic and social changes—the end of slavery and exhaustion of soils devoted single-mindedly to sugar cane—contributed to this result; but black epidemiological advantages in resisting malaria also helped.
²⁹

Overall, the disaster to Amerindian populations assumed a scale that is hard for us to imagine, living as we do in an age when epidemic disease hardly matters. Ratios of 20:1 or even 25:1 between pre-Columbian populations and the bottoming-out point in Amerindian population curves seem more or less correct, despite wide local variations.
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Behind such chill statistics lurks enormous and repeated human anguish, as whole societies fell apart, values crumbled, and old ways of life
lost all shred of meaning. A few voices recorded what it was like:

Though Amerindians were certainly the main victims of the new disease regime, other populations also had to react to the changed patterns of disease dissemination arising from transoceanic shipping, and the altered patterns of interior trade routes that the rise of such shipping involved. Details are for the most part irrecoverable, yet an over-all pattern is quite clearly discernible.

First of all, previously isolated populations like the Amerindians, when brought into contact with European and other seafarers, regularly experienced a series of drastic die-offs, like that which so massively altered American history. Which civilized diseases wreaked the greatest damage differed from case to case, depending partly on climate, partly on the mere chance of what infection arrived when. But the vulnerability of isolated populations to such diseases was an epidemiological fact of life—and death. Locally disastrous die-offs therefore became recurrent phenomena of all the centuries after 1500.

Among civilized populations, however, the effect was just the opposite. More frequent contacts across ocean distances tended to homogenize infectious disease. As this took place, sporadic and potentially lethal epidemics gave way to endemic patterns of infection. To be sure, in the first centuries after ships began to ply the oceans of the earth and united all the coastlines of the world into a single intercommunicating network, the process of homogenization of disease distribution involved expansion of some diseases onto new ground. Such
arrivals, at more and more frequent intervals, could and did produce locally destructive epidemics. Cities like London and Lisbon became notorious in Europe as seats of disease, and deservedly so. By about 1700, however, sailing ships had done what they could to spread new diseases to new lands. Thereafter, the demographic significance of epidemic outbreaks began to drop off. Where other factors did not supervene to mask the phenomenon, the result was to open the way for our modern experience of persistent, pervasive growth among the disease-exposed and disease-experienced populations of all the earth.

Such a contrast between radical decay of previously isolated communities on the one hand and a globally enhanced potential for population growth among disease-experienced peoples on the other, acted to tip the world balance sharply in favor of the civilized communities of Eurasia. The cultural and biological variety of humankind was reduced correspondingly, as the age-old process of epidemiological disruption and absorption of survivors into the expanding circle of civilized society accelerated everywhere on earth.

Details are only occasionally recoverable. Thus, although epidemiological disaster to previously isolated populations occurred in parts of Africa, e.g., among the Hottentots of the Far South, no one can say which disease caused the principal die-offs or exactly when. In western and central Africa, the slave trade also led to mixing of populations, and movement from one to another natural disease environment on a scale far greater than had prevailed previously. The effect must surely have been to extend patterns of infection toward their natural limits, but it is impossible to tell whether any important changes for human life ensued. Clearly nothing demographically disastrous occurred on a mass scale, since the supply of slaves did not slacken, despite the undoubted damage raiding parties brought to innumerable inland villages.

But whatever demographic effects the brisker circulation of infections within sub-Saharan Africa may have had—and they must have been substantial—any increased mortality from
disease was masked and in most cases more than compensated for by improved nutrition resulting from the rapid spread of maize and manioc among African farmers.
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Heightened caloric yields that these American imports made possible lifted older ceilings on population densities per cultivated acre; and while no statistics are available, it certainly seems not merely possible but probable that large regions of sub-Saharan Africa shared with other parts of the Old World in the population advance starting in the second half of the seventeenth century.
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As usual, we are far better informed about disease events in Europe. Three new infections assumed spectacular forms during the age of the oceanic explorations, 1450–1550; and each of them came to European attention as a by-product of wars. One, the so-called “English sweats,” disappeared after a brief career; the other two, syphilis and typhus, have lasted to our time.