Archaeologist Stuart Fiedel's Prehistory of the Americas is an excellent resource for those interested in the history (or prehistory) of the peoples inhabiting the American continents during the 10,000 years since the end of the last ice age, before the permanent arrival of Europeans at the end of the 15th century a.d.  We're particularly interested today in Fiedel's comments concerning the differing natures of epidemic disease in the histories of the Old World vis-a-vis pre- and post-Columbian America.  Impearls will return to this subject again in a later posting.  Here's what Fiedel had to say: ¹ 

Several differences in the development of Old and New World cultures may help to explain why, when they finally came into contact, the American civilizations collapsed before the onslaught of the European invaders.  For one thing, the Native Americans never made any practical use of the wheel.  Finds of wheeled toys demonstrate that the basic principle was known to the ancient Mexicans ²; but as they lacked any domesticated animal larger than the dog, vehicles offered no obvious advantage over the human back as a mode of transport.  In the Andes, the domesticated llama was used as a pack animal, like its Old World cousin, the camel.  The steep mountain slopes would have rendered wheeled vehicles useless.  In Europe, the wheel was the basic device from which all advanced technology involving pulleys, gears, cogs and screws was derived.  However, despite the obvious advantage that the Spanish invaders held because of their crossbows, cannon, sailing ships, and other military hardware, the Aztecs successfully drove them out of Tenochtitlan.  Superior wheel-based technology certainly contributed to the Spanish victory, but it was not the decisive factor.

Cortes's troops carried steel swords, and wore steel armor; the Aztec warriors wore cotton armor, and their swords were edged with sharp, but brittle, obsidian.  Metalworking had not been introduced to Mexico until after a.d. 900.  Gold and copper were used almost exclusively for nonutilitarian objects.  The techniques of metalworking had probably diffused northward from the Andes, where copper smelting seems to have begun as early as 1200 b.c., in the southern Titicaca basin.  At about the same time, gold was being worked in the central Andes.  In Peru, some tools were made of copper and (by the time of the Incas) bronze; but, as in Mexico, metal was used primarily for ornaments and ceremonial objects.  Iron smelting, which began in the Near East before 1000 b.c., was never developed by New World metalworkers.  Again, as in the case of the wheel, the defeats suffered by Spanish forces at the hands of obsidian-armed Aztec warriors suggest that the natives' lack of iron or steel did not predetermine the outcome of their struggle with the Europeans.

The critical factor seems instead to have been the Native Americans' lack of antibodies against Old World microorganisms.  Few, if any, infectious diseases were endemic in American populations.  Several depictions in Mexican and Peruvian art of hunchbacks suggest that tuberculosis may have been present aboriginally, but if so, it was not a common ailment.  A form of nonvenereal syphilis also seems to have been known in Mesoamerica before contact, and there is archaeological evidence of its early presence in North America: several skeletons dating from ca. 4000-3000 b.c., found at the Carrier Mills site in the lower Ohio Valley, displayed lesions that have been attributed to syphilis (Muller 1986). ³  However, it was the arrival of the white man that first exposed the Native Americans to the viruses that cause smallpox and measles, and the rickettsia that cause typhus.  An infected black soldier in the army led by Cortes's rival, Narvaez, brought smallpox from Cuba to the Mexican coast.  The disease was soon carried to Tenochtitlan, where it ravaged the defenders of the city; among the dead was Cuitlahuac, who had organized the successful uprising against the Spanish.  Decimated and demoralized, the Aztecs could no longer hold off Cortes's army, and Tenochtitlan fell (Diaz 1963). ⁴  Within five years, smallpox spread through Central America, and reached Peru in 1525.  The death of the Inca ruler, which precipitated the civil war between his successors and thus facilitated Pizarro's conquest of the empire, was caused by smallpox.  These devastating smallpox epidemics were followed by outbreaks, in Mexico and Peru, of measles in 1530, and of a disease that was probably typhus in 1546.  The cumulative effect of these uncontrollable epidemics was a population loss of almost unimaginable dimensions (Ashburn 1947). ⁵  Reasonable estimates of the Native American population at the time of contact are on the order of 57 million; some 21 million people lived in Mesoamerica, about 7.5 million inhabited the Inca empire, and the population of the Intermediate area and Caribbean islands may have been 14 to 15 million (Denevan 1976). ⁶  It is thought that disease had wiped out 90% of the population of the nuclear zone (Mesoamerica, Peru, and the Intermediate area) by 1568; in other words, more than 39 million people had perished in less than 50 years following the initial outbreak of smallpox.

Why were there no American diseases to afflict the European invaders with equally terrible virulence?  It has long been thought that syphilis was such a disease, because the first well-reported outbreak in Europe occurred shortly after Columbus's return from the New World.  However, it now appears more likely that a nonvenereal strain of syphilis had always been present in Europe.  When Europeans, reacting to the colder weather of the Little Ice Age, began to wear more clothing indoors, thus hindering the usual skin-to-skin transmission of the spirochete bacillus, the microbe responded by taking the venereal route (McNeill 1976). ⁷  The virulence of the European outbreak might also have been caused by hybridization of Old and New World viral strains following contact.

Syphilis is the only disease for which an American origin is even arguable.  There are two possible explanations for the absence of endemic diseases in the New World.  The first is that microbes like the smallpox virus can only become established in human populations that are dense enough to permit frequent transmission from one human host to another, and numerous enough for there always to be disease-resistant survivors in which the virus can reside until the next outbreak — in other words, these germs can only flourish in urban situations.  Densely occupied cities appeared in the New World 3,000 years later than they did in the Old World; nevertheless, the first probable smallpox epidemic struck the Mediterranean region as late as the third century a.d.  Evidently, even in a hospitable urban environment, a human virus may take a long time to evolve.  Perhaps the 1,500 or 2,000 years of urban life in the Americas were not enough time for this process to occur.  However, early references to pestilence in the literature of both Mesopotamia and Egypt show that some form of contagious disease was already present in the Near East by 2000 b.c., only 1,000 years after the beginnings of urbanism.  So lack of time in the New World does not seem to be an adequate explanation of the absence of endemic diseases in such dense settled areas as the Valley of Mexico.

The near absence of diseases in pre-Columbian America can be more convincingly attributed to the paucity of domesticated mammals.  Most of the microbes that caused the Old World diseases seem to have originally infected animals, and then shifted to human hosts.  Thus, smallpox was evidently derived from cowpox, measles from rinderpest, and influenza from a disease that affects pigs (McNeill 1976). ⁸  For the same reasons that endemic human diseases require large, dense populations, microbes more often afflict herd animals than the more solitary species.  As we have seen, the people of Mesoamerica never domesticated any herd animals.  They did, of course, have the dog; but the dog, which lived in small packs in the wild, was not the primary host for diseases that would attack humans.  This explanation therefore seems to be valid for Mexico, but it does not account very well for the Peruvian case.  In Peru, llama herding seems to have been practiced by 2000 b.c., and possibly began as early as 4000 b.c.; the raising of guinea pigs may be of comparable antiquity.  So not only was there a long period during which the ancient Peruvians maintained close contact with large camelid herds, but they also kept domesticated rodents in their dwellings.  In the Old World, of course, the dreaded bubonic plague was transmitted by fleas from rodents to humans.  If we hope to explain the absence of infectious disease in the native human population of Peru, we must first ask why the domesticated animals did not suffer from diseases similar to those that afflicted their Old World counterparts.  Unfortunately, no one has come up with a very good answer to this question.

We can only speculate about the possible outcome of the confrontation between the Old and New Worlds, had disease not played so crucial a role.  Might the highly-organized Incas, and the less efficient but equally fierce Aztecs, have successfully resisted the European invasion?  Japan was never subjugated by the Europeans, and although China and India fell under Western domination for a century or two, the colonizers were ultimately driven out.  Similarly, white colonists were ultimately forced to cede most of Africa to the native populations, retaining only the southern tip of the continent.  In contrast, only tiny remnants of the native population survived the wave of European colonization that swept over North America and much of South America.  In the nuclear zone, a few million native people were left alive when the epidemics subsided.  They abandoned the gods who had failed them in their time of need, and adopted the god of the Catholic priests.  Unable to offer effective resistance, they generally resigned themselves to political domination and economic exploitation, although rebellions against the Spanish elite did flare up from time to time.  Although the native ideologies and political systems were obliterated by the conquest, many aspects of aboriginal culture, including some of the ancient languages, persisted among the rural villagers.  After centuries of dominance, Hispanic culture has become so firmly entrenched, and the commingling of the native and alien races has proceeded so far, that full restoration of the indigenous traditions is impossible.  Nevertheless, there has been a recent resurgence of interest and pride in the achievements of the Indian ancestors.  This trend was nicely exemplified by the decision to demolish several seventeenth- and eighteenth-century buildings in the heart of Mexico City, in order that the central pyramid of Tenochtitlan might be excavated and restored.
 
 

¹ Stuart J. Fiedel, Prehistory of the Americas, Second Edition, 1992, Cambridge University Press, Cambridge; pp. 362-366.

² “[A]ncient Native Americans were not ignorant of the principle of the wheel.  Toy ceramic dogs, mounted on four wheels, have been found in Mexico, near Veracruz.”  Figure 55: “Dog figurine on wheels, Veracruz, Mexico, Classic period.”  Fiedel, op. cit., pp. 182-183.

³ J. Muller, Archaeology of the Lower Ohio Valley, 1986, Academic Press, New York.

⁴ Bernal Diaz, The history of the conquest of New Spain, translated by A. P. Maudsley, 1963, Pelican, Baltimore.

⁵ P. M. Ashburn, The ranks of death: a medical history of the conquest of America, 1947, Coward-McCann, New York.

⁶ W. M. Denevan, ed., The native population of the Americas in 1492, 1976, University of Wisconsin Press, Madison.

⁷ W. H. McNeill, Plagues and peoples, 1976, Anchor Press, Garden City, New York.

⁸ McNeill, op. cit.