9. Manpower and slavery
Legacy of the last Ice Age
During the last Ice Age, the Bering Strait between Asia and North America became a land bridge joining the two continents. Primitive Asian tribes wandered across into North America and migrated southward. As Earth warmed up again, the ice retreated, and some 10,000 years ago, contact between America and Asia was sundered. For some ten millennia, the inhabitants of the American continent remained isolated from the rest of mankind. During this critical period, most of the epidemic diseases characteristic of the Old World made their appearance.
About 500 years ago, contact resumed when Portugal and Spain, soon followed by the other European naval powers, discovered and conquered the Americas. The result was one of the most spectacular population crashes in history. During the century following contact, the indigenous population of the American continent declined by some 95% due to epidemics. Although the European invaders inflicted some military casualties, the overwhelming number of fatalities were due to infectious disease. The indigenous population of America had no previous exposure to the diseases circulating among Europeans and dropped like flies. Historians ask whether the European conquest would have been successful without the help of infectious disease. Did the Europeans deliberately spread epidemics? What role did religion play in the response to the imported epidemics? In contrast, biologists wonder why no American diseases were capable of wiping out 95% of the population of Europe or Asia. For that matter, what diseases did precontact Americans suffer from?
The New World before contact
From a biological perspective, two outstanding issues are noteworthy. First is the apparent lack of major epidemic infections circulating in the Americas before contact. Second, although the American civilizations were technologically still in the Stone Age, they produced remarkably dense populations, especially in Central America. Some accounts suggest that the Aztecs and Incas had almost no major epidemic diseases and lived unusually long lives before European contact. Other sources recount major epidemics, often following periods of famine.
Archeological data indicates that life expectancies in pre-Columbian America were short, perhaps around 24 years in the early classic Maya period and declining thereafter. These estimates are even lower than for medieval Europe and raise the question of what pre-Columbian Americans died of. The dense agricultural populations of Mesoamerica depended excessively on maize (corn) as a staple foodstuff and suffered from dietary deficiency due to a shortage of meat and fresh vegetables. Consequently, their susceptibility to a variety of intestinal and respiratory diseases was greatly elevated. Overcrowding and poor sanitation also contributed.
Several serious insect-borne infections were present in pre-contact America: Chagas disease, Leishmaniasis, Carrion’s disease, Lyme disease, and Rocky Mountain spotted fever. These are all caused by protozoa or bacteria and are restricted in range by the insects that carry them. What the Americas lacked was any major virus disease that spread from person to person. Though hard to believe, this appears to be confirmed by the fact that no epidemics from America devastated Europe. The only major disease the Americans contributed seems to be syphilis. Although syphilis is a serious problem, it does not cause virulent, fast-moving epidemics such as smallpox, measles, or influenza. Tuberculosis and perhaps typhus were also present on the American continent before Columbus made contact.
Little information seems to be available on the precontact rate of infant mortality or its causes. Several respiratory and gastrointestinal infections that can kill infants but have only mild effects on adults probably were in circulation in America and were carried back to join the large number of similar infections already circulating in Europe without attracting much attention.
Indigenous American infections
Examination of pre-Columbian corpses from tropical areas of the Americas has shown moderate levels of infestation with parasitic worms and protozoa. However, inhabitants of tropical regions of Africa or Asia typically have much heavier parasite burdens than precontact Americans. In particular, the three most fearsome tropical diseases, malaria, sleeping sickness, and yellow fever, were absent from the Americas.
Chagas disease is found only in South America and is caused by the protozoan Trypanosoma cruzi, a relative of the trypanosome that causes African sleeping sickness. Chagas disease causes fever, chills, muscle pain, and nosebleeds. Many recover after this initial phase, but other victims develop a chronic disease of the internal organs, especially the digestive tract and heart. Today about 17 million Latin Americans are infected, and approximately 50,000 die each year. DNA sequences specific for Trypanosoma cruzi have been identified in mummified corpses that are several thousand years old. The mummies are from the Atacama Desert, found where Peru and Chile meet. This area has served as a burial ground for about 9,000 years for Chilean and Peruvian Indians, who buried their dead in shallow graves. The Atacama Desert is so dry that space scientists use it to simulate Mars. Corpses buried there have been desiccated and preserved, although they were not deliberately mummified. About 25% of the mummies tested positive for Chagas disease, compared to 10% to 15% of the modern-day population of Chile.
Chagas disease is spread by the kissing bug, which lives in cracks in house walls. This inch-long vampire emerges to suck blood from its human victims at night. The trypanosome is spread when the bug’s droppings infect the wounds it made to suck blood. Charles Darwin probably contracted Chagas disease during his famous voyage around South America on the Beagle. Consequently, he was a semi-invalid later in life. This could be the major reason he settled down to write The Origin of Species instead of gallivanting off around the world on more naturalistic expeditions.
Another insect-borne South American infection is Carrion’s disease, also known as Oroya fever. Carried by sandflies, it is caused by Bartonella, a member of the degenerate rickettsia group of bacteria (other species of Bartonella cause “trench fever” and “cat scratch disease”). The death rate is about 40% nowadays. Some of the survivors suffer continuing skin lesions, referred to as verruga Peruana. Carrion’s disease is solely a human disease. This contrasts with another indigenous American infection, Lyme disease. This is spread by ticks that normally live by sucking the blood of wild deer. Lyme disease is primarily an animal disease and infects humans only by accident. When humans penetrate woodland areas inhabited by deer, ticks carrying Lyme disease sometimes bite them. Although Lyme disease is debilitating, it is rarely fatal. Currently, Lyme disease is largely located in the northeastern United States, but it is spreading slowly. In pre-Columbian times, sporadic infections with Lyme disease presumably occurred but were of little overall importance.
Lack of domesticated animals in America
Pre-Columbian American populations were substantial. Perhaps as many as 20 million to 30 million inhabitants were present in what is now Mexico, 10 million to 20 million in the Inca Empire, and another 10 million to 20 million in North America. Archeological evidence and skeletal samples suggest that these high populations were relatively recent and were severely straining the natural resources available to societies with stone-age technology. As large animals grew scarcer, the people became more dependent on maize. As in the Old World, sedentary agriculture supported a denser population at the cost of a lower-quality diet, with less meat and more cereals.
When Old World populations crowded together in this manner some thousands of years earlier, a series of epidemic diseases emerged. From an Old World perspective, the New World was overdue for such epidemics. Some evidence suggests that epidemic diseases were beginning to appear. The Aztecs recorded several outbreaks. In particular, a drought followed by famine and disease occurred in the early 1450s, fewer than 50 years before the Europeans arrived. The descriptions are too vague to identify any disease with certainty; however, typhus acting on a weakened population is a plausible suggestion.
Virulent epidemic diseases cannot emerge from a vacuum. Indeed, most Old World epidemic diseases originated from infections of domestic animals. The immigrants who populated America split off from the rest of mankind before most animals were domesticated and had only the domestic dog to take with them. Very few animals were domesticated after entering the American continent. These were the turkey, Muscovy duck, guinea pig, and llama and alpaca (both from the same original wild progenitor). These animals did not exist in huge herds before domestication, and their numbers remained relatively small afterward. Llamas, for example, never spread beyond the Andes. Large herds of horses and cattle did roam the New World until around 11,000 years ago, when the last Ice Age ended. Whether these herds were exterminated by early Indian hunters or by the changing climate is debatable. In either case, their demise meant a lack of animals suitable for domestication and, hence, the absence from the New World of mankind’s major source of novel infectious diseases.
The first epidemic in the Caribbean
Although smallpox normally takes pride of place in the litany of pestilence that struck down the indigenous peoples of the Americas, it was not actually first ashore. In 1494, an epidemic spread from Columbus’s ships and ravaged the island of Hispaniola (today split between Haiti and the Dominican Republic). From there, it was spread to Cuba, Jamaica, and other Caribbean Islands partly by the Spanish and partly by islanders fleeing from Hispaniola. About a third of the Spaniards fell ill, though few fatally. Vast numbers of the islanders died. The identity of this disease has remained puzzling to this day. Malaria, smallpox, yellow fever, and bacterial dysentery have all been blamed, yet none fits the bill. These diseases did assault the Americas in due course and were recognized when they arrived. Several investigators have suggested an intestinal infection of some sort, based on the symptoms observed.
A recent theory blames influenza carried by pigs taken aboard Columbus’s fleet in the Canary Islands. The extremely rapid spread and the high proportion of people infected are typical of flu. In addition, most of the symptoms would fit with a virulent outbreak of swine flu. However, there are also arguments against this. An influenza epidemic did invade the New World in the 1550s and was unambiguously identified. Furthermore, influenza in the 1500s was still new enough among Europeans that the death rate was around 20%, far higher than seen in 1494 among the Spanish. It is hard to imagine a virus as incredibly transmissible as flu failing to spread to the mainland. Yet the 1494 epidemic does not seem to have moved beyond the Caribbean. It is also hard to imagine that a full third of the Spaniards remained uninfected by the flu until they made landfall on Hispaniola. We would expect most of the Spanish to have been infected and developed immunity during the early part of the voyage, with one or two stragglers barely keeping the virus in circulation until they reached America. Although an aberrant strain of influenza remains a reasonable contender, the identity of the 1494 outbreak is still uncertain.
Epidemics sweep the American mainland
The first major epidemic to harry the mainland started when smallpox reached Hispaniola in 1518. From there it was a short step to Mexico, where smallpox arrived in 1520, just in time to save Cortez from an Aztec counterattack. The Aztecs, with overwhelming numbers on their side, had driven Cortez out of their capital city, Tenochtitlan, and things looked bleak for the conquistadors. Smallpox arrived with the Spanish relief expedition, and disease fought alongside the Spaniards. The Aztecs were devastated. Those whom smallpox did not kill were immobilized by shock. From then on, the legions of Old World viruses raced ahead of the conquistadors. By the time Pizarro reached the Inca Empire in present-day Peru, smallpox had already done its work, arriving in 1525–1526. The ruling emperor and his immediate heir had both succumbed to smallpox, and civil strife over the succession to the Inca throne had ensued. Unlike Cortez, Pizarro met no significant military resistance.
Rough estimates suggest that around a third of the total population died of smallpox. The death rate was doubtless higher among those crowded in large cities, whereas many smaller, isolated communities escaped the worst effects. This is remarkably similar to the first arrival of smallpox in Japan in the 700s. In the cities, two-thirds or more died, and the overall death toll was about one-third. Thus, there was nothing magical about the effects of smallpox on the Amerindian population. Exposure of Old World populations to new and virulent infections has had much the same effect.
Measles followed smallpox, and the contrast between European and American susceptibility was even greater. Smallpox killed Europeans, albeit less often than Amerindians, but measles was rarely lethal to those of European descent. The measles epidemic of 1530–1531 raged through the Aztec domains and then followed smallpox into the Inca territory in South America. In 1546, a third epidemic followed whose identity is still uncertain. In any case, eventually 95% or more of the indigenous population of the Americas was exterminated by these successive epidemics.
Interestingly, the next major epidemic was rather different. Influenza ravaged Europe in 1556–1560. An estimated 20% of the population died in England, and fatalities were probably comparable in the rest of Europe, although records are less complete. Yes, 20%. Influenza was still a relatively new disease to Europeans at that time and was still dangerous. An outbreak of “coughing violence” was also recorded in Japan in 1556, and large numbers reportedly died. Then as now, influenza presumably came from China, where different virus strains from pigs, poultry, and people hybridized generating new variants. The flu epidemic of 1556 reached America in 1558 and so was the first true worldwide pandemic to achieve a major death toll in both the Old World and the New World.
A variety of other Old World diseases, such as mumps and diphtheria, migrated to the New World over the next couple centuries. Smallpox and measles, the two biggest killers, broke out every so often. Relatively isolated tribes often survived unexposed for several centuries. The Mandan tribe of North America was reduced from several thousand to only 30–40 in 1837. They were besieged by the Sioux and crowded together, unable to get away, when an epidemic broke out. The Cayapo tribe of South America was safely isolated until a single missionary visited them in 1903. By 1927, the tribe had shrunk from about 7,000 to less than 30.
The religious implications
The colossal death toll among the indigenous inhabitants convinced the Christian invaders of North America that their occupation of the Americas was approved and foreordained by God. Conversely, the Aztecs and Incas felt that their own gods were angry and had disowned them in favor of the Europeans. Neither side understood the nature of disease, but the fact that the same diseases that decimated the American Indians caused so few casualties among the Europeans was decisive to both. The Aztecs and Incas were demoralized, and the survivors were easy prey to Catholic missionaries spreading Christianity. It made sense to worship the God of the victors.
The Puritans who founded the Plymouth colony believed that God cleared away the Indians for their benefit. Only divine intervention could account for the incredible mortality among the Indians while leaving the colonists essentially unscathed. According to Puritan leader Cotton Mather, “the woods were almost cleared of these pernicious creatures, to make room for a better growth.” Perhaps it is hardly surprising that the Puritans regarded themselves as favored by God. In the days before science revealed microorganisms to human view, there was no other convincing explanation.
One outstanding theological problem at that time was the origin of the indigenous Americans. If Adam and Eve had been created in the Garden of Eden, somewhere in the Middle East, how did America get its pre-Columbian population? Many Puritans believed that the devil had lured the Indians to America. Here in splendid isolation, the devil was free to rule over the Indians without worrying that the Gospel might intrude.
When smallpox, measles, and other virulent viral diseases first appeared, they doubtless devastated Old World civilizations, much as America was devastated in the years following Columbus. The responses to the pestilence that swept the American continent yield some insight into the behavior of ancient Europeans and Asians, who faced similar catastrophes long before accurate records were kept. Both invaders and the invaded agreed that the massive death toll could have had only one cause: God’s will. The invaders were convinced that the Almighty had foreordained their occupation of America. When we find historical Old World cultures utterly convinced that God is on their side, we might well wonder if it is for the same reason. For instance, the Bible tells how the Angel of the Lord killed 185,000 Assyrians in one night, so relieving the siege of Jerusalem by Sennacharib the Assyrian.
Deliberate use of germ warfare
In 1763, during the French and Indian War, Lord Jeffrey Amherst ordered blankets contaminated with smallpox to be distributed among enemy tribes of Indians. Captain Ecuyer gave blankets from the smallpox hospital at Fort Pitt to two Indian chiefs. Although there was a severe outbreak of smallpox among the Indian tribes of the Ohio Valley, it is debatable whether the blankets caused it. Smallpox was already in the area, hence the local smallpox hospital from which the blankets came. Many other stories exist of items contaminated with smallpox or measles being given to North American Indians, and tales of settlers deliberately passing on these diseases are part of colonial folklore.
Until the late nineteenth century, disease was thought to originate in dirt, sewage, refuse, and swamps, and the odors and vapors arising from them. Thus, in 1699, a German missionary commented, “The Indians die so easily that the bare look and smell of a Spaniard causes them to give up the ghost.” Many colonists may well have believed that contact with something soiled, such as blankets in which a smallpox victim had slept, was necessary to spread the disease. Having seen the devastating effects of smallpox or measles on Indians, they naturally concluded that the Indians had somehow obtained contaminated materials. So many of the tales are probably later attempts at rationalization more than historical observation.
Today we know that measles and smallpox are transmitted from person to person through the air, in tiny droplets breathed out by infected victims. Although viruses can indeed survive for some time on inert objects before they infect another victim, this is not nearly as effective as direct droplet transmission. Once European diseases reached the American continent, they needed little help in transmitting themselves and often moved ahead of the European invaders. For example, in 1616–1617, a major epidemic devastated the Massachusetts Bay area. The Pilgrims did not land until three years later, by which time the indigenous population had already been thinned out.
Slavery and African diseases
One result of the massive die-off of the indigenous Americans was a shortage of cheap labor. The colonial powers responded by importing slaves from the Old World, who were consequently relatively resistant to Old World diseases. In practice, this meant enslaved Africans who brought a variety of tropical diseases with them, notably malaria and yellow fever. These two diseases caused havoc in the tropical parts of the New World and are still major problems today in parts of South America. Of course, these diseases were also current among the Europeans and would have reached America whether or not slavery was practiced.
It is sometimes suggested that many human diseases originated in Africa. Doubtless some original human diseases (such as malaria, typhoid, and herpes) came from Africa because Africa is the home of the human species. However, until relatively recently, the population of sub-Saharan Africa was rather sparse. It is unlikely that most Old World epidemic diseases originated in sub-Saharan Africa. The dense populations of Mesopotamia, the Indus Valley, the Yellow River Valley in China, and the Nile Valley are more likely sites of origin.
Exposure of islands to mainland diseases
The islands of the Pacific Ocean were isolated from the rest of Eurasia, and not surprisingly, the various European voyages of discovery had much the same effect on the natives of the Pacific islands as on the Native Americans. For example, in 1875, measles reached the island of Fiji. Between 25% and 30% of the population died. Because individual islands are scattered over vast expanses of ocean, the smaller and lonelier ones have often remained uninfected until recently. They were usually exposed to one new disease at a time, giving their populations time to recover between onslaughts.
The islands of Britain and Japan were both relatively isolated from the neighboring continental mainland in early medieval times. Only after more efficient ships were developed and trading increased significantly did they reach infectious equilibrium with their respective mainlands. Consequently, England and Japan both experienced major die-offs due to epidemics brought from the disease-ridden mainland. Their population densities lagged well behind that of the mainland until relatively late in the Middle Ages. The Japanese population crossed the “epidemic threshold” and doubled between 1100 and 1300, whereas in England, this was delayed until after the Black Death of the mid-1300s.
Cholera and good intentions
Moralizers often blame the spread of epidemic disease on imperialism and exploitation. However, neither infectious agents nor their insect vectors subscribe to human ethics, and the spread of infections is neither hastened nor hindered by the moral (or immoral) intentions of the humans who carry them. Consider the spread of cholera. During the first worldwide cholera pandemic in the early nineteenth century, British ships carried cholera, which originated in India, to Muscat in Arabia. The British landed an expeditionary force there in 1821 to suppress slavery. From Muscat, cholera spread to the East Coast of Africa with the retreating slave traders. It then spread to the Persian Gulf and much of the Middle East.
Most contact between groups of people is the result of trading rather than the two extremes of invasion or charity. Regardless of human motivation, the spread of viruses such as smallpox, measles, and influenza merely requires close human contact. If Cortez had sailed to America to trade with the Aztecs, he would still have carried smallpox, measles, and influenza. If an international charity had sent Cortez to provide aid, the viruses would have gone, too. The overall demographic results would have been much the same in all cases.
The issue of biological isolation
Various authors have suggested that typhus and tuberculosis were present in both the New World and the Old World before contact. If so, the ancestors of these infectious agents must have crossed the Bering Strait with migrating humans around 10,000 years ago and then been isolated along with their human hosts. This generates a major biological paradox because microorganisms evolve rapidly. After 10,000 years of isolation, the New World and Old World descendents of any microorganism should have differed significantly in DNA sequence—and probably in clinical symptoms, too. Indeed, the Old World and New World species of trypanosome that cause sleeping sickness and Chagas disease, respectively, are quite distinct. Trypanosomes are protozoan parasites that evolve much more slowly than the bacteria responsible for typhus and tuberculosis. From an evolutionary perspective, it is extremely unlikely that descendents of such bacteria could remain indistinguishable if isolated for 10,000 years on different continents.
Such biological considerations imply that typhus and tuberculosis might have been present before contact in either the New World or the Old World, but not both. If the continents were truly isolated, we are therefore forced to choose one homeland for each of these infections. But just how isolated were the Eurasian and American continents from the perspective of infectious microorganisms?
Flocks of birds routinely migrate across the Atlantic Ocean. The microbiological consequences of this were recently illustrated by the appearance of West Nile Virus in New York in 1999. West Nile Virus infects a wide range of birds, among which it is spread by blood-sucking insects. Within the United States, it is spread by mosquitoes. The virus is widely distributed in Africa and the Middle East, but it had not previously been seen in the Americas. Birds carried the virus across the Atlantic, and DNA analysis suggests an origin among domestic geese in Israel. The issue is complicated by the modern possibility that birds sometimes rest briefly on ships, and insects can be carried accidentally by aircraft.
Spotted fevers and rickettsias
According to the records of the Aztecs and Incas, spotted fevers of some sort were present in precontact America. Degenerate bacteria known as rickettsias cause this group of closely related diseases. Rickettsias are much smaller than typical bacteria. They have degenerated and become so dependent on the host cells they infect that they cannot be grown in culture as normal bacteria can. (Note that the bone disease rickets has nothing to do with rickettsias. Rickets results from vitamin D deficiency, not infection.)
Rickettsias are spread by lice, fleas, or ticks. They are primarily infections of animals, transmitted to humans when their carriers jump from animals to nearby humans and bite them. Two major groups of rickettsial spotted fevers exist, each containing several closely related infections that are difficult to tell apart clinically because all cause spots and fever. The most famous is typhus, best known for devastating Napoleon’s armies. The typhus fevers are generally regarded as Old World diseases, whereas the other spotted fevers, such as Rocky Mountain spotted fever, are of New World origin. However, things are not as clear-cut as they might seem.
Murine typhus primarily infects mice and other rodents. It is spread by fleas and lice, which can pass on murine typhus to humans by jumping or crawling from rodent to man. Epidemic typhus is a derivative that has adapted to humans. It is carried by human lice. Sophisticated diseases (such as malaria and yellow fever) do not usually kill their insect vectors. Similarly, murine typhus does not kill the fleas or lice that transfer it. In contrast, epidemic typhus does kill human lice, suggesting that epidemic typhus is a relatively novel variant, not yet fully adapted to its carriers.
The origins of typhus are uncertain
Although earlier reports indicate epidemics that might or might not have been typhus, the first unambiguous outbreaks were in the early 1500s, when the French and Spanish were fighting for control of Italy. From the beginning, typhus was associated with military campaigns and seems to have taken a clear dislike to the French, in particular. In 1528, the French were forced to withdraw from Naples after losing 30,000 men to typhus, which they presumably caught from the Spanish. From a focus in Spain, typhus spread around Europe. According to Spanish author Joaquin Villalba, the typhus epidemic of 1557–1570 depopulated much of the Iberian Peninsula. The timing and location supports the view that typhus might have been a New World import.
Supposed outbreaks of “typhus” in the 1400s in Germany or France are sometimes mentioned. In England, an outbreak of jail fever in 1444 killed 5 jailers and 64 prisoners. In recent centuries, “jail fever” has come to mean some version of typhus. However, back in the good old days, before different diseases were distinguished, jail fever was just that—what people caught in jail.
The Chinese medical classic the Zhouhou Beijifang lists a variety of diseases present in the Far East in the fourth century A.D. Among these is “Japanese river fever” or “sand-lice disease,” often identified by modern commentators as tsutsumagoshi fever, or scrub typhus. The symptoms given are fever, bodily aching, and a rash. Several diseases fit these symptoms, but, if anything, the severe aching suggests dengue fever, which is widespread in the Far East and spread by mosquitoes.
In 1576, typhus, referred to as cocoliztli, swept Mexico, killing an estimated two million people. Supposedly, the Spanish rarely died. This does not square well with Villalba’s claim that the 1557–1570 typhus epidemic depopulated the Iberian Peninsula. Nor does the higher death rate among the Aztec population support an American origin for this disease. However, we should remember that typhus is typically a disease of colder climates that relies on dirty clothing to harbor the lice that carry it. If typhus did come from America, it probably came from the colder, mountainous Inca lands instead of Central America. Thus, for the people of Mexico, typhus might well have been a new disease, brought back from Peru by the Spanish.
Although we cannot be sure, it seems likely that typhus and the related spotted fevers originated in the New World. Upon contact, typhus traveled back to Europe with the Spanish. In Europe, it increased in virulence over the next couple centuries as warfare provided it with a convenient means of transmission. Although more diseases have traveled from the Old World to the New, typhus and syphilis (see Chapter 7, “Venereal Disease and Sexual Behavior”) appear to have been acquired in exchange. Admittedly, this is hardly fair trade, but virulent infections did not all travel in one direction, as is often suggested.
What about the Vikings?
In reality, Columbus was not first to discover America. The Vikings beat him to it. In 981, Eiríkr Thorvaldsson, better known as Eric the Red, explored Greenland. Eric’s father was banished from Norway and went to live in Iceland. Eric himself was banished from Iceland and so set sail westward to explore. He found Greenland. After returning to Iceland, he led an expedition of 25 ships to Greenland because it had better grazing land than Iceland. Eric the Red apparently named the island Greenland to attract settlers. From Greenland, Leif the Lucky, son of Eric the Red, sailed to Newfoundland on the American mainland. The Vikings referred to the mainland as Vinland, and they settled there for about three years before they were driven away by the American Indians, whom they referred to as “Skrælings.” Although Vinland was visited from Greenland several more times, no further settlement was attempted.
Notice that the Skrælings were not annihilated by diseases that the Vikings brought from Europe. This contrasts sharply with what happened when the Aztecs met the Spanish. Does this imply that smallpox, measles, and influenza were not current in Europe during this period of history? An alternative explanation is that the population of Iceland, the staging post for these voyages, was too small to maintain such diseases in circulation. Any epidemics brought from the European mainland to Iceland burned themselves out. Hence, the Vikings were relatively germ-free when they set sail and consequently failed to wipe out the Skrælings and colonize North America.
Although it seems clear that the Vikings did not bring any spectacular epidemic virus diseases to America, they may have brought other, less dramatic infections. Did they carry typhus? Typhus is spread by lice that inhabit human hair and clothes. Dirty clothes that are not changed or washed for the duration of an ocean voyage are ideal for lice to live and lay their eggs in. Because fur coats provide better homes for lice than loincloths, typhus is typically a disease of the colder regions. If typhus was extant in Europe at the time, it is hard to imagine the Vikings failing to take it with them. Here, then, we have an alternative scenario for typhus as a European disease that the Vikings carried to America before the Spanish invasion.
The Viking settlement in Greenland survived until the second half of the fourteenth century. Planetary cooling during this period made Greenland progressively colder and less fertile. But the final blow was plague. The Black Death of the mid–fourteenth century killed around 50% of the people of Scandinavia and Iceland. From there, it hit Greenland, probably in the winter of 1350. The details are unknown, but when the Norwegians visited Greenland in the early 15th century, they found only deserted villages. Presumably, the Greenlanders were wiped out before they could pass the Black Death on to the Skrælings.