Plagues and Peoples By: William H. McNeill INTRODUCTION • McNeill considers the influence that disease has had on human history and how the two have evolved together. • It explores the impact disease had on cultures and how in affected every area of world history including the political, demographic, ecological, and psychological aspects. Thesis The evolution of disease coincides with the evolution of humanity. Man The Hunter • Food Chain • • • • Before human populations evolved, our ancestors fit into an ecological balance which was mainly supported by the food chain. They preyed upon some forms of life, and they in turn were preyed upon by others Parasites also sought food in our ancestors’ bodies and became a important element in balancing the system that humans were a part of. Our Ancestors • Pre-human and proto-skeletal bones and tools that have been discovered abundantly in sub-Saharan Africa points to an arboreal habitat for our ancestors meaning that they lived in the trees. • Dentition also suggests an omnivorous diet based on nuts, fruit, vegetable shoots instead of animal flesh until about 500,000 years ago. Man the Hunter In the warmth and moisture of a rainforest a single cell parasite can survive outside of a host for a long period of time. This means that even if there are few hosts to be found in the forest, the parasite can wait . Applied to our human ancestors, it was still possible for them to pick up a lot of parasites The rainforest, for millions of years, had a highly evolved natural balance between the things humans ate and the things that ate us. Non-biological Evolution Because biological evolution is so slow, any change that would occur in humans could be compensated for in the genetic makeup and behavioral patterns of both prey and predator. As long as the biological evolution of our ancestors kept pace with the evolution of parasites, predators and prey, the ecological balance could remain stable. When humankind began to acquire new skills and elaborate learned behavior into symbolic meanings, the biological balance was disturbed. Development of weapons and tools allowed for the killing of large animals that were on the grasslands of the African savanna. Language and New muscular skills allowed new precision in hunting What does this have to do with Disease? When our ancestors started to come down from the trees to run walk, run, and hunt in the open grassland they were susceptible to new kinds of diseases. As rainforest types of infection thinned out new parasites contracted from animals in the savanna start to affect humankind Meat from the hunted animals contained a lot of disease. Ex. Various types of worms can transfer to humans when we consume their eggs contained in meat Tsetse fly contains trypanosome that causes sleeping sickness. It causes no sickness in the fly (an example of stable, ancient parasite), but when injected into a human it causes death. This fly basically set limits on where early humans could hunt for game. The new skills that our ancestors acquired allowed for a much larger food supply which in turn caused human numbers increase. As human numbers increased, opportunities for transfer of parasites multiply because there are more hosts Parasites Evolving Many of the parasites in Africa do not provoke immune reactions which helps maintain an ecological balance. If human numbers increase, the rate of infection also increases. Expansion As hunting bands started to cause extinction of many of the large animals that were feeding them they had to find food elsewhere. Invention of clothes Allowed for bands of hunters to move north and attack animal populations that could not be reached previously. Consequences were similar to what happened when our ancestors came down from the trees. Hunting bands entered Australia about 40,000 yrs. ago, 5,000 – 15,000 yrs. Ago crossed Bering Strait from Asia and entered into Americas. In the next few thousand years, expanded across North and South America First time a large-bodied species was able to spread across the globe Cultural adaptation and invention (which can happen almost instantly) made biological adjustment (which can take thousands of years) unnecessary Warm clothing housing Expansion The hunting communities were still facing the problem of killing off their food supply. One calculation suggests that human hunters exterminated most large-bodied game in 1,000 years. Parasites were still lurking and waiting. They were able to travel with the hunting communities as long as the infection acted slowly and did not kill off too many human hosts or incapacitate them too suddenly Food Production Hunting communities realized they couldn’t keep killing off all the animals. Food Production The evolution of agriculture and domestication of animals permitted a rapid rise in the number of people that could thrive in a community. Led to rise of cities and civilizations. Once humans started to form large communities and cities, an optimal hunting ground was created for potential parasites and diseases. Food Production Slash and burn methods of agriculture cleared the way for multiplied breeding of a kind of mosquito that carries malaria and that prefers to feed on human blood. Irrigation farming recreated favorable conditions for parasites that prevailed in moist tropical conditions Blood fluke - involves mollusks and men as hosts. Moves from one to the other freely in water. Affects 100 million people today. Settling Prolonged or permanent settling brought many risks of parasitic invasion. Increased contact with human feces as it accumulated in close living quarters could allow for intestinal parasites to move freely In contrast, a hunting band constantly on the move could avoid this Contaminated water supplies In regions where food crops were being domesticated human population density became 10-20 times greater than hunting densities had ever been in the same areas in just a few hundred years. Eventually agricultural populations became dense enough to sustain bacterial and viral infections even without a non-human intermediate host. Civilizations Civilized societies began to form and disease became a unknowingly potent biological weapon. Trade, war, and exploration also brought the exchange of disease – sometimes wiping out or “digesting” whole societies. CONFLUENCE OF CIVILIZED DIESASE POOLS OF EURASIA 500 B.C.TO A.D. 1200 MIDDLE EAST People were exposed to new types of parasites with the expansion of irrigation farming and frequent wading in irrigation water Those who wrote at this time paid no attention to the life conditions of the peasantry Earliest references to epidemic diseases date back to 2000 B.C., had been time for other infectious diseases to establish themselves that were not mentioned or recorded CHINA People moved southward to better farming regions to increase development of rice paddies and urban lifestyles Sharp climatic difference between northern and southern China Warmer climates of the south allowed a larger variety of parasites to flourish (compared to the north) Those from the north did not have built up immunities to these foreign parasites Diseases in the south included: malaria, yellow fever, Schistosomiasis INDIA Extensive kingdoms developed in the Ganges Valley around 600 B.C. Buddha articulated a world view that became widely influential The Ganges Valley experienced monsoons providing abundant rainfall and shelter from the Himalayas; temperatures never approached freezing Climate permitted a variety of parasites to develop as soon as human populations came to existence in the valley Today the Ganges region contains: cholera, malaria, dengue fever and other diseases characteristic of cities and civilizations MEDITERRANEAN Civilizations cultivated wine and oil through vines and olives that already existed in the region (men of power) Grain growers of remote coastlands were forced to feed the city dwellers and get nothing in return Coastlands however offered a relatively disease free environment for populations to expand Cropping patterns are not believed to have brought new diseases to the Mediterranean Population growth attributed to the rise of disease, one that we are sure of is malaria Hippocrates concluded that diphtheria, tuberculosis and influenza also existed at this time He did not however account for smallpox, measles or bubonic plague Remained a relatively healthy place for human beings Human population growth appears to survive and multiply for a few generations until natural limits again interfere INDIA’S CLIMATE Warm climatic conditions such as those in India better allow for the survival of infectious organisms For that reason the assumption that smallpox originated in India may be perfectly sound Bubonic plague and cholera may also be indigenous to India DISEASE TRAVELED Disease traveled less easily overland than by sea Long distance traveling by humans, whether by land or sea, allowed for the possibility of new infections to be brought to “virgin host populations” “Virgin” populations- those groups of people who have never been exposed to a particular disease and therefore lacked the ability to buildup an immune system to it Often times disease was carried through the process of trading This only occurred in profitable trading where the demand for the goods desired was high enough that it was worth the risks and costs of the long and dangerous journeys that had to be endured CHRISTIAN ERA Trade between the eastern Mediterranean, India and China operated on a regular basis Regular movement back and forth created exchanges of infections as well as goods New and unfamiliar diseases spread to susceptible populations Second century A.D. populations in the Mediterranean and China were said to have experienced “sever blows” from epidemic disasters Evidence suggests that India and the Middle East were effected little by the presence of new infections MEASLES AND SMALLPOX Second to third centuries where when these diseases are said to have broken out in the Mediterranean populations A.D. 165 and 180 A.D. 251 to 266 No overall estimate of population loss has been made Must have been very high because civil unrest was also occurring on Roman frontiers CHRISTIANITY AND PLAGUES Christians had an advantage over their pagan contemporaries because they recognized caring for the sick as a religious duty Strengthened Christian churches when most other institutions where being discredited Teachings made life meaningful amid all the death and suffering The Impact of the Mongol Empire on Shifting Disease Balances 1200-1500 Mongol Movement • Intensified overland caravan movement across Asia – Communication: post messengers were capable of traveling 100 miles a day for weeks – Traveled new routes intensively – Political/Military reasons Before Mongol Movement • The plague was endemic in one or more natural foci among communities of burrowing rodents where human populations had found a customary pattern of behavior that minimized chances of infection • Natural focus points: borderland b/n India, China, and Burma in the Himalayan foothills, another in central Africa – The Eurasia steppelands not yet focus of plague After Mongol Movement • In the 2nd half of the 13th century Mongol horsemen penetrated Yunnan and Burma – C.1252-53 – They entered regions where the rodents host the bacillus on a chronic basis – Mongol invaders into this region disregard local rules to protect humans from plague – The great speed of the horsemen meant infection was able to travel great distances – For nearly 100 years it moved from one rodent community To the next Effect of Mongol Movement on Europe • Traveled by the black rats getting on ships from Asia for trade purposes • 1291- a Genoese admiral opened the Strait of Gibraltar to Christian shipping for the first time by defeating Moroccan forces • Then circumstances turned for the worst Europe and the Plague • Severity of winters caused crop devastation and resulting deaths and more migration • Initial shock of the “Black Death” in 1346-50 was severe because of these situations • Fleas, Human • MR: 60-70% • The plague would come and go several times to the same areas • Socioeconomic shifts Main Idea • The disease disasters that attacked the people of the steppes in the 13th and 14th centuries due to the Mongols were soon followed by 2 other blows: – The circumnavigation of Africa by European seamen – Systematic opening up of sea routes b/n Europe and other major centers of civilization. • After this the caravans were no longer most economic way of moving goods • Habits/customs Effect of Mongols • Response to changed Communication patterns • Massive epidemics due to military/political upheavals – And the rodents that came along for the ride • Greater interests in travel and exchange led to more travel and movement causing plague to spread Transoceanic Exchanges 1500-1700 • Amerindian epidemics and disease before Spaniards erroneous • First instance of epidemic on the Amerindians found in Aztec’s • There were no human populations dense enough to sustain human-human disease chains. Transoceanic Exchanges 1500-1700 • Only dense areas of population were areas in Mexico and Peru where a considerable amount of crops were grown. • These areas are where epidemics began. – Decline of Amerindian populations began after Cortez allowed exchanges b/n Amerindian and European settlements • The population of Mexico shrunk 90% Transoceanic Exchanges 1500-1700 • Once again with more military and political movement came the spread of such diseases as smallpox, measles, and typhus • People coming to America rarely contracted any diseases from the Amerindians and this made the Indians feel as if they were naturally inferior Pre-Columbus to 1700 Impact of diseases in the new and old worlds. 1500-1700 Transoceanic Exchanges 1500-1700 • In 1616-1617 a great pestilence of some sort swept through the Massachusetts bay area. (God prepared the way for the pilgrims). • 1633 smallpox outbreak convinced colonists that Divine Providence was indeed on their side in conflicts with the Indians. • Malaria and yellow fever establish themselves in the New World from Africa, both affected settlement and survival in tropical and subtropical parts. Contrary evidences show that they two diseases existed in the America’s before Columbus. •Malaria completed the annihilation of Amerindians in the tropical lowlands. Transoceanic Exchanges 1500-1700 • Yellow fever announced its successful transfer from west Africa to the • • • • Caribbean in 1648. Yucatan and Havana were the first reports. Specialized species of mosquito Aedes aegypti arose. It is highly domesticated, for its breading places were small bodies of water that doesn’t have natural mud or sand, but in a water cask, cistern, or calabash for laying eggs. Crossed over on a ship, couldn’t propagate at first until weather conditions were met (72 degrees F). Mosquito’s carrying yellow fever would travel from sailor to sailor and remained on these ships for weeks. “Yellow Jack” dreaded by sailors of the Caribbean and other tropical seas. African Americans took place of the Amerindians along the Caribbean coast and neighbor islands because of the human labor needed for the Caribbean plantation enterprises. Africans loss to malaria and yellow fever was very minimal because of past exposure. Amerindians populations drastic die-offs decreased to ratios of 20:1 and 25:1. Transoceanic Exchanges 1500-1700 • In 1450-1550 three new infectious diseases break out in • • • Europe. “English sweats”, syphilis, and typhus. Syphilis and typhus appeared in Europe during the Italian wars (1494-1559) first breaking out in the army spreading the diseases to all far and wide adjacent lands. Syphilis was considered a new disease in Europe even though in 1498 there was a break out in India as wells as China and Japan in 1505. The disease being new to the Old World it was thought that a strain of spirochete from America causing yaws found a way to shortcirculating the increasingly ineffective path of skin-skin. By the end of the century syphilis began to recede. Transoceanic Exchanges 1500-1700 • Typhus made its debut in European soil in 1490 when it • • was brought to Spain by soldiers who had just been fighting in Cyprus. In 1526 it hit a French army forcing them to withdraw due to the damage of the disease. It continued to spread disrupting armies, depopulating jails, poorhouses, and other institutions all the way to WWI when 2-3 million had already died of this infection. Typhus was a disease of crowding and poverty it brought death quicker compared to the other infections present. Transoceanic Exchanges 1500-1700 • The “English Sweats” had a opposite effect than typhus • • • socially for it affected the upper classes yet it mysteriously disappeared by 1551. Symptoms resembled scarlet fever though it did not have a big enough effect all over the continent to be a demographic effect on the continents. During this time there were high rates of infant mortality due to older persons high level of immunity through prior exposures. For costs of giving birth and rearing another child to replace one that had died was hard. After these occurrences of epidemic disease and severe weather conditions affecting crop northern Europe's population continued to slowly increase. Transoceanic Exchanges 1500-1700 • Doubling of recorded instances of epidemic disease in the sixteenth • • • • century corresponds with which the epidemics arrived in China. China’s population increased by 85million people between 14001600. The growth relates to the slowing of western europe’s population growth in the same period. Agriculture advances in Europe from American and China. Maize, potatoes, tomatoes, chili peppers, peanuts, and manioc came from America. Oranges originating from China. Changes in diseases patterns and increase in productivity with the spread of American food corps were the two main factors in triggering population growth. People became knowledgeable about diseases and prevention of them. Europeans discovered that oranges prevented the disease scurvy and bathing clothing and bodies was necessary was well to prevent disease. The Ecological impact of medical science and organization since 1700 • Medical schools and hospitals were significant in producing more systematic responses to new disease experiments. For hospitals gave opportunities for repeated observation of the symptoms and course of the disease. If they found a cure once they would try it again on anther patient. • In England 1721 a deliberate resort to smallpox inoculation, it was successfully immunized the next year with the royal children. They transferred the infection into a slight wound on the patients skin. Then in 1840’s the safer method of vaccination with cowpox was introduced. • In 1850 the practice of medicine and the organization of medical services begant to make large-scale differences in human survival rates and population growth. The Ecological impact of medical science and organization since 1700 • Cholera was introduced from Bengal to other parts of • Europe and seemed capable of penetrating any quarantine. Though after Cholera is swallowed the bacillus survives the stomach juices, it is capable of swift multiplication in the human alimentary tract and produces violent symptoms such as vomiting, fever, and death often within a few hours of the first signs of the illness. Cario had 13% of total population got Cholera. A new cholera epidemic arose in Bengal in 1826 it filtered all over Europe. It got to America from Ireland and America gave it to Mexico (1833). Germs and Methods • The first such germs to be detected were the bacilli of • • • anthrax and tuberculosis, discovered by Louis Pasteur between 1877 and 1879 and Robert Koch. Jame Lind installed sea-water distilleries and fresh drinking water. “Spit and Polish” was a ritual for cleanliness for the European sailors. Edwin Chadwick was to construct narrow sewers out of the smooth ceramic pipe to flush out the sewage. Had to develop more powerful pumps and pipes. Vaccines • 1829 bacillus was discovered and an effective vaccine • • • • • • developed by 1896. Diphtheria bacilli identified in 1883 and antitoxin was effective in 1891. 1866 Board of health was established in New York City. WWII chemicals-DDT, sulfas, penicillin, and Atabrine used. 1937 cheat and effect vaccine for yellow fever. 1948 World Heath Organization was set up. “Birth control may in time catch up with death control” (pg. 294) GOOD POINTS The author is able to identify patterns in the diseases that occurred with limited amounts of data and statistics The book describes the diseases that took place over large periods of time and throughout many countries The author makes many connections between disease and humanity that would have otherwise gone unnoticed because of the lack of data. BAD POINTS The book tends to jump around a lot between the diseases that occurred in different countries and those that occurred in differing time periods Failed to describe the diseases themselves but rather focused primarily on how they came about Draws conclusions on very sketchy evidence and data. Only discusses AIDS in the preface of the book.