Germs, Genes, & Civilization: How Epidemics Shaped Who We Are Today Read online

  Germs, Genes, & Civilization

  How Epidemics Shaped Who We Are Today

  David P. Clark

  Department of Microbiology,

  Southern Illinois University

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  © 2010 by Pearson Education, Inc.

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  Printed in the United States of America

  First Printing May 2010

  ISBN-10: 0-13-701996-3

  ISBN-13: 978-0-13-701996-0

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  This book is dedicated to my younger brother, Andrew, who has always enjoyed a good argument.

  Contents

  Preface

  Chapter 1: Introduction: our debt to disease

  Epidemics select genetic alterations

  Every cloud has a silver lining: our debt to disease

  Crowding and culling

  The message of this book

  Chapter 2: Where did our diseases come from?

  Africa: homeland of mankind and malaria

  Many human diseases originated in animals

  Are new diseases virulent to start with?

  Diseases from rodents

  Leprosy is a relatively new disease

  What goes around comes around

  Chapter 3: Transmission, overcrowding, and virulence

  Virulence and the spread of disease

  Infectious and noninfectious disease

  Many diseases become milder with time

  Development of genetic resistance to disease

  Hunting and gathering

  How do microorganisms become dangerous?

  Chapter 4: Water, sewers, and empires

  Introduction: the importance of biology

  Irrigation helps agriculture but spreads germs

  The class system, water, and infection

  The origin of diarrheal diseases

  Cholera comes from the Indian subcontinent

  Cholera and the water supply

  The rise and fall of the Indus Valley civilization

  Cities are vulnerable to waterborne diseases

  Cholera, typhoid, and cystic fibrosis

  How did disease affect the rise of Rome?

  How much did malaria contribute to the fall of Rome?

  Uncivilized humans and unidentified diseases

  Bubonic plague makes an appearance

  Chapter 5: Meat and vegetables

  Eating is hazardous to your health

  Hygiene in the home

  Cannibalism is hazardous to your health

  Mad cow disease in England

  The political response

  Mad cow disease in humans

  Fungal diseases and death in the countryside

  Fungal diseases and cereal crops

  Religious mania induced by fungi

  Catastrophes caused by fungi

  Human disease follows malnutrition

  Coffee or tea?

  Opportunistic fungal pathogens

  Friend or enemy

  Chapter 6: Pestilence and warfare

  Who kills more?

  Spread of disease by the military

  Is it better to besiege or to be besieged?

  Disease promotes imperial expansion

  Protozoa help keep Africa black

  Is bigger really better?

  Disease versus enemy action

  Typhus, warrior germ of the temperate zone

  Jails, workhouses, and concentration camps

  Germ warfare

  Psychology, cost, and convenience

  Anthrax as a biological weapon

  Amateurs with biological weapons are rarely effective

  Which agents are used in germ warfare?

  World War I and II

  Germ warfare against rabbits

  Germ warfare is unreliable

  Genetic engineering of diseases

  Chapter 7: Venereal disease and sexual behavior

  Venereal disease is embarrassing

  Promiscuity, propaganda, and perception

  The arrival of syphilis in Europe

  Relation between venereal and skin infections

  AIDS is an atypical venereal disease

  Origin of AIDS among African apes and monkeys

  Worldwide incidence and spread of AIDS

  The Church, morality, and venereal infections

  Moral and religious responses to AIDS

  Public health and AIDS

  Inherited resistance to AIDS

  The ancient history of venereal disease

  Chapter 8: Religion and tradition: health below or heaven above?

  Religion and health care

  Belief and expectation

  Roman religion and epidemics

  Infectious disease and early religious practices

  Worms and serpents

  Sumerians, Egyptians, and ancient Greece

  Hygiene and religious purity

  Protecting the living from the dead

  Diverting evil spirits into animals

  Cheaper rituals for the poor

  Vampires, werewolves, and garlic

  Divine retribution versus individual justice

  The rise of Christianity

  Coptic Christianity and malaria

  Messianic Taoism during the collapse of Han China

  Buddhism and smallpox in first-millennium Japan

  The European Middle Ages and the Black Death

  The Great Plague of London

  Loss of Christian faith in industrial Europe

  Cleanliness is next to godliness

  Chapter 9: Manpower and slavery

  Legacy of the last Ice Age

  The New World before contact

  Indigenous American infections

  Lack of domesticated animals in America
<
br />   The first epidemic in the Caribbean

  Epidemics sweep the American mainland

  The religious implications

  Deliberate use of germ warfare

  Slavery and African diseases

  Exposure of islands to mainland diseases

  Cholera and good intentions

  The issue of biological isolation

  Spotted fevers and rickettsias

  The origins of typhus are uncertain

  What about the Vikings?

  Chapter 10: Urbanization and democracy

  Cities as population sinks

  Viral diseases in the city

  Bacterial diseases in the city

  The Black Death

  Climatic changes: the “Little Ice Age”

  The Black Death frees labor in Europe

  Death rates and freedom in Europe

  The Black Death and religion

  The White Plague: tuberculosis

  The rise of modern hygiene

  The collapse of the European empires

  Resistant people?

  How clean is too clean?

  Where are we now?

  Chapter 11: Emerging diseases and the future

  Pandemics and demographic collapse

  The various types of emerging diseases

  Changes in knowledge

  Changes in the agent of disease

  Changes in the human population

  Changes in contact between victims and germs

  The supposed re-emergence of tuberculosis

  Diseases are constantly emerging

  How dangerous are novel viruses?

  Transmission of emerging viruses

  Efficient transmission and genuine threats

  The history and future of influenza

  The great influenza epidemic of 1918–1919

  Disease and the changing climate

  Technology-borne diseases

  Emergence of antibiotic resistance

  Disease and the food supply

  Overpopulation and microbial evolution

  Predicting the future

  Future emerging diseases

  Gloom and doom or a happy ending?

  Further reading

  Index

  Preface

  Humans typically labor under the illusion that they control their own destiny. This book argues that, in reality, invisible microbes often control human activities. Recent findings have shown that animals that develop without their natural bacterial inhabitants have defective immune systems and poor health. Thus, we and other animals depend on the bacteria for our healthy development. On a larger scale, we now recognize that microbes maintain the global ecosystem and are partly responsible for keeping our planet healthy. The amount of “good” bacteria that work to recycle nutrients and degrade waste is greater by far than the amount of “bad” bacteria that threaten human health.

  Here I enter the intermediate zone between individual development and planetary ecology, to discuss how microbes have decided major historical events and shaped cultural trends. Furthermore, the emergence of resistance to infectious diseases has selected alterations in genes that affect human behavior.

  This book is not a history of public health, medicine, or microbiology, although it does mention these issues. Instead, this book describes how infections have shaped both individual humans and their societies from the very beginning of civilization. Disease has influenced our cultural and religious beliefs, as well as determined the outcome of wars and major historical events. I have tried to show how beneficial long-term effects have resulted from epidemics that were terrible tragedies to those caught up in them.

  Philosophically, we are just emerging from a period of transition between the perfectionist and selfish views of nature. The classic example, in the area of disease, is the idea that, over the ages, infectious agents will adapt to their hosts. Eventually, all diseases will become no worse than a bad cold. This is an attempt to retain a utopian future while allowing evolution to occur. Recently, we have come to realize that although some diseases become milder, others might evolve with greater virulence. We now see nature more as an arms race between life forms deploying assorted genetic strategies.

  A second aspect of this more modern viewpoint, is to realize that the scale on which we view events is important. Improving a species through evolution inevitably involves the death of many less fit individuals. Applying this Darwinian idea to human populations lets us see that whereas mass fatalities from a plague are tragedies at the personal level, they can have positive effects when seen from a long-term perspective.

  These positive effects vary from genetic changes that make us more resistant to the disease responsible for the epidemic (and often to related infections), to effects on human society that are hard to pin down and quantify. Epidemics have undoubtedly affected the outcome of many wars and conflicts. Whether these interventions were a good thing obviously depends on which side you support. Less ambiguous is the contribution of epidemics to the development of a free, technologically based society in the West. More ambiguous are the possible effects on religious belief and human behavior.

  Modern progress in DNA technology and human genetics is generating a vast amount of data. Analyzing and checking this will take time. The next few years should reveal many connections between infection, disease resistance, and alterations in genes that affect not only our physical characteristics, but also brain function or development and thus impact human behavior. We live in exciting times!

  David Clark

  Carbondale, Illinois

  Acknowledgments

  I would like to thank Donna Mueller for commenting on some early drafts, and Kirk Jensen for long-term editorial support through several versions of the manuscript.

  About the Author

  David Clark was born June 1952 in Croydon, a London suburb. After winning a scholarship to Christ’s College, Cambridge, he received his Bachelor of Arts degree in 1973. In 1977, he earned his Ph.D. from Bristol University for work on antibiotic resistance. David then left England for postdoctoral research at Yale and then the University of Illinois. He joined the faculty of Southern Illinois University in 1981 and is now a professor in the Microbiology Department. In 1991, he visited Sheffield University, England, as a Royal Society Guest Research Fellow. The U.S. Department of Energy funded David’s research into the genetics and regulation of bacterial fermentation from 1982 till 2007. David has published more than 70 articles in scientific journals and graduated more than 20 masters and Ph.D. students. He is unmarried and lives with two cats: Little George, who is orange, and Ralph, who is mostly black and eats cardboard. David is the author of Molecular Biology Made Simple and Fun, now in its third edition, as well as three more serious textbooks.

  1. Introduction: our debt to disease

  Early in the fifth century A.D., the Huns, led by Attila, emerged from the Asian steppes and swept across Europe. They faced no serious resistance. What was left of the greatest civilization the world had seen, the Roman Empire, was a tottering wreck. One more good shove and the remains of Roman civilization would have taken a final nose-dive. But strangely, on the verge of storming Rome itself, Attila withdrew. Why?

  For many centuries the official answer was that God had intervened in some mysterious way to protect his chosen city, Rome, seat of the papacy. In more recent times, such supernatural explanations have fallen out of favor and the question has arisen anew. Some have suggested that Attila was overawed by the sanctity of Rome. But why would a pagan warlord like Attila stand in awe of a Christian center? Attila was by no means an ignorant barbarian: For example, he invited Roman and Greek engineers into Hun territory to install bathing facilities. However, his respect for Roman civilization was clearly of a pragmatic rather than a religious nature. Another theory is that Attila was worried about leaving unattended his newly acquired homeland, in what is now Hungary. But then why did he venture out almost as far as Rome and hang around indecisively
for so long before returning? All these explanations founder on the same point. It seems clear that Attila did indeed set out with every intention of taking Rome, but his expedition came to a premature halt.