Germs, Genes, & Civilization
How Epidemics Shaped Who We Are Today
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First Printing May 2010
ISBN-10: 0-13-701996-3
ISBN-13: 978-0-13-701996-0
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Library of Congress Cataloging-in-Publication Data
Clark, David P.
Germs, genes & civilization : how epidemics shaped who we are today / David P. Clark.
p. cm.
Includes index.
ISBN 978-0-13-701996-0 (hardback : alk. paper) 1. Diseases and history. 2. Epidemics.
3. Civilization. 4. Human evolution. 5. Human genetics. I. Title. II. Title: Germs, genes,
and civilization.
R702.C63 2010
614.4—dc22
2009048726
Contents
Chapter 1: Introduction: our debt to disease
Epidemics select genetic alterations
Every cloud has a silver lining: our debt to disease
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?
Leprosy is a relatively new disease
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
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
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
Cannibalism is hazardous to your health
Fungal diseases and death in the countryside
Fungal diseases and cereal crops
Religious mania induced by fungi
Human disease follows malnutrition
Opportunistic fungal pathogens
Chapter 6: Pestilence and warfare
Spread of disease by the military
Is it better to besiege or to be besieged?
Disease promotes imperial expansion
Protozoa help keep Africa black
Typhus, warrior germ of the temperate zone
Jails, workhouses, and concentration camps
Psychology, cost, and convenience
Anthrax as a biological weapon
Amateurs with biological weapons are rarely effective
Which agents are used in germ warfare?
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
The ancient history of venereal disease
Chapter 8: Religion and tradition: health below or heaven above?
Infectious disease and early religious practices
Sumerians, Egyptians, and ancient Greece
Protecting the living from the dead
Diverting evil spirits into animals
Vampires, werewolves, and garlic
Divine retribution versus individual justice
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
Loss of Christian faith in industrial Europe
Cleanliness is next to godliness
Chapter 9: Manpower and slavery
Indigenous American infections
Lack of domesticated animals in America
The first epidemic in the Caribbean
Epidemics sweep the American mainland
Deliberate use of germ warfare
Exposure of islands to mainland diseases
The issue of biological isolation
Spotted fevers and rickettsias
The origins of typhus are uncertain
Chapter 10: Urbanization and democracy
Bacterial diseases in the city
Climatic changes: the “Little Ice Age”
The Black Death frees labor in Europe
Death rates and freedom in Europe
The White Plague: tuberculosis
The collapse of the European empires
Chapter 11: Emerging diseases and the future
Pandemics and demographic collapse
The various types of emerging diseases
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
Emergence of antibiotic resistance
Overpopulation and microbial evolution
Gloom and doom or a happy ending?
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.