Of Men and Microbes

By Peter Stoler

PLAGUES AND PEOPLES

by WILLIAM H.McNEILL

369 pages. Anchor Press/Doubleday. $10.

Empires rise and fall. Tribes, nations, peoples flourish and vanish. Customs and cultures evolve. Why? Is it God's will? Sheer chance? The power of greed? The pattern of history? All of the above is probably the safest answer. But even taking that much into account, argues University of Chicago Professor William McNeill, historians miss one of the prime catalysts in human history: infectious disease.

Caste System. In Plagues and Peoples McNeill, who won the 1964 National Book Award for The Rise of the West, offers a provocative medical man's view of why the world took some of the turns it did. Most writers figure that Rome succumbed to outer Goths and inner decadence. McNeill maintains that a series of epidemics--measles, smallpox, plague--so depleted the empire's population that by the middle of the 3rd century A.D. it was no longer able to resist the barbarians. Disease, rather than religion, also lay at the roots of India's caste system, according to McNeill; its rigid rules developed as the country's Aryan invaders sought to protect themselves from the diseases carried by the people whose lands they had overrun.

Even the colonization of the New World may owe as much to epidemic disease as to gunpowder and the quest for gold. The Aztecs, McNeill notes, were on the verge of ousting Cortes from Mexico when an outbreak of smallpox blunted their assault. The disease spared the Spanish, who had already developed some immunity, but so devastated the Indians that even 50 years later the population of central Mexico was only one-tenth what it had been before Cortes landed.

Humanity's experience with illness began millenniums ago when microparasites--bacteria and viruses--evolved into the same ecological niche as man. Disease organisms presented few problems as long as humans were few and their communities small; pathogenic, or disease-causing, microbes can flourish only in a large human reservoir. But population growth and the development of cities provided a perfect breeding ground for epidemic illness. Outbreaks of various kinds killed Babylonians and Egyptians, stalked the streets of ancient China.

Microbes, like people, are always in a process of evolution. They have also proved marvelously mobile. They have marched with every army ever fielded, and claimed more victims than bronze spears, muskets or machine guns. From 1803 to 1815, Napoleon lost more of his men to typhus than he did to bullets or bayonets. During the Crimean War in 1854-56, disease killed ten times as many British soldiers as did Russian cannons. Even at the turn of our present century, British combat deaths during the Boer War were only a fifth as high as losses due to disease. Indeed, it was not until the Russo-Japanese War in 1904, when the Japanese introduced inoculation, that military casualties from disease began to fall below those from enemy action.

Naturally, McNeill soon turns from war to peacetime plagues. The most famous, bubonic plague, was carried westward from China and Manchuria by the marauding Mongol hordes, and decimated Asia before being brought by ship to Europe. There, it hit the unprepared Continent like evidence of God's displeasure; between 1346 and 1350, plague killed a third of Europe's population, and it disrupted social and governmental structures for centuries. Disease apparently took a hand in ecclesiastical history too.

Observed Reality. McNeill is usually convincing, though his originality is demonstrated less through the use of new research than through the application of an unexpected point of view. His ingenuity reaches tenuous heights when he says that man's inability to deal with disease delayed the onset of the Enlightenment. After all, he writes, "A world where sudden and unexpected death remains a real and dreaded possibility . . . makes the idea that the universe is a great machine whose motions are regular, understandable, and even predictable, seem grossly inadequate to account for observed reality."

Antibiotics and vaccines have reduced many an ancient malady to little more than a memory. Onetime killers like measles and chicken pox have been downgraded into childhood diseases capable of producing lasting immunities in their survivors. Inoculation and modern sanitation have all but eliminated smallpox. Cholera remains endemic only on the Indian subcontinent. But, McNeill concludes, "knowledge and organization alter but cannot cancel humanity's vulnerability to invasion by parasitic forms of life." Microbes have already shown that they are more flexible than man, and can move easily from animal hosts into humans. The swine flu virus seems to be making the jump today. No one can guess which microbe might massively cross the same barrier tomorrow. Or what the results might be for man and history.

Peter Stoler

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