Born in Wilmette, Ill., to physicist father, Arno, and psychologist mother, Sara; wife, Christine Bayer, two children

Pursued sociobiology but has concentrated on evolutionary medicine; Ph.D. in zoology from University of Washington, 1980

Publishes with freelance physicist Gregory M. Cochran¿source of idea about infectious causation of chronic illness

Hobby and primary mode of 10-mile commute: bicycling " data-pin-do="buttonBookmark">

PAUL W. EWALD: EVOLUTION OF A HOSTPAUL W. EWALD: EVOLUTION OF A HOST

• Born in Wilmette, Ill., to physicist father, Arno, and psychologist mother, Sara; wife, Christine Bayer, two children
• Pursued sociobiology but has concentrated on evolutionary medicine; Ph.D. in zoology from University of Washington, 1980
• Publishes with freelance physicist Gregory M. Cochran¿source of idea about infectious causation of chronic illness
• Hobby and primary mode of 10-mile commute: bicycling

Image: KATHLEEN DOOHER

AMHERST, MASS.¿Newton had a falling apple. Darwin mused on finches. Paul W. Ewald's inspiration was diarrhea. "I wish I had something more romantic," says the Amherst College evolutionary biologist. It gets uglier: Ewald, then a graduate student studying bird behavior, was camped near a Kansas garbage dump. As he waged a three-day battle against his sea of troubles, he contemplated the interactions between a host¿himself, in this case¿and a pathogen. "There's some organism in there," Ewald remembers thinking during that 1977 experience, "and this diarrhea might be my way of getting rid of the organism¿or it might be the organism's way of manipulating my body" to maximize its chances of passage to the next victim by, for example, contaminating the water supply. "If it's a manipulation and you treat it, you're avoiding damage," he notes. "But if it's a defense and you treat it, you sabotage the host."

Host-pathogen relationships have dominated Ewald's thoughts ever since, leading to numerous articles, two books and, depending on whom you talk to, the respect or scorn of scientists and physicians. The admiration comes from those who think he was on to something really big in his earlier publications, which he summed up in his 1994 book Evolution of Infectious Disease. "I think that Paul Ewald has been a pioneer in using evolutionary theory to attack hard questions in pathogenesis," comments Stephen Morse, a virologist and epidemiologist at Columbia University. "His work has, for the first time, shown a way to generate testable hypotheses to study such questions as the evolution of virulence¿once thought intractable¿and infectious causes of chronic diseases." Indeed, the Atlantic Monthly referred to Ewald as "the Darwin of the microworld" (to which Ewald responds, "No, Darwin is Darwin of the microworld, too").

This article was originally published with the title A Host with Infectious Ideas.

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