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David Quammen has made his career writing about nature. A former Rhodes Scholar and novelist, he spent 15 years writing the “Natural Acts” column for Outside Magazine, getting an on-the-job education in ecology, biology, and evolution. In 1997, he published his first non-fiction bestseller, “The Song of the Dodo,” an exploration of geography and evolution. We recently discussed his latest book, “Spillover”, about diseases that spread from animals to humans. This phenomenon is called zoonosis, and it is increasing as humanity seeps further into undisturbed habitats.