Douglas H. Erwin is a senior scientist and Curator of Paleobiology at the National Museum of Natural History of the Smithsonian Institution, and an external faculty member@the Santa Fe Institute. He received his Ph.D. from the University of California, Santa Barbara in 1985. His research interests include evolutionary radiations, the end-Permian mass extinction and the history of Paleozoic gastropods. He is the author of Extinction: How Life on Earth Nearly Ended 250 Million Years Ago (Princeton University Press, 2006) and several other books. He is currently completing a book with Jim Valentine titled The Cambrian Explosion: The Construction of Animal Diversity. Address: Department of Paleobiology, MRC-121, National Museum of Natural History, Washington, DC 20560. Internet: Erwin.Doug@nmnh.si.edu