Mark A. S. McMenamin is professor of geology at Mount Holyoke College. He is the author of a number of groundbreaking books on paleobiology and evolution, including The Emergence of Animals: The Cambrian Breakthroughand Hypersea: Life on Land(with Dianna L. S. McMenamin), both published by Columbia. He edited and annotated the English translation of Vladimir Vernadsky's The Biosphere,and is also the coeditor (with Lynn Margulis) of the English translation of L. Khakhina's Concepts of Symbiogenesis.