Randolph M. Nesse, MD, is Professor of Psychiatry and Professor of Psychology at the University of Michigan, where he directs the Evolution and Human Adaptation Program. He collaborated with George Williams to write several seminal works on Darwinian Medicine, including Why We Get Sick: The New Science of Darwinian Medicine. His early research on the neuroendocrinology of anxiety has been transformed into a focus on how selection shapes mechanisms that regulate defenses such as pain, fever, anxiety and low mood. He is devoted to the mission of helping to organize the growing Evolution and Medicine community via writing, speaking and EvolutionAndMedicine.org.