William R. Clark is Professor Emeritus of Immunology in the Department of Molecular, Cell and Developmental Biology at the University of California, Los Angeles. He is the author of a number of books about biology, immunology, and evolution, including Sex and the Origins of Death, A Means to an End: The Biological Basis of Aging and Death, and The New Healers: The Promise and Problems of Molecular Medicine in the Twenty-First Century. His website is: http://www.wrclarkbooks.com. Michael Grunstein is Professor of Biological Chemistry at the UCLA School of Medicine and Molecular Biology Institute.