Dr. Rada Dyson-Hudson is associate professor in the Department of Anthropology, Cornell University. In the past, she was associate professor and research associate in the Department of Pathobiology at the School of Hygiene, Johns Hopkins University. Her attempt to reconcile the implications of natural selection theory with a commitment to social equality led to a rethinking of human adaptation and, among other things, the organization of the symposium at the American Anthropological Association of which this book is a result. Dr. Michael A. Little is professor of anthropology at the State University of New York at Binghamton. He has been scientific coordinator of the Human Adaptability Section of the International Biological Program and is coauthor of Ecology, Energetics, and Human Variability (1976).