Robert Lee Burgess (Ph.D., Washington University in St. Louis, 1969) is Professor of Human Development at the Pennsylvania State University. He has degrees in anthropology, psychology, and sociology. He has published numerous articles in journals and chapters in books dealing with such topics as theory construction, the development of criminal behavior and illicit drug use, cooperation and competition in children's groups, the development and consequences of power differences in dyads involved in exchange relationships, and the role of imitation in retarded children. He is also co-author (with Don Bushell, Jr.) of Behavioral Sociology: The Experimental Analysis of Social Process and (with Ted L. Huston) of Social Exchange in Developing Relationships. Drawing upon research methods developed by primatologists, he conducted one of the first observational studies of abusive and neglectful families in their own homes. Recently, he has published articles examining the convergence of evolutionary biology and behavior genetics for understanding human development. Kevin MacDonald is Professor of Psychology at California State University Long Beach. After receiving a Masters degree in evolutionary biology, he received a Ph. D. in Biobehavioral Sciences, both at the University of Connecticut. Since assuming his position at California State University Long Beach, his research has focused on developing evolutionary perspectives on culture, developmental psychology and personality theory, the origins and maintenance of monogamous marriage in Western Europe, and ethnic relations (group evolutionary strategies). He is the author of Social and Personality Development: An Evolutionary Synthesis (1988), A People That Shall Dwell Alone: Judaism as a Group Evolutionary Strategy (1994), Separation and Its Discontents: Toward an Evolutionary Theory of Anti-Semitism (1998), and The Culture of Critique: An Evolutionary Analysis of Jewish Involvement in Twentieth-Century Intellectual and Political Movements (1998). He has also edited three books, Sociobiological Perspectives on Human Development (1988), Parent-Child Play: Descriptions and Implications (1994), and Evolutionary Perspectives on Human Development (2004).