'The Essential Tension' explores how agents that naturally compete come to act together as a group. The author argues that the controversial concept of multilevel selection is essential to biological evolution, a proposition set to stimulate new debate. The idea of one collective unit emerging from the cooperative interactions of its constituent (and mutually competitive) parts has its roots in the ancient world. More recently, it has illuminated studies of animal behavior, and played a controversial role in evolutionary biology. In Part I, the author explores the historical development of the idea of a collectivity in biological systems, from early speculations on the sociology of human crowd behavior, through the mid-twentieth century debates over the role of group selection in evolution, to the notion of the selfish gene. Part II investigates the balance between competition and cooperation in a range of contemporary biological problems, from flocking and swarming to experimental evolution and the evolution of multicellularity. Part III addresses experimental studies of cooperation and competition, as well as controversial ideas such as the evolution of evolvability and Stephen Jay Gould's suggestion that "spandrels" at one level of selection serve as possible sources of variability for the next higher level. Finally, building on the foundation established in the preceding chapters, the author arrives at a provocative new proposition: as a result of the essential tension between competition and cooperation, multiple levels may be essential in order for evolutionary processes to occur at all.

HEALTH BEHAVIOR AS BASIC RESEARCH Health behavior is not a traditional discipline, but a newly emerging interdisciplinary field. It is still in the process of establishing its identity. Few institutional or organizational structures, i. e., departments and programs, reflect it, and few books and journals are directed at it. The primary objective of this book is thus to identify and establish health behavior as an important area of basic research, worthy of being studied in its own right. As a basic research area, health behavior transcends commitment to a particular behavior, a specific illness or health problem, or a single set of determinants. One way of achieving this objective is to look at health behavior as an outcome of a range of personal and social determinants, rather than as a set of risk factors or as targets for intervention strategies directed at behavioral change. The book is thus organized pri marily in terms of the size of the determinants of concern, rather than in terms of specific health behaviors, or specific health problems or conditions. With the first part of the book establishing working defmitions of health behavior and health behavior research as basic frameworks, the second part moves from smaller to larger systems, informing the reader about basic research that demonstrates how health behavior is determined by personal, family, social, institutional, and cultural factors. These distinctions reflect some arbitrar iness: the family, organizations, and institutions, for example, are social units."

HEALTH BEHAVIOR AS BASIC RESEARCH Health behavior is not a traditional discipline, but a newly emerging interdisciplinary field. It is still in the process of establishing its identity. Few institutional or organizational structures, i. e., departments and programs, reflect it, and few books and journals are directed at it. The primary objective of this book is thus to identify and establish health behavior as an important area of basic research, worthy of being studied in its own right. As a basic research area, health behavior transcends commitment to a particular behavior, a specific illness or health problem, or a single set of determinants. One way of achieving this objective is to look at health behavior as an outcome of a range of personal and social determinants, rather than as a set of risk factors or as targets for intervention strategies directed at behavioral change. The book is thus organized pri marily in terms of the size of the determinants of concern, rather than in terms of specific health behaviors, or specific health problems or conditions. With the first part of the book establishing working defmitions of health behavior and health behavior research as basic frameworks, the second part moves from smaller to larger systems, informing the reader about basic research that demonstrates how health behavior is determined by personal, family, social, institutional, and cultural factors. These distinctions reflect some arbitrar iness: the family, organizations, and institutions, for example, are social units."