Living things are constantly engaged in a struggle for existence, and ingenious devices for the purpose of self-preservation can be seen in all types of animal and plant life. This book states that, however, nature also displays phenomena that are not related to survival or that seem clearly to violate the principle of self-preservation.

Introduction; I: Altruistic Behavior and Social Organization; 1: On the Effects of Selection on Social Insects; 2: The Genetical Evolution of Social Behavior. I.; 3: The Genetical Evolution of Social Behavior. II.; II: Adaptive Regulation of Population Density; 4: Intergroup Selection in the Evolution of Social Systems; Group Selection and Kin Selection: A Rejoinder; A Reply to Maynard Smith's Rejoinder; Survival of Young Swifts in Relation to Brood-Size; A Rejoinder to Perrins; III: Higher Levels of Organization; 5: The Evolution of Stability in Marine Environments: Natural Selection at the Level of the Ecosystem; IV: Sex Ratio; 6: Natural Selection and the Sex Ratio; 7: Evolutionary Origin of Sexual Differentiation and the Sex Ratio; 8: Comments on the Two Preceding Papers; V: Sex; 9: The Origin and Maintenance of Sex; 10: Evolution in Sexual and Asexual Populations; 11: Evolution in Sexual and Asexual Populations; 12: Evolution in Sexual and Asexual Populations