Chapter 5: Group Selection & Altruism

Group Selection & Altruism establishes a hierarchy of selection levels, distinguishing between individual selection, kin selection (operating on families), and interdemic or interpopulation selection (operating on entire breeding populations or demes). A significant portion of the text evaluates the plausibility of pure interdemic selection counteracting individual selection, utilizing mathematical models such as the Levins model and the Boorman-Levitt model. These models analyze metapopulations—clusters of populations subject to varying extinction rates—to determine if altruistic genes can survive through differential extinction events, specifically distinguishing between r extinction in colonizing groups and K extinction in established populations. The chapter critically assesses and largely refutes V.C. Wynne-Edwards’ hypothesis of social conventions and epideictic displays, arguing that most density-dependent controls are better explained by competition or kin selection rather than voluntary population regulation. The discussion then pivots to W.D. Hamilton’s concept of inclusive fitness, which mathematically grounds altruism, selfishness, and spite by weighing the costs and benefits of actions against the coefficient of relationship between actors and recipients. This genetic theory is applied to explain sterile castes in social insects and cooperative behaviors in vertebrates. Furthermore, the chapter introduces Robert Trivers' concept of reciprocal altruism to explain cooperation among non-relatives, exploring the evolutionary instability caused by "cheating" and the necessary conditions for cooperative networks to function. Empirical evidence is reviewed extensively, covering phenomena such as distraction displays in birds, alarm calls and mobbing behavior, "stotting" in gazelles, cooperative breeding in turkeys and birds, food sharing (trophallaxis), and ritualized combat, all while weighing competing hypotheses regarding their adaptive significance.