Self-destructive motivation: An evolutionary perspective

Drawing upon the theory of inclusive fitness1 in evolutionary biology (Hamilton, 1964), Denys deCatanzaro (1986) formulated a mathematical model of the evolution of both selfpreservative and self-destructive motivational mechanisms in humans and certain other social species (e.g., social Hymenopterans). The model predicts self-destructive motivation for those with low individual reproductive potential, for example, due to old age, inadequate heterosexual relationships, poor health, financial hardship, or who feel like a burden to genetic relatives. Under these conditions, staying alive could compromise the individual's inclusive fitness. It is important to note that deCatanzaro's model focuses on past recurrent evolutionary contingencies, providing an explanation for the evolution of self-destructive motivation in humans and some other highly social species. Thus, there is no a priori reason to expect that the model should predict all or even most forms of suicidal thinking and behavior in the present. Nevertheless, despite substantial cultural change over time, there is increasing evidence to suggest that the model helps us predict and understand manifestations of self-destructive behavior in contemporary environments, as we shall see. Arguments for the evolutionary plausibility of suicide are not unique to deCatanzaro. For example, Lonergan and Travis (2003) have argued that the evolution of a suicide gene is logically and mathematically plausible, and Mascaro, Korb and Nicholson (2001) used game theoretic methods to show that suicide can become an evolutionarily stable strategy. Such arguments are given additional credence by (a) findings from family correlational studies that are consistent with a genetic basis for suicide and suicidal behavior, independent of related psychopathological disorders (e.g., Kim, Seguin, Therrien, Riopel, Chawky, Lesage & Turecki, 2005; Lieb, Bronisch, Höfler, et al., 2005; Pedersen & Fiske, 2010); (b) welldocumented evidence for cell suicide caused by the activation of specific genes (Duke, Ojcius & Young, 1996; Elmore, 2007); (c) evidence suggesting kin-selected suicidal behavior in social insects (e.g., Hölldobler & Wilson, 1990; Wilson, 2006; Tofilski, Couvillon, Evison, et al., 2008; Rueppell, et al., 2010); and (d) reports of apparent altruistic suicide in humans (Durkheim, 1897/1951; Leighton & Hughes, 1955; Pape, 2005).