Evolution and Altruism

Theory and research on altruism attempt to illuminate a fundamental characteristic of human nature. Philosophers throughout the ages have debated whether humans actually intend to perform actions beneficial to others and costly to themselves without any clear resolution. In recent years, psychologists have addressed the enduring debate with data on the mental experiences leading to helping behaviors, however there studies produce conflicting results. Thus, it would be useful to frame the altruism question in light of the most powerful theory in the Life Sciences, evolution by natural and sexual selection. The following papers examine issues of altruism and helping from both the proximate (psychological) and ultimate (evolutionary fitness) perspectives.

Butler, T.J., & Kruger, D. J. (2011). Altruistic tendencies are sensitive to sex-specific mate selection criteria. Journal of the Evolutionary Studies Consortium, 4, 1-12.

Natural selection and sexual selection are usually seen as either two different and separate processes or with sexual selection being a subset of natural selection but distinct from other processes such as kin selection. In this paper, we investigate the possibility of a connection between discriminatory altruistic behaviors consistent with kin selection and the sex-specific criteria that men and women are evaluated on by potential partners in the process of mate selection. Many studies document discriminatory altruistic behaviors consistent with kin selection, including tendencies to favor closely related family members for costly assistance. Considerable research also demonstrates the existence of sex-specific mate selection criteria. When selecting a suitable mate, men show a preference for fecundity cues in women, such as the waist-to-hip ratio, which indicates a woman's ability to conceive and bear children. Women show a preference for high resource potential and high social status in men, indicating a man's ability to provide resources for the woman and offspring. We tested whether sex-specific mate selection criteria influences patterns of assistance and whether nepotistic tendencies are stronger for each sex within the domains in which women and men are differentially valued. Undergraduate students reported altruistic behaviors that benefited another individual's social status, resource potential, or physical attractiveness, as well as the relationship between the participant and whom he or she helped. We did not find evidence for nepotistic tendencies indicative of kin selection. Results did provide moderate support for the hypothesis that sex specific mate selection criteria influences the type of altruistic behavior, although both male and female participants were more likely to provide assistance to those of the same sex overall.

Kruger, D. J. (2003). Evolution and altruism: Combining psychological mediators with naturally selected tendencies. Evolution and Human Behavior, 24, 118-125.

This study integrates psychological predictors of helping intentions and naturally selected tendencies enhancing inclusive fitness for a more comprehensive understanding of altruism. Psychological mediators of helping intentions, empathic concern and oneness, and psychological processes facilitating kin selection and reciprocal altruism were combined in a structural equation model to predict participants' (N = 643) intentions to perform a risky rescue behavior. The tendency for reciprocal altruism and kinship were the strongest predictors of rescue intentions. Confirming previous research, empathic concern made a significant but small contribution in predicting helping intentions. Proximate mechanisms currently in the psychological literature did not entirely account for the effect of kinship on helping intentions.

Kruger, D. J. (2001). An Integration of Proximate and Ultimate Influences for Altruistic Helping Intentions. Dissertation Abstracts International: Section B: The Sciences & Engineering, 62 (1-B), 601. (University Microfilms International; 2001, 601). Available On-line: http://www-personal.umich.edu/~kruger

This is the Dissertation length version of the above paper, with additional content and analyses.

Kruger, D. J. (2001). Inclusive fitness and judgments of helping behaviors: Adaptations for kin directed altruism. Social Behavior and Personality, 29, 323-330.

This questionnaire study sheds light on the psychological component of kin selecting tendencies predicted by Hamilton's (1964) inclusive fitness theory of discriminatory altruistic behavior based on genetic similarity. Participants rated donations of assistance aiding survival and material wealth as more rational and ethical when these actions were performed for closer relatives. Participants also felt a greater obligation to perform these acts for a close relation. A comparison condition where assistance was unlikely to affect survival or reproductive success did not exhibit these tendencies.

Male relatives benefit more from kin selecting tendencies enhancing social status

This paper suggests a link between kin selecting tendencies and human mate selection criteria. Kin selection was evident for assistance impacting survival/health, material wealth, and social status. The kin selecting effect was stronger for male targets than for female targets with benefits enhancing social status, which males are valued for in sexual selection.

The data in this paper were presented in:

Kruger, D.J. (1998, May). Relative worth across disparate types of assistance. Poster session presented at the annual meeting of the Midwestern Psychological Association, Chicago.