Encyclopedia of Evolutionary Psychological Science

Living Edition
| Editors: Todd K. Shackelford, Viviana A. Weekes-Shackelford

Benefits to Kin

  • Kristen SymeEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-16999-6_596-1



One evolutionary theory of suicide terrorism proposes that the act is committed in order to benefit the close kin of the attacker.


Suicide terrorism is a politically motivated aggressive act wherein the perpetrator willingly sacrifices his or her life with the goal of inflicting harm on typically civilian causalities. One evolutionary theory of suicide terrorism proposes that terrorist organizations manipulate followers into embarking on suicide missions in order to benefit genetic kin. This theory of suicide terrorism is rooted in kin selection (Smith 1964), a form of altruism based on Hamilton’s rule (rb > c) where r is the degree of genetic relatedness, b is the reproductive benefits to related kin, and c is the cost to the agent (Hamilton 1963). According to this theory, an organism should act altruistically when the reproductive benefits to its kin are greater than the costs of the act to the organism. Kin selection demonstrates how traits that harm individual organisms can be maintained by natural selection; thus, an organism can, therefore, increase genetic representation in future generations even if that organism fails to reproduce (Liddle et al. 2011). There is evidence to suggest that suicide terrorism can function to benefit the fitness close kin.

Theoretical Overview: Suicide and Benefits to Kin

Though there is scant data on suicide in nonhuman animals, self-sacrifice through death is evidenced in a variety of species such as sterile castes of the order Hymenoptera for the purpose of colony defense (Preti 2007). Likewise, in E. coli self-sacrifice might function to limit the transmission of a bacteriophage to related organisms (Refardt et al. 2013).

In regards to humans, psychologist Denys deCatanzaro proposed that one with low reproductive potential who is imposing net fitness costs on biological kin would improve his or her inclusive fitness by committing suicide (de Catanzaro 1981; 1984; 1991). Though theorists have not directly applied deCatanzaro’s inclusive fitness model to suicide terrorism, aspects of the model are relevant. Moreover, the end goals are identical: to increase fitness by increasing the reproductive success of close genetic kin at a cost to the self. A suicide terrorist should have relatively low reproductive potential (e.g., poor prospects for mating opportunities) such that the reproductive benefits to kin should outweigh the costs to the suicide attacker. There are two means through which attackers might benefit their kin that when combined are unique to the context of suicide terrorism: monetary compensation and heightened familial reputation.

Terror organizations such as Hamas and Hezbollah promise to provide financial compensation to the families of prospective suicide attackers. As of 2002, Hamas, for instance, paid the families of suicide attackers between $10,000 and $25,000 and often in addition offered medical services. In cultures such as those in the Middle East, this money can contribute to bride’s wealth wherein the groom provides payment to the bride’s family in the form of money, goods, or other services. Thus, financial gains to one’s siblings can promote their reproductive success, which might factor into the decision of one to opt into suicide terrorism or for a parent to encourage offspring to execute such missions. Blackwell (2006) modeled the inclusive fitness benefits of suicide terrorism, finding that theoretically suicide terrorism can incur inclusive fitness benefits, particularly in large, middle class families with many males. In fact, suicide attackers and their families tend to be wealthier on average than their social counterparts (Krueger and Malečková 2003).

Heightened social reputation is another asset that is bestowed upon the families of suicide attackers that might benefit their fitness. Motivations such as these could be fostered through cultural values such as collectivism and honor-based codes of conduct, which are endemic to regions where suicide terrorism is found. In fact, honor cultures strongly encourage retaliation against external threats and aggressors for the sake of both the individual and their social group, and evidence suggests that such strategies could be evolutionarily stable in certain contexts (Nowak et al. 2016). Suicide terrorism is a form of political retaliation typically employed to combat more powerful opponents (Pape 2005; Hafez 2006). In these communities, members celebrate suicide attackers as religious “martyrs” and heroes of their homeland, and they might devote shrines and websites to honor their sacrifice (Hafez 2006). The reputational benefits often extend to the kin of the suicide attackers, which could confer reproductive benefits such as additional income and access to mates. At present, however, data is lacking to sufficiently demonstrate that the reputational benefits of suicide attack translate into inclusive fitness benefits.


Empirical evidence indicates that suicide terrorists might be motivated to benefit their kin through the attack, thus increasing their inclusive fitness. However, more research is necessary to confirm these models.



  1. Blackwell, A. D. (2006). Terrorism, heroism, and altruism: The behavioral ecology of Palestinian suicide attack as a model for the evolution of self-sacrificial behavior in humans. (Doctoral dissertation, University of Oregon).Google Scholar
  2. de Catanzaro, D. (1981). Suicide and self-damaging behavior: A sociobiological perspective. Academic Press.Google Scholar
  3. de Catanzaro, D. (1984). Suicidal ideation and the residual capacity to promote inclusive fitness: a survey. Suicide and Life-Threatening Behavior, 14(2), 75–87.Google Scholar
  4. de Catanzaro, D. (1991). Evolutionary limits to self-preservation. Ethology and Sociobiology, 12(1), 13–28.Google Scholar
  5. Hafez, M. M. (2006). Rationality, culture, and structure in the making of suicide bombers: A preliminary theoretical synthesis and illustrative case study. Studies in Conflict & Terrorism, 29(2), 165–185.Google Scholar
  6. Hamilton, W. D. (1963). The evolution of altruistic behavior. The American Naturalist, 97(896), 354–356.CrossRefGoogle Scholar
  7. Krueger, A. B., & Malečková, J. (2003). Education, poverty and terrorism: Is there a causal connection? The Journal of Economic Perspectives, 17(4), 119–144.CrossRefGoogle Scholar
  8. Liddle, J. R., Bush, L. S., & Shackelford, T. K. (2011). An introduction to evolutionary psychology and its application to suicide terrorism. Behavioral Sciences of Terrorism and Political Aggression, 3(3), 176–197.CrossRefGoogle Scholar
  9. Nowak, A., Gelfand, M. J., Borkowski, W., Cohen, D., & Hernandez, I. (2016). The evolutionary basis of honor cultures. Psychological Science, 27(1), 12–24.CrossRefPubMedGoogle Scholar
  10. Pape, R. (2005). Dying to win: The strategic logic of suicide terrorism. New York: Random House.Google Scholar
  11. Preti, A. (2007). Suicide among animals: A review of evidence. Psychological Reports, 101(3), 831–848.CrossRefPubMedGoogle Scholar
  12. Refardt, D., Bergmiller, T., & Kümmerli, R. (2013). Altruismcan evolvewhen relatedness is low: Evidence from bacteria committing suicide upon phage infection. Proceedings of the Royal Society B: Biological Sciences, 280(1759), 20123035.CrossRefPubMedPubMedCentralGoogle Scholar
  13. Smith, J. M. (1964). Group selection and kin selection. Nature, 201(4924), 1145–1147.CrossRefGoogle Scholar

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© Springer International Publishing AG 2018

Authors and Affiliations

  1. 1.Washington State UniversityVancouverUSA

Section editors and affiliations

  • Doug P. VanderLaan
    • 1
    • 2
  1. 1.Department of PsychologyUniversity of Toronto MississaugaMississaugaCanada
  2. 2.Child, Youth and Family DivisionCentre for Addiction and Mental HealthTorontoCanada