1.3 The evolution of intergroup coalitionary aggression in humans  (Page 7/7)

Research on warfare from an evolutionary behaviorist perspective using modern theories of individual natural selection appears to be limited. A complete and coherent view of the evolutionary nature of human coalitionary aggression remains elusive, and the field would benefit form an increased understanding of the evolutionary factors that lead humans into warfare. Human aggression is highly dependent upon social cues as well, so learning to understand these can help to reduce instances of aggression by making other, more peaceful options favorable (Lore and Schultz 1993). Any person, whether politician, scientist, or layperson, who seeks to understand human warfare and prevent further violence, can benefit from an increased understanding of the evolutionary basis of intercoalitionary aggression.

Discussion questions

• From an evolutionary perspective, why would human females be less likely to engage in physical aggression?
• In what ways is intergroup coalitionary aggression an adaptive strategy for human males? For chimpanzee males?
• Under what circumstances are human males unlikely to engage in intergroup coalitionary aggression?

Glossary

• Adaptation – A trait that increases an individual’s fitness.
• Anthropology – The study of human beings and ancestral species. It is frequently divided into the subfields of cultural anthropology, archaeology, linguistic anthropology, and physical anthropology.
• Intergroup coalitionary aggression – Violent behaviors committed by one group of humans against members of another group.
• Community – Term used to describe a group of chimpanzees.
• Conspecific – A member of the same species as another individual.
• Cross-species comparison – Method of study in evolutionary biology completed by comparing two species that exhibit a similar trait or behavior.
• Evolutionary psychology – The study of human psychological processes as products of evolutionary selection.
• Fitness – The genetic contribution of an individual to the next generation.
• Imbalance of Power Hypothesis – This theory posits that intergroup coalitionary aggression will only occur if the risk of costs to the aggressors is sufficiently low.
• Polygyny – Type of marriage system in which a man may have multiple wives.
• Proximate Cause – An explanation for a behavior or trait involving the biological mechanisms that result in the behavior or trait.
• Raiding – Type of coalitionary aggression in which one group invades the territory of another group in order to obtain resources or harm members of the rival group.
• Resource Competition Theory – This theory posits that male intergroup coalitionary aggression evolved as a strategy for obtaining resources. According to this theory, greater control of resources results in an increase in fitness.
• Sociobiology – A field, developed largely by E.O. Wilson, attempting to study social behavior in terms of evolutionary theory.
• Testosterone – Male sex hormone essential to the development of male reproductive organs. Testosterone is hypothesized to play a role in aggressive behaviors in humans, though the precise nature of the relationship remains unclear.
• Ultimate Cause – The evolutionary explanation for the existence of a behavior or trait.

Bibliography

• Archer, John. 2009. Does sexual selection explain human sex differences in aggression? Behavioral and Brain Sciences. 32: 249-311.

  This article hypothesizes that sex differences in aggression can be explained as an adaptive result of sexual selection, rather than the biosocial social role theory

• Archer, John. 1991. The influence of testosterone on human aggression. British ournal of Psychology. 82: 1-28.
• Book, Angela S., Starzyk, Katherine B., Quinsey, Vernon L. 2001. The relationship between testosterone and aggression: a meta-analysis. Aggression and Violent Behavior. 6: 579-599.
• Buss, David M., Dedden, Lisa A. 1990. Derogation of competitors. Journal of Social and Personal Relationships. 7: 395-422.
• Buss, David M. 1989. Sex differences in human mate preferences: evolutionary hypotheses tested in 37 cultures. Behavioral and Brain Sciences. 12: 1-49.
• Buss, David M., Shackelford, Todd K. 1997. Human aggression in evolutionary psychological perspective. Clinical Psychology Review. 17: 605-619.

  This article examines seven evolutionary hypothesis for aggression in humans, including as a means of gaining access to others’ resources, defense against attack, decreasing the fitness of same-sex rivals, gaining social dominance, deterring against future attack, detering mates from engaging in sexual activities with multiple partners, and limiting the resources spent on genetically-unrelated offspring.

• Chagnon, Napolean A. 1983. Yanomamo (3rd ed.) New York: Holt, Rinehart,&Winston. Cited by Buss and Shackelford 1997
• Chagnon, Napoleon A. 1988. Life histories, blood revenge, and warfare in a tribal population. Science. 239: 985-992.
• Durham, William H. 1976. Resource Competition and Human Aggression, Part I: A Review of Primitive War. The Quarterly Review of Biology. 51: 385-415.

  This article examines human intergroup aggression as a product of resource competition between social groups. It proposes a model where intergroup aggression would be advantageous for gaining fitness, and compares this model with real-life examples of aggression between small, stateless human societies.

• Ember, Carol R., Ember, Melvin. 1992. Resource unpredictability, mistrust and war: a cross-cultural study. The Journal of Conflict Resolution. 36: 242-262.

  This article examines the relationship between natural disasters and the outbreak of war. It hypothesizes that war may be an attempt to co-opt the resources of others, particularly after a natural disaster, which causes a lack of certainty in the stability of one’s resource supply.

• Fuentes, Agustin. 2004. It’s not all sex and violence. American Anthropologist. 106: 710-718.
• Fukuyama, Francis. 1998. Women and the Evolution of World Politics. Foreign Affairs. 77: 24-40.
• Geary, David C., Bjorklund, David F. 2000. Evolutionary developmental psychology. Child Development. 71: 57-65.
• Geary, David C., Byrd-Craven, Jennifer, Hoard, Mary K., Vigil, Jacob, Numtee, Chattavee. 2003. Evolution and development of boys’ social behavior. Developmental Review. 23: 444-470.

  This article examines both one-on-one and coalition competition between males from an evolutionary perspective. It then applies this analysis to the social development of young boys, including “rough and tumble play.”

• Lore, Richard K., Schultz, Lori A. 1993. Control of human aggression: a comparative perspective. American Psychologist. 48: 16-25.
• Manson, Joseph H., Wrangham, Richard W. 1991. Intergroup aggression in chimpanzees and humans. Current Anthropology. 32: 369-390.

  This article examines the similarities in intergroup aggression in humans and chimpanzees, a cross-species comparison. It addresses the questions of under what circumstances is intergroup aggression favored by evolution, why are males the main actors in intergroup aggression, and when is the target of intergroup aggression access to females rather than other material resources.

• Mazur, Allan, and Booth, Alan. 1998. Testosterone and dominance in men. Behavioral and Brain Sciences. 21: 353-397.
• Mesquida, Christian G., Wiener, Neil I. 1995. Human collective aggression: a behavioral ecology perspective. Ethology and Sociobiology. 17: 247-262.

  This article examines collective aggression as perpetuated by young adult males aged between 15 and 30 years. It proposes that such behavior is a fitness-enhancing behavior. It then compares this model to the correlation of a large population of young adult males and inter- and intra-state aggression.

• Mesquida, Christian G., Wiener, Neil I. 1999. Male age composition and severity of conflicts. Politics and the Life Sciences. 18: 181-189.

  This article examines the occurrence of warfare as a form of collective aggression of predominantly young males. It uses the percentage of young males in a population to account for variation in the occurrence and severity of such conflicts.

• Moller, Herbert. 1968. Youth as a Force in the Modern World. Comparative Studies in Society and History. 10: 237-260.
• Sanchez-Martin, JR, Fano, E, Ahedo, L, Cardas, J, Brain, PF, Azpiroz, A. 2000. Relating testosterone levels and free play in social behavior in male and female preschool children. Psychoneuroendocrinology. 25: 773-783.
• Trivers, Robert L. 1971. The evolution of reciprocal altruism. The Quarterly Review of Biology. 46: 35-57.
• Van Schaik, Carel P., Pandit, Sagar A., Vogel, Erin R. 2004. A model for within-group coalitionary aggression among males. Behav Ecol Sociobiol. 57: 101-109.

  This article explores the formation of coalitions among primate males. It examines the conditions under which coalitions may form, and proposes a model for the formation of ranks and rank-changing within these coalitions. It then applies this model to non-human primate examples.

• Williams, Jennifer M., Oehlert, Gary W., Carlis, John V., Pusey, Anne E. 2004. Why do male chimpanzees defend a group range? Animal Behaviour. 68: 523-532.
• Wilson, Edward O. 1978. What is sociobiology? Society. 15: 10-14.
• Wrangham, Richard W. 1999. Evolution of Coalitionary Killing. Yearbook of Physical Anthropology. 42: 1-30.

  This article proposes an explanation for the presence of intergroup coalitional aggression, called the “imbalance-of-power hypothesis.” This hypothesis suggests that intergroup coalitional killing, observed in species such as humans, chimpanzees, and wolves, is an evolutionary adaptation to achieve dominance over one’s neighbors. This paper will likely provide essential information in the form of an evolutionary explanation for the presence of intergroup aggression in humans.

About the author

Rachel Mis will graduate from Rice University in May 2010 with a BA in psychology, after which she hopes to travel the world before attending graduate school in psychology. She loves dogs, coffee, silly conversations, and attempting to unravel the mysteries of the human mind.

She may be contacted via email at Rachel.Mis87@gmail.com

Photo by friend of the author