Human Nature

, Volume 25, Issue 3, pp 359–377 | Cite as

The Two Sides of Warfare

An Extended Model of Altruistic Behavior in Ancestral Human Intergroup Conflict
  • Hannes Rusch


Building on and partially refining previous theoretical work, this paper presents an extended simulation model of ancestral warfare. This model (1) disentangles attack and defense, (2) tries to differentiate more strictly between selfish and altruistic efforts during war, (3) incorporates risk aversion and deterrence, and (4) pays special attention to the role of brutality. Modeling refinements and simulation results yield a differentiated picture of possible evolutionary dynamics. The main observations are: (a) Altruism in this model is more likely to evolve for defenses than for attacks. (b) Risk aversion, deterrence, and the interplay of migration levels and brutality can change evolutionary dynamics substantially. (c) Unexpectedly, one occasional simulation outcome is a dynamically stable state of “tolerated intergroup theft,” raising the question as to whether corresponding patterns also exist in real intergroup conflicts. Finally, possible implications for theories of the coevolution of bellicosity and altruism in humans are discussed.


Intergroup conflict Cooperation Public goods Altruism Warfare 



I thank Max Albert, Charlotte Störmer, Eckart Voland, and Human Nature’s anonymous reviewers for very valuable criticism. Prudent copy-editing by Mary June-el Piper is gratefully acknowledged. This publication represents a component of my doctoral thesis (Dr. rer. nat.) in the Faculty of Biology at the Justus-Liebig-University Giessen, Germany.

Supplementary material

12110_2014_9199_MOESM1_ESM.pdf (3.3 mb)
ESM 1 (PDF 3.32 mb)


  1. Bach, L. A., Helvik, T., & Christiansen, F. B. (2006). The evolution of n-player cooperation—threshold games and ESS bifurcations. Journal of Theoretical Biology, 238, 426–434.CrossRefGoogle Scholar
  2. Balliet, D., Li, N. P., Macfarlan, S. J., & van Vugt, M. (2011). Sex differences in cooperation: a meta-analytic review of social dilemmas. Psychological Bulletin, 137, 881–909.CrossRefGoogle Scholar
  3. Beckerman, S., Erickson, P. I., Yost, J., Regalado, J., Jaramillo, L., Sparks, C., et al. (2009). Life histories, blood revenge, and reproductive success among the Waorani of Ecuador. Proceedings of the National Academy of Sciences, 106, 8134–8139.CrossRefGoogle Scholar
  4. Boehm, C. (2012). Ancestral hierarchy and conflict. Science, 336, 844–847.CrossRefGoogle Scholar
  5. Bowles, S. (2009). Did warfare among ancestral hunter-gatherers affect the evolution of human social behaviors? Science, 324, 1293–1298.CrossRefGoogle Scholar
  6. Brosnan, S. F., Salwiczek, L., & Bshary, R. (2010). The interplay of cognition and cooperation. Philosophical Transactions of the Royal Society, B: Biological Sciences, 365, 2699–2710.CrossRefGoogle Scholar
  7. Chagnon, N. A. (1988). Life histories, blood revenge, and warfare in a tribal population. Science, 239, 985–992.CrossRefGoogle Scholar
  8. Choi, J.-K., & Bowles, S. (2007). The coevolution of parochial altruism and war. Science, 318, 636–640.CrossRefGoogle Scholar
  9. Durham, W. H. (1976). Resource competition and human aggression: Part I: a review of primitive war. Quarterly Review of Biology, 51, 385–415.CrossRefGoogle Scholar
  10. Fry, D. P., & Söderberg, P. (2013). Lethal aggression in mobile forager bands and implications for the origins of war. Science, 341, 270–273.CrossRefGoogle Scholar
  11. Gat, A. (2009). So why do people fight? Evolutionary theory and the causes of war. European Journal of International Relations, 15, 571–599.CrossRefGoogle Scholar
  12. Gebre-Michael, Y., Hadgu, K., & Ambaye, Z. (2005). Addressing pastoralist conflict in Ethiopia: The case of the Kuraz and Hamer sub-districts of South Omo zone. Saferworld. Accessed 9 July 2013.
  13. Ginges, J., & Atran, S. (2011). War as a moral imperative (not just practical politics by other means). Proceedings of the Royal Society B – Biological Sciences, 278, 2930–2938.CrossRefGoogle Scholar
  14. Glowacki, L., & Wrangham, R. W. (2013). The role of rewards in motivating participation in simple warfare. Human Nature, 24, 444–460.CrossRefGoogle Scholar
  15. Gneezy, A., & Fessler, D. M. T. (2011). Conflict, sticks and carrots: war increases prosocial punishments and rewards. Proceedings of the Royal Society B: Biological Sciences, 279, 219–223.CrossRefGoogle Scholar
  16. Goodall, J. (1986). The chimpanzees of Gombe: Patterns of behavior. Cambridge: Belknap Press of Harvard University Press.Google Scholar
  17. Halevy, N., Weisel, O., & Bornstein, G. (2012). “In-Group Love” and “Out-Group Hate” in repeated interaction between groups. Journal of Behavioral Decision Making, 25, 188–195.CrossRefGoogle Scholar
  18. Henrich, J., & Boyd, R. (2008). Division of labor, economic specialization, and the evolution of social stratification. Current Anthropology, 49, 715–724. doi: 10.1086/587889.CrossRefGoogle Scholar
  19. Hill, K. R., Walker, R. S., Bozicevic, M., Eder, J., Headland, T., Hewlett, B. S., et al. (2011). Co-residence patterns in hunter-gatherer societies show unique human social structure. Science, 331, 1286–1289.CrossRefGoogle Scholar
  20. Jaeggi, A. V., Burkart, J. M., & van Schaik, C. P. (2010). On the psychology of cooperation in humans and other primates: combining the natural history and experimental evidence of prosociality. Philosophical Transactions of the Royal Society B, 365, 2723–2735.CrossRefGoogle Scholar
  21. Keeley, L. H. (1996). War before civilization: The myth of the peaceful savage. New York: Oxford University Press.Google Scholar
  22. Kelly, R. C. (2005). The evolution of lethal intergroup violence. Proceedings of the National Academy of Sciences, 102, 15294–15298.CrossRefGoogle Scholar
  23. Kerr, B., & Godfrey-Smith, P. (2002). Individualist and multi-level perspectives on selection in structured populations. Biology and Philosophy, 17, 477–517.CrossRefGoogle Scholar
  24. Kohler, T. A., & Kramer Turner, K. (2006). Raiding for women in the pre‐hispanic Northern Pueblo Southwest? A pilot examination. Current Anthropology, 47, 1035–1045.CrossRefGoogle Scholar
  25. Konrad, K. A., & Morath, F. (2012). Evolutionarily stable in-group favoritism and out-group spite in intergroup conflict. Journal of Theoretical Biology, 306, 61–67.CrossRefGoogle Scholar
  26. Lehmann, L., & Feldman, M. W. (2008). War and the evolution of belligerence and bravery. Proceedings of the Royal Society B: Biological Sciences, 275, 2877–2885.CrossRefGoogle Scholar
  27. Lehmann, L., Keller, L., West, S. A., & Roze, D. (2007). Group selection and kin selection: two concepts but one process. Proceedings of the National Academy of Sciences, 104, 6736–6739.CrossRefGoogle Scholar
  28. Mason, W. A., & Mendoza, S. P. (1993). Primate social conflict. Albany: State University of New York Press.Google Scholar
  29. Mathew, S., & Boyd, R. (2011). Punishment sustains large-scale cooperation in prestate warfare. Proceedings of the National Academy of Sciences (USA), 108, 11375–11380.CrossRefGoogle Scholar
  30. McDonald, M. M., Navarrete, C. D., & van Vugt, M. (2012). Evolution and the psychology of intergroup conflict: the male warrior hypothesis. Philosophical Transactions of the Royal Society, B: Biological Sciences, 367, 670–679.CrossRefGoogle Scholar
  31. Modell, J., & Haggerty, T. (1991). The social impact of war. Annual Review of Sociology, 17, 205–224.CrossRefGoogle Scholar
  32. Modell, J., & Steffey, D. (1988). Waging war and marriage: military service and family formation, 1940–1950. Journal of Family History, 13, 195–218.CrossRefGoogle Scholar
  33. Pitman, G. R. (2011). The evolution of human warfare. Philosophy of the Social Sciences, 41, 352–379.CrossRefGoogle Scholar
  34. Pratto, F., Sidanius, J., & Levin, S. (2006). Social dominance theory and the dynamics of intergroup relations: taking stock and looking forward. European Review of Social Psychology, 17, 271–320.CrossRefGoogle Scholar
  35. Rusch, H. (2013). Asymmetries in altruistic behavior during violent intergroup conflict. Evolutionary Psychology, 11, 973–993.CrossRefGoogle Scholar
  36. Rusch, H. (2014). A threshold for biological altruism in public goods games played in groups including kin. MAGKS Joint Discussion Paper Series in Economics, No. 29-2014.Google Scholar
  37. Saaksvuori, L., Mappes, T., & Puurtinen, M. (2011). Costly punishment prevails in intergroup conflict. Proceedings of the Royal Society B: Biological Sciences, 278, 3428–3436.CrossRefGoogle Scholar
  38. Smirnov, O., Arrow, H., Kennett, D., & Orbell, J. (2007). Ancestral war and the evolutionary origins of “Heroism.” Journal of Politics, 69, 927–940.Google Scholar
  39. Tomasello, M., Melis, A. P., Tennie, C., Wyman, E., & Herrmann, E. (2012). Two key steps in the evolution of human cooperation. Current Anthropology, 53, 673–692.CrossRefGoogle Scholar
  40. Tooby, J., & Cosmides, L. (2010). Groups in mind: The coalitional roots of war and morality. In H. Høgh-Olesen (Ed.), Human morality and sociality: Evolutionary and comparative perspectives (pp. 191–234). Basingstoke: Palgrave Macmillan.Google Scholar
  41. van Vugt, M., de Cremer, D., & Janssen, D. P. (2007). Gender differences in cooperation and competition: the male-warrior hypothesis. Psychological Science, 18, 19–23.CrossRefGoogle Scholar
  42. Walker, R. S., & Bailey, D. H. (2013). Body counts in lowland South American violence. Evolution and Human Behavior, 34, 29–34.CrossRefGoogle Scholar
  43. Watts, D., & Mitani, J. (2001). Boundary patrols and intergroup encounters in wild chimpanzees. Behaviour, 138, 299–327.CrossRefGoogle Scholar
  44. West, S. A., Griffin, A. S., & Gardner, A. (2007). Social semantics: altruism, cooperation, mutualism, strong reciprocity and group selection. Journal of Evolutionary Biology, 20, 415–432.CrossRefGoogle Scholar
  45. West, S. A., El Mouden, C., & Gardner, A. (2011). Sixteen common misconceptions about the evolution of cooperation in humans. Evolution and Human Behavior, 32, 231–262.CrossRefGoogle Scholar
  46. Wrangham, R. W. (1999). Evolution of coalitionary killing. American Journal of Physical Anthropology, 110, 1–30.CrossRefGoogle Scholar
  47. Wrangham, R. W., & Glowacki, L. (2012). Intergroup aggression in chimpanzees and war in nomadic hunter-gatherers. Human Nature, 23, 5–29.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  1. 1.Behavioral and Institutional Economics, JLU GiessenGiessenGermany

Personalised recommendations