This paper tests the proposal that chimpanzees (Pan troglodytes) and humans have similar rates of death from intraspecific aggression, whereas chimpanzees have higher rates of non-lethal physical attack (Boehm 1999, Hierarchy in the forest: the evolution of egalitarian behavior. Harvard University Press). First, we assembled data on lethal aggression from long-term studies of nine communities of chimpanzees living in five populations. We calculated rates of death from intraspecific aggression both within and between communities. Variation among communities in mortality rates from aggression was high, and rates of death from intercommunity and intracommunity aggression were not correlated. Estimates for average rates of lethal violence for chimpanzees proved to be similar to average rates for subsistence societies of hunter - Gatherers and farmers. Second, we compared rates of non-lethal physical aggression for two populations of chimpanzees and one population of recently settled hunter - Gatherers. Chimpanzees had rates of aggression between two and three orders of magnitude higher than humans. These preliminary data support Boehm's hypothesis.
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Acknowledgements RWW thanks Toshisada Nishida for his invitation to share the celebration of his retirement, for his hospitality in Mahale in 1971, and for his inspiration over four decades. Doug Jones assisted in finding homicide data. We are grateful to Chris Boehm, Polly Weissner and two anonymous reviewers for comments, and to Sylvia Amsler, Tofiki Mikidadi, Carson Murray, Hogan Sherrow and David Watts for access to unpublished data. RWW thanks the National Science Foundation for funds (proposal 0416125).
- Lethal aggression
- Mortality rate
- Physical attack