Comparative rates of violence in chimpanzees and humans (original) (raw)
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American Journal of Primatology, 2008
Intercommunity aggression in chimpanzees and primitive warfare in humans possess striking similarities, such as the common occurrence of large male coalitions, systematic control of territory boundaries, and lethal attacks on isolated individuals from neighboring groups. However, an important apparent contrast is the absence of recurrent peaceful interactions between neighboring groups of chimpanzees. We observed a remarkable range of behavior in intergroup encounters among three habituated communities of chimpanzees in Taï National Park, Côte d'Ivoire. Lethal attacks are documented in these study groups for the first time, as well as year-long exchanges of parous adult females and peaceful intergroup visits of mothers with infants. Demographic factors, including group size and number of adult males, are shown to affect the nature of intergroup interactions in ways not considered previously. A reconsideration of the difference in intergroup interactions between eastern and western chimpanzees is proposed including a more important consideration of the female's perspective. The inclusion of the new complexities in intergroup interactions in chimpanzees allows new parallels to be drawn with the evolution of primitive warfare in humans. Am.
International Journal of Primatology, 2017
Lethal coalitionary aggression is of significant interest to primatologists and anthropologists given its pervasiveness in human, but not nonhuman, animal societies. Chimpanzees (Pan troglodytes) provide the largest sample of recorded lethal coalitionary aggression in nonhuman primates, and most long-term chimpanzee study sites have recorded coalitionary killing of conspecifics. We report an inferred lethal attack by resident males on a former alpha male chimpanzee (P. t. verus) at Fongoli in Senegal. We describe the male's presence in the Int J Primatol
American Journal of Primatology, 2013
Chimpanzees (Pan troglodytes) are capable of extreme violence. They engage in inter-group, sometimes lethal, aggression that provides the winners with an opportunity to enlarge their territory, increase their food supply and, potentially, attract more mates. Lethal violence between adult males also occurs within groups but this is rare; to date, only four cases (three observed and one inferred) have been recorded despite decades of observation. In consequence, the reasons for within-group lethal violence in chimpanzees remain unclear. Such aggression may be rare due to the importance of coalitions between males during inter-group encounters; cooperation between males is also thought to be key in the defense or advancement of social rank within the group. Previous accounts of within-group lethal violence concern victims who were low-ranking males; here we provide the first account of the killing of an incumbent alpha male by a coalition of adult males from the same community. We found no clear evidence that the alpha male’s position was under threat during the months before the lethal attack: the male dominance hierarchy was highly stable, with low rates of male-male aggression, and there were no significant changes in social interactions (i.e. grooming and aggression) between the alpha male and the other adult males. Two of the four attackers were former alpha males and were the individuals with whom the victim appeared, in the period preceding his death, to be most strongly affiliated: his most frequent grooming partners and those with whom he spent most time in proximity. The lethal attack triggered a period of instability in the male hierarchy and was likely an opportunistic attempt to seize alpha status by the third-ranking male.
Lethal aggression in Pan is better explained by adaptive strategies than human impacts
Nature 513: 414-419, 2014
Observations of chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) provide valuable comparative data for understanding the significance of conspecific killing. Two kinds of hypothesis have been proposed. Lethal violence is sometimes concluded to be the result of adaptive strategies, such that killers ultimately gain fitness benefits by increasing their access to resources such as food or mates 1-5 . Alternatively, it could be a non-adaptive result of human impacts, such as habitat change or food provisioning 6-9 . To discriminate between these hypotheses we compiled information from 18 chimpanzee communities and 4 bonobo communities studied over five decades. Our data include 152 killings (n 5 58 observed, 41 inferred, and 53 suspected killings) by chimpanzees in 15 communities and one suspected killing by bonobos. We found that males were the most frequent attackers (92% of participants) and victims (73%); most killings (66%) involved intercommunity attacks; and attackers greatly outnumbered their victims (median 8:1 ratio). Variation in killing rates was unrelated to measures of human impacts. Our results are compatible with previously proposed adaptive explanations for killing by chimpanzees, whereas the human impact hypothesis is not supported.