Natural born killers: Chimpanzee violence is an evolutionary strategy (original) (raw)
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American …, 1993
Discussion of infant killing in free-ranging primates has focused on the sexual selection hypothesis developed by Hrdy during the mid-1970s. This hypothesis suggests that infant killing is a form of sexual competition whereby an infanticidal male gains a reproductive advantage by selectively killing the offspring of his male rivals. Despite criticisms that the evidence in support of the hypothesis is distorted by misinterpretation of data and observer bias, the sexual selection hypothesis, bolstered in part by additional reports of infanticide in a variety of species, has become entrenched as the primary explanatory hypothesisfor primate infanticide. However, the majority of reliably documented instances of infanticide inprimates come from a very small number of species, and a careful examination of the specific context of each of these episodes fails to support the interpretation of infanticide as a primatewide adaptive complex. Most importantly, the atmosphere of generalized inter-and intrasexual aggression that surrounds the majority of infant killings obscures the evolutionary significance of this behavior.
Infant killing as an evolutionary strategy: Reality or myth?
Evolutionary Anthropology, 2005
The students nodded. They had all studied animal behavior, and they knew, for example, that when a new male took over a lion pride, the first thing he did was kill all the cubs. The reason was apparently genetic: the male had evolved to disseminate his genes as widely as possible, and by killing the cubs he brought all the females into heat, so that he could impregnate them.
Intra-community infanticide in wild, eastern chimpanzees: a 24-year review
Primates, 2019
Infanticide is well documented in chimpanzees and various hypotheses have been proposed to explain this behavior. However, since infanticide by chimpanzees is relatively rare, it has thus far not been possible to thoroughly test these hypotheses. Here we present an analysis of the largest dataset of infanticides from a single community of chimpanzees, a full record of all intra- community infanticides and failed attempts at infanticide over a 24-year period for the Sonso community of chimpanzees in the Budongo Forest, Uganda. We use these data to test four hypotheses for this behavior: the sexual selection hypothesis, male mating competition, resource competition, and meat acquisition. Our dataset consisted of 33 attacks on 30 victims, 11 of which were ‘definite’ infanticides, four of which ‘almost certain’, and nine were ‘suspected’, while nine were ‘attempted’ infanticides. The majority of attacks where the perpetrators were known (23) had only male attackers and victims were disproportionately young (two-thirds of victims with known ages were under 1 week old). Our data best support the sexual selection hypothesis for infanticide. Cannibalism was infrequent and partial, suggesting meat acquisition was a by-product of infanticide, and there was no evidence to suggest that infanticide was part of a male strategy to eliminate future competi- tors. Infanticide by females was rare, but we suggest sexual selection, operating through intra-sexual competition, may also be responsible for infanticide by females.
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.
Infanticide: Let's not throw out the baby with the bath water
Evolutionary Anthropology: Issues, News, and Reviews, 2005
RajasthaniIndia): Recent observations and a reconsideration of hypotheses. Primates 28:163-197. 15 Dolhinow P (in press) A mystery: Explaining behavior. In Strum SC, Lindburg DG, Hamburg DA (eds) The New Plzvsical Antlzro-16 Hrdy SB (1979) Infanticide among animals: A review, classification, and examination of the implications for the reproductivc strategies of females. Ethol Sociobiol 1:1340. 17 Hrdy SB (1984) Assumptions and evidence regarding the sexual selection hypothesis: a reply to Boggess. In Hausfater G, Hrdy SB (eds) Infanticide: Comparative and Evolutionaty Perspectives, pp. 315-319. New York: Aldine. 18 Newton PN (1988) The variable social organization of Hanuman langurs (Presbytis entellus). Infanticide and the monopolization of females. Int J Primatol 9:59-77. 19 Arnold S, Wade M (1 984) On the measure-pology. ment of natural selection: Theory. Evolution 38:709-719. 20 Phillips P, Arnold S (1989) Visualizing multivariate selection. Evolution 43: 1209-1 222. 21 Schluter D (1988) Estimating the form of natural selection on a quantitative trait. Evolution 45:849-861. 22
Evolutionary Perspectives on Violence, Homicide, and War
The Oxford Handbook of Evolutionary Perspectives on Violence, Homicide, and War, 2012
We review and discuss the evolutionary psychological literature on violence, homicide, and war in humans and nonhumans, and in doing so we argue that an evolutionary perspective can substantially enhance our understanding of these behaviors. We provide a brief primer on evolutionary psychology, describing basic tenets of the field. The theories of sexual selection and parental investment are explained and subsequently used to highlight the evolutionary logic underlying the use of violence by humans and other animals. Our ...
Killing Babies: Hrdy on the Evolution of Infanticide
Biology and Philosophy, 2005
Sarah Hrdy argues that women 1) possess a reproductive behavioral strategy including infanticide, 2) that this strategy is an adaptation and 3) arose as a response to stresses mothers faced with the agrarian revolution. I argue that while psychopathological and cultural evolutionary accounts for Hrdy's data fail, her suggested psychological architecture for the strategy suggests that the behavior she describes is really only the consequence of the operation of practical reasoning mechanism(s) -and consequently there is no reproductive strategy including infanticide as such, nor could the alleged strategy be sufficiently mosaic to count as an adaptation. What might count as an adaptation is a 'window' before bonding that permits practical reasoning about the reproductive value of infants and hence variable maternal investment, and which, contra 3) arose early in hominid history due to a combination of increases in infant dependency and increased human abilities for conditional practical reasoning.
American Journal of Primatology, 2002
We document here an unusual case of intense aggression against an infant male from another group by chimpanzees (Pan troglodytes schweinfurthii) of the Mahale Mountains National Park, in Tanzania. Adult males of the study group collectively attacked an unknown male infant. Although an unknown female, probably the mother, tried to retrieve him, the infant was seriously injured and most likely died. During this incident, the unknown female attacked and injured two researchers. After the aggressive encounter, it was found that six of the nine adult males in the study group were wounded. Attacking the extragroup male infant may have the effect of weakening the future power of the neighboring group, leading to better access to resources and enhanced safety in the future for the study group. Am.