Infant Killing; a Possible Consequence of a Disputed Leader Role

This report gives the results of a series of experimental situations designed to prevent the habitual killing of infants in a group of 27 captive hamadryas baboons (Papio hàmadryas), which were studied sociologically over a year. Unlike the typical hamadryas one-male group, the captive group had a multi-male organisation similar to that described for savanna baboons. Of at least 20 infants born in the group before the experimental period, all but 3 died, due to severe abuse by the leader male - the biological father of the victims. Detailed analysis showed that mothers and infants re-introduced into the group attaracted disproportional attention from other group members, temporarily upsetting the structure: The leader male's status is seriously undermined in this stituation. By appropriating the infant - and subsequent (ab-)use - the leader male manages to regain his social position and reinforce his high status. The infant is thus instrumental in the regulation of group-dynamics - its death almost an accident. The currently common sociobiological approach to the killing of infants in animal societies is to consider it as an adaptive trait. Such a conclusion is justified only if it can be shown that the behaviour is programmed in such a manner as to contribute systematically to the inclusive fitness of the performer. Such an effect was clearly absent in the present case. The nature of the proximate mechanism revealed by our study suggests that it is more plausible to consider infant killing as a possible - and occasional - outcome of a behaviour the proximate goal of which is to achieve social control and dominance. A review of the literature suggests that this approach may fit all cases of infant killing in primate societies, including infant-abuse in human societies.