ABSTRACT
Twenty five years have passed since the first observation of infanticide in nonhuman primates in the wild was reported by Sugiyama (1965). Although his report was largely ignored at that time, the interpretation of the adaptive significance of infanticide has been one of the most controversial topics since the sexual selection hypothesis was presented by Hrdy (1974). Infanticide in nonhuman primates, as well as in other animals and man, has been well known for a long time. Until Hrdy's paper, however, it was usually regarded as abnormal and not worth analyzing. It was partly because the phenomenon was rarely seen and, probably, partly because of our human nature which makes us turn our eyes away from such a cruel incident.
