s cited by Bartlett, Sussman, and Cheverud 1993) Since the area of living for langurs was growing smaller and smaller, the langurs found themselves in closer proximity to one another. Aggression, including infanticide, became more frequent in troop life. (Yoshiba as cited by Rees 2001) Therefore, the possible high rate of infanticide and aggression towards infants at Sugiyama's site is the "result of crowding and human disturbance and are not characteristic of langurs in undisturbed areas." (Boggess, Curtin, and Dolhinow as cited by Bartlett, Sussman, and Cheverud 1993 p. 959)
             Hrdy disagreed with the social pathology hypothesis. She believes that among langurs and other nonhuman primates, infanticide occurs regularly and under conditions that are normal for the species. (Hrdy as cited by Rees 2001) Hrdy created a "hypothetical scenario of the life cycle of a langur troop." (Hrdy as cited by Rees 2001 p. 511) The troop consisted of a single adult male and a number of females. At some point, a force of bachelor males will drive out the adult male of the troop. One of the bachelors will then drive out his former allies and establish himself as troop leader. In doing so, the new male leader will kill off any infants sired by the old male leader. Hrdy called this the sexual selection hypothesis. (Hrdy as cited by Rees 2001)
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