The paper reviews the evolution of female social relationships in nonhuman primates, focusing on the variation in agonism and cooperation between females and their interactions with males. The authors propose an "ecological model" that explains these variations from an evolutionary perspective, emphasizing ecological factors such as predation risk and food distribution. According to this model, predation risk forces most diurnal primate females to live in groups, and the intensity of within-group competition for resources determines the nature of female relationships. These relationships are categorized as Dispersal-Egalitarian, Resident-Nepotistic, Resident-Nepotistic-Tolerant, or Resident-Egalitarian. The model has been successfully applied to explain various phenomena, but some cases require additional factors like infanticide risk and habitat saturation. The authors also discuss alternative models and test their hypotheses through comparative and experimental studies, highlighting the importance of ecological conditions, demographic processes, and social factors in shaping female social strategies.The paper reviews the evolution of female social relationships in nonhuman primates, focusing on the variation in agonism and cooperation between females and their interactions with males. The authors propose an "ecological model" that explains these variations from an evolutionary perspective, emphasizing ecological factors such as predation risk and food distribution. According to this model, predation risk forces most diurnal primate females to live in groups, and the intensity of within-group competition for resources determines the nature of female relationships. These relationships are categorized as Dispersal-Egalitarian, Resident-Nepotistic, Resident-Nepotistic-Tolerant, or Resident-Egalitarian. The model has been successfully applied to explain various phenomena, but some cases require additional factors like infanticide risk and habitat saturation. The authors also discuss alternative models and test their hypotheses through comparative and experimental studies, highlighting the importance of ecological conditions, demographic processes, and social factors in shaping female social strategies.