霊長類における離乳過程の種間比較： ヒトの「離乳時期の早期化」への洞察

抄録

In this paper, I discuss the relationship between social organization and offspring-rearing methods, which are starting to be used as a novel indicator in interspecies societal comparisons. Additionally, I clarify the relationship between the intimacy of the mother–offspring relationship and the development of foraging in the offspring. I suggest that the establishment of a base camp in human evolution is important not only to facilitate effective hunting and gathering but also for immature individuals to reduce the cost of accompanying adults and engage in their own foraging activities.

I also attempt to deconstruct weaning from the offspring’s perspective, which often focuses on the mother’s decision to stop breastfeeding. Specifically, I focus on the development of the offspring’s ability to acquire food independently and the offspring’s behavior away from its mother. I suggest that there is no significant difference between humans and African apes in the timing when the offspring significantly reduces its dependence on breast milk. This paper also depicts “early weaning” as a characteristic of the unique life history of humans, in which the mother conceives a second offspring at the same time as or even before the offspring becomes much less dependent on the mother’s milk.