Abstract
This paper examines the phenomenon of adolescent subfecundity in humans and some great apes from the perspectives of biological anthropology and evolutionary biology. Owing to their altricial nature, humans require considerable energy and time to reach full maturity, and they exhibit a unique developmental pattern in which the onset of menarche and the optimal timing for reproduction (i.e., pregnancy and childbirth) are misaligned. Consequently, a period emerges during which reproductive capability is only partially realized despite incomplete physical readiness. In this study, we review the developmental physiological mechanisms underlying subfecundity, with particular emphasis on the immaturity of the hypothalamic-pituitary-ovarian (HPO) axis, incomplete hormonal feedback regulation, and metabolic disturbances related to nutritional status and energy balance. We further discuss the prevalence of this phenomenon by drawing on evidence from hunter-gatherer societies and research on great apes. Additionally, by preliminarily analyzing the influence of life history variables-such as average adult female body mass, age at menarche, age at first reproduction, and survival probability until age 15-on the duration of subfecundity, we propose three evolutionary hypotheses: the growth-reproduction trade-off hypothesis, the inclusive fitness enhancement hypothesis, and the beginner mate-search hypothesis. A comprehensive understanding of adolescent subfecundity from an evolutionary perspective will require further research involving diverse populations, including hunter-gatherers, as well as mathematical modeling within a biological anthropology framework.