Cultural endocrinology: Menarche, modernity, and the transformative power of social reconfigurations.

摘要

This dissertation proposes a new evolutionary hypothesis, mother-daughter-reproductive-competition, to explain epidemiological variations in menarcheal timing. Although menarcheal variations have been recorded since the time of Aristotle their causes remain unknown and, among the many putative causes of menarcheal variance, few are universal. The "mother-daughter-reproductive-competition hypothesis" assumes that mothers, under certain conditions, can increase their reproductive fitness by delaying the reproductive maturation of their daughters. The hypothesized mechanism for this phenomenon is pheromonal inhibition by the mother of the daughter's GnRH production and is based on a survey of several observations: First, historically, menarche has varied with certain similar patterns of social interactions determined by cultural systems. Second, animal studies have demonstrated the adaptive advantage of mothers regulating their daughters' sexual maturation in response to environmental conditions. And third, recent studies have shown that the human ovary is responsive to the reproductive status of other women. Additive evidence suggesting maternal inhibition of the GnRH production in daughters (mediated through pheromones) is proposed as the mechanism by which this phenomenon is realized.;The current study consists of 59 girls and young women from the remote Eastern Highlands of Papua New Guinea where menarcheal ages have been known to be the latest ever recorded. Interviews were conducted with the girls and age, age of menarche, diet and years of schooling were recorded. Estimated ages of pre-menarcheal girls were calculated using log survival curves so that all 59 cases were analyzed. Additionally a non-traditional behavior index (NTBI), comprised of ten culturally and life-stage specific variables, independent of schooling, was constructed. The results showed that, while controlling for many of the putative causes of menarcheal variance, girls who had any school at all had menarche nearly three years earlier than girls who had no schooling, but that the number of years of schooling did not have a significant effect. Additionally, the NTBI showed a strong positive correlation with years of schooling and a negative correlation with age of menarche. These findings suggest that modes of mother-daughter interaction affect the rate of the daughter's sexual maturation.