Developmental energetics, sibling death, and parental instability as predictors of maturational tempo and life history scheduling in males from Cebu, Philippines.

OBJECTIVES: Cross-species comparisons show that high extrinsic mortality favors the evolution of "faster" life histories. There is interest in applying this principle to human life history plasticity, based on the idea that psychosocial stressors that correlate with extrinsic mortality accelerate reproductive pace. Most prior studies have been conducted in settings in which psychosocial stressors co-occur with the maturation-accelerating influence of nutritional abundance. MATERIALS AND METHODS: We evaluate cues of local mortality (sibling death) or low parental investment (paternal instability; maternal absence) and energetic measures during development as predictors of life history scheduling among males (n = 754) in a Philippine population with marginal developmental nutritional. RESULTS: Males who had more favorable nutritional status during childhood, as reflected in linear growth, skinfold thickness, and caloric intake, were more maturationally advanced in adolescence (all P < 0.05). Taller stature and higher caloric intake during childhood also predicted earlier ages at first sex (both P < 0.01), which persisted after controlling for the effect of nutrition on pubertal maturation. While psychosocial stressors did not predict accelerated maturation, males who as children grew up with an unstable paternal presence had sex earlier (P < 0.05) and tended to become fathers sooner than those with a stable fatherly presence. Those who had a sibling die became fathers sooner than those who did not (P < 0.05). DISCUSSION: Our findings point to important energetic constraints on the onset of reproductive maturity, while psychosocial stressors accelerate entry to parenthood, which may be comparatively more socially, rather than biologically, constrained. Am J Phys Anthropol 158:175-184, 2015. © 2015 Wiley Periodicals, Inc.

Age at menarche and parity are independently associated with Anti-Müllerian hormone, a marker of ovarian reserve, in Filipino young adult women.

OBJECTIVES: Despite ample evidence of variation in timing of menopause, little is known about the extent or underlying causes of individual variation in ovarian reserve and age-related follicular decline. Anti-Müllerian hormone (AMH), a hormonal marker of ovarian reserve, may be a useful tool to clarify these questions. We describe AMH in a cohort of Filipino young adult women, and evaluate whether ovarian reserve in early adulthood relates to measures of life history scheduling (menarcheal age) and reproductive effort (parity). METHODS: Data and samples are obtained from 294 nonpregnant participants (21.5 years ± 0.3) in the Cebu Longitudinal Health and Nutrition Survey. Plasma AMH was assayed using an enzyme immunoassay and relationships between AMH, menarcheal age, and parity were examined. RESULTS: Mean AMH was 4.3 ng/mL. In multiple regression models, women who experienced menarche earlier had significantly higher AMH as young adults (P < 0.05). Women with two (P < 0.05) and three or more (P < 0.01) children had significantly lower AMH than those with no children. These associations were independent of age, smoking, and body mass index. CONCLUSIONS: These findings suggest that individual variation in life history scheduling and reproductive history could contribute to variation in ovarian reserve. Moreover, they demonstrate the utility of AMH as a tool for human reproductive ecology, and highlight the need for further research clarifying the extent of human population variation in ovarian reserve and the behavioral and ecological influences underlying this variation.