Sex ratio and maternal age in a natural fertility, subsistence population: Daughters, sons, daughters

ALTMAN, RACHEL M.; VILLASEÑOR, FERNANDO A.; RAPAPORT, TOMAS; NEPOMNASCHY, PABLO A.

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY

WILEY-LISS, DIV JOHN WILEY & SONS INC

Año: 2019 vol. 169 p. 368 - 376

0002-9483

Objective: To evaluate putative links between birth sex ratios (BSR = male:female births) and maternal age in a traditional, agricultural, natural fertility population. Metabolic energy, social support, and the costs and benefits associated with producing sons versus daughters can affect BSR. These variables fluctuate with maternal age. Most studies evaluating links between maternal age and BSR have been based on industrialized populations, which differ importantly from traditional indigenous communities in terms of the aforementioned socio-ecological variables. Materials and methods: We analyze data from 108 mothers and their 603 children living in an agricultural, pronatalist, Kakchiquel Mayan community. Results: A logistic regression model, including linear and quadratic maternal age terms and women-specific random effects, shows a nonmonotonic (p =.028) relationship between log BSR and maternal age. For maternal age ≤ 22, the upper bound of the 95% confidence interval (CI) for BSR is