Ontogeny of sexual size dimorphism and environmental quality in Guatemalan children.

Objectives: Human growth data from Guatemalan school children were analyzed to test the hypothesis that the degree of sexual size dimorphism (SSD) in height is reduced for people living under more adverse environmental quality. Methods: The sample consists of 2,560 girls and 3,262 boys, 6-16.99 years of age, from the two major Guatemalan ethnic groups, Maya of very low socioeconomic status (SES) and Ladino of high, middle, and low SES. SES was esti- mated by questionnaire and ethnographic observation. All data are from the Longitudinal Study of Child Development of the Universidad del Valle de Guatemala. Significance of SSD was tested within each whole year age category (e.g., 6.0-6.9 years) by SES for Ladinos and Maya. Ethnic groups were then compared for each age category to determine whether the SSD values were significantly different between groups. Results: Statistically significant height SSD was found for 10 of the 11 age categories for the high SES Ladinos, 8 of the 11 age categories for middle SES Ladinos, 3 of the 11 low SES Ladino age categories, and 0 of the 11 very low SES Maya age categories. For all SES and ethnic groups SSD tended to decrease between 6 and 11 years of age and then increase after age 12 years. Conclusions: A poor quality environment for growth and development, as estimated by SES, was found to reduce or eliminate statistically significant SSD. Patterns of biological maturation before and after puberty also seem to contrib- ute to age changes in SSD. Am. J. Hum. Biol. 00:000-000, 2013. V C 2013 Wiley Periodicals, Inc.