Familial similarity in body size in an isolated Zapotec-speaking community in the valley of Oaxaca, southern Mexico: Estimated genetic and environmental effects

Abstract

Objective: The study used path analysis to estimate genetic and environmental determinants of familial similarity in anthropometric characteristics among children from a rural subsistence agrarian community in the Valley of Oaxaca in southern Mexico. Methods: Anthropometric dimensions included height, weight, arm circumference and triceps skinfold; the BMI was calculated. Parent–offspring pairs (n = 34) were constructed from pedigrees and prior studies using listwise case deletion for parent–male child and parent–female child, respectively. Path coefficients for genetic and environmental effects were computed using linear regression. Age effects were held constant by computing residuals after parameter regression on age and age2. Environmental effects were analysed using a previously published factor analysis of village ecology. Results: By path analysis, the paternal effect was low-to-moderately strong on males (0.21–0.57) but low on females (0.13–0.23). Maternal effects were low, inconsistent and negligible on males (−0.16–0.09), but high on females (0.57–0.81), except for height (0.19). Estimated environmental effects on sibling similarity were low (0.12–0.27). Conclusion: The environment exerts a relatively consistent effect on growth status, and probably accounts for the low path coefficients (i.e. sibling correlations, parent–offspring regressions). Sex-specific effects are apparent in a strong paternal influence on male offspring height and moderate influences on weight, triceps skinfold, and arm circumference. Maternal influences are small on the anthropometric characteristics of males, but are exceptionally large on female weight, triceps skinfold and arm circumference. Estimated environmental effects on sibling similarity are low-to-moderately high.