Genetic and environmental influences on somatotype components: family study in a Spanish population

Parent-offspring, sibling, and spouse resemblances for Heath-Carter somatotype components were assessed in 261 nuclear families from the Madrid, Spain, area. Each phenotype was adjusted for the effect of (1) age and sex and (2) family environment variables and age and sex by means of multiple regression. Age and sex explained a significant (p < 0.001) proportion of observed variation, but in no case did the addition of family environment variables appreciably alter the amount of variance accounted for by age and sex. Familial correlations were estimated by maximum-likelihood procedures for each somatotype component after adjusting for age, sex, and the other two somatotype components. Furthermore, several hypotheses regarding sex-specific and generational differences among correlations were assessed for each phenotype. No spouse resemblance was found for somatotype components. Significant parent-offspring and sibling correlations point out consistent familial aggregation for somatotype components, especially for mesomorphy. Familial correlations for mesomorphy were significantly (p < 0.05) influenced by the sex of parents (offspring were more similar to their mothers than to their fathers) and to a lesser extent (0.05 < p < 0.10) by the sex of the offspring. The sex of siblings did not significantly alter sib correlations for any of the somatotype components studied.