Body dimensions and differential fertility in !Kung San males from Namibia

Abstract

The relationship between paternal somatic morphology and number and sex of the offspring was investigated with 114 !Kung San males from Namibia. Significant correlations were observed between measures of facial and distal robustness and the total number of sons and daughters as well as for the sex ratio of children and the ratio of living to dead children. Anthropometric characteristics of !Kung San men correlated with the number of daughters more frequently than with the number of sons, and the majority of correlation coefficients were negative. This indicates that more slender men tend to have more daughters, while the positive correlations between body dimensions and the number of sons demonstrate that more robustly built and tall men tend to have more sons. Mortality of children also differs relative to the paternal body build. The mortality rate in children of more slender fathers is higher than in those of more robust fathers. Robust men have more male children and these children have a better chance to survive. The differential fertility of the !Kung may be explained by the association between a high social rank and robustness of physique which may lead to typical patterns of sexual selection. The results of the present study are consistent with the Trivers-Willard hypothesis, which describes differential sex-biased parental investment under different socioeconomic conditions. © 1994 Wiley-Liss, Inc.