The associations patterns between reproductive success, measured by the total number of offspring, number of living offspring and number of dead offspring, and parental body size, estimated by stature, body weight and Body mass index, were tested in 65 female and 103 male members of a !Kung San population ageing between 25 and 40 years (x = 30.2 yr.) from northern Namibia. In both sexes a significant interaction between fertility patterns and body dimensions was found. Nevertheless, the association patterns differed markedly between the two sexes. While in males tallness and an improved weight status was associated significantly with a higher number of surviving offspring, smaller and lighter females had significantly more surviving children. In males a directional selection towards increased stature and better weight status is in accordance with the well known secular trend of acceleration. In females first of all the postpartum changes in body composition and body weight, resulting from exhausting infant feeding practices seem to support the maternal depletion hypothesis.