At military recruitment centres in France, data were collected from some 40,000 subjects on their social environment, the amount of education received and occupation, and measurements were taken on height, weight, and performance in tests of mental and physical ability.
The secular increase in mean stature is continuing. Offspring of consanguineous unions are of lower mean stature and mental capacity, and it seems that the effect is most marked among those already below average. There is an independent effect of endogamy, but the effect of heterosis seems to be less than previously thought. Family size and composition affect stature, weight and mental capacity, and this effect is independent of socio-professional status.