ABSTRACT
The significance of differential fertility with respect to occupation, locality, and income has been dealt with in the introduction to the first part and in Chapters III and IV. It was there discussed with special reference to its bearing on the social agencies which favour or obstruct the maintenance of the survival minimum. Differential fertility, more particularly differential fertility with respect to occupation, raises issues of another kind. The personnel of different groups depends on a process of social selection involving many extraneous conditions. Thus choice of occupation is partly determined by the capability of the individual, and partly by social status, income, family tradition, and education. In so far as different individual capabilities depend upon genetic differences, differential fertility therefore involves a process of genetic selection.
