Biological factors affecting family size.

Latterly much attention has been attracted, and rightly so, to the number, variety, and potency of the socio-economic factors which strongly incline married couples deliberately to restrain their fertility and thereby to limit the size of-their families. A tendency to overlook a number of purely biological factors which work in the same direction is to be discerned. These latter are for the most part not under the control of the will of the individual and are as yet far beyond the powers of the medical and social sciences in application. It is not suggested that these factors, as judged by their effects, play as important a role in determining family size as do the socio-economic, or that pronatalist policies are mistaken when based on the demonstrably reasonable assumption that if only the people could be persuaded to unleash their fertility the total size of our population could easily be maintained at its present level or even enlarged. Nevertheless, it is surely desirable when population policies are being fashioned that all and not merely the more potent factors known to affect fertility shall be taken into account.