I do not mean that the adult Martians are unnecessarily or intentionally cruel to the young, but theirs is a hard and pitiless struggle for existence upon a dying planet, the natural resources of which have dwindled to a point where the support of each additional life means an added tax upon the community into which it is thrown.

By careful selection they rear only the hardiest specimens of each species, and with almost supernatural foresight they regulate the birth rate to merely offset the loss by death.