Where the social conditions of life are so simple that, in addition to bearing and suckling the child, it is reared and nourished through childhood almost entirely through the labour and care of the mother, requiring no expenditure of tribal or family wealth on its training or education, its value as an adult enormously outweighs, both to the state and the male, the trouble and expense of rearing it, which falls almost entirely on the individual woman who bears it.

The man who has twenty children to become warriors and labourers is by so much the richer and the more powerful than he who has but one; while the state whose women are prolific and labour for and rear their children stands so far insured against destruction.

Incessant and persistent child-bearing is thus truly the highest duty and the most socially esteemed occupation of the primitive woman, equalling fully in social importance the labour of the man as hunter and warrior.
Even under those conditions of civilisation which have existed in the centuries which divide primitive savagery from high civilisation, the demand for continuous, unbroken child-bearing on the part of the woman as her loftiest social duty has generally been hardly less imperious.
Throughout the Middle Ages of Europe, and down almost to our own day, the rate of infant mortality was almost as large as in a savage state; medical ignorance destroyed innumerable lives; antiseptic surgery being unknown, serious wounds were still almost always fatal; in the low state of sanitary science, plagues such as those which in the reign of Justinian swept across the civilised world from India to Northern Europe, well nigh depopulating the globe, or the Black Death of 1349, which in England alone swept away more than half the population of the island, were but extreme forms of the destruction of population going on continually as the result of zymotic disease; while wars were not merely far more common but, owing to the famines which almost invariably followed them, were far more destructive to human life than in our own days, and deaths by violence, whether at the hands of the state or as the result of personal enmity, were of daily occurrence in all lands.
Under these conditions abstinence on the part of woman from incessant child-bearing might have led to almost the same serious diminution or even extinction of her people, as in the savage state; while the very existence of her civilisation depended on the production of an immense number of individuals as beasts of burden, without the expenditure of whose crude muscular force in physical labour of agriculture and manufacture those intermediate civilisations would, in the absence of machinery, have been impossible.

Twenty men had to be born, fed at the breast, and reared by women to perform the crude brute labour which is performed today by one small, well-adjusted steam crane; and the demand for large masses of human creatures as mere reservoirs of motor force for accomplishing the simplest processes was imperative.

So strong, indeed, was the consciousness of the importance to society of continuous child-bearing on the part of woman, that as late as the middle of the sixteenth century Martin Luther wrote: "If a woman becomes weary or at last dead from bearing, that matters not; let her only die from bearing, she is there to do it;" and he doubtless gave expression, in a crude and somewhat brutal form, to a conviction common to the bulk of his contemporaries, both male and female.
Today, this condition has almost completely reversed itself.
The advance of science and the amelioration of the physical conditions of life tend rapidly toward a diminution of human mortality.