This section is from the book "The Principles Of Economics With Applications To Practical Problems", by Frank A. Fetter. Also available from Amazon: The Principles of Economics, With Applications to Practical Problem.
1. In the earlier stages of human history, population is limited mainly by biologic factors. The biologic stage continues so long as there are no artificial restraints put on the birth-rate, and no deliberate destruction of offspring for the purposes of limiting the size of the family. There the limits are all objective; they are found in scantiness of the food-supply, or in destruction by enemies, animal or human. Each species has an average or normal birth-rate, great or small. Just why this varies, why the rabbit produces a score of young in a year, and the elephant but one in three years, is a question capable of a rational answer, but it is one for the natural scientist rather than for the economist. Each species is impelled by instinct to realize this birth-rate, to bring into existence as many young as possible.
No human society known to us is so primitive that it has not passed this stage, but many societies have risen but little above it. In most savage tribes, where starvation, disease, and war are constantly at work, the difficult task is to maintain the population. Few of those born arrive at maturity. The custom of the adoption of captives from hostile tribes is wide-spread, because the efficiency and even the survival of the tribe depends upon keeping up its number of warriors.
The biologic stage of human population.
War among primitive societies.
2. War for the possession of limited resources is the first rude social remedy for an excess of population. War is the normal condition of most primitive tribes. Its cause usually appears to be standing feuds and ancient enmities, but the deeper and abiding cause is the struggle for hunting-grounds, for pasturage, for natural resources. The rude industry and economy of hunting, fishing, or pastoral peoples, or of those in the earlier stages of agriculture, requires a large area for a small population. Distant excursions and frequent forays, when food fails, develop rival claims to favored districts, and war is the only settlement. Fighting under these conditions is an activity of such economic importance that much of the energy of the tribe must be strenuously given to it. The ceaseless loss of life in savage wars is almost incredible to modern minds. The invasion of the Roman Empire by the Teutonic tribes, the later successive inundations of medieval Europe by the fierce pastoral tribes from central Asia, are more recent and familiar examples of the economic and political effects of the increase of population and of the outgrowing of resources by barbarian peoples. When the custom arises of capturing enemies and reducing them to slavery instead of killing them, forces are set into operation to reorganize society and to create new checks on the growth of population.
Crude beginnings of volitional control.
3. Volitional control of population begins by the destruction of offspring before or after birth. The population problem ceases to be simply biologic, and takes on its sociological aspect, when the awakening intelligence of man first grasps the mystery of birth, and when the first attempts are made in any way to regulate family relations or to interfere with the growth of numbers. The student of primitive peoples finds in the methods applied to prevent the birth of children an almost inconceivable brutality. The same methods to a large degree persist in savage communities today. Infanticide was generally practiced in ancient times among peoples of advanced civilization, as, for example, in Sparta and Rome, where not only deformed and weak children, but unwelcome ones, commonly were destroyed. The practice, if not legalized, is at least permitted even today by public opinion in great portions of India, China, and other densely populated districts of the world. It is one of the dark spots on our own civilization.
4. The pressure of increase of numbers on resources is confined by individual industry and by private property to special portions of the population. A condition of communism, where all the members of the tribe or family share equally, means that all enjoy together when food and wealth are abundant, and all starve together when it becomes scarce. Along with a fierce enmity for other tribes, is found in many early societies a close approximation to tribal communism. Private property alters the nature of the struggle for subsistence and of the motives for limiting population. Society divides into a number of partially independent classes or family groups, each holding its share of wealth apart, not in common with the tribe. A society with private property is like a ship divided into a number of water-tight compartments. In communistic conditions if population increases, all sink together into want. The self-interest of those having private property keeps them from dividing their property, and starvation is confined to the propertyless members. This acts in two ways: it increases the motive for the production of wealth; it gives a motive for the limitation of the consumers of the wealth. A smaller family with larger resources means a wider margin between numbers and misery. This converts the problem of population from a material one of a balance of food and physical needs, to a psychic one of a balance of motives in the minds of men. When this stage is reached, the extreme objective limit of the birth-rate or of increase of population is no longer attained in the well-to-do classes, although it may still continue to be in the less provident.
Private property limits population.
The problem a psychic one.
5. Volitional control is effective in very different degrees in different families and industrial classes. The possession of property is both a sign of forethought and an incentive to it. Concern for the welfare of children is one of the most powerful motives, especially after social distinctions become marked. It may become abnormally strong, leading parents to sacrifice their own welfare or their own lives foolishly for their children, as is done often in the accumulation of property. Among the classes with property the provision for the children depends not only upon the amount of wealth, but upon the number among whom it is to be divided. It is simple division: wealth the dividend, number of children the divisor. Among the poorer classes very different motives operate. After the first few years the parents' income is increased by the earnings of the children, both on the farm and in the factory districts if the laws do not prohibit child labor. Moreover, when the children are grown, their wages will depend on the general labor market, not upon "the number of their brothers and sisters. So, according as the family income is from rents or from wages, the motives of the parents differ.
Social classes differ in volitional control.
Motives in volitional control.
Postponement of marriage must be classed as a mode of volitional control of population. The average age of marriage, both of men and women, is higher in the classes of greater wealth and ambition than in the poorer classes. The contrast in this regard between civilized and savage peoples is likewise noteworthy. The failure to marry, from whatever cause, is, in the social view of the question, volitional control. It is rare that the motive is directly and immediately the wish to avoid parenthood; now it is religious zeal, again it is disappointed sentiment; here it is conflicting duty, and there it is the individual selfish wish to retain an undivided income for one's own enjoyment. By countless strands of motive in the form of sentiments, social institutions, and interests, the primitive impulses of humanity are firmly bound; and in varying degrees, in different classes, the enormous possibilities of reproduction are controlled by human volition.
 
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