Popular Science Monthly/Volume 25/September 1884/The Problem of Population



IN passing through the open galleries of that busy ant-hill called a city, with its endless ebb and flow of human beings, intent on their various pursuits of business or pleasure, and succeeding each other in a seemingly endless procession of busy life, there is apt to rise forcibly before our minds the vital questions of human fecundity, and of the ability of the earth to sustain its increasing multitude of human inhabitants. But in reading the statistics of this subject our interest in it redoubles. When we find men in all nations and in all ages pressing sharply on the means of subsistence, the loss by famine quickly replaced by new food for famine, the ravages of war and pestilence rapidly obliterated by new-growing populations, and apparently nothing but the pressure of sheer want and misery able to limit human fecundity, we may well question if this is to be the continued destiny of mankind, and if there is no possible limit to population within this sharp boundary of distress.

Nearly a century has elapsed since Malthus published his disheartening researches on this subject, and his conclusions yet remain only in part refuted. If it really be, as he declares, that population tends to increase in a geometrical ratio, while the food-supply increases only in an arithmetical ratio, his conclusion, that population has a constant tendency to run ahead of subsistence, seems inevitable. Fortunately, however, his hypothesis, so far, has been proved only by arguments, not by irrefutable facts. The numbers of mankind, it is true, have frequently passed the boundary which divides want from plenty. But the other requirement of the Malthusian doctrine was not, in those cases, attained. Food-production has never yet reached its limit, and the suffering so far caused by want of food might have been entirely obviated had the earth been fully cultivated. It may, however, be claimed by disciples of Malthus that this fact has nothing to do with the question, and that, when the utmost food-production has been attained, population will still press beyond it to the starvation limit. This argument we venture to dispute. The attainment of a great food-production introduces certain conditions into the problem which may give it an entirely different aspect. Such excessive production will require, for instance, a marked advance in human intelligence, and the replacement of much of the muscular labor of mankind by an active mental labor. It is our purpose to consider what effect this changed condition of the human race will have upon the increase of population. It is easy to point to modern instances in which the rapid increase of population has been checked without special exercise of the starvation influence. The population of France, for instance, has been almost stationary for many years, its increase being much below the corresponding increase of wealth in that country. Thus France furnishes a practical argument against the Malthusian hypothesis, and shows that the growth of population may decline from other causes than vice, misery, and disease.

There exist, in fact, three separate checks to the increase of population. These may be here classed as the physical, the mental, and the physiological. The first and second of these have been fully considered by writers on political economy. The third has been barely glanced at. And yet this third may contain the true solution of the difficult problem, and through its active operation the geometrical increase of Malthus may, perhaps, be succeeded by a stationary condition of human population.

By the physical check we mean the effect of all the forces which act from outside upon the individual—such agencies as war, famine, pestilence, exposure, climatic changes, and all similar destructive influences. The mental check refers to influences proceeding from the mind of the individual. It is what is usually called the prudential check, through which individuals wisely decline to bring into the world children who must be exposed to inevitable misery, or governments restrain injudicious marriages by enactments looking to the same end. The physiological check is also internal in its origin, but not voluntary. It consists of that limit to human fecundity which is caused by employment of the organic forces in other directions.

Of these three checks to population the second only is fully under the control of the individual himself. The physical check largely arises from the action of other individuals, such as the war-making powers. It also largely flows from the hostile energies of Nature, and may, in this direction, be partly set aside by individual effort, through attention to the laws of health, and prudent avoidance of injurious conditions. The physiological check is beyond the reach of the will. It is a natural effect of human development, needs no forced restraint from marriage for its operation, and is consistent with the most natural and desirable of human relations.

Of the three checks to population here named, we will, in this paper, consider only the physiological. The others have been written upon so abundantly that there is little new to be said concerning them. It will suffice here to remark that the physical check—that which acts through the agency of famine, violence, disease, and similar influences—has ruled almost supreme in the past ages of the world, and is still vigorously active upon the great mass of mankind. The prudential check, which acts through forced desistance from marriage and childbearing, is now actively effective in several of the more advanced European nations, probably most fully in France, and has gone far toward negativing the action of the Malthusian law. The physiological check, which we have here to consider, has also been somewhat effective in the past, but its highest influences are only now coming into play, and it promises to become an efficient and desirable agent in hindering the undue increase of human population in the future.

The principle to which we here allude has been very greatly neglected by writers on the subject of population. Those who have dealt with it have done so only cursorily, and have failed to consider it in all its bearings. It is therefore a problem that is open to further investigation. And in entering upon this inquiry it is necessary to begin with some thoughts upon organic physiology in its general relations, as preliminary to the special results desired.

The animal frame is a material organism which is kept in activity by certain energies. These energies are constantly exhausted and constantly renewed, but their vigor at any fixed period is limited, and can not be indefinitely increased. The force received from without is variously employed within the organism. It acts successively as muscular, nervous, temperature, and reproductive energy. But being limited in quantity, if it be employed by any of these organic agencies, its use by the others is restricted or prevented. Much of the energy received is used up in alimentary processes—the pursuit, seizure, mastication, and digestion of food. Only the excess over this is available for the other organic necessities. And, if this excess force be exhaustively employed by any one of the bodily agencies, it becomes unavailable for the others.

The fact here briefly stated is one which might be illustrated by numerous instances drawn from the lower animal world. A very interesting example of its influence may be perceived in the organic conditions of the ants, and, to a lesser extent, in other insect tribes. Ants, though possessed of all the organic force agencies, do not employ them all in any one individual. The males and the fully developed females exhaust all their life-force in reproduction, with little display of muscular and none of mental vigor. The remaining members of the tribe, divided into workers and soldiers, devote all their life-force to muscular and mental labor. They are, functionally, females, but their organic energies are entirely withdrawn from the reproductive agencies, and devoted to other life-purposes. Of these two classes the workers appear to have the highest mental development. The soldiers understand the whole business of fighting, but beyond that they seem incapable, and take no part in the nest-building, the food-gathering, or any other of the ant-industries. Indeed, they are too dull or too proud to even feed themselves. They would starve unless fed by the workers or slaves. And in the occasional ant-migrations the soldiers are carried bodily by the workers, neither resisting nor aiding in the labor necessary to move their high dignities. In the workers the exercise of muscular force seems to be accompanied by a considerable employment of mental energy, since they perform many actions which appear to indicate an advanced intelligence.

This illustration from the ants might be extended to the bees, and to some other insects. We might also describe the very curious and diversified separation of function in the members of the Siphonophoræ, or compound polyps. But there is no occasion to multiply illustrations. If we ascend to the higher animals we find no such division of function. And yet circumstances largely govern the extent to which the organic force is applied in any one direction. But we must make here a distinction which facts yet to be described render very evident. The exertion of muscular force, unless exhaustively employed, seems not injurious to the reproductive functions. Mental exertion, on the contrary, seems to restrict reproductive energy, even when not employed exhaustively.

But the animals below man do not employ mentality to any great extent. Their principal exertion is muscular, and this hinders reproduction only in case of the whole vigor of the animal being exhausted. If, for instance, the food-supplies of any animal tribe be diminished or its numbers increased, a greater exercise of agility is required to satisfy its appetite. And if it depend on cunning or shrewdness to obtain food, its mental faculties must become very actively exercised. If these efforts become exhaustive, reproduction is necessarily restricted; while the young born under such circumstances are apt to be constitutionally weak, and unable to bear the strain of an excessive effort in food-getting. There is thus in this effect a strong check on population from strictly physiological causes.

The conclusion here reached applies equally to the lower orders of mankind. A diminution of food-supply must have an effect upon savages similar to its influence upon the lower animals. Excessive muscular exertion, extensive migratory movements, warlike efforts, and exercise of mental vigor in food-getting, which become more physically exhaustive the greater the difficulty in obtaining food, must act to greatly restrict reproductive energy, and to enfeeble the children who may be born during such an exhausted condition of their parents. The lack of sufficient nutriment is a correlative agency under the same conditions.

The physiological check, therefore, in this phase of its action, tends to prevent the Malthusian law from being other than an abstract possibility. Decrease in food-supply causes a decrease in food-consumers, through the exhaustion of organic energy in other directions than that of reproduction. And the new generation of consumers is constitutionally enfeebled, and unsuited to bear the sharp struggle of life, so that the population becomes diminished during the continuance of such conditions.

But the physiological check, in this form of its application, brings mankind too near the starvation limit to be at all desirable. There is, however, another mode in which it exercises itself, yielding far more promising results. For there is reason to believe that active mental labor is far more exhaustive of reproductive energy than is equally vigorous muscular exertion. Just what is the organic cause of this we shall not attempt to guess. It is possible that the brain, in its action, may exhaust some material necessary to germ-formation—perhaps phosphorus, which seems to be an element both of the sperm-cells and of the brain. But it is the visible results, rather than the organic causes, with which we are just now concerned.

It is an undoubted fact that the families of the poor are, as a rule, larger than those of the rich. And it is equally certain that brain-workers have, ordinarily, smaller families than muscle-workers. The industrial classes of our day do not perform exhaustive labor. Nor are they usually in the habit of strong mental exercise. The physical labor they perform seems to have no limiting effect upon their procreative powers. The families of day-laborers are usually above the average in number. And it has been observed that the pioneer inhabitants of a new country are very prolific. While physical assault upon Nature is the rule, with food abundant and easily obtained, the physiological check upon increase does not seem to strongly operate. When this first severe duty is over, and men settle down to a mental assault upon Nature, their fecundity considerably decreases. The extensive families of the pioneer settlers of this country are being replaced by the small families of the active brain-workers among their posterity.

As to whether animals that depend mainly on shrewdness are less prolific than those that trust chiefly to strength and agility, we have not sufficient facts at hand to decide. Among the lower human races there is a marked chastity and infertility in the hunter and pastoral as compared with the agricultural tribes. But the former pass lives of much greater mental excitement than the latter. The steady, regular labor of the agriculturist is replaced in the nomad by rapid variations from excessive exertion to extreme inactivity, while a constant exercise of cunning and shrewdness is necessary in the rapidly fluctuating perils and difficulties of the nomadic life.

As to the relations existing between the various classes in civilized nations, it may be mentioned that the population of country districts appears, as a rule, to be more prolific than that of cities. Until within a recent period there was hardly one of the large cities of Europe that kept up its population by the natural increase of its inhabitants. Their increasing numbers were due to continual supplies from the rural districts. The much greater mental activity of civic populations as compared with those of the country is, at least, significant in this connection. If, again, we consider the higher classes in civilized nations, it at once appears that there is a constant tendency to decrease of population in these classes, and a necessity of frequent replacement from the lower grades of society. Thus there has been, in every century, a rapid thinning out of the families in the British peerage. An incessant creation of new peers has taken place, and yet they have hardly kept up their numbers, while very few of the original noble families have an existing representative. The same thing appears in the history of ancient Rome. The early noble families were almost extinct in the time of Claudian. Those created in the reigns of Cæsar and Augustus were nearly exhausted at the period of Tacitus. Malthus says that, in the town of Berne, of 487 wealthy families, 379 became extinct in two centuries. In 1623 the sovereign council was composed of members of 112 different families, of which only 58 were in existence in a century and a half afterward.

If we consider special cases of noted men, the great generals of the world, the commanding statesmen, the distinguished scientists, the celebrated authors—all, in fact, who have become distinguished for superior mental ability—an almost universal result appears: they have either left no descendants, or their families were very small. And, for that matter, we need but to look at evidences everywhere surrounding us. We think it will be found to be a general rule that persons constantly exercised in mental labor have few or no children; those of less active minds have larger families; while the largest families belong to those who do not trouble themselves to think at all.

There is abundant reason to believe, then, that such a physiological check to population really exists; and, in its operation, it is not difficult to perceive a rich promise for the future of the human race. For it is in no sense, in its superior phase, a starvation check. Nor does it need any of the violent repression of natural desires exercised in the prudential check. At first sight, it appears as if its tendency must be to constantly place the cultured at a disadvantage in numbers as compared with the dull and ignorant. But this disadvantage is more than counterbalanced by the progress of education and the brain-incitements of modern civilization. Thus, the class of brain-workers is being continually recruited, despite its lack of fecundity, and we can see indications of an immense future augmentation of this class of the population at the expense of the unthinking, and consequently of a new barrier to the progress of population, whose efficacy is now but beginning to appear.

It is a process which must in time do away with the "starvation check" to population, and replace it with a new and far more desirable limiting principle. For when nerve-energy largely replaces muscular energy, and advanced education greatly increases the percentage of the cultured, there may be a corresponding decrease in the birth-rate, through the operation of the causes just considered. And, as human want decreases and comfort advances, the developed needs of mankind must extend the prudential check on early marriage, which is so active now in the middle classes. In this another limiting force will be brought to bear upon the increase of population.

Thus, as the sum of human wealth increases, through the exercise of intelligence in industrial operations, it will necessarily be divided among a population not increasing in an equal ratio. The average wealth of all classes of the community must increase in consequence, the necessary amount of active muscular labor be reduced, and more time be given for rest, enjoyment, or indulgence in mental culture.

The more rapidly that wealth accumulates in proportion to population, and, the more vigorously that culture forces its way downward through the community, the greater must be the effect of the prudential and physiological checks to increase of population; the final result, perhaps, being one in which the birth-rate and death-rate shall become closely allied, and a virtually stationary condition of population ensue. We have here indications of a rich promise for the future of the human race. If the numbers of mankind become thus checked, while wealth continues to grow, and culture, with its advanced needs, becomes a general possession, the standard of desire must rise, until absolute want may no longer mean, as now, physical misery and starvation, but may mean the deprivation of what would now be considered luxuries beyond the reach of the poor. In such a case the population of the earth could never sink, as now, to press upon the sharp edge of absolute destitution. It would be too far above this limit to sway so far downward, and misery from want of food might become an obsolete tradition of the past.