Fertility and care for offspring seem as a rule to vary inversely. The latter is the path of biological progress, and is characteristic of all viviparous animals. That any degree of parental attention is incompatible with the immense fecundity of the lower organisms needs no demonstration. Such fertility is not necessary to keep up the numbers of the higher species, which find abundant food in the swarming progeny of the lower types, and are not themselves exposed to wholesale slaughter. Speaking of fishes, Sutherland says:
Of species that exhibit no sort of parental care, the average of forty-nine gives 1,040,000 eggs to a female each year; while among those which make nests or any apology for nests the number is only about 10,000. Among those which have any protective tricks, such as carrying the eggs in pouches or attached to the body, or in the mouth, the average number is under 1000; while among those whose care takes the form of uterine or quasi-uterine gestation which brings the young into the world alive, an average of 56 eggs is quite sufficient.
Man is no exception to these laws. His evolution has been steadily in the direction of diminishing fertility and increasing parental care. This does not necessarily imply that the modern European loves his children better than the savage loves his. It is grim necessity, not want of affection, which determines the treatment of children by their parents over a great part of the world, and through the greater part of human history. The homeless hunters, who represent the lowest stage of savagery, are now almost extinct. In these tribes the woman has to follow the man carrying her baby. Under such conditions the chances of rearing a large family are small indeed. Very different is the life of the grassland nomads, who roam over the Arabian plateau and the steppes of Central Asia. These tribes, who really live as the parasites of their flocks and herds, depending on them entirely for subsistence, often multiply rapidly. Their typical unit is the great patriarchal family, in which the sheikh may have scores of children by different mothers. These children soon begin to earn their keep, and are taken care of. If, however, the patriarch so chooses, Hagar with her child is cast adrift, to find her way back to her own people, if she can. The grasslands are usually almost as full as they can hold. A period of drought, or pressure by rivals, in former times sent a horde of these hardy shepherds on a raid into the nearest settled province; and if, like the Tartars, they were mounted, they usually killed, plundered, and conquered wherever they went, until the discovery of gunpowder saved civilisation from the recurrent peril of barbarian inroads. Barbarians of another type, hunters with fixed homes, seldom increase rapidly, partly because the dangers of forest-life for young children are much greater than on the steppe.
In the primitive river-valley civilisations, such as Egypt and Babylonia, the conditions of increase were so favourable that a dense population soon began to press upon the means of subsistence. In Egypt the remedy was a centralised government which could undertake great irrigation works and intensive cultivation. In Babylonia, for the first time in history, foreign trade was made to support a larger population than the land itself could maintain. There was little or no infanticide in Babylonia, but the death-rate in these steaming alluvial plains has always been very high.
When we turn to poor and mountainous countries like Greece, the conditions are very different. It was an old belief among the Hellenes that in the days before the Trojan War 'the world was too full of people.' The increase was doubtless made possible by the trade which developed in the Minoan period, but the sources of food-supply were liable to be interfered with. Hence came the necessity for active colonisation, which lasted from the eighth to the sixth century B.C. This period of expansion came to an end when all the available sites were occupied. In the sixth century the Greeks found themselves headed off, in the west by Phoenicians and Etruscans, in the east by the Persian Empire. The problem of over-population was again pressing upon them. Incessant civil wars between Hellenes kept the numbers down to some extent; but Greek battles were not as a rule very bloody, and every healthy nation has a surprising capacity of making good the losses caused by war. The first effect of the check to emigration was that the old ideal of the 'self-sufficient life,' which meant the practice of mixed farming, had to be partially abandoned. The most flourishing States, and especially Athens, had to take to manufactures, which they exchanged for the food-products of the Balkan States and South Russia. The result was an increasing urbanisation, and a new population of free 'resident aliens.' Conservatives hated this change and wished to revive the old ideal of a small self-supporting State, with a maximum of 20,000 or 30,000 citizens. Plato, in his latest work, the 'Laws,' wishes his model city to be not too near the sea, the proximity of which 'fills the streets with merchants and shopkeepers, and begets dishonesty in the souls of men.' On the other side Isocrates, the most far-seeing of Athenian politicians, realised that the day of small city-states was over, and that the limited, 'self-sufficient' community would not long maintain its independence. He urged his countrymen to pursue a policy of peaceful penetration in Western Asia, as the Greeks were soon to do under the successors of Alexander. But the prejudice against industrialism was very strong. Greece in the fifth century remained a poor country; her exports were not more than enough to pay for the food of her existing population; and that population had to be artificially restricted. The Greeks were an exceptionally healthy and long-lived race; their great men for the most part lived to ages which have no parallel until the nineteenth century. The infant death-rate from natural causes may have been rather high, as it is in modern Greece, but it was augmented by systematic infanticide. The Greek father had an absolute right to decide whether a new-comer was to be admitted to the family. In Ephesus alone of Greek cities a parent was compelled to prove that he was too poor to rear a child before he was allowed to get rid of it.[10] Even Hesiod, centuries earlier, advises a father not to bring up more than one son, and daughters were sacrificed more frequently than sons. The usual practice was to expose the infant in a jar; anyone who thought it worth while might rescue the baby and bring it up as a slave. But this was not often done. At Gela, in Sicily, there are 233 'potted' burials in an excavated graveyard, out of a total of 570.[11] The proportion of female infants exposed must have been very large. The evidence of literature is supported by such letters as this from a husband at Oxyrhynchus: 'When—good luck to you—your child is born, if it is a male, let it live; if a female, expose it.'[12] Besides infanticide, abortion was freely practised, and without blame.[13] The Greek citizen married rather late; but as his bride was usually in her 'teens this would not affect the birth-rate. Nor need we attach much importance, as a factor in checking population, to the characteristic Greek vice, nor to prostitution, which throughout antiquity was incredibly cheap and visited by no physical penalty. As for slaves, Xenophon recommends that they should be allowed to have children as a reward for good conduct.[14]
A rapid decline in population set in under the successors of Alexander. Polybius ascribes it to selfishness and a high standard of comfort, which is doubtless true of the upper and middle classes;[15] but the depopulation of rural Greece can hardly be so accounted for. Perhaps the forests were cut down, and the rainfall diminished. It was the general impression that the soil was far less productive than formerly. The decay of the Hellenic race was accelerated after the Roman conquest, until the old stock became almost extinct. This disappearance of the most gifted race that ever inhabited our planet is one of the strangest catastrophes of history, and is full of warnings for the modern sociologist. Industrial slavery, indifference to parenthood, and addiction to club-life were certainly three of the main causes, unless we prefer to regard the two last as symptoms of hopelessness about the future.
The same disease fell upon Italy, and was coincident not with the murderous war against Hannibal and the subsequent campaigns, costly though they were, in Spain, Syria, and Macedonia, but with the Hellenisation of social life. Lucan, under Nero, complains that the towns have lost more than half their inhabitants, and that the country-side lies waste. Under Titus it was estimated that, whereas Italy under the Republic could raise nearly 800,000 soldiers, that number was now reduced by one-half. Marcus Aurelius planted a large tribe of Marcomanni on unoccupied land in Italy. In the fourth century Bologna, Modena, Piacenza, and many other towns in North Italy were in ruins. The land of the Volscians and Aequians, once densely populated, was a desert even in Livy's time. Samnium remained the wilderness that Sulla had left it; and Apulia was a lonely sheep-walk.
The causes of this depopulation have been often discussed, both in antiquity and in our own day. Slavery, infanticide, celibacy, wars and massacres, large estates, and pestilence have all been named as causes; but I am inclined to think that all these influences together are insufficient to account for so rapid a decline. The toll of war was lighter by far than in periods when the population was rising; infectious disease (unless we suppose, as some have suggested, that malaria became for the first time endemic under the Roman domination) invaded the empire in occasional and destructive epidemics, but a healthy population recovers from pestilence, as from war, with great rapidity. The large grazing ranches displaced farms because corn-growing in Italy was unprofitable, but there was a large supply of grain from Sicily, Africa, and other districts. Slavery undoubtedly accounts for a great deal. This institution is excessively wasteful of human life; it is never possible to keep up the numbers of slaves without slave-hunting in the countries from which they come. And we must remember that ancient civilisation was almost entirely urban. The barbarians found ample waste lands between the towns, which they did not as a rule care to visit, probably because those who did so soon fell victims to microbic diseases. The sanitary condition of ancient cities was better than in the Middle Ages; but the death-rate was probably too high to permit of any increase in the population. But after admitting that all these causes were operative, it may be that we shall be obliged to acknowledge also a psychological factor. If a nation has no hopes for the future, if it is even doubtful whether life is worth living, if it is disposed to withdraw from the struggle for existence and to meet the problems of life in a temper of passive resignation, it will not regard children as a heritage and gift that cometh from the Lord, but rather as an encumbrance. That such was the temper of the later Roman Empire may be gathered not only from the literature, which is singularly devoid of hopefulness and enterprise, but from the rapid spread of monasticism and eremitism in this period. The prevalence of this world-weariness of course needs explanation, and the cause is rather obscure. It does not seem to be connected with unfavourable external conditions, but rather with a racial exhaustion akin to senile decay in the individual. But there is no real analogy between the life of an individual and that of a nation, and it would be very rash to insist on the hypothesis of racial decay, which perhaps has no biological basis.
The influence of Christianity on population is very difficult to estimate. Nothing is more unscientific than to collect the ethical precepts and practices of nations which profess the Christian religion, and to label them as 'the results of Christianity.' The historian of religion would indeed be faced by a strange task if he were compelled to trace the moral ideals of Simeon Stylites and of Howard the philanthropist, of Francis of Assisi and Oliver Cromwell, of Thomas Aquinas and Thomas à Becket, to a common source. The only ethical and social principles which can properly be called Christian are those which can be proved to have their root in the teaching and example of the Founder of Christianity. But the Gospel of Christ was a product of Jewish soil. It is historically connected with the Jewish prophetic tradition, which it carried to its fullest development and presented in an universalised and spiritualised form. Its social teaching consists chiefly of general principles which have to be applied to conditions unlike those contemplated by its first disciples, who were under the influence of the apocalyptic expectations prevalent at the time. Jewish morality was in its origin the morality of a tribe of nomad Bedouins; and we have seen that infant life is held sacred by these peoples. Marriage is regarded as a duty, and childlessness as a misfortune or a disgrace. The forward look, characteristic of the Hebrews from the first, made every Jew desirous to leave descendants who might witness happier times, and one of whom might even be the promised Deliverer of his people. No Hebrew of either sex was allowed to be a servant of vice; abnormal practices, though screened by Canaanite religion, were far less common than in Greece or Italy. To this wholesome morality Christianity added the doctrines of the value, in the sight of God, of every human life, and of the sanctity of the body as the 'temple of God.' To the Pagans, the continence of the Christians was, next to their affection for each other, their most remarkable characteristic. From the first, the new religion set itself firmly against infanticide and abortion, and won one of its most signal moral triumphs in driving underground and greatly diminishing homosexual vice. Its encouragement of celibacy, especially for those who followed the 'religious' vocation, was an offset to its healthy influence on family life, and ultimately, as Galton has shown, worked great mischief by sterilising for centuries many of the gentlest and noblest in each generation; but this tendency was adventitious to Christianity, and would never have taken root on Palestinian soil. The cult of virginity has lasted on, with much else that belongs to the later Hellenistic age, in Catholicism.
In the Middle Ages the population question slumbered. The miserable chaos into which the old civilisation sank after the barbarian invasions, the orgies of massacre and plunder, the almost total oblivion of medical science, and the pestiferous condition of the medieval walled town, which could be smelt miles away, averted any risk of over-population. Families were very large, but the majority of the children died. Millions were swept away by the Black Death; millions more by the Crusades. Such books as that of Luchaire, on France in the reign of Philip Augustus, bring vividly before us the horrible condition of society in feudal times, and explain amply the sparsity of the population.