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.