Chap. III Upon what Principles, and from what natural Causes do Mankind multiply? And what are the Effects of Procreatio

The multiplication of mankind has been treated of in different ways; some have made out tables to show the progression of multiplication, others have treated the question historically. The state of numbers in different ages of the world, or in different countries at different times, has been made the object of inquiry; and the most exact scrutiny has been made into ancient authors, as the means of investigating the truth of this matter. All passages relative to the subject have been laid together, and accompanied with glosses and interpretations the most plausible, in order to determine the main question. The elaborate performances of Mr Hume, and Dr Wallace, who have adopted opposite opinions in regard to the populousness of the ancient world, have left nothing new to be said upon this subject; at least the application they appear to have given in examining the ancients, is a great discouragement to any one who might otherwise still flatter himself to find out circumstances in them, proper to cast a new light upon the question.

My intention in this chapter is not to decide, nor even to give my opinion upon that matter, far less to combat the arguments advanced on either side. I am to consider the question under a different point of view; not to inquire what numbers of people were found upon the earth at a certain time, but to examine the natural and rational causes of multipliCation. If we can discover these, we may perhaps be led to judge how far they might have operated in different ages and in different countries.

The fundamental principle of the multiplication of all animals, and consequently of man, is generation; the next is food: generation gives existence, food preserves it. Did the earth produce of itself the proper nourishment for man with unlimited abundance, we should find no occasion to labour in order to procure it. Now in all countries found inhabited, as in those which have been found desolate, if the state of animals be inquired into, the number of them will be found in proportion to the quantity of food produced by the earth, regularly throughout the year, for their subsistence. I say, regularly throughout the year, because we perceive, in those animals which produce in great abundance, such as all the feathered sort, that vast multitudes are destroyed in winter; they are brought forth with the fruits of the earth, and fall in proportion to their decay. This principle is so natural, that I think it can hardly be controverted.

As to man, the earth does not spontaneously produce nourishment for him in any considerable degree. I allow that as some species of animals support life by devouring others, so may man; but it must be observed, that the species feeding must always be much inferior in number to the species fed upon. This is evident in reason and in fact.

Were the earth therefore uncultivated, the numbers of mankind would not exceed the proportion of the spontaneous fruits which she offers for their immediate use, or for that of the animals which might be the proper nourishment of man.

There is therefore a certain number of mankind which the earth would be able to maintain without any labour: allow me to call this quantity (A). Does it not, from this exposition of the matter, appear plain, that without labour (A) never can increase any more than animals, which do not work for themselves, can increase beyond the proportion of food provided for them by nature? Let it be however observed, that I do not pretend to limit (A) to a determinate number. The seasons will no doubt influence the numbers of mankind, as we see they influence the plenty of other animals; but I say (A) will never increase beyond the fixed proportion above mentioned.

Having resolved one question with regard to multiplication, and shewn that numbers must become greater or smaller according to the productions of nature, I come to the second thing proposed to be treated of in the chapter; to wit, what will become of the generative faculty after it has produced the full proportion of (A), and what effects will afterwards follow.

We see how beneficent, I might have said prodigal, nature is in bestowing life by generation. Several kinds of animals, especially insects, multiply by thousands, and yet the species does not appear annually to increase. Nobody can pretend that particular individuals of any species have a privilege to live, and that others die from a difference in their nature. It is therefore reasonable to conclude, that what destroys such vast quantities of those produced, must be, among other causes, the want of food. Let us apply this to man.

Those who are supposed to be fed with the spontaneous fruits of the earth, cannot, from what has been said, multiply beyond that proportion; at the same time the generative faculty will work its natural effects in augmenting numbers. The consequence will be, that certain individuals must become worse fed, consequently weaker. consequently, if, in that weakly state, nature should withhold a part of her usual plenty, the whole multitude will be affected by it; a disease may take place, and sweep off a far greater number than that proportioned to the deficiency of the season. What results from this? That those who have escaped, finding food more plentiful, become vigorous and strong. generation gives life to additional numbers, food preserves it, until they rise up to the former standard.

Thus the generative faculty resembles a spring loaded with a weight, which always exerts itself in proportion to the diminution of resistance: when food has remained some time without augmentation or diminution, generation will carry numbers as high as possible; if then food come to be diminished, the spring is overpowered; the force of it becomes less than nothing. Inhabitants will diminish, at least, in proportion to the overcharge. If, upon the other hand, food be increased, the spring which stood at 0, will begin to exert itself in proportion as the resistance diminishes; people will begin to be better fed; they will multiply, and, in proportion as they increase in numbers, the food will become scarce again.

I must here subjoin a remark very analogous to this subject. That the generative faculty in man (which we have compared to a spring), and the care and love we have for our children, first prompt us to multiply, and then engage us to divide what we have with our little ones. Thus from dividing and subdividing it happens, that in every country where food is limited to a certain quantity, the inhabitants must be subsisted in a regular progression, descending down from plenty and ample subsistence, to the last periods of want, and even sometimes starving for hunger.

Although the examples of this last extremity are not common in some countries, yet I believe they are more so than is generally imagined; and the other stages of want are productive of many diseases, and of a decay which extinguishes the faculty of generation, or which weakens it, so as to produce children less vigorous and less healthy. I appeal to experience, if this reasoning be not just.

Put two or three pairs of rabbits into a field proper for them, the multiplication will be rapid; and in a few years the warren will be stocked: you may take yearly from it a hundred pairs, I shall suppose, and keep your warren in good order: give over taking any for some years, you will perhaps find your original stock rather diminished than increased, for the reasons above mentioned. Africa yearly furnishes many thousands for the cultivation of America; in this she resembles the warren. I have little doubt but that if all her sons were returned to her at once, by far the greater part would die of hunger.