It is certain that the reproductive faculty in the human species is less powerful than in any other, and it ought to be so. Man, in the superior situation in which nature has placed him, as regards intelligence and sympathy, ought not to be exposed to destruction in the same degree as the inferior animals. But we are not to suppose that physically he escapes from that law in virtue of which all species have the faculty of multiplying to a greater extent than space and nourishment permit.
I say physically, because I am speaking here only of the physiological law.
There is a wide difference between the physiological power of multiplying and actual multiplication.
The one is an absolute organic power when freed from all obstacle and all limitation ab extra—the other is the effective resulting force of this power combined with the aggregate of all the resistance which limits and restrains it. Thus the power of multiplication of the poppy may be a million a year, perhaps; but in a field of poppies the actual reproduction may be stationary or even decrease.
It is this physiological law that Malthus essayed to reduce to a formula. He inquired in what period of time a given number of men would double, if their space and food were unlimited.
We can see beforehand that as this hypothesis of the complete satisfaction of all wants is never realized in practice, the theoretic period must necessarily be shorter than any period of actual doubling which has ever been observed.
Observation, in fact, gives very different results for different countries. According to the results obtained by M. Moreau de Jonnès, taking for basis the actual increase of population, the period of doubling would require—in Turkey, 555 years; in [p404] Switzerland, 227; in France, 138; in Spain, 106; in Holland, 100; in Germany, 76; in Russia and in England, 43; and in the United States of America, 25 years, deducting the contingent furnished by immigration.
Now, what is the reason of such enormous differences? We have no reason to think that they are the result of physiological causes. Swiss women are as well formed and as prolific as American women.
We must conclude, then, that the absolute generative power is restrained by external obstacles. And what proves this beyond doubt is, that it is manifested as soon as circumstances occur to remove these obstacles. Thus an improved agriculture, new manufactures, some new source of local wealth, leads invariably in that locality to an increase of population. In the same way, when a scourge like a plague, or a famine, or war, destroys a great part of the population, we immediately find that multiplication is more rapidly developed.
When an increase of population, then, is retarded, or stops, we find that space and nourishment are awanting, or likely to be so; that it has encountered an obstacle, or is scared by one.