Seite - 79 - in The Origin of Species

GEOMETRICAL RATIO OF INCREASE 79 birds to devour and thus disseminate its seeds. In these sev- eral senses, which pass into each other, I use for conveni- ence sake the general term of Struggle for Existence. GEOMETRICAL RATIO OF INCREASE A struggle for existence inevitably follows from the high rate at which all organic beings tend to increase. Every being, which during its natural lifetime produces several eggs or seeds, must suffer destruction during some period of its life, and during some season or occasional year, other- wise, on the principle of geometrical increase, its numbers would quickly become so inordinately great that no country could support the product. Hence, as more individuals are produced than can possibly survive, there must in every case be a struggle for existence, either one individual with an- other of the same species, or with the individuals of distinct species, or with the physical conditions of life. It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms; for in this case there can be no artificial increase of food, and no prudential restraint from marriage. Although some species may be now increas- ing, more or less rapidly, in numbers, all cannot do so, for the world would not hold them. There is no exception to the rule that every organic being naturally increases at so high a rate, that, if not destroyed, the earth would soon be covered by the progeny of a single pair. Even slow-breeding man has doubled in twenty-five years, and at this rate in less than a thousand years, there would literally not be standing-room for his progeny. Lin- naeus has calculated that if an annual plant produced only two seeds—and there is no plant so unproductive as this— and their seedlings next year produced two, and so on, then in twenty years there would be a million plants. The ele- phant is reckoned the slowest breeder of all known animals, and I have taken some pains to estimate its probable mini- mum rate of natural increase ; it will be safest to assume that it begins breeding when thirty years old, and goes on breeding till ninety years old, bringing forth six young in the interval, and surviving till one hundred years old; if this