102 THE ORIGIN OF SPECIES 



several eggs or seeds, must suffer destruction during 

 some period of its life, and during some season or occa- 

 sional year, . otherwise, on the principle of geometrical 

 increase, its numbers would quickly become so inordi- 



' ^^<'lilately great that no country could support the product. 

 Hence, as more individuals are produced than can possi- 

 bly survive, there must in every case be a struggle for 

 existence, either one individual with another 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. _f_orcft 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 increasing, 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 



AU standing-room for his progeny. Linnaeus has calculated 

 that if an annual plant produced only two seeds— and 

 there is no plant so unproductive as this — and their seed- 

 lings next year produced two, and so on, then in twenty 

 years there would be a million plants. The elephant is 

 reckoned the slowest breeder of all known animals, and I 

 have taken some pains to estimate its probable minimum 

 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 



