CHARLES DARWIN 229 



conditions, would tend to be preserved ; and natural selection would 

 have free scope for the work of improvement. 



We have good reason to believe, as shown in the first chapter, that 

 changes in the conditions of life give a tendency to increased varia- 

 bility ; and in the foregoing cases the conditions have changed, and 

 this would manifestly be favourable to natural selection, by aflford- 

 ing a better chance of the occurrence of profitable variations. Unless 

 such occur, natural selection can do nothing. Under the term of 

 "variations," it must never be forgotten that mere individual differ- 

 ences are included. As man can produce a great result with his 

 domestic animals and plants by adding up in any given direction in- 

 dividual differences, so could natural selection, but far more easily 

 from having incomparably longer time for action. Nor do I be- 

 lieve that any great physical change, as of climate, or any unusual 

 degree of isolation to check immigration, is necessary in order that 

 new and unoccupied places should be left for natural selection to fill 

 up by improving some of the varying inhabitants. For as all the 

 inhabitants of each country are struggling together with nicely bal- 

 anced forces, extremely slight modifications in the structure or 

 habits of one species would often give it an advantage over others; 

 and still further modifications of the same kind would often still 

 further increase the advantage, as long as the species continued under 

 the same conditions of life and profited by similar means of sub- 

 sistence and defense. No country can be named in which all the 

 native inhabitants are now so perfectly adapted to each other and to 

 the physical conditions under which they five, that none of them could 

 be still better adapted or improved ; for in all countries, the natives 

 have been so far conquered by naturalized productions, that they 

 have allowed some foreigners to take firm possession of the land. 

 And as foreigners have thus in every country beaten some of the 

 natives, we may safely conclude that the natives might have been 

 modified with advantage, so as to have better resisted the intruders. 



As man can produce, and certainly has produced, a great result by 

 his methodical and unconscious means of selection, what may not 

 natural selection effect? Man can act only on external and visible 

 characters : Nature, if I may be allowed to personify the natural 

 preservation or survival of the fittest, cares nothing for appearances, 

 except in so far as they are useful to any being. She can act on 



