122 EVOLUTION AND NATURAL THEOLOGY. 



unconscious, and afterwards methodical) would 

 come into play immediately ; but though this 

 has been practised from time immemorial, ages 

 of experience would have been required before 

 high cultivation, weeding out, and skilful breed- 

 ing could be carried on with anything like our 

 present success. 



Nor have the most variable or useful species 

 always been selected for domestication. Many 

 animals will not breed freely in confinement ; and 

 unless an animal would do so to a certain extent, 

 its complete and thorough domestication would 

 be impossible. 



Nevertheless, in the early ages of the world, 

 animals when tamed, would generally have to 

 find their own living, and would otherwise be 

 exposed to less artificial conditions of life than 

 would be the case now ; and thus their tendency 

 to sterility under changed conditions might be 

 gradually overcome.* With respect to plants, 

 Darwin suggests that we probably owe our 

 knowledge of their properties to our prede- 

 cessors having been forced by famine to attempt 



* Vide antea pp. 75 77, where this subject has been already dis- 

 cussed in greater detail. 



