54 THE THEORY OF NATURAL SELECTION 



have arisen. This last consideration will account for 

 the frequency with which apparently adaptive like- 

 nesses are to be found in nature, even if we suppose 

 that their origin was ' accidental,' or simply due to 

 the operation of similar external causes. The same 

 criticism applies to all cases of adaptation of whatever 

 kind, so far as concerns their supposed method of origin 

 by the action of natural selection upon individual 

 differences. 



Perhaps a still more serious criticism of the methods 

 of those who spend their time in seeking out or devising 

 cases of adaptation has been made by Bateson, who 

 points out the logical difficulty that we can never 

 make any quantitative estimate of the amount of 

 benefit or the reverse which any particular structure 

 may afford to its possessor. It is easy enough to 

 imagine particular circumstances in which an organ 

 developed in a particular way may be of undoubted 

 service, but whether the net amount of such service 

 throughout the life of the creature considered is 

 greater or less than the strain upon its resources caused 

 by the development of such an organ is quite beyond 

 our powers of determination. 



' The students of adaptation forget that even on the 

 strictest application of the theory of selection it is 

 unnecessary to suppose that every part an animal has, 

 and everything which it does, is useful and for its good. 

 We, animals, live not only by virtue of, but also in 

 spite of what we are. It is obvious from inspection 

 that any instinct or organ may be of use ; the real 

 question we have to consider is how much use it is. 



