37° Evolution and Adaptation 



Darwinian theory meets with difficulties at every turn by 

 assuming that new forms are built up through the action 

 of selection, the mutation theory escapes most of these diffi- 

 culties, because it applies no such rigid test as that of selec- 

 tion to account for the presence of new forms. 



Length of Life as an Adaptation 



It has been pointed out in the first chapter that the length 

 of life of the individual has been supposed by some of the 

 most enthusiastic followers of Darwin to be determined by 

 the relation of the individual to the species as a whole. In 

 other words, the doctrine of utility has been applied here also, 

 on the ground that it would be detrimental to the species to 

 have part of the individuals live on to a time when they can 

 no longer propagate the race or protect the young. It is 

 assumed that those varieties or groups of individuals (unfor- 

 tunately not sharply defined) would have the best chance 

 to survive in which the parent forms died as soon as they 

 had lost the power to produce new individuals. Sometimes 

 interwoven with this idea there is another, namely, that death 

 itself has been acquired because it was more profitable to 

 supplant the old and the injured. individuals by new ones, 

 than to have the old forms survive, and thus deprive the 

 reproducing individuals of some of the common food supply. 



This insidious form that the selection theory has taken in 

 the hands of its would-be advocates only serves to show to 

 what extremes its disciples are willing to push it. On the 

 whole it would be folly to pursue such a will-o'-the-wisp, when 

 the theory can be examined in much more tangible examples. 

 If in these cases it can be shown to be improbable, the re- 

 maining superstructure of quasi-mystical hypothesis will fall 

 without more ado. 



That the problem of the length of life may be a real one 

 for physiological investigation will be granted, no doubt, with- 



