22 ETHICAL ASPECTS OF EVOLUTION 



on the adults. Of the misadaptations which cut short 

 the natural length of life, the most destructive is disease. 

 In its worst and most repulsive forms of leprosy and syphilis 

 it is peculiar to the human race ; various kinds of mental 

 malady are nearly so, and all these appear to be increasing 

 rapidly among civilized races. Even if medical science 

 more than keeps abreast with the development of disease 

 and that is doubtful the preservation of large numbers 

 of aged individuals, who would otherwise have given 

 place to the more vigorous, will not necessarily prove of 

 unmixed advantage to the race. Disease, which is the usual 

 cause of death among men, counts for little or nothing among 

 the lower animals. 



It is, however, unconvincing to compare single processes, 

 one with another, in respect to the advantages or disadvan 

 tages attached to each. The facts admit of a more general 

 statement, namely, that every fresh modification, even if it 

 answers, as most of them obviously do, some special purpose, 

 at the same time is attended by new risks and disadvantages 

 to the organism as a whole. This point has been so admir 

 ably expressed by Prof. Bateson, in the introduction to his 

 Materials for the Study of Variation, that I venture to make 

 use of his words : 



It is obvious from inspection that any instinct or any 

 organ may be of use ; the real question we have to consider 

 is of how much use it is. To know that the presence of 

 a certain organ may lead to the preservation of a race is 

 useless if we cannot tell how much preservation it can effect, 

 how many individuals it can save that would otherwise be 

 lost ; unless we know also the degree to which its presence 

 is harmful ; unless, in fact, we know how its presence affects 

 the profit and loss account of the organism. We have no 

 right to consider the utility of a structure demonstrated, 

 in the sense that we may use this demonstration as evidence 

 of the causes which have led to the existence of the structure, 

 until we have this quantitative knowledge of its utility, 

 and are able to set off against it the cost of the production 

 of the structure, and all the difficulties which its presence 

 entails on the organism. ... In the absence of correct and 

 final estimates of utility, we must never use the utility of 



