EVOLUTION 1029 



secretions or hormones, or by some other disturbance of the normal 

 routine of metabolism. 



SEX AND EVOLUTION.— The establishment of sexual repro- 

 duction had many more or less immediate rewards : it meant more 

 economical means of continuing the race ; it was a device for secur- 

 ing the persistence of a successful genetic constitution and for screen- 

 ing the offspring from disadvantageous dints made on the parent's 

 body; it implied more opportunities for rearrangements of the here- 

 ditary items at the beginning of each new life. The separation of 

 sperm-producers (or males) and egg-producers (or females) , differing 

 deeply in constitution, would also tend to increase the possible 

 range of cross-fertilisation, which is often advantageous, and would 

 permit of a profitable division of labour between the two parents 

 in their relations to the offspring; and so on. But in the course of 

 ages the sex-divergence attained another justification; it became 

 the basis of love, it served as a liberator and educator of emotions 

 which have enriched and ennobled the lives of many creatures. As 

 Darwin clearly recognised, characters which were primarily selected 

 in relation to mating, might become secondarily diverted by a 

 function-change to even wider issues. 



In his Studies in Animal Behaviour (1916), Mr. S. J. Holmes has 

 an interesting chapter on "the role of sex in the evolution of mind". 

 "The primary function of the vocal apparatus of the Vertebrates 

 was probably to furnish a sex call, as is now its exclusive function 

 in the Amphibia. Only later and secondarily did the voice come to 

 be employed in protecting and fostering the young, and as a means 

 of social communication. And the evolution of the voice in Verte- 

 brates doubtless influenced to a marked degree the evolution of the 

 sense of hearing. It is not improbable, therefore, that the evolution 

 of the voice, with all its tremendous consequences in regard to the 

 evolution of mind, is an outgrowth of the differentiation of sex." 

 There can be little doubt that the biology of the future will attach 

 not less but more importance to sexual selection. For it seems 

 likely that characters and qualities originally established in this 

 way have often influenced both body and behaviour in reaches now 

 more or less remote from the tides of sex-impulses. 



In regard to sexual selection in mankind, four remarks may per- 

 haps be permitted, (a) The careful selection of attractive wives, 

 under what we may call the patriarchal regime, has probably been 

 contributory to the evolution of the beauty of women in certain 

 selected stocks, (h) Conversely, a restriction of the range of choice 

 in isolated regions and among people with few opportunities of 

 changing their social environment, even for a short time, has 

 probably been, in the absence of a contrary tradition, contributory 

 to the evolution of commonplaceness. Many facts of life point to 



