SEX BIOLOGY AND SEX 

 PSYCHOLOGY ^ 



THE biology of sex is a vast subject. Not 

 only are there questions of sex-determina- 

 tion, but the whole sexual selection problem 

 has to be considered, together with the evolutionary 

 function of sex, and its first origin. I can only 

 attempt, in the short space at my disposal, to deal 

 with one or two of the chief points, and only in so 

 far as they bear on questions of human sex psychology. 



In the first place, then, we have to consider the 

 evolutionary history of sex. Of its origin we can say 

 only that it is veiled in complete obscurity. Once 

 present, however, it appears to have a definite function 

 by making possible, through sexual reproduction, all 

 the various combinations of any heritable variations 

 that may arise in different individuals of a species, 

 and so conferring greater evolutionary plasticity on 

 the species as a whole. - 



Primarily, sex implies only the fusion of nuclei 

 from two separate individuals ; there is no need for 



1 Read before the British Society for Sex Psychology, 

 October 1922. * See East and Jones, '19. 



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