Chap. VII. THE KACES OF MAN. 249 



special service to him. The intellectual and moral or 

 social faculties must of course be excepted from this re- 

 mark ; but differences in these faculties can have had 

 little or no influence on external characters. The vari- 

 ability of all the characteristic differences between the 

 races, before referred to, likewise indicates that these 

 differences cannot be of much importance ; for, had 

 they been important, they would long ago have been 

 either fixed and preserved, or eliminated. In this 

 respect man resembles those forms, called by naturalists 

 protean or polymorphic, which have remained extremely 

 variable, owing, as it seems, to their variations being of 

 an indifferent nature, and consequently to their having 

 escaped the action of natural selection. 



We have thus far been baffled in all our attempts 

 to account for the differences between the races of man ; 

 but there remains one important agency, namely Sexual 

 Selection, which appears to have acted as powerfully 

 on man, as on many other animals. I do not intend 

 to assert that sexual selection will account for all the 

 differences between the races. An unexplained resi- 

 duum is left, about which we can in our ignorance 

 only say, that as individuals are continually born with, 

 for instance, heads a little rounder or narrower, and 

 with noses a little longer or shorter, such slight dif- 

 ferences might become fixed and uniform, if the un- 

 known agencies which induced them were to act in a 

 more constant manner, aided by long-continued inter- 

 crossing. Such modifications come under the provi- 

 sional class, alluded to in our fourth chapter, which for 

 the want of a better term have been called spontaneous 

 variations. Nor do I pretend that the effects of sexual 

 selection can be indicated with scientific precision ; but 

 it can be shewn that it would be an inexplicable fact if 

 man had not been modified by this agency, which has 



