6o8 The Descent of Man. Part ill. 



importance, some indeed of considerable importance, have been 

 gained through sexual selection. 



No doubt man, as well as every other animal, presents 

 structures, which seem to our limited knowledge, not to be now 

 of any service to him, nor to have been so formerly, either for the 

 general conditions of life, or in the relations of one sex to the 

 other. Such structures cannot be accounted for by any form of 

 selection, or by the inherited effects of the use and disuse of 

 parts. We know, however, that many strange and strongly- 

 marked peculiarites of structure occasionally appear in our 

 domesticated productions, and if their unknown causes were to 

 act more uniformly, they would probably become common to all 

 the individuals of the species. We may hope hereafter to 

 understand something about the causes of such occasional modi- 

 fications, especially through the study of monstrosities: hence 

 the labours of experimentalists, such as those of M. Camille 

 Dareste, are full of promise for the future. In general we can 

 only say that the cause of each slight variation and of each 

 monstrosity lies much more in the constitution of the organism, 

 than in the nature of the surrounding conditions ; though nesv 

 and changed conditions certainly play an important part in 

 exciting organic changes of many kinds. 



Through the means just specified, aided perhaps by others 

 as yet undiscovered, man has been raised to his present state. 

 But since he attained to the rank of manhood, he has diverged 

 into distinct races, or as they may be more fitly called, sub- 

 species. Some of these, such as the Negro and European, are 

 so distinct that, if specimens had been brought to a naturalist 

 without any further information, they would undoubtedly have 

 been considered by him as good and true species. Nevertheless 

 all the races agree in so many unimportant details of structure 

 and in so many mental peculiarities, that these can be accounted 

 for only by inheritance from a common progenitor ; and a pro- 

 genitor thus characterised would probably deserve to rank as man. 



It must not be supposed that the divergence of each race from 

 the other races, and of all from a common stock, can be traced 

 back to any one pair of progenitors. On the contrary, at every 

 stage in the process of modification, all the individuals which 

 were in any way better fitted for their conditions of life, though 

 in different degrees, would have survived in greater numbers 

 than the less well-fitted. The process would have been like that 

 followed by man, when he does not intentionally select particular 

 individuals, but breeds from all the superior individuals, and 

 neglects the inferior. He thus slowly but surely modifies hi3 

 stock, and unconsciouslv forms a new strain. So with respect 





