THE EVOLUTION OF MAN 197 



single Order a Family may be so separated as in the case of 

 the Mole family. It is not easy to find a genus so distinguished. 

 Man thus appears to have the rank of a family. The condition 

 of the hair in man might possibly be regarded as a diagnostic 

 character which is not adaptive ; if the absence of hair on the 

 body be explained by uselessness, still the special development 

 on the head looks like a non-adaptive feature. It is difficult 

 then to regard man as merely a genus of anthropoid apes. 



On the other hand, we do not find that man can obviously be 

 divided into a number of distinct species as other families of 

 mammals can, or as even a genus can be divided. There are dis- 

 tinct races of man, and the question is whether these correspond 

 with species among other animals. To discuss this question 

 we have to consider the diagnostic characters of these races. 

 Darwin considers them very carefully in the work I have 

 already mentioned, and comes to two remarkable conclusions, 

 which are of chief importance in relation to the object of this 

 paper : first, that these characters graduate into each other so 

 that the races cannot be absolutely defined ; secondly, that they 

 are in no sense adaptational. He says that, so far as we can 

 judge, none of the differences between the races of man are of 

 any direct or special service to him, nor can they be accounted 

 for in a satisfactory manner by the direct action of the con- 

 ditions of life, nor by use and disuse, nor through the principle 

 of correlation. He then proceeds to inquire whether they can 

 be explained by sexual selection. He concludes that this pro- 

 cess will not explain all the differences, but that there is a 

 residuum which must, provisionally at least, be regarded as due 

 to spontaneous variations, which have become constant and 

 general without selection. Thus we find Darwin in this case 

 compelled to adopt the view which in my opinion still holds 

 good in man as in other animals, that there are two cate- 

 gories of characters, namely the adaptive and the non-adaptive. 

 The latter are of the same kind as those which are called 

 mutations by modern biologists, while the former, in my 

 opinion, are directly due to stimuli. Where the stimulus is 

 functional, the modification is such as to render organs and 

 structures more fitted for the functions ; but certain conditions 

 may produce a direct result which has no connection with 

 function, and which is therefore not in the ordinary sense useful 

 or adaptive : for example, the absence of the stimulus of light 



