XXI 



MENTAL FACTORS IN EVOLUTION 

 By C. Lloyd Morgan, LL.D., F.R.S. 



In developing- his conception of organic evolution Charles Darwin 

 was of necessity brought into contact with some of the problems of 

 mental evolution. In The Origin of Species he devoted a chapter 

 to "the diversities of instinct and of the other mental faculties in 

 animals of the same class 1 ." When he passed to the detailed con- 

 sideration of The Descent of Man, it was part of his object to show 

 " that there is no fundamental difference between man and the higher 

 mammals in their mental faculties 2 ." " If no organic being excepting 

 man," he said, " had possessed any mental power, or if his powers had 

 been of a wholly different nature from those of the lower animals, 

 then we should never have been able to convince ourselves that our 

 high faculties had been gradually developed 3 ." In his discussion of 

 The Expression of the Emotions it was important for his purpose 

 " fully to recognise that actions readily become associated with other 

 actions and with various states of the mind 4 ." His hypothesis of 

 sexual selection is largely dependent upon the exercise of choice on 

 the part of the female and her preference for "not only the more 

 attractive but at the same time the more vigorous and victorious 

 males 5 ." Mental processes and physiological processes were for 

 Darwin closely correlated ; and he accepted the conclusion " that 

 the nervous system not only regulates most of the existing functions 

 of the body, but has indirectly influenced the progressive develop- 

 ment of various bodily structures and of certain mental qualities 6 ." 



Throughout his treatment, mental evolution was for Darwin in- 

 cidental to and contributory to organic evolution. For specialised 

 research in comparative and genetic psychology, as an independent 

 field of investigation, he had neither the time nor the requisite 

 training. None the less his writings and the spirit of his work have 



1 Origin of Species (6th edit.), p. 205. 



2 Descent of Man (2nd edit. 1888), Vol. i. p. 99; Popular edit. p. 99. 3 Ibid. p. 99. 



4 The Expression of the Emotions (2nd edit. ), p. 32. 



5 Descent of Man, Vol. n. p. 435. 6 Ibid. pp. 437, 438. 



