MENTAL EVOLUTION IN THE PRIMATES 1 33 



and by man than in their respective perceptual experiences, 

 creative imagination, insight, foresight, and thought. 



It is said that apes possess a vocal mechanism similar to 

 that of man and are capable of producing a variety of sounds. 

 The fact that they communicate otherwise than by talking 

 possibly should be attributed to lack of special tendency to 

 reproduce or imitate sounds in such manner as to facihtate 

 the growth of a system of vocal expressions. Certain it is 

 that they imitate inteUigently many actions that they see. 



Probably the most important single difference in the 

 intellectual expressions of ape and man is the hnguistic. 

 For whereas our ideas, memories, imaginings, thoughts, and 

 intents are expressed by spoken or written language, the 

 relatively meager and simple cognitive experiences of the 

 apes gain expression through bodily attitude, facial expres- 

 sion, gesture, trunk and hmb movements, and vocahzation. 

 There is no single system of signs or symbols comparable 

 with human speech, or indeed with any other highly organ- 

 ized form of language. One must grasp and understand 

 or interpret the total picture of ape behavior instead of 

 depending, as is possible among ourselves, on some single 

 form or aspect of behavior, such as vocal symbol. It may not 

 be doubted, however, that the apes, despite their hnguistic 

 inferiority to man, communicate readily and to an eminently 

 serviceable degree. 



Scarcely more than the beginnings of symboKsm have 

 been discovered in the primates, but from those begin- 

 nings, as from the modes of behavioral adaptation which 

 are obse^rvable in monkeys and apes, it is possible, and we 

 think probable, that human symbolism and even speech 

 have evolved. The subject demands and richly deserves 

 more systematic, persistent, ingenious, and determined 

 investigation. Curiously enough, for every unit of human 

 energy expended on observation of animal symbohsm, a 

 hundred have been used for surmise and speculative dis- 

 cussion. Why is man so ready to ignore discoverable fact 

 and to indulge in vain imaginings? 



Since man is preeminently and undeniably the talking 

 animal, and since further his elaborate system of vocal 

 symbols immeasurably facihtates both self-adaptation and 



