Il8 HUMAN BIOLOGY 



tural resemblances which have been exhibited in the earher 

 chapters of this volume. We presume to make this general 

 statement because the remainder of our chapter is an 

 exposition of the facts upon which it rests. 



Standing as guide posts in the path of individual develop- 

 ment and in that of descent are certain signally important 

 groups of psychobiological phenomena. They include: 

 (i) receptivity, or the psychobiological relation of organism 

 to environment through the senses; (2) behavioral adap- 

 tivity, dr the adjustment of organism to environment, (a) 

 bhndly, (b) with insight, or (c) with foresight — phenomena 

 which are distinctively organic and primarily if not exclu- 

 sively psychobiological; (3) ideational processes, creative 

 imagination, abstraction and generahzation, as conditions 

 for adaptation through modification of the environment 

 instead of by self-adjustment- — a long step in primate 

 evolution; (4) the use of symbols, the growth of language, 

 and the final dominance of speech^ — phenomena which, 

 although appearing in other classes of primate, become 

 conspicuously important in man; (5) inborn reactive tend- 

 encies, emotions, sentiments, drives, and ideals, and (6) 

 social relations in experience, organization, and institution. 



To each of these vast assemblages of phenomena in the 

 life of the primate we shall in turn briefly attend, for together 

 they clearly mark the main highway of individual develop- 

 ment and the less readily followed, because less direct, 

 course of mental evolution. 



RECEPTIVITY AND THE PRESENT DOMINANCE OF DISTANCE 



RECEPTORS 



It is observable that in the development of man the senses 

 of touch, temperature, smell and taste become functional 

 prior to those of vision and hearing. Likewise among the 

 classes of primates appear diff^erences in the senses which 

 roughly correspond to those of individual development. 

 Crudely put, in evolution as in development we pass from 

 the dominance of mechanical and chemical stimulation to 

 that of vibrational. The observable trend is from sensitivity 

 to and awareness of the immediately present object or event 

 to that of the spatially or temporally distant. For touch 



