384 



The Journal of Heredity 



apart from the tree climbing, for these 

 competent hands to do. 



The ape is tied down absolutely to his 

 experience, and has only a very limited 

 ability to anticipate the results even of 

 relatively simple actions, because so 

 large a proportion of his neopallium is 

 under the dominating influence of the 

 senses. 



Without a fuller appreciation of the 

 conseqvienccs of its actions than the 

 gibbon is capable of, the animal is not 

 competent to make the fullest use of the 

 skill it undoubtedly possesses. What 

 is imijlied in acquiring this fuller 

 appreciation of the meaning of events 

 taking place around the animal' The 

 state of consciousness awakened by a 

 simple sensory stimulation is not merely 

 an appreciation of the physical proper- 

 ties of the object that supplies the 

 stimulus; the object simply serves to 

 bring to consciousness the results of 

 experience of similar or contrasted 

 stimulations in the past, as well as the 

 feelings aroused by or associated with 

 them, and the acts such feelings excited. 

 This mental enrichment of a mere sen- 

 sation so that it acquires a very precise 

 and complex meaning is possible only 

 because the individual has this extensive 

 experience to fall back upon; and the 

 faculty of acquiring such experience 

 applies the possession of large neopallial 

 areas for recording, so to speak, these 

 sensation factors and the feelings asso- 

 ciated with them. The "meaning" 

 which each creature can attach to a 

 sensory impression presvimably depends, 

 not on its experience onl3% but more 

 especially upon the neopallial provision 

 in its brain for recording the fruits of 

 such experience. 



Judged Vjy this standard, the human 

 brain V)ears am]jle witness, in the expan- 

 sion of the great temporo-parietal area, 

 which so obviously has 1)een evolved 

 from the regions into which visual, 

 auditory, and tactile imjjulscs are 

 poured, to the jjcrfection of the physical 

 counter])art of the enrichment of mental 

 structure, which is the fundamental 

 characteristic of the human mind. 



The second factor that came into 

 operation in the evolution of the human 



brain is merely the culmination of a 

 process which has been steadily advanc- 

 ing throughout the primates. I refer 

 to the high state of perfection of the 

 cortical regulation of skilled movements, 

 man}' of which are acquired by each 

 individual in response to a compelling 

 instinct that forces every normal human 

 being to work out his own salvation by 

 perpetually striving to acquire such 

 manual dexterity. 



MAN AND GORILLA. 



This 1)rings us to the consideration of 

 the nature of the factors that have led 

 to the wide differentiation of man from 

 the gorilla. Why is it that these two 

 primates, structiirally so similar and 

 derived simultaneously from common 

 parents, should have become separated 

 by such an enormous chasm, so far as 

 their mental abilities are concerned? 



There can be no doubt that this 

 process of differentiation is of the same 

 nature as those which led one branch of 

 the Eocene tarsioids to become monkeys 

 while the other remained prosimiae; 

 advanced one group of primitive 

 monkeys to the catarrhine status, while 

 the rest remained platyrrhine; and con- 

 verted one division of the Old World 

 apes into anthropoids, while the others 

 retained their old status. Put into this 

 form as an obvious truism, the conclu- 

 sion is suggested that the changes which 

 have taken place in the brain to convert 

 an ape into man are of the same nature 

 as, and may be looked upon merely as a 

 continuation of, those processes of 

 evolution which we have been examining 

 in the lowlier members of the primate 

 series. It was not the adoption of the 

 erect attitude or the invention ot 

 articulate language that made man from 

 an ajic, but the gradual perfecting of the 

 brain and the slow upbuilding of the 

 mental structure, of which erectncss of 

 carriage and speech are some of the 

 incidental manifestations. 



The ability to perfomi skilled mo\'e- 

 ments is conducive to a marked enrich- 

 ment of the mind's structure and the 

 high develo])ment of the neoi)allium, 

 which is the material ex]:)ression of that 

 enrichment. There are several reasons 



