320 COSMIC FSIL0S0PR7. [ft. H. 



take the thousands of centuries during which the human race 

 has covered both the eastern and the western hemispheres, 

 and compare witli them the entire duration of recorded 

 human history, we shall have set before us a profitable subject 

 of reflection. Since the period during which man has pos- 

 sessed sufficient intelligence to leave a traditionary record oj 

 himself is hut an infinitesimal fraction of the period during 

 which he has existed upon the earth, it is hut fair to conclude 

 that, during those long ages of which none hut a geologic record 

 of his existence remains, he was slovAy ACQUIRIXG that superior 

 intelligence vjhich now so widely distinguishes him from all 

 other animals} Throughout an enormous period of time, his 

 brain-structure and its correlated intellectual and emotional 

 functions must have been constantly modified both by natural 

 selection and by direct adaptation, while his outward physical 

 appearance has undergone few modifications ; and of these 

 the most striking would seem to be directly or indirectly 

 consequent upon the cerebral changes.* 



1 The reader will not fail to note that, even were the question otherwise 

 left open, after the conclusive evidence summaiized in chapter ix., this point 

 by itself is a point of truly enormous weight in favour of the theory of man's 

 descent from some lower animal. Upon the theory that the human race was 

 created by a special miraculous act, its long duration in such utter silence is 

 a meaningless, inexplicable fact ; whereas, upon the derivation theory, it is 

 just what might be expected. 



^ To the general observer, as to the anatomist, the most notable points of 

 difference between civilized and uncivilized man, as well as between man and 

 the chimpanzee or gorilla, are the differences in the size of the jaws and the 

 inclination of the forehead. The latter diff>'rence is directly consequent upon 

 increase of intelligence ; and the former is indirectly occasioned by the same 

 circumstance. For the diminution of the jaws, entailed by civilization, is, 

 no doubt, primarily due to disuse ; and the disuse is occasioned partly by dif- 

 ference in food, and partly by the employment of tools, and the consequent 

 increased reliance upon the hands as prehensile organ.s. All these circum- 

 stances are the result of increased intelligence. And in addition to this, it is 

 probable that increased frontal development has directly tended, by correla- 

 tion of growth, to diminish the size of the jaws, as well as to push forward 

 the bridge of tlae nose. To the increased reliance upon the hands as prehen- 

 sile organs— a circumstance which we have seen to be in an especial degree 

 characteristic of developing intelligence — is probably also due the complete 

 attainment of the erect position of the body, already })artially obtained by 

 the anthrojioid apes. Cerebral development thus accounts for all the con 

 spicuous physical ])eculiarities of man except his bare skin, — a phenomeno? 

 lor which no satisfactory explanation has yet^been suggestedL 



