166 DOCTRINE OF EVOLUTION 



hands and knees in the position of a tailed monkey, 

 the eyes look straight into the ground, for the bulging 

 cranium has pushed out over the jaws and face so that 

 they lie under the brain-case instead of in front. A 

 person in this position can bend back the head so as to 

 look ahead, but the strain is too great for comfort. 

 Rising to the knees, and lifting the hands from the 

 ground, a feeling of ease at once succeeds that of tension. 

 In the course of evolution accomplished primarily by 

 the increase of the higher portions of the brain, the 

 erect position has been assumed gradually and naturally, 

 and to maintain it has necessitated many other changes 

 in skeleton and muscles ; for example, the pelvis has 

 broadened to support the intestines, which bear down- 

 wards instead of upon the abdominal walls ; a double 

 curve has arisen in the axis of the vertebral column, 

 giving an easier balance to the upper part of the body 

 and the head. Countless structures of the human 

 frame testify to an originally four-footed position and to 

 a rotation of the longer axis through an angle of ninety 

 degrees, as evolution has produced the human type. 



The conclusion that the human brain has made 

 mankind is thus established as one of fundamental 

 importance. Proceeding further, we learn that this 

 organ proves to be essentially the same as the brain 

 of lower primates ; it does not gain its greater size and 

 efficiency by the origination of wholly new and unique 

 parts, but solely by the further elaboration of the ones 

 present in lower forms. In a word, it is only a differ- 

 ence in degree and not in essential kind that separates 

 man from the apes and other primates. Human nature 

 is animal nature, and human structure is animal struc- 



