520 THE EVOLUTION OF THE HUMAN FOOT. 



course did it follow? What organ preceded the others and led to 

 their gradual moditication ? Such are the questions that arise, and 

 we may readil}' see that they deal with a very complex problem. The 

 researches made during- the last few years in comparative anatomy, 

 though they may not enable us to give a linal answer to these ques- 

 tions, at least permit us to form serious h} potheses, and 1 think that 

 we are now authorized to suppose that, in the series of successive 

 moditications, the foot and the lower limbs have played a predominant 

 part. We may, then, according to the opinion expressed by M. Man- 

 ouvrier in his remarkable studies on the Pithecanthropus, consider 

 that the following were the successive steps of this evolution: 



Impelled by a necessity whose causes we can not now determine, 

 and which were, perhaps, due to changes in the fauna, the flora, or the 

 climate, our ancestors nuist, apparently, have descended by insensible 

 degrees from the trees and become accustomed to live on the ground. 

 In order to effect an adaptation to this new kind of existence, the 

 pelvic limb was naturally the first to be modified; the mobility of the 

 toes had to be diminished, the great toe to become less and less oppos- 

 able. It was also necessary that the knees should become straighter; 

 that the movement of the joints should be amplilied and, at the same 

 time, that the distal insertions of the ischio-ti))ial nuiscles should be 

 shifted to a higher position; it was necessary that the femur should 

 be lengthened, should acquire force. These moditications in the pelvic 

 limbs, which put them in advance of the rest of the organism, had at 

 the same time the adv^antage, as M. Manouvrier also remai'ks, of allow- 

 ing the thoracic limbs to become adapted in a more perfect manner 

 to the functions of prehension and to become gradual!}' transformed 

 into those highly improved organs that w^e now possess; they also 

 permitted the head to be raised and moved about in every direction, 

 opening a way in brief to all the other moditications. 



By this series of moditications it resulted that, at the end of the 

 Tertiary, during the Pliocene^ epoch, our arboreal ancestor was trans- 

 formed into an animal presenting, from certain points of view, vague 

 resemblances to the gibbon of the present day, and which seems to be 

 represented, according to the opinion of the most competent anato- 

 mists, by PithecanfJiropus erect us^ that form whose remains were found 

 In Java a few years ago. Even a superficial examination of the femur 

 of this creature shows that it was no longer a climber, but already a 

 walker in the full sense of the term, although it must have possessed, 

 more than the men of the present day, features of resemblance to its 

 ar})oreal ancestor. 



The passage from this ancestral type to man was easy, and it was 

 probably effected either at the end of the Pliocene or the beginning of 

 the Pleistocene. 



