372 



PHYSIOLOGY 



CHAP. 



There are other questions with regard to which scientists are 

 either not agreed or have so far failed to solve ; of these we will 

 consider two : the part of the world in which the transformation 

 of man took place and the precise determination of the progenitor 

 of man. Two theories strive for the pre-eminence : one considers 

 that man is derived from a single animal form and that his trans- 

 formation therefore took place in a single spot (monogenism or 

 the monopliiletic theory} ; the other that the different human 

 races are derived from various anthropomorphous forms, and that 

 the transformation took place in different parts of the world 

 (polygenism or the polyphiletic theory}. 



B. 



FIG. 138. Median curves of the Neander Valley skull and of an ancient Egyptian skull 

 }. Schwalbe. (M. Hoernes.) 



byG. 



The arguments adduced in favour of one or other of these 

 theories are all of a more or less indirect nature, and cannot be 

 called absolutely convincing. They refer to the morphological 

 characteristics common to the various existing human races or 

 differing in them, and to those extinct characteristics of which 

 we have fossil remains ; to the general properties of heredity and 

 reciprocal fruitfulness between individuals of the different races ; 

 to the characteristics of civilisation and culture distinguishing 

 the various races from one another, etc. It will thus be seen 

 that this problem is intimately connected with the fundamental 

 question of evolution upon which we dwelt briefly in Chap. II. 

 of Vol. I. 



