Chap. IV.] MANNER OF DEVELOPMENT. 103 



CHAPTER IV. 



ON THE MANNER OF DEVELOPMENT OF MAN FROM SOME 

 LOWER FORM. 



Variability of Body and Mind in Man. — Inlieritancc— Causes of Varia- 

 bility. — Laws of Variation the same in Man as in the Lower Animals. 

 — Direct Action of the Conditions of Life. — Effects of the Increased 

 Use and Disuse of Parts. — Arrested Development. — Eeversion.- — Cor- 

 related Variation. — Eate of Increase. — Checks to Increase. — Natural 

 Selection. — Man the most Dominant Animal in the World. — Impor- 

 tance of his Corporeal Structure. — The Causes which have led to his 

 becoming erect. — Consequent Changes of Structure. — Decrease in 

 Size of the Canine Teeth. — Increased Size and Altered Shape of the 

 Skull. — ^Nakedness. — Absence of a Tail. — Defenceless Condition of 

 Man. 



We have seen in the first chapter that the homological 

 structure of man, his embryological development and the 

 rudiments which he still retains, all declare in the plainest 

 manner that he is descended from some lower form. The 

 possession of exalted mental powers is no insuperable ob- 

 jection to this conclusion. In order that an ape-like crea- 

 ture should have been transformed into man, it is neces- 

 sary that this early form, as well as many successive links, 

 should all have varied in mind and body. It is impossible 

 to obtain direct evidence on this head ; but if it can be 

 shown that man now varies — that his variations are in- 

 duced by the same general causes, and obey the same 

 general laws, as in the case of the lower animals — tliere 

 can be little doubt that the preceding intermediate links 



