2 SOCIAL HEREDITY AND SOCIAL EVOLUTION 



human skulls that have as yet been found there are 

 several that indicate a being of lower brain capacity 

 than man of to-day; and there are one or two that 

 seem to be so distinctly intermediate between man 

 and the ape that there has been a dispute as to 

 whether they were really men or some especially 

 highly developed ape. Moreover, these human 

 fossils carry the history of man back to a much 

 earlier age than was at one time thought possible, 

 and thus have given a far longer period to human 

 evolution than we formerly supposed. Embryology 

 teaches the same lesson. The human embryo, like 

 that of other animals, passes through a series of 

 stages more or less representing the earlier types 

 of animals in the earth's history. At one period it 

 develops gill slits on the sides of its neck like a fish ; 

 at another it possesses a well developed tail; in 

 short, like the embryo of a cat or a dog, it passes 

 through stages that in a measure represent the past 

 history of the animal kingdom. 



It has been these lines of argument primarily 

 that have led to the general acceptance of the doc- 

 trine of organic evolution. Now, we may perhaps 

 deny their cogency entirely and therefore refuse to 

 accept the theory of evolution in toto; but if we 

 accept them as sujB&cient to convince us of a gen- 

 eral evolutionary history of animals, it is simply 

 mental suicide to refuse to apply them to mankind. 

 Logical thinking forces us either to accept the evo- 

 lution doctrine as applying to physical man or to 

 deny entirely the truth of any evolutionary history 

 of animals. Since the patient search for evidence 

 during the half century or more since Darwin has 

 convinced thinkers generally of the truth of the 



