6 SOCIAL HEREDITY AND SOCIAL EVOLUTION 



add a third in the fact that man alone universally 

 develops societies and government. It is true that 

 societies are not wanting among lower animals, and 

 some sort of government occasionally appears. But 

 these are commonly based upon a somewhat differ- 

 ent principle from those of mankind. This point we 

 will not dwell upon here, for it is the primary topic 

 for discussion in this whole work, and will be exten- 

 sively developed in later chapters. 



Natural Forces Sufficient to Explain Natural Phenomena. — 

 The acceptance of the reality of a natural origin of 

 the human race by evolution thus comes to rest upon 

 exactly the same basis as that of the rest of the 

 animal kingdom, and it stands and falls with the 

 general theory of evolution. Now, no thinker can 

 fail to realize that the evolutionary theory has re- 

 ceived its almost universal acceptance from two gen- 

 eral lines of reasoning. The first is the direct evi- 

 dence derived from the collection of facts such as 

 above mentioned. The second is a broader one and 

 lies in the fact that this conception falls into line 

 with the general tendency of thought. For cen- 

 turies science and philosophy have been endeavoring 

 to group the facts of nature under the influence of 

 definite forces acting by definite laws. As we have 

 studied more and more deeply into nature we have 

 found ourselves able to remove from the realm of 

 miracle one after another of the former mysteries 

 of nature and put them in their place as due to 

 known forces acting by known laws. Step by step 

 has this comprehension of nature advanced as as- 

 tronomy, chemistry, physics, geologj^ have been sub- 

 jected to more and more rigid scrutiny, and every 

 step taken has been leading in one general direction. 



