SOCIAL LIFE OF ORGANISMS 435 



Among many species of birds and mammals there is a degree of 

 social life that extends somewhat beyond mere gregariousness. The 

 Russian explorer Peter Kropotkin has brought together in his very 

 interesting book, " Mutual Aid a Factor in Evolution," hundreds 

 of examples of animals that hunt in groups, or post sentinels to 

 guard against danger, or fight off attacks of enemies through con- 

 certed action, or in other ways show mutual interrelations within 

 the species. 



462. Interdependence. Every one of us is dependent upon 

 others of the same species in hundreds of ways. As members 

 of the community we are dependent upon each other for vari- 

 ous kinds of personal and specialized services. We depend 

 upon community action for our safety from various plants and 

 animals, as well as from antisocial individuals who would 

 prey upon the rest, and from inanimate dangers, such as 

 fire and flood and storm. We depend upon each other as 

 members of the state or nation in the exchange of materials 

 that are found in some regions but not in others, and upon 

 this is founded all of our commerce. As members of the 

 state or nation we depend upon joint action for the regu- 

 lation of those things that affect the very conditions of exist- 

 ence, as the resources of the soil and the waters, the safety 

 of highways and waterways, the protection of food sup- 

 plies, the prevention of infection of man or domesticated 

 plants and animals, and so on. As members of the human 

 race we are dependent upon those of other countries, not 

 only for materials that are restricted in their distribution, 

 but even more for ideas arising out of different experiences. 

 Modern science, upon which rests so much of our present- 

 day advance in general welfare, is altogether an international 

 product. Every discovery and every invention rests upon hun- 

 dreds of other discoveries and inventions made by men and 

 women of many nations and of several generations. What 

 we call civilization is an accumulation of the most valuable 

 thoughts of all peoples. 



