CHAPTER LI 



PEOPLE FOR THE EARTH 



Questions. 1. In what ways is the human race improving? 2. How 

 are improvements in the race brought about ? 3. Why did civiHzations 

 die out in the past ? 4. If all the babies were given the same kinds of 

 feeding, treatment, and so on, would they grow up to be more alike? 

 5. Are all the children of the same parents alike in every way ? 6. Are 

 the children of educated people more intelligent than the children of 

 ignorant people ? 7. Is insanity inherited ? Is criminahty ? Is alcohol- 

 ism ? 8. Is it wrong for cousins to marry ? 



414. Who shall inherit the earth? In every inhabited area the 

 composition of plant life and of animal life is constantly shift- 

 ing. Some species are increasing and spreading out, others giv- 

 ing way in numbers or moving into new regions. Any existing 

 species may become extinct, as have many species of plants and 

 animals in the past ; and any existing species of comparatively 

 little importance may in the future, under special conditions, 

 come to be a great factor in the total life. Man in his wander- 

 ings has carried with him his domesticated plants and animals. 

 He has also distributed many of the parasites of his own body 

 and of his cultivated organisms. These movements and migra- 

 tions may upset the balance of life in a new locality. In some 

 places insects or weeds will take possession and effectively hold 

 the earth against man. The jungle has to be conquered bit by 

 bit. Man is determined to dominate the earth, and he has the 

 capacity to rule. It is by no means certain, however, that the 

 gains of the past will continue, or that what we call civilization 

 will endure forever. We know at least that civilizations in the 

 past rose to great heights and then fell to pieces. 



415. Dangers in civilization. The conquest of infectious dis- 

 ease, together with the application of our knowledge regarding 



s8o 



