584 HUMAN BIOLOGY 



efficiency. While these improvements of environment and 

 of development do not directly improve heredity they do 

 open the way to an indirect attack upon that problem. 

 Whatever is accompHshed in the way of eugenics or euthenics 

 must be through inteUigence, education and social coopera- 

 tion and of these three factors education is the one that can 

 be most readily controlled. Education in the broadest sense 

 is the chief hope of human progress. 



THE DISTANT FUTURE , 



When one looks back upon a billion years of hfe upon 

 this planet and forward to another possible billion years, 

 he cannot fail to inquire whether there is likely to be any 

 such evolutionary progress in the future as there has been 

 in the past. Will the human race persist and become more 

 perfect in body, mind and society, or will it also go the way 

 of every species of former geological ages? Of course one can 

 only speculate about such questions, but there are certain 

 scientific data that may serve as a basis for such speculations. 



In the past, progressive evolution has led to increasing 

 specialization and integration of increasing numbers of 

 living units; to increasing complexity and perfection of 

 structures, functions and adaptations; to increasing respon- 

 siveness, capacity of profiting by experience, intelligence, 

 control over environment, freedom. The pressure of over- 

 production of individuals and variations has forced living 

 things, like plastic clay, into every possible crack and 

 cranny and way of escape. Whenever in the past evolution 

 has gone as far as possible in any single line, some other path 

 of outflow has been found. Organisms have probably already 

 explored every path that was possible to them. But in the 

 course of past ages new paths have been made possible not 

 only by changes in environment but also by changes in the 

 organisms themselves. 



One of the most important lines of evolution in the past 

 was the path of multicellularity, by which multitudes of 

 cells are integrated into tissues, organs, systems, persons, 

 thus affording means of progress in size and in differentiation 

 and perfection of structures, functions and adaptations, 



