CHAPTER 24 



CONTINUITY OF THE RACE 



In the last two chapters we have followed 

 the duplication of cells and tlie develop- 

 ment of an individual. Now we come to the 

 next great problem, namely, the linking of 

 each generation to the next. From the be- 

 ginning of life on the earth every generation 

 of living things has been tied to the preced- 

 ing through the tiny genes that are handed 

 on with meticulous care. It is staggering to 

 reflect that the next generation of human 

 beings on this earth, over two billions of 

 them, will come from nuclear material that 

 will not quite fill a thimble. Just how this 

 material is passed from one generation to 

 the next is the subject of genetics, the sci- 

 ence of heredity. It is an infant science, 

 having gained recognition as a science only 

 during the present century, although its 



beginnings extend back many thousands of 

 years. 



HISTORICAL BACKGROUND 



The fact that "like begets like" has been 

 known by man since early times. This ob- 

 servation probably came from his first 

 efforts at domestication of plants and ani- 

 mals. Records indicate that one of the first 

 animals to have its life interwoven with the 

 lives of early men was the dog. Undoubtedly 

 the first association was casual, but through 

 selection tlie animal became more and more 

 the kind of beast that best fitted man's per- 

 sonality and habits. It must have required 

 thousands of years of selection, intentional 

 or accidental, to produce an animal so beau- 



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