THE EVOLUTION OF THE BRAIN 



searching for the truth and is competent to appreciate the 

 significance of the facts revealed in the great adventure of 

 exploring the structure of the human body cannot fail to 

 discover that he himself is carrying about with him, inscribed 

 in the very texture of his body, the record of his ancestry 

 and of an inheritance that links him to all other living 

 creatures. 



It is often contended that such an interpretation of the 

 evidence is merely a theory, or even nothing better than a 

 mere working hypothesis. I want to assure my readers that 

 such statements are very misleading — that they are actually 

 evasions of the truth. Man's kinship with other living crea- 

 tures is established by evidence afforded by his own struc- 

 ture, by the mode of development of his body, by the mode 

 of action of his every tissue. We can clearly see, in the most 

 concrete application of the term, a blood relationship. 



For special consideration I have selected one particular 

 organ of the body, the brain, because it raises the problem, 

 of the evolution, not merely of man's physical body, but of 

 his mind, which, after all, is his most distinctive attribute. 

 By virtue of his mental endowment man enjoys a wide vision 

 of the world in which he lives and a high appreciation of its 

 beauties. This endowment confers upon him powers of 

 insight and foresight that are denied to all other living crea- 

 tures. By means of speech, which the human brain makes 

 possible, he is able to share his knowledge with his fellows, 

 to learn from them, and to hand on the results of his accu- 

 mulated experience from one generation to another. 



Remembering what the human mind has achieved, the 

 wide range of thought it has attained, the feeling for truth 

 and beauty it has cultivated, the wonderful institutions it 

 has created, the flights of constructive imagination it has 

 expressed in literature and science in interpreting the mean- 



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