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 creatures is established by evidence afforded by his own structure, 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 creatures. 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 accumulated 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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