MEDICAL ADVANCEMENT AS PRECLUDING HUMAN EVOLUTION 23 1 



Whenever a favorable tropism by means of variation accompanies 

 a physical character in an organism that is maintained by natural selec- 

 tion, it is also a step toward the ultimate* development of consciousness. 



Before consciousness develops, and consequently the power to learn 

 by experience, adaptation of the organism takes place entirely through 

 selection. In ever-changing conditions lower animals must have their 

 bodies constantly modified in order to survive. They must become 

 smaller to escape detection, must have greater teeth and claws for defense, 

 they must have their fur thickened when migrating into a colder climate. 



When the stage of learning by experience is reached mind becomes 

 the principal factor of selection, and the advancement of intelligence 

 is comparatively rapid. The bodily form becomes fairly stable and 

 tends to change only where mental and physical characters are correlated. 

 Wallace has pointed out that the faculties in man are variable just as 

 physical characters are and these variations tend to be inherited. They 

 would, therefore, be advanced and perfected by natural selection. 



Sagacity, reason, imitation, and sociability are variations which are 

 mental in their character. In rudest society according to Darwin 1 

 the most sagacious individuals who would, therefore, invent and use 

 the best weapons would be most powerful and also rear the most off- 

 spring because of the increased control over Nature and their fellows 

 which they would have. The tribes including the greater number thus 

 endowed would supplant the other tribes. Reason also develops through 

 variation and is seized upon for fitness. Those that cannot be caught 

 in a trap and can devise strategies have an advantage over their fellows. 

 Imitation also is a powerful factor in the selection for intelligence. 

 Those individuals who cannot imitate the strategies in which their 

 most intelligent fellows participate will be eliminated by competition. 



Sociability, or rather gregariousness, develops long before there is 

 intelligence. This also may be regarded as a form of tropism. This 

 gregariousness is manifested by many lower forms, and even decap- 

 itated they will still in some cases maintain the instinct, this shows the 

 mechanical nature of it. Just as the hydrogen atoms will collect together 

 at the carbon pole in a battery so will these creatures aggregate in local- 



1 Descent of Man, Chap. 5. 



