Epilogue: What Comes of Studying Vertebrates 811 



vertebrates from the necessity of living at any time in or near bodies 

 of water. The third was when feathers enabled reptile-like animals to 

 achieve aerial locomotion. Each of these three great events, all depend- 

 ing on structural modification, required tens or hundreds of thousands 

 of years for its consummation. Then, in comparatively recent geologic 

 time, something unique happened. Some prehuman or apelike primate; 

 used an external object as a tool. Prior to that, action upon the en- 

 vironment had been by direct impact of tooth, claw, or nail. There may 

 have been a long period of vague groping and occasional accomplish- 

 ment of unforeseen results by random wielding of some object grasped 

 by the hands. But eventually came a time when a primate purposefully, 

 and with prevision of the result, interposed a stick or other implemenl 

 between his hand and the object to be affected, and so the first step 

 toward the "Machine Age" of man was taken. It may have happened 

 in a second, but it is impossible to say what long ages may have been 

 required for the building up of the mental faculties of which the act 

 gives evidence, and for the development of the cerebral mechanism 

 concerned in their mediation. However that may have been, that 

 simple act announced that the vertebrates, having long since made 

 conquest of water, land, and air, had arrived at the threshold of a new 

 domain. Thenceforth evolution was to proceed in the realm of ideas. 

 Has primate intelligence increased since that day when a tool was 

 first used? We regard the invention of the telephone and radio as great 

 achievements. But it must be remembered that each of these marvelous 

 modern inventions has developed slowly and step by step in an en- 

 vironment already rich in a stimulating variety of mechanisms of the 

 same general sort. The first primate tool was a complete innovation. 

 It is even possible that, in an environment quite devoid of tools, it may 

 have required nearly as much imagination to conceive the idea of 

 definitely fashioning an implement of wood or stone as it did to think 

 up, one by one, the numerous gadgets which collectively constitute 

 a telephone. However, in view of the fact that, from primitive insecti- 

 vore up to higher primate, there has been a steady advance in the 

 degree of development of the brain and a corresponding progress 

 toward the achievement of intelligent behavior, it seems fair to assume 

 that mental faculties have continued to improve since the days of the 

 first toolmaker. But it is a slow process, presumably because increase 

 of intelligence must be linked with structural changes in the brain. 

 The content of the human mind, knowledge, has vastly increased, but 

 there is no convincing evidence that intelligence has increased within 

 the relatively short period of recorded human history. Aristotle's brain 

 was certainly quite as good as any modern brain. 



