October, 1928 



EVOLUTION 



TACE Seven 



especially trouble. But more contacts meant more sensation-facts 

 about the world, more things to consider and more actions to 

 decide on. It took brains to develop sensitivity of touch and sight 

 and hearing, brains to boss the lively body, brains to acquire skill 

 in hands and feet and body and eyes. Mammal activity brought 

 lots of troublesome problems and it took brains to work out prac. 

 tical solutions. In this active and aggressive world in which these 



ancestors of ours lived, better brains counted for moie than ever. 

 Natural selection did the rest. Keen competition and climatic 

 severity, those were two big selective factors that forced the 

 growth of the brains that made the man. 



The next article will take us back to the fishes, where our 

 hearing and posing and sense of balance began. 



The Plated Lizard Stegosaurus 



ALL the dinosaurs are extraordinary, but none more 

 extraordinary than Stegosaurus, the plated lizard. 

 He was about as tall as an elephant, but counting his 

 tail, somewhat longer. Unlike some of the dinosaur 

 tribe, he walked on all four feet, but his front legs were 

 relatively small, the tall and massive hind legs being 

 so centered as to carry the burden of his great weight. 

 Along the back of his body, neck and most of his 

 tail, ran two rows of thin, sharp-edged and alternating 

 plates, like the teeth of great saws. The largest were 

 two feet high and wide and an inch thick, except at the 

 heavier base where it einbedded in the beast's tough 

 hide. In life, the plates were probably covered with 

 horn, making them somewhat larger. 



Skeleton of Stegosaurus. 



Near the tip of the tail, two pairs of large spines 

 took the place of the plates. These spines varied in 

 length with different species, ranging from eight inches 

 to nearly three feet, with the largest base fully six inches 

 ill diameter. Like the back plates, the tail spines were 

 increased in outward size by a covering of horn. Swung 

 by the massive tail eight to ten feet long, the tail spines 

 made a most formidable weapon. 



But at his other end he was weak, for the head was 

 much too small and the brain inside proportionately 

 even smaller. Intelligence was utterly lacking, the 

 routine functions of life being conducted by the nerve 

 matter of the spinal cord. In fact, a portion of the 

 spinal cord at the base of the tail was enlarged to twenty 

 times the bulk of the brain. When Professor 0. C. 

 Marsh made and announced this discovery, the news- 

 papers made the most of it by reporting a creature with 

 two brains and B. L. T. of the Chicago Tribune took 

 the poetic liberty of ascribing doubled intelligence to 

 this most stupid of beasts. His poem makes poor science, 

 but excellent reading. 



"Behold the mighty dinosaur. 

 Famous in prehistoric lore. 

 Not only for his weight and strength 

 But for his intellectual length. 



"You U'ill observe by these remains 

 The creature had two sets of brains — 

 One in his head (the usual place). 

 The other at his spinal base. 



"Thus he could reason a priori 

 As well as a posteriori. 

 No problem bothered him a bit; 

 He made both head and tail of it. 



"So wise he tvas, so wise and solemn. 

 Each thought filled just a spinal column. 

 If one brain found the pressure strong 

 It passed a few ideas along. 



"If something slipped his forward mind, 

 'Twas rescued by the one behind. 

 And if in error he was caught. 

 He had a saving afterthought. 



"As he thought twice before he spoke. 

 He had no judgment to revoke; 

 For he could think, without congestion, 

 Upon both sides of every question. 



"Oh, gaze upon this model beast. 

 Defunct ten millions years at leasts 



This "model beast" may be gazed upon at the Ameri- 

 can Museum of Natural History, New York City, which 

 has a statuette restoration by Charles R. Knight. Yale 

 University has a mounted specimen and the National 

 Museum a life-size reconstruction. 



Statuette ot Stegosaurus 

 Courtesy American Museum of Natural History 



