afforded men opportunities to specialize in many different 

 occupations in which they made many discoveries of new 

 ways in which to control their environment. The resulting 

 increased effectiveness of material production led to men 

 having time for thought about their world, which gave 

 rise to science based on experiment. 



Although Man is clearly a still evolving species, and 

 we cannot of course predict with certainty to what new 

 species he will give rise in future millenia, we can examine 

 the nature of the long-term evolutionary changes under- 

 gone by earlier types of animals. Some well studied 

 animal evolutionary lines are those of the dinosaurs, the 

 elephants, the fish, the horse, and to some extent the apes 

 leading to man. 



The dinosaurs evolved from a group of reptiles known 

 as theriodonts, which lived in the Triassic period, the 

 theridonts having evolved from the cotylosaurs (Permian), 

 the cotylosaurs from the labyrinthodonts (Carboniferous), 

 and the labyrinthodonts from the choanicthyes (Devonian). 

 The choanicthyes were primitive armoured fishes, while 

 the labyrinthodonts were amphibious reptiles; the latter 

 became extinct in the Triassic period, but their primitive 

 reptilian cotylosaurian descendants gave rise to the more 

 advanced reptilian theriodonts before this happened. The 

 cotylosaurs themselves experienced extinction at the end 

 of the Permian period, while the theriodonts suffered the 

 same fate late in the Triassic period. However the therio- 

 donts had given rise to the dinosaurs before their extinction, 

 the first dinosaurs being only about six inches long. But these 

 reptiles continued to evolve into ever greater sizes, attain- 

 ing lengths of over 80 feet in some species, through the 

 Jurassic and into the Cretaceous periods, where the whole 

 group became extinct. Thus an evolutionary line, lasting 



