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In order to gain knowledge regarding the probable 

 future evolutionary development of the human species, 

 we may consider the evolution of some pre-human species 

 which have lived on the Earth, or the descendants of which 

 continue to live on the Earth. The vertebrate line of ani- 

 mals, of which Man is a product, may be traced to the 

 early armoured fish (ostracoderms) which first appeared 

 in the seas in the Ordovician period which started 500 

 million years ago. There followed the sea-scorpions in the 

 Silurian period starting 440 million years ago, and then the 

 ancestors of modern fish (with scales) in the Devonian 

 period starting 400 million years ago. Early amphibious 

 animals appeared at the end of the Devonian, and continued 

 to develop into the Carboniferous period which began 350 

 million years ago. During this period reptiles became the 

 first animals to breed on land, and they rose to terrestrial 

 dominance in the succeeding Permian period starting 270 

 million years ago. In the next geological period, the Tri- 

 assic, beginning 225 million years ago, the first mammals 

 evolved from the reptiles, but these forerunners of Man 

 remained small throughout the next two periods (the 

 Jurassic, starting 180 million years ago, and the Creta- 

 ceous, starting 135 million years ago) in comparison 

 with the dinosaurs which ruled the land until their ex- 

 tinction during the mountain building activity starting at 

 the end of the Cretaceous period. By this time the placental 



