12 THE HUMAN SPECIES 



Xenophanes argued from the occurrence of fossilised marine 

 animals in high mountains that the earth had passed from a 

 semi-fluid to a solid state. Parmenides, like Democritos, 

 thought the development of man due to the influence of the 

 sun's heat on the earth. In the works of Plato and Aristotle, 

 his disciple, nothing is to be found on the origin of living- 

 organisms. Aristotle, the naturalist so far in advance of his 

 contemporaries, limits himself to a classification of plants, 

 animals and man, in a regular system, and a description of the 

 same on general lines, but as regards their origin he preserves 

 a complete silence. 



It is owing to the predominant influence of Aristotle on 

 the philosophy of the Middle Ages that the scholastics and 

 their followers so seldom ventured to formulate independent 

 theories on the origin of the world and of man. Strange to 

 say, Ebn Tophail, the Arabian philosopher who died towards 

 the end of the twelfth century, mentions in his celebrated book 

 an earthborn autochthon. " In the temperate zones," he 

 says, " autochthones may actually have existed in former times, 

 the earth producing out of itself, per generationem <zquivocam> 

 human forms capable of absorbing the rational spirit, eternally 

 radiating from the Godhead." Even the anti-scholastic Andreas 

 Caesalpinus in the seventeenth century, held it to be possible 

 that animals originated in their perfect form from the effect 

 of the sun's heat on the earth, since they could not have been 

 produced by generation. Other independent thinkers of the 

 sixteenth and seventeenth centuries, while adopting a monistic 

 standpoint, leave us nevertheless in doubt as to their conception 

 of the actual origin of organisms out of "divine substance, 

 itself one with God ". 



We pass on to the latter half of the eighteenth century 

 when cosmology seemed to enter upon a new era with Kant's 

 theory of the formation of the world. After stating that our 

 solar system with its moons and planets has been evolved 

 from nebulae, and showing that our earth must have required 

 an enormously long period of cooling and consolidation before 

 water could be formed on its surface, it might have been ex- 

 pected that he would extend the theory to organisms, but in 

 his later works, for instance, in the Criticism of the Teleo- 



