12 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 



prophecy of the importance of oxygen and oxidation in vital processes. 

 Anaximenes also introduced the idea of abiogenesis (spontaneous 

 generation of living substance), his idea being that animals and plants 

 arose out of a primordial terrestrial slime wakened into life by the sun's 

 heat. This primordial terrestrial slime is perhaps a prophecy of 

 Oken's "Urschleim" or of protoplasm. 



Xenophanes (576-480 B.C.), probably another pupil of Anaxi- 

 mander, "agreed with his master so far as to trace the origin of man 

 back to the transition period between the fluid or water and solid or 

 land stages of the development of the earth." He was the first to 

 recognize fossils as the remains of animals once alive, and to see 

 in them proof that once the seas covered the entire surface of the 

 earth. 



Heraclitus (535-475 B.C.), the first of a group of physicists, was the 

 great proponent of the philosophy of change. He was imbued with 

 the idea that all was motion, that nothing was fixed. '''Everything 

 was perpetually transposed into new shapes. " Although Heraclitus 

 did not apply his ideas to living creatures and their evolutions, his 

 philosophy was influential in molding the ideas of his successors. 



Empedocles (495-435 B.C.) " took a great stride beyond his predeces- 

 sors, and may justly be called the father of the Evolution idea 



He believed in Abiogenesis, or spontaneous generation, as the explana- 

 tion of the origin of life, but that Nature does not produce the lower 

 and higher forms simultaneously or without an effort. Plant life 

 comes first, and animal life developed only after a long series of trials." 

 He thought that all creatures arose through the fortuitous combina- 

 tion of scattered and miscellaneous parts which were attracted or 

 repelled by the forces of love or hate (the two great forces in Nature). 

 Thus arose every sort of combination of parts, some more or less har- 

 monious and complete, others with ill-assorted organization, lacking 

 in some parts, double or triple in others. Some of these combinations 

 could not survive, because of their incompleteness and incongruity, 

 but "other forms arose which were able to support themselves and 

 multiply. " This is a sort of vague prophecy of the survival of the 

 fittest or of natural selection. Four sparks of truth may be found in 

 Empedocles' philosophy, "first, that the development of life was a 

 gradual process; second, that plants were evolved before animals; 

 third, that imperfect forms were gradually replaced (not succeeded} 

 by perfect forms; fourth, that the natural cause of the production of 

 perfect forms was the extinction of the imperfect. " 



