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.” 
