PART III 

 EVOLUTION OF THE VERTEBRATES 



The Greek philosophers and scientists, under the influence of 

 Empedocles and Aristotle, realized that species of plants and 

 animals were not immutable, and that special creation could not 

 account for the innumerable changes which have occurred among 

 living organisms. But after the destruction of Greek civilization 

 in Greece and Alexandria science became static, or retrogressed, 

 under the influence of tradition and authority. AYith the revival 

 of Greek culture evolution again crept into the philosophical 

 literature; but it was not until Descartes carried the mechanistic 

 theory to its logical conclusion that any coherent effort was made 

 to controvert the prevailing idea that each species was created 

 as an unchanging unit. 



So rock-bound had the dogma of special creation become that 

 Buffon, one of the first revivers of the evolutionary theory, 

 found it necessary in the middle of the eighteenth century to 

 qualify his scientific speculations with the statement that all 

 divine creations were immutable. Toward the end of the century 

 the grandfather of Charles Darwin, Erasmus Darwin, conjec- 

 tured that ''one and the same kind of living filament is and has 

 been the cause of all organic life". 



A few years after Darwin, Lmnarclz in 1809 published his 

 Philosophy of Zoology, a work which has gained permanence 

 as the first clear statement of the theory. Unfortunately the in- 

 fluence of the dead Linnaeus and the contemporary Cuvier were 

 sufiicient to obscure the results of the great naturalist's observa- 

 tions; and it was not until fifty years later that the theory 

 of evolution was placed upon a firm foundation. 



Although during the years between 1809 and 1859 a number 

 of papers had been published which gave hints of a workable 

 theory as to the cause of evolution, the essential facts of evolu- 

 tion remained unnoticed until 1858 when two papers were read 

 before the Royal Society in London. One was by Wallace who 

 had been working in the East Indies, and the other by Charles 

 Darwin who for twenty years had carefully collected data in 

 England and during a long scientific voyage. 



