II 



DARWIN'S PREDECESSORS 

 BY J. ARTHUR THOMSON. 



Professor of Natural History in the University of Aberdeen. 



IN seeking to discover Darwin's relation to his predecessors it 

 is useful to distinguish the various services which he rendered to 

 the theory of organic evolution. 



(I) As everyone knows, the general idea of the Doctrine of 

 Descent is that the plants and animals of the present-day are the 

 lineal descendants of ancestors on the whole somewhat simpler, that 

 these again are descended from yet simpler forms, and so on back- 

 wards towards the literal " Protozoa " and " Protophyta" about which 

 we unfortunately know nothing. Now no one supposes that Darwin 

 originated this idea, which in rudiment at least is as old as Aristotle. 

 What Darwin did was to make it current intellectual coin. He gave 

 it a form that commended itself to the scientific and public intelli- 

 gence of the day, and he won wide-spread conviction by showing with 

 consummate skill that it was an effective formula to work with, a key 

 which no lock refused. In a scholarly, critical, and pre-eminently 

 fair-minded way, admitting difficulties and removing them, fore- 

 seeing objections and forestalling them, he showed that the doctrine 

 of descent supplied a modal interpretation of how our present-day 

 fauna and flora have come to be. 



(II) In the second place, Darwin applied the evolution-idea to 

 particular problems, such as the descent of man, and showed what a 

 powerful organon it is, introducing order into masses of uncorrelated 

 facts, interpreting enigmas both of structure and function, both 

 bodily and mental, and, best of all, stimulating and guiding further 

 investigation. But here again it cannot be claimed that Darwin was 

 original. The problem of the descent or ascent of man, and other 

 particular cases of evolution, had attracted not a few naturalists 

 before Darwin's day, though no one [except Herbert Spencer in the 

 psychological domain (1855)] had come near him in precision and 

 thoroughness of inquiry. 



(III) In the third place, Darwin contributed largely to a know- 

 ledge of the factors in the evolution-process, especially by his analysis 



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