THE UNIQUENESS OF THE INDIVIDUAL 



Research on evolution was never so lively and pointed as it 

 is to-day. It runs along several different lines. First, beginning 

 in the 1920s, was the refounding of Darwinism upon the prin- 

 ciples of Mendelian genetics — the formulation of a genetical 

 theory of natural selection — and this was mainly the work 

 of R. A. Fisher, J. B. S. Haldane and Sewall Wright, though 

 the names of Norton and Lotka are by no means to be for- 

 gotten. At first these endeavours were purely theoretical, but 

 in due course, and with all the economy of labour that only a 

 deep theoretical grasp of the problem could have made possible, 

 its predictions were tested in the laboratory and in the field. 

 (It is indeed only in genetics that there can be said to be a 

 ""theoretical biology**, in the sense in which theoretical physics 

 is so described.) Thanks very largely to the work of the new 

 Oxford school of evolutionists under E. B. Ford it is now 

 possible to witness the act and not merely the accomplished 

 fact of evolution; we have now an altogether new understand- 

 ing of the extraordinary delicacy and responsiveness with 

 which the genetical structure of a population can be remoulded 

 by selective forces. Standing a little aside from these accom- 

 plishments, because it took origin from the study of develop- 

 ment rather than of heredity, is C. H. Waddington''s important 

 demonstration of how a change which was at first brought about 

 by the action of the environment may, under the influence of 

 selection, become genetically ingrained: habit becoming herit- 

 age, or nurture nature, as you will. Then, finally, there are the 

 grand speculations on evolution that perpetuate an older 

 tradition of thought. For example, it has become ever clearer, 

 since Garstang and de Beer first turned our thoughts in that 

 direction, that paedomorphosis is a fundamental stratagem of 

 evolution — that animals can, so to speak, slough away the 

 latter ends of their life histories and build their lineages anew 

 upon larval or even embryonic forms. There can be little reason- 

 able doubt that vertebrate animals arose in this manner from 



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