تکامل: سنتز مدرن Evolution : the modern synthesis

In 1936, I had to find a subject for the presidential address to the Zoology Section of the British Association. After some hesitation, I chose “Natural Selection and Evolutionary Progress”, since it seemed to me that these were two interrelated topics of fundamental biological importance, yet on which much misapprehension existed. Even among professional zoologists the modern conception of natural selection and its mode of operation is quitedifferent from that of Darwin’s day, but much of the research on which the changed oudook is based is so recent that the new ideas have not spread far. The idea of evolutionary progress, on the other hand, has been undeservedly neglected. Thus it seemedto me valuable to attempt to give a broad account of the two concepts and their relation to each other.The result exceeded my expectations. So many of my colleagues expressed interest and the wish that the address might be available in more extended and more permanent form, thatI decided to essay expanding it into a book.The result is the present volume. I am fully conscious of its limitations and imperfections, but I believe that it will serve a useful purpose. The writing of it has so much clarified my own thinking, and the discussion of the problems that arose with colleagues has resulted in so many ideas and points of view which were novel both to them and to myself, that I am encouraged to believe it will be of general service. I also feel sure that aclassification and analysis of evolutionary trends and processes as observed or deduced in nature, and the attempted relation of them to the findings of genetics and systemadcs, is of first-class importance for any unified biological outlook; and since others better equipped than I seem reluctant to attempt the task, I have tried my hand at it.