DARWINISM AND MODERN GENETICS 



the non-human biological world. It is only for those human 

 variations which affect the bodily structure and composition- 

 such things, for instance, as variation in blood group antigens, 

 or shapes and colours of hair, skin, and other organs— that the- 

 ories of biological inheritance are an adequate guide to human 

 affairs. In all the other, and much more important, human 

 variations, which affect mental qualities, we must never omit 

 from our consideration man's alternative system of inheritance 

 which arises from his existence as a social being who can, and 

 indeed must, learn from his ancestors. 



This human system of social inheritance clearly follows quite 

 different laws from those of biological inheritance, and the evo- 

 lution of man's mental and cultural abilities does not follow 

 the laws of sub-human evolution. Cultural influences, that is 

 to say, those that can be transmitted from one individual to 

 another by processes of teaching and learning, can produce 

 changes in man with incomparably greater speed than could 

 be achieved by the biological mechanism of heredity. 



An extremely striking case of this has ecently been described 

 in detail by the American anthropologist Margaret Mead (1956). 

 In 1928 she made a detailed study of the Manus tribe in New 

 Guinea, a people who, at that time, were living in conditions 

 comparable to those of the Stone Age. During the Second 

 World War large numbers of American and Australian troops 

 were based in this region, and the Manus people were brought 

 into extensive contact with men in the twentieth-cenutry phase 

 of cultural and political evolution. Mead made a renewed 

 study of the Manus in 1953, and showed how they had acquired 

 at least the rudiments of a democratic and technologically mod- 

 ern society. This stupendous evolutionary advance from the 

 Stone Age to the present has taken place within the lifetime of 

 single individuals; that is to say, it cannot have depended at all 

 on changes in the genetic constitution of the population. 



Man's endowment of biologically determined potentialities 

 is, in fact, not so much the means by which the evolution is 

 brought about, but rather the stabilizing factor that prevents 

 retrogressive evolutionary changes going too rapidly. Even 

 men who have lived for many generations under social and 

 political conditions which prevent the development of the 



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