THE UNIQUENESS OF THE INDIVIDUAL 



How it is that the force of natural selection becomes attenu- 

 ated with increasing age I hope to explain very fully later. 

 What is important in the meantime is that one should realize 

 how, in the last seventy-five years, the whole pattern of the 

 incidence of selective forces on civilized human beings has 

 altered. We are not now waiting for our ageing population to 

 produce biological changes of first-class importance, as some 

 demographers seem to suggest. The changes have already 

 happened. We have already entered a new era in the biological 

 history of the human race. 



II 



It is a curious thing that there is no word in the English 

 language that stands for the mere increase of years; that is, for 

 ageing silenced of its overtones of increasing deterioration and 

 decay. At present we are obliged to say that Dorian Gray did 

 not exactly 'age% though to admit that he certainly grew older. 

 We obviously need a word for mere ageing, and I propose to use 

 ''ageing'' itself for just that purpose. 'Ageing' hereafter stands 

 for mere ageing, and has no other innuendo. I shall use the 

 word ''senescence'' to mean ageing accompanied by that decline 

 of bodily faculties and sensibilities and energies which ageing 

 colloquially entails. Dorian Gray aged, but only his portrait 



influence the mode of propagation of their genes. A gene for grandmotherly 

 indulgence should therefore prevail over one for callous indifference, in 

 spite of the fact that the gene is propagated per procurationem and not by 

 the organism in which its developmental effect appears. Selection for 

 grandmotherly indulgence I should describe as 'indirect', and the indirect 

 action of selection becomes important whenever there is any high degree of 

 social organization. The genes that make for efficient and industrious 

 worker bees, for example, are of vital importance to the bee community, 

 though not propagated by the worker bees themselves. Dr Kermack points 

 out that the distinction between 'direct' and 'indirect' selection can easily 

 be misleading, because in the outcome their effects are both the same. Let 

 us admit, however, that there is a distinction of genetical procedure, though 

 it might well have been embodied in better-chosen terms. 



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