THE UNIQUENESS OF THE INDIVIDUAL 



to see in detail how senescence has become shaped into its 

 distinctive pattern — the early onset and slow progressive fulfil- 

 ment that the curve of the force of mortality so conspicuously 

 reveals. Some of the agencies described seem to suggest a 

 rather precipitous onset of senescence — more like that which 

 befell the expatriates of Shangri-La than that suffered by the 

 inhabitants of the world at large. But even allowing this short- 

 coming, I think it must be clear that the origin and evolution 

 of senescence is not an insoluble genetical mystery, however 

 mysterious it may be in other ways. The geneticist can see how 

 it might well have happened; its occurrence does not outrage 

 his sense of the fitness of things. So perhaps I was unduly 

 disrespectful to Weismann's memory when I poked fun at his 

 conjectures on senescence. In very broad outline they were 

 probably not erroneous, at least in so far as natural selection 

 was recognized as the instrument of its origin and perpetuation. 

 I said earlier, as you may remember, that there was some truth 

 amidst a good deal of what we can now see to be nonsense, and 

 that it would stir up his successors to think up a more polished 

 and cogent explanation. Not much more than this can be said 

 of any biological theory of comparable pretensions, and I shall 

 count myself lucky if I hear an equally sympathetic criticism 

 of my own. 



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