2 



An Unsolved Problem 

 of Biology 



The problem I propose to discuss is that of the origin and 

 evolution of what is commonly spoken of as *'ageing\^ It is a 

 problem of conspicuous sociological importance. Everyone now 

 knows that the proportion of older people in our population is 

 progressively increasing, that the centre of gravity of the 

 population is shifting steadily towards old age. Using a plaus- 

 ible combination of hypotheses, one among several, the Stat- 

 istics Committee of the Royal Commission on Population 

 predicts that in half-a-century''s time one-quarter of our popu- 

 lation will be not less than sixty years of age. The economic 

 consequences of such an age-structure are all too obvious. Now 

 biological research is by no means uninfluenced by the econ- 

 omic importunities of the times, and there can be little doubt 

 that the newly awakened interest of biologists in ageing — or 

 the hard cash that makes it possible for them to gratify it — is a 

 direct reaction to this economic goad. Unfortunately, scientists 



^ [The preamble appropriate to an Inaugural Lecture has been left out.] 

 I have kept closely to my lecture as it was actually delivered, except that 

 (a) I have left out an argument which, on further reflection, seems much 

 less relevant and convincing than I formerly believed it, and {b) I have 

 tried to answer in footnotes some particularly cogent criticisms by my 

 colleagues. I have had the good fortune to consult with Professor L. S. 

 Penrose on certain problems relating to the action of natural selection on 

 human beings, and have had the most valuable advice from Professor 

 J. B. S. Haldane, some of whose ideas are presented here as if they were 

 my own. 



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