INTRODUCTORY AND HISTORICAL 



Man throughout history, and every individual since his child- 

 hood, has been aware that he himself, and those animals which 

 he has kept in domestication, will undergo an adverse change 

 with the passage of time. Their fertility, strength and activity 

 decreases, and their liability to die from causes which, earlier 

 in life, they could have resisted, increases. 



This process of change is senescence, and senescence enters 

 human experience through the fact that man exhibits it him- 

 self. This close involvement with human fears and aspirations 

 may account for the very extensive metaphysical literature of 

 ageing. It certainly accounts for the profound concern with 

 which humanity has tended to regard the subject. To a great 

 extent human history and psychology must always have been 

 determined and moulded by the awareness that the life-span of 

 any individual is determinate, and that the expectation of life 

 tends to decrease with increasing age. The Oriental could say 

 'O King, live for ever!' in the knowledge that every personal 

 tyranny has its term. Every child since the emergence of 

 language has probably asked 'Why did that man die?' and has 

 been told 'He died because he was old.' 



Interesting psychological and historical speculation could be 

 made on the part which this awareness has played in human 

 affairs. From the biologist's standpoint, its main importance has 

 been the bias which it has injected into the study of senescence. 

 The child who asks the question, and receives the answer, is 

 familiar with 'old' clothes and 'old' toys. He has always known 

 that he, his pets, his cattle and his neighbours will become 

 increasingly prone to breakdown and ultimate death the older 

 they get. He has observed from the nursery that inanimate and 



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