Conclusion 



In fact, the social correlates of longevity, which are probably 

 its most important practical aspects, have been omitted alto- 

 gether from consideration in this book. It is clear throughout 

 phylogeny that there is a relation between survival into the 

 senile period and the existence of a social mode of life. In some 

 cases longevity has evolved as a prerequisite of social organiza- 

 tion, in others social organization itself increases the possibility 

 of survival into old age, while the social group very probably 

 draws adaptive benefits from the existence of old individuals. 

 Both these trends appear to be at work in social primates. The 

 potential life-span in palaeolithic man probably resembled our 

 own: its realization has been possible through the development 

 of a complex social and rational behaviour. While therefore it 

 is legitimate to abstract the idea of an evolutionary programme 

 in morphogenetic or physiological terms when we discuss the 

 development and senescence of an individual man or of a 

 worker bee, in neither case is this 'programme' really detach- 

 able from the social programme which coexists with it, and 

 which plays an equally important part in the determination of 

 selection or survival. The irrelevance of discussing the biology 

 of individual animals, even of non-social species, divorced from 

 their ecology, has long been evident. Prolongation of the social 

 activity and significance of the individual human being almost 

 certainly leads to a change in the shape of the life-table, others 

 things being equal. Continuance of active work, retention of 

 interests, of the respect of our fellows, and of a sense of signi- 

 ficance in the common life of the species, apparently make us 

 live longer — loss of these things makes us die young. This is a 

 result we might have expected, but which we still largely ignore 

 in practice. How much of senile 'involution' is the effect of the 

 compulsory psychological and social 'winding-up' imposed on 

 the human individual by our form of society and our norms 

 for the behaviour of old people we do not yet know, but it is 

 certainly a very considerable part, and the most important 

 measures for the prolonging of useful individual life which come 

 within the range of the immediately practicable are all con- 

 cerned with social adjustment. The contrast between the place 

 of the (relatively few) aged in primitive societies (Simmonds, 

 1945, 1946) and the relatively many in our own (Sheldon, 1949; 



193 



