Actuarial Aspects of Human Lifespans 5 



Later, in a discussion of another paper on fitting a mathe- 

 matical law to l^ of the mortality table (Ogborn, 1953), Perks 

 suggested that reference to the probability models of the 

 biological field and the data of simple populations was the 

 only way in which an advance would be made in the develop- 

 ment of a satisfactory theory of a life-table. It is a pity that 

 this suggestion has not yet been exploited as, if linked with 

 the idea of loss of biological organization, it seems to the 

 present author to open up an important line of approach. But 

 we are straying from the objective of this historical introduc- 

 tion. 



In 1954 Phillips returned to consideration of the curve of 

 deaths and hypothesized the existence of a basic curve of 

 deaths "to which all curves of deaths are, as it were, striving 

 to attain". 



Clarke's division of deaths into "anticipated" and "sene- 

 scent" has been further developed by Barnett (1955 and 

 1958) but applied to the force of mortality, not the curve of 

 deaths. On the basis of cause of death grouping and the 

 actual shape of the curve of observed age rates of mortality 

 Barnett distinguished several different groups of anticipated 

 deaths. 



We may now return to Clarke's paper. 



The earlier approach 



The objective of Clarke's approach was the forecasting of 

 the rates of mortality which would operate in the future. His 

 hypothesis was that every individual carried with him from 

 birth a genetically endowed term of life beyond which it was 

 impossible for him to survive, and that if we knew these 

 terms for every member of the population we could form a 

 frequency distribution similar to that of any other biometric 

 quantity. This distribution would represent a limiting form 

 of the curve of deaths. Clarke went further and supposed 

 that this distribution would not shift as a whole toward later 



