16 Discussion 



to draw this line. At the end of this meeting I may know a Uttle bit 

 more about where it should go. 



Jalavisto: One should perhaps think about three curves — one 

 independent of age, running horizontally, a second one beginning at 

 middle age and rising with advancing age as a result of inadequate 

 living habits, and a third one representing the random distribution 

 of species-specific lifespan. 



Have you studied the difference between the mortality curves for 

 males and females ? In your symmetrical component curve I would 

 expect the base to be narrower for the females. In the female and 

 male mortality rates the Gompertz rule holds fairly well for males 

 but in the females the assumption of a random distribution around 

 the age of 75 years would fit the facts better. 



Benjamin: The width of the symmetrical distribution for women 

 is only slightly narrower than that for men. You would like to take 

 a slice off the bottom right across ? 



Jalavisto : Yes, but furthermore there would be one group which is 

 quite clearly a result of externally induced pathological changes, i.e. 

 through accumulation during decades of carcinogenic substances, of 

 cholesterol deposits following high fat diet, slowly developing 

 deficiency diseases, etc. Of course, they tend to increase the mortality 

 with advancing age because they are just a function of the chrono- 

 logical age. These three groups, as far as I can see, can result in any 

 form of mortality curve according to their mutual relationships. 

 But in any case the end-point as part of a normal distribution curve 

 comes out very clearly, I think. 



Berg: There is no difference in the nature of the diseases that 

 cause death at age 50 and those that cause death at age 80. The 

 diseases of senescence also occur at age 50. In animals, as well as in 

 man, the so-called diseases of senescence occur in early life. 



Benjamin: That is precisely what I want to learn. 



Maynard Smith: The anticipatory deaths you mentioned were 

 presumably deaths due to causes which would kill a person at any 

 age, and not merely if they were old. What worries me is that, 

 whatever those causes are, it is assumed in your analysis that no- 

 body dies from them after the ages of about 60 to 70. If there are 

 causes which will kill people at any age they presumably will kill 

 old people. If you allowed for the fact that old people are dying from 

 accidental causes, as well as young people, there might be no in- 

 crease in the modal age at death in the later life-tables. In other 

 words if you continued the anticipatory death curve throughout the 

 whole period of life, the peak might stay at about 70 to 72 instead of 

 shifting to the right. 



