Discussion 19 



what I suggested that you should do here and took a look at the 

 application of probability theory to people who, as it were, made the 

 change from organization to disorganization, when degeneration 

 begins, you would have to revert to operation on the force of 

 mortality. 



Danielli: It has been alleged that people exposed to increased 

 radiation have a decreased expectation of life. What would happen 

 to the right-hand peak in your death curves with this particular 

 group ? 



Benjamin: I don't think there is sufficient evidence yet. 



Rotblat: The general population has had such a small increase in 

 radiation compared with natural background radiation that one 

 would not expect to see any effect on the death curves. On the other 

 hand we should consider various theories of ageing, for example the 

 recent theory of Szilard, who suggests that we all start with a certain 

 load of faults, or mutants as he calls them, and that these determine 

 the lifespan of a population. If we accept the fact that radiations 

 cause mutations which may influence the lifespan, then one might 

 have expected that in the course of time there would be an increase 

 of these faults within us, because we accumulate the radiation 

 from generation to generation. I would expect, therefore, that 

 the whole curve would gradually shift to the left rather than to the 

 right. 



Prof. Griineberg, is there an equilibrimn which we may expect to 

 reach and which would take care of this ? How would such an 

 equilibrium be affected by the fact that nowadays people who 

 formerly would have died younger, now live longer because of con- 

 ditions in a welfare state ? 



Griineberg: I think the effects of radiation fall into two categories. 

 We may expect the ultimate appearance of more or less deleterious 

 mutations in the homozygous condition ; however, as close inbreeding 

 is restricted in man, the appearance of recessive mutations in homo- 

 zygous condition will take a long time. On the other hand, right 

 from the beginning, we may experience the effect of these same 

 mutations in heterozygous condition. It is now becoming increas- 

 ingly clear that at least some of these mutations in heterozygous 

 condition can be advantageous even if they are disadvantageous in 

 homozygous condition. One might thus expect an advantageous 

 result in the early stages of radiation when we are mainly concerned 

 with heterozygotes ; this would ultimately be counteracted by dis- 

 advantageous effects when the mutations become homozygous. It 

 is between these opposite effects that equilibrium is likely to estab- 

 lish itself in the end. 



