THE UNIQUENESS OF THE INDIVIDUAL 



which the chances of dying do not change with age. The curve 

 it outhnes is of a sort very famihar in science. Fig. 3 illustrates 

 this very elementary triusm: the older the test-tubes are, the 



lOO 





0) 



O 



c 





lO 



15 



20 



monthly aqe groups 

 Fig. 3 



fewer there will be of them — not because they become more 

 vulnerable with increasing age, but simply because the older 

 test-tubes have been exposed more often to the hazard of being 

 broken. Do not therefore think of a potentially immortal 

 population as being numerically overwhelmed by dotards. 

 Young animals outnumber old, and old animals those still 

 older. 



VII 



As a first step in animating this model, I want you to imagine 

 that the test-tubes now do for themselves exactly what the 

 steward has hitherto been doing for them, i.e. they reproduce 

 themselves, no matter how, at an average rate of 10 per cent, 

 per month in order to maintain their numbers. Since the popu- 

 lation is potentially immortal, the rate of reproduction of its 

 members will not vary with their age. It follows that each 

 'living' test-tube of the existing population will make the same 



60 



