The influence of the medical care on the human life expectancy in 20(th) century and the Penna ageing model

The expression of many genetic defects may be suppressed by proper medical care or even by changing the environmental conditions. We have used the Pen na model of ageing to show that such effects may be responsible for increas ing the human life expectancy during the 20(th) century. This effect is equ ivalent to the shift of the threshold (T) in the Penna model, which determi nes how many deleterious, expressed mutations kill an organism. For long ge nomes, the shift of T changes the age distribution significantly with negli gible relative changes in the maximum life span, while for short genomes, t he shift of T changes both, the age distribution as well as the maximum age . Unfortunately the same simulations show that the strategy of enhancing th e medical care requires more and more effort to keep the mortality rate of our populations at the same lower level and that some new defects could be exposed to selection.