Keith Nuttle wrote in reply to my:   >> >> We can only make guesses about this. A general increase in adult life expectancy could be down, say, to better air quality. >> >> >> What is certainly the case is that an adult will survive significantly longer in non-polluted areas than in polluted ones - a significant factor again probably being air quality. >> > Nothing has to change in the life of an adult for the AVERAGE life > expectancy to increase.  All you have to do is decrease the infant > deaths and the death on women in child birth. > exp.  average of  10, 12,  50, 60, and 70 is 40.4 years > exp. average 50, 60, and 70  is 60 years. > This change has nothing to do with environment, pollution or any other > factor; than preventing the deaths of the young children. > As you I would expect the average life expectancy of people living in a > large city like New York or Los Angeles to be less that some one living > in Harlan Indiana or Chatfield Ohio.  In both areas the biological life > spans will be the same, the averages will be skewed down because of the > death of the younger people.  Of course Harlan and Chatfield do not have > the murder and crime rates of the large cities.   Yes, you're quite right. I realised the nonsense of my post when I looked back on it. The reason it became nonsense was the pruning shear!     My post started as an argument that the biological life span has likely increased (so the frequency of 111-year olds [say] today may be equivalent to the frequency of 101-year olds two hundred years ago). But then I cut all that out.   I was wondering how long it would take for someone to notice.     Chris