Man , this is stupid. The reason for the depressed life expectancy WAS childhood death and infant morality. If you made it to 20 you had a great chance of hitting 70.Sorry but if we look at our society today we find that there is a much greater number of people who are over 60. To say that it the same is completely wrong when we factor health, environment and nutrition.
We simply have to look at life expectancy which slowly increased to now in the 70+ (western world).
FYI: when western world brought in old age pensions in the middle of the 20th century most used age 65 as retirement age. What is not known was that life expectancy at the time was 63.