Actually most of the gains have been due to the decline in infant mortality. Take a look at the people you know from the founding era (These are adults. You didn't get a chance to learn about the children.) and you will see that most lived to a ripe old age.
ML/NJ
Nope, I’ve looked at the stats and that just ain’t so. This is a big part of the problem with Social Security. When it was first set up, with 65 as the retirement age, most people didn’t live a whole lot longer than that, and plenty died younger AFTER reaching an age where they had paid substantial amounts into the system. Just comparing people who reach adulthood, life expectancies have increased dramatically.
If it seems like a lot of well-known people from centuries past lived to what we now consider a ripe old age, keep in mind that those were not average people. Their success was probably in large part due to the fact that they were of above average robustness to begin with, and also lived long enough and in good enough health to continue making significant contributions to society for many years after acquiring the experience and wisdom of what was then an average lifespan.