John Adams lived to 90, Sam Adams to 81, Ben Franklin to 84, John Jay to 83, Thomas Jefferson to 83, James Madison to 85. Some of their lives could definitely have been extended, but I think people generally misunderstand human longevity. The peaks of ages have not really changed much at all, and a reasonable chunk of people who made it past childhood/birth (where there were indeed extremely high mortality rates), would make it there. For instance Hippocrates, of the Hippocratic Oath, lived to beyond 90, back in 400BC.

Something else has changed.