The way I have always heard civilized human age demographics explained is that living past 30 was a royal pain. Very very hard to do. If you could do it, keep a fairly steady diet, and avoid Vikings you were nearly indestructible and were near guaranteed to live well past 50 and on into the early seventies.
There was a great game called Kingmaker based on the war of Roses. It had a mechanic that killed off the heads of your households with plague, but they included an apology at the end since noone who had survived to be the head of a noble house would ever die of plague.
That said, there are some aquatic creatures, sharks and some reef fish, who are pretty sophisticated and live a long to underdeterminedly long time.