[drewgross]

People continue to influence their children long after they stop reproducing. Genes that help you children have more children are selected for, so something like a gene that keeps you alive long enough to care for your grandchildren seems plausible.

[IanCal]

Although there are also clear costs to this, and as you look at longer timescales the benefits become less pronounced.

I'd at least say I don't see a strong evolutionary pressure for extended lifespans.