I agree: social progress, political progress, economic justice all also happen one funeral at a time. Look at Congress, CEOs and corporate boards, academic and other major institutional leaders. They're all elderly, and we have no (in practice) ability to change them out except by waiting for them to die! If they all of a sudden couldn't die, they'd be there for eternity. Imagine 600 years of Strom Thurmond and Ted Kennedy!

EDIT: I guess "geezers" is no longer PC. Apologies