If people are depressed by this minimal loss since the 60’s, they’re going to explode when they read research like that of Lynne Kelly on what we’ve actually lost from indigenous cultures. Here’s a good place to start: Knowledge and Power in Prehistoric Societies: Orality, Memory and the Transmission of Culture though her TED talk gives a bit of the flavor without the heavier, but worthwhile, reading–in part, because it will give us some ideas about how to turn back the clock and recover some of what we’ve lost.