A front page story came up that DNA tests confirmed Aboriginal Australians' oral histories which claimed they'd been there for 50000 years.
I'm curious though, over a mere 2000 years, English has changed quite substantially, to the point where old English is entirely unintelligible to most of us.
So how do oral histories survive linguistic changes? Do their caretakers adjust them to deal with linguistic changes, if so, how do they ensure the meaning is retained? Are they so important that the language is forced to remain stable around them? Do the languages where oral histories are common simply not change much for other reasons?
For all the changes that occur, one generation tends to understand the one before, and that is all that is needed to pass oral tradition through time. Since a given generation does not receive its oral traditions from its great-great-great-great grandparents, who may have spoken differently, language change is not a factor.
While it is possible to find examples of older people remarking on how differently young people speak, the drift is typically not enough to prevent communication.