I am one generation removed from a traditional Lakota life and I think that one thing people forget is how important oral history was to people in the ancient world. You would hear a story when you were young and it was paramount to learn it and repeat it exactly as before. And as time went on, if you deviated or embellished the story, you were shunned because everyone knew the story. Imagine your favorite grandparent telling you something and telling you that you must repeat it exactly to your grandchildren when that time comes. You would not disrespect your favorite relative and spoil your place in passing on the story. So millennia does not matter as much when you think about that. Without outside influence, language changes only slightly and stories that are considered the “truth” about life, are super important and passed on as such.