I'm sure I've read the following idea written by a linguist somewhere. I didn't manage to find the reference and I'd love to have serious references for that. The following is mainly a first person description of my native language's grammar, on an aspect which is not taught at school, but seems obvious in retrospect.
Such an indigenous language is my native modern French ! The tense corresponding to mythological/ancestral past is passé simple (French Wikipedia link, with more details, but in French).
Basically, this past tense was used for distant past event (older than 24h) in the 18th century but totally disappeared from oral speech by the beginning og the 20th century. It stayed in formal writing, and by now only appears in old text and fairy tales. For example, when my 8 years old niece invents a fairy tale, it is at the passé simple tense, and it is the only occasion she ever uses this tense.