I am talking about records from 5000-7000BC (deducing from Sanskrit literature) by which time they had already been orally transmitted for eons. So they are truly ancient with layers upon layers of grafting of realities/myths/stories over time.
The Itihasas/Puranas talk about vast time scales populated by different beings with different lifespan lengths in a very specific and detailed manner. It contains both cosmic and civilizational histories all bound together in a single multi-branched narrative. Hence it is a very unique historical corpus from which much can be gleaned and mapped against modern studies.
Some resources:
Hindu units of time - https://en.wikipedia.org/wiki/Hindu_units_of_time
Yuga cycle - https://en.wikipedia.org/wiki/Yuga_cycle
As an example, The events in the Ramayana are dated towards the end of "Treta Yuga" but the text itself mentions a very long list of continuous lineage before coming to Rama. Look up "Treta Yuga" in the above pages and you can see how far back this particular narrative goes; you could calculate it as; "length of dvapara yuga + length of kali yuga to current date" and it comes to >800,000 years into the past!. Now add the lineages mentioned in the text itself and you go even longer into the past.
The interesting thing is that each of those timelines have some sort of Human/other beings in it!
My comments are to do with highlighting the different unique narratives (w.r.t. Human/Other beings) in Sanskrit literature which are self-consistent within that corpus. It is just a fact (of History and Geography) that it is only found in Hindu (and Buddhist/etc. derivative) cultures to a very large extent. Cultural Anthropologists/Archaeologists/Geomythologists nowadays do study these independent of its religiosity as "Deep Time" oral traditions/histories to better understand our own evolution and history. Hence it is not a question of accepting them blindly so much as expanding and exploring the range of possibilities of our own histories.