Well, the ancients themselves (and later, early AD researchers on them) were often noting that supposedly previous iterations of civ existed tens of thousands of years before them.
For example in the very important work (10 books) by Diogenes Laertios, in the 3rd century AD, about the early Greek philosophy, he begins in the very first page mentioning some calculations of some past 'sages' according to which some forty thousand years had passed from the age of the events of the mythical circles (eg Troy) to the time of the first philosophers (7th century BC). (he likely does not urge to take those at face value, but they are known enough for him to include them in his first passages in the book, even if attacking the position that Greek Philosophy owes its birth to barbaric -term used- priests in Egypt, or barbarians such as druids and sages in general, etc)
Well, i do not recall currently what the earliest events were about, and maybe it was not Troy or other tales of Homer, but it is also well known that in ancient Greece there was the myth of a past civ, before the great flood of Deucalion (and there was even an older great flood).
I wouldn't be that surprised if past civs did exist, and ended due to cataclysmic events or a full ice-age.
