In the introductory essay, "Homer and his Influence," to the anthology A Companion to Homerpublished by Macmillan in 1962, J.A.K. Thomson remarks that Homer, while standing at the head and beginning of the Western tradition of literature of which we know, may in turn have been the culmination of a whole other literary tradition. This remark barely caught my attention the first time I read it, but later it sort of blew my mind.
An entire literature known to us only through Homer. How far into the past before Homer may this literature have stretched? For how long was it written if, before Homer, it was written at all? The experts say that it is clear that Homer is very close to oral storytelling. But that does not tell us how long, if at all, written and oral Greek literature may have existed side by side before Homer. And what does that mean, "before Homer" ? Was there ever an individual poet named Homer? If so, when did he live? Could he write? (Could he see?) Are the Illiadand Odysseyin any meaningful sense the work of an individual (Or two individuals?) or are they the result of a long communal process of storytelling?
As far as I know, the answer of leading scholarship to all of these questions and many related ones remains a resounding "We don't know." There are certainly strong opinions on all these questions, but not much certainty. The Iliad and Odyssey were probably in written form by the 6th century BC in Athens. Some scholars would argue that this was their first written form, others that they were written in Linear B several centuries earlier, and plenty of others for all sorts of dates for the first written version in between.
In some respects -- the dates postulated, the variety and vehemence of opinions about the dates, the cultural implications of the current state of knowledge and possible future discoveries -- the debate about the composition of the Homeric epics resembles that over the composition of the Bible. The Exodus, if it ever happened, is supposed to have occurred in roughly the same era as the Trojan War, it it ever happened. 1200-1400 BC in each case, give or take a few centuries. Traditionally it was believed that Moses wrote the first books of the Bible, now it's not all certain whether he existed, and if he did, if he or any other of his people were literate at all. Did the Greek alphabet originally come from the Hebrew? Or vice versa? Who knows? Not me. They appear to be rather closely related, and both to have come from hieroglyphs and cuneiform, which appeared in Egypt and Mesopotamia sometime before 3000 BC. "Appeared," that is: that's when the experts date the earliest known writing. Probably older in Mesopotamia, it probably spread to Egypt from there. Nobody knows for certain.
In any case, it seems clear that neither Homer nor the Old Testament can lay claim to being the oldest written literature of all, for the Mesopotamian epic of Gilgameshis preserved on clay tablets some of which date to the 3rd millenium BC, making it the oldest longer literary text. Of which we know. So far. Maybe Gilgamesh represents the culmination of a literature which stretches thousands of years further back into the past...
All I know is that older and older human artifacts are being discovered all the time. Artworks from more than 30,000 years ago. Stone weapons and tools made by humanoids millions of years ago. Long, mysterious, tantalizing gaps between the ages of the artifacts discovered so far. We're a long way from figuring out how we got to be the way we are.