The very first Bajoran Story "Ensign Ro" said that Bajorans were civilized before humans walked upright (and thus for at least hundreds of thousands of years).
But a DS9 story about the ancient lost city of Bahala indicated it was legendary and only about 20,0000 years old.
My theory is that civilization firs arose on Bajor hundreds of thousands of years ago and later fell, leaving ruins of Bajor and/or other orlds in the Bajoran system studied by archaeologists. The present Bajoran civilization would have begun only about 20,000 years ago making Bahala one of the oldest cities of that cycle of civilization.
Bajorans have been recording dates that can be converted to their current dating system for at least 20,000 years I guess since it has been said in the first episode of DS9 that the orbs of the Prophets have appeared in the skies over Bajor for that long.
I'm not sure if the orbs have been falling out of the sky to the ground for 10,000 years or if they have appeared in orbit around Bajor and were detected from the ground by Bajorans for 10,000 years and the Bajorans eventually developed spaceflight to bring the orbs down to Bajor. In any case I think that for hundreds of thousands of years the advanced or primitive Bajorans had totally different religions and did not worship the Prophets. Finding the orbs caused the Bajoran religion of Prophet worship to develop and spread over all Bajor in the last 10,000 years.
I have a theory that Bajor and Cardassia are very close together and have been so for tens or hundreds of thousands of years. Eventually their stars on their separate orbits will become farther apart. Thus every time civilization develops on Bajor or cardassia it invents star travel and travels to the other solar system first and the natives of the second solar system learn advanced technology from the natives of the first. Perhaps Bajor and Cardassia alternated in developing civilization and advanced technology and star travel and teaching the other society. Eventually the Bajorans and Cardassians would fight and destroy civilization on both their worlds, and civilization would eventually arise again after tens of thousands of years.
Posssibly space travelling Bajorans and/or Cardassians sometimes discovered the wormhole mouth, and fought over control of it leading to the collapse of their civilizations.
Anyway, if both Bajor and Cardassia have been too primitive and backward for space travel for the vast majority of the hundreds of thousands of years since the first civilization on either of those planets, they would have been incapable of discovering the wormhole mouth for most of those hundreds of thousands of years.