I was claiming myself long time ago, that we have on this planet bunch of lost civilizations over the life time of earth.
Civilizations that vanished.
Civilizations who were here long before “missing link”.
They keep discovering such a possibility’s,…
Some of those civilizations lasted in time much longer than ours and we in our arrogance not believing  or we not admit that they may achieved much higher level of knowledge and technical advantage then “WE”.
Anything what we don’t understand, we tend to explain with silly theory’s, or by outside influence of extraterrestrials, or we not rather talk about it at all.
It is a hard find any evidence, if everything had been destroyed by some natural disasters such as hit collision with a  meteor large enough to wipe out all evidences. Or they destroyed themselves as we tend to do.
Anyway, that is my thought, just trying fill out empty space in planet existence , probably 5 billion years old.