There's a virtual certainty alien life exists and no reason to discount the possibility that they visited the earth in the past but the evidence this occurred before 1500 BC is, in my opinion, virtually non-existent except as indirect evidence or as interpretations of direct evidence. This isn't to suggest it didn't occur. Indeed, it is the possibility it occurred that all the discounted ideas should be put back on the table.
I don't know who died and left us nothing but superstitious ancestors but it's exceedingly apparent that archaeology and anthropology has simply excluded every other possibility.
When you exclude every other possibility before you begin what you are left with are your assumptions. If the evidence were reexamined in light of known facts there might well be different conclusions than current assumption. We are taking a tiny bit of fact and extrapolating a whole lot of reality. All of this extrapolation says everything about us and our beliefs and nothing at all about our ancestors. It can only be true to the degree our ancestors were exactly like us, and it might not even be that true.
It is entirely possible that we are more like aliens than our ancestors and this is how we forgot. Or perhaps it's our ancestors who were alien-like. Or maybe there were no aliens at all.