The lack of any real human history before 2000 BC has to make our understanding of everything from before this time tentative at best. That some high culture existed seems apparent but at the same time there's very weak evidence that this culture was strictly terrestrial. Of course there's no stronger evidence it was extraterrestrial. The utter lack of technology or scientific metaphysics associated with any high culture should give us all pause. The implication is that that either ancient people survived with magic, they had extraterrestrial help, or they had science which we can't recognize.
While modern people believe the ancients were superstitious the fact is such people could not have competed against tribes who used logic to guide their decisions. Superstitious people would have died out at every place given sufficient time and people using common sense would have prevailed. So in the real world there are really only two possibilities; aliens and "atlantis".
Of course by "Atlantis" I mean some unknown high culture that died out. By some means knowledge of this culture was lost. If this is the case my best guess is that they were lost by a change in language. It's entirely possible that everything can be explained by aliens but it's also quite possible that both a high culture and aliens existed. Perhaps one led to the other. Perhaps aliens were simply investigating how talking apes could succeed so well.
It's a shame that orthodoxy has essentially closed the book on such questions and put away the science that could answer some of the questions. It's a bigger shame that so little evidence and no ancient books survive.
I believe when we finally get some of the answers everyone is going to be surprised and no one will be happy. Orthodox beliefs about times before 4,000 years ago are a trainwreck in slow motion that has been unfolding for 150 years. They still have their feet on the accelerators and can't figure out why they're slowing down.