I think it doesnt matter, we are aliens or not. Pretty sure, we almost ruined the planet, and it become a shitty place for lot of people... Maybe its time to pull the heads out from ass...
Aliens and ancient civilizations are secondary questions.

Yep, we have genetic memory. Yep, this pictures are disturbing, but not due our memory, due the fact, these beings are ugly...
And if they are arrive from another place, okay, we kill them. The mankind is pretty good in this, killing the "differents".