“we sill have no idea who built it, why and how”
So let's assume that it was a part of ancient civilization... ? GT structures are not that advanced. They show that humans were making gradual progress over thousands of years on the way to build the first civilizations.
You're done here because you've got nothing to back up your claim that there were some civilizations over 12k years ago, let alone the world wide civilization.
Yep made my troll list - now go away.