I can't tell if it's a crinoid or not from that picture. If you break it in half and look at the pattern inside of it, it should be pretty easy to tell if it's a metal screw or a segmented sea creature.
That said, I think we're probably not Earth's first civilization. Probably not even it's second or third.
I've always wondered why they lie about it all the time. Because it'll make religion irrelevant? The fact judaism exists already does that. I think there really are several rovers on Mars but they are showing us footage from Devon Island. Why? Because there are tons of alien shit up there. NASA would lie about bacteria living under a rock on an asteroid.
If there are other civs out there that have been watching the whole time, it creates problems.
Imagine if they (people from Atlantis, space aliens, evolved dinosaurs, or whoever the fuck) say they have video of Mohammed lying about his divinity and raping kids. If they start commenting on their anthropology on our religions it'll be a mess.
They probably also have surveillance records of 911, JFK, Epstein, Pearl Harbor, Auschwitz, and God knows what other scandals and sacred cows.
Then there's the WMD problem. The proliferation of NBC (nuclear, biological, chemical) weapons is already a problem.
What if The Others have a technology that let's you easily create plutonium in your garage?
Imagine every dune coon, disgruntled 14 year old, and sketchy kike with their own dirty bomb or fusion weapon.
So if the library of historical and technical data from these other groups got out there might be a mass freak out followed shortly by a lot of big booms.
Or maybe we'd get through to the other side and experience a golden age of post scarcity wealth.
I don't know, but I understand why The Powers That Be are defaulting to secrecy and denial.
That said, I think we're probably not Earth's first civilization. Probably not even it's second or third.
I member watching a video theorizing on "If humanity ceased to exist tomorrow, how long would it take for all traces to disappear?"
IIRC they mentioned something like 100,000 years, which is insignificant compared to the age of earth (4.7B years)
If there is dense foliage like the Amazon, it can be grown over so that even large cities and pyramids would blend into the area (being covered by trees) in less than 100 years.
Covered, but unlike ancient constructions made out of large stones, limestone and marble, modern constructions are using (composite) materials that wouldn't last more than a few hundreds years before starting to disintegrate, especially when soaked with humidity.
Look at Chernobyl site. It took only 50 years for the buildings in the exclusion zones to fall apart.
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