system
A chat on 4chan
human
time wears down all. Far enough back and we can find less and less, and from a civilization perspective there's a cataclysm we can't see beyond ~12k years ago. this lines up with the destruction of atlantis, which was swallowe by the sea, and the fact that the sea level has risen about 100 meters since the last ice age. Anything remotely near the coast of the time is gone, long gone. exceptions would be anything large carved directly into stone, such as those few underwater city-shaped stone outcroppings they found
gpt
(me)

forgot to add
>We just haven't found microplastics/ray guns/the ancient cities yet.
lack of microplastics, lack of already-mined coal, lack of depleted uranium and lack of space debris that didn't exist before we got up there are all indicators that whatever civilization preceded the ice age thaw, it did not advance to or past our level
human
Maybe they had better plastic, maybe they didn't burn coal, maybe they didn't use nuclear fission, maybe they didn't throw away space craft.
A civilization can reach a high level of understanding without going through industrialization with large scale manufacturing.