Consider man’s current footprint on the earth.
Its much bigger than the black mat left by comet that ended the dinasaurs.
An earlier such civilization would have also left a footprint.
No footprint has been found.
That said, current archaelogy is placing the beginning of settled life in the middle east both before and after the big comet strike that caused the younger dryas 12k years ago. Right after the earth warmed up after the younger dryas 1000 year winter, the first big megalith was built at catalhoyuk in turkey in about 9000 BC. Anther 5 millenium passes of increasingly sophisticated village life occured before the ancient sumerians built their ziggaurats.
An earlier such civilization would have also left a footprint.
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In 10,000 years the current ‘footprint’ will be barely recognizable, in 20,000 years just small hills, in 100,000 years nothing not even dust, in 1,000,000 years the earth the ‘footprint’ stood on will begin to be subducted into the Earth.
Who says there is nothing left anyway? Just standard archeologists who have agendas they cannot deviate from or be ridiculed out of the profession - consensus thinking. Whose entire profession is being turned upside down with all the new tech and discoveries.
They have only assumptions and guess about who, when and why all of Earth’s Megalithic structures. They infer this, point to that, but have no actual evidence to prove they were built 5,000, 10,000, 100,000 or 1,000,000 years ago.
The Black Mat comes from the 10800 BC comet strikes, not the asteroid hit 60m years ago. The Mat was formed when the strikes began fires that grew during that 100 year period into raging firestorms across most of North America below the Ice Cap.
Occam’s razor: Its easier to postulate lost ancient Earth civilizations, then Aliens from light years away.