Could There Have Been an Advanced Civilization on Earth Millions of Years Ago?

TLDR The possibility of an advanced civilization existing millions of years ago is difficult to determine due to the remote odds of finding fossilized artifacts and the geologic timescales involved. However, evidence of past civilizations could potentially be found through the presence of radioactive isotopes, changes in carbon ratios, and the exploration of space.

Timestamped Summary

00:00 If an advanced civilization existed millions of years ago, how would we know?
02:22 The episode explores the question of whether there could have been an advanced civilization on Earth millions of years ago and how we would know.
04:17 If an advanced industrial lizard civilization existed over 400 million years ago, we would potentially find their ancient artifacts as we do with other ancient human civilizations.
06:16 The odds of any living thing becoming a fossil are extremely remote, and even if the lizard people were fossilized, the odds of us finding those fossils are slim, and the timescales we'd be talking about are geologic, so it's unlikely that we would find any evidence of their civilization.
08:10 Evidence of an industrial civilization in the geological record could potentially be found through the presence of radioactive isotopes and changes in the carbon-13 to carbon-12 ratio caused by burning fossil fuels.
10:07 Signs of a past industrial civilization could potentially be found in the geologic record through the presence of fossil fuels, nitrogen-15 ratios, synthetic chemicals, and microplastics, although alternative explanations such as volcanism and meteor strikes must be considered.
11:55 Evidence of past civilizations may be best found in space, as satellites and other objects in high orbit or on neighboring moons could remain relatively undisturbed for millions of years, making it difficult for future civilizations to detect signs of our own existence on Earth.
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