Could Ancient Earth Have Hosted Lost Alien Civilizations?

Kurzgesagt – In a Nutshell · Explainer · 10 min · 2022 · YouTube title: Are There Lost Alien Civilizations in Our Past?

Why it's here

HN brings it up in threads on ancient civilizations and detecting past technology in geology.

What it covers

Kurzgesagt asks whether advanced civilizations could have existed on Earth in the deep past and left little evidence. It looks at time as a dimension for searching for alien civilizations and the limits of the geological record.