If another advanced civilization lived on Earth before us, would we know?

Key Points:

• Astrobiologist Adam Frank and NASA scientist Gavin Schmidt proposed the "Silurian hypothesis," exploring whether an advanced civilization could have existed on Earth millions of years ago and left detectable traces, despite no known evidence of such civilizations.
• They investigated past climate events like the Paleocene-Eocene Thermal Maximum, which saw rapid temperature spikes and ecosystem collapse, questioning if these could have been influenced by ancient civilizations rather than purely natural causes.
• The hypothesis considers potential geological, chemical, and fossil evidence that might indicate prior technological activity, such as altered atmospheric chemistry, persistent plastics, or heavy metals, but acknowledges that tectonic and erosional processes would make such evidence hard to find.
• While neither Frank nor Schmidt claim the hypothesis is true, they emphasize its value as a thought experiment highlighting humanity's current climate crisis and the potential vulnerability of advanced civilizations to self-induced environmental change.
• Experts note the idea is provocative but stress that human industrial activity leaves a uniquely strong geological footprint, making it unlikely that a civilization like ours existed undetected in Earth's deep past; the hypothesis mainly encourages reflection on our own civilization’s sustainability.