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" in 2018, exploring whether an advanced civilization could have existed on Earth millions of years ago and left detectable traces despite the planet's geological changes.
• The hypothesis was inspired by mysterious ancient climate events, such as the Paleocene-Eocene Thermal Maximum around 55 million years ago, which saw rapid global warming and ecosystem collapse, paralleling current human-driven climate change.
• Frank and Schmidt argue that evidence of a past civilization might be found in chemical signatures in geological strata, persistent synthetic materials like plastics, and heavy metals in sediments, though direct artifacts would likely be erased over millions of years.
• While neither scientist believes the hypothesis is proven, they emphasize its value as a thought experiment highlighting humanity's current environmental impact and the potential vulnerability of advanced civilizations to self-induced climate crises.
• Some experts, like geologist Jan Zalasiewicz, appreciate the idea's provocative nature but contend that the extensive and unique footprint of modern human civilization would be difficult to miss in the geological record, effectively ruling out prior advanced societies similar to ours.