Could Evidence of Past Civilizations on Earth Remain Hidden?

WHO:

CNN - Adam Frank, a University of Rochester professor and astrobiologist.

CNN - Gavin Schmidt, a NASA scientist.

CNN - Katharine Hayhoe, an atmospheric scientist at Texas Tech University.

CNN - Jan Zalasiewicz, a geologist, paleontologist, and emeritus professor at the University of Leicester in the UK.

WHAT:

CNN - Frank and Schmidt investigated the possibility of advanced civilizations existing on Earth millions of years ago.

CNN - They published a paper on the "Silurian hypothesis" in 2018.

CNN - The Paleocene-Eocene Thermal Maximum occurred around 55 million years ago, with global temperatures spiking up to 15 degrees Fahrenheit.

CNN - Only around 1% of the Earth's surface is urbanized today.

CNN - Dinosaurs roamed the Earth for about 180 million years, but only a few thousand near-complete fossils have been discovered.

WHERE:

CNN - The Negev Desert in southern Israel is noted as the Earth's oldest large-scale stretch of land, around 1.8 million years old.

WHEN:

CNN - The Paleocene-Eocene Thermal Maximum was first noted in the 1990s.

CNN - Zalasiewicz co-wrote the book "Discarded: How Technofossils Will be Our Ultimate Legacy" in 2025.

WHY:

CNN - The investigation was prompted by the question of whether advanced civilizations would inevitably trigger climate shifts, similar to current human activities.

CNN - The Silurian hypothesis raises questions about the trajectory of advanced civilizations and their sustainability.

HOW:

CNN - Frank and Schmidt explored possible evidence of past advanced civilizations through geological and chemical changes in the Earth’s strata.

CNN - They considered the potential future evidence humans might leave behind, such as plastics and artificial chemicals.

(UPDATED July 26, 2026 05:55 UTC)

A team of scientists, including University of Rochester professor Adam Frank and NASA scientist Gavin Schmidt, has been investigating the possibility of advanced civilizations existing on Earth millions of years ago, leading to the publication of their paper on the "Silurian hypothesis" in 2018. Their research, which also includes insights from atmospheric scientist Katharine Hayhoe and geologist Jan Zalasiewicz, raises important questions about the sustainability of advanced civilizations and the potential climate shifts they may trigger, similar to those caused by current human activities. Notably, Zalasiewicz co-wrote a book titled "Discarded: How Technofossils Will be Our Ultimate Legacy," which is set to be released in 2025, further exploring the evidence of past civilizations through geological and chemical changes in the Earth's strata.