\n Schmidt immediately cut him off. \u201cHow do you know that?\u201d he asked.\n <\/p>\n
\n It was a record scratch moment, Frank said, and it started the two scientists off on an investigation. If an advanced civilization had lived on Earth millions of years ago, powered themselves with energy and wiped themselves out, would we know? Would they have left traces of their presence etched into the record of our planet?\n <\/p>\n
\n They called the idea the \u201cSilurian hypothesis\u201d \u2014 after a fictional advanced race of reptiles in the TV show \u201cDoctor Who\u201d \u2014 and published a paper<\/a> on it in 2018.\n <\/p>\n \n It is a mind-bending idea that not only looks deep into the Earth\u2019s past but also far into its future, as humans change the climate swiftly and dramatically by burning fossil fuels. \u201cIt is a thought experiment, but one that exposes our potential vulnerability globally,\u201d said Katharine Hayhoe, an atmospheric scientist at Texas Tech University, who was not involved in the research.\n <\/p>\n \n The Silurean hypothesis opens big questions about the trajectory of advanced civilizations and whether all those that harness energy on a global scale are destined to burn out, or whether there\u2019s a chance to live sustainably and survive for millions of years.\n <\/p>\n \n \u201cThese questions are all relevant to exactly the moment that we\u2019re in,\u201d said Frank. \u201cWe are pushing the planet into a new climate regime \u2026 we know this is true, right? And yet we\u2019re not doing anything about it.\u201d\n <\/p>\n \n The reason Schmidt had been mulling the possibility of previous advanced civilizations on Earth was an event deep in the past.\n <\/p>\n \n Around 55 million years ago, the planet\u2019s climate signals went haywire. Global temperatures spiked up to 15 degrees Fahrenheit and ecosystems collapsed, as huge amounts of planet-heating carbon were injected into the atmosphere.\n <\/p>\n \n This period, known as the Paleocene-Eocene Thermal Maximum and first noted in the 1990s, may have been the result of an enormous volcanic eruption, or maybe a sudden release of methane. But exactly why it happened is still something of a mystery. What intrigued Schmidt were the similarities to what\u2019s happening now as humans push up temperatures<\/a> and drive extinctions<\/a>.\n <\/p>\n \n And it\u2019s not the only unexplained change deep in the planet\u2019s past that echoes our present, other periods have seen oceans starved of oxygen<\/a> and sharp hikes in temperature.\n <\/p>\n \n The likelihood is these are natural climate events, but what if they weren\u2019t? How would we know? In their report, Frank and Schmidt go through the chain of possible evidence that might exist in support of a past advanced civilization.\n <\/p>\n \n Today, only around 1% of the Earth\u2019s surface is urbanized and it wouldn\u2019t take long for what we\u2019ve built to be erased. The further back in time a hypothetical civilization existed, the harder it would be to find direct evidence, like objects.\n <\/p>\n \n Over millions of years, the planet is resculpted as tectonic plates shift, volcanoes erupt and land erodes. The Earth\u2019s oldest large-scale stretch of land is the Negev Desert in southern Israel, at around 1.8 million years old.\n <\/p>\n \n Surface features may not provide much evidence, so the scientists looked at fossils. A vanishingly small fraction of animal species is fossilized, however, and even fewer are ever found. Dinosaurs roamed the Earth for about 180 million years, but only a few thousand near-complete fossils have been discovered.\n <\/p>\n \n It might be easy to miss a civilization that only existed for 100,000 years, a mere blip in the 400-million-year-old history of complex life on the planet.\n <\/p>\n \n The researchers then considered traces left by chemical changes. Think of the Grand Canyon, Frank said, where you can see line after line representing different ages of the Earth. \u201cEvery one of those strata is ground up rock that keeps a memory of what the chemistry of the Earth was like then.\u201d If a previous civilization had altered the planet\u2019s chemistry \u2014 as humans have done by releasing vast amounts of carbon pollution<\/a> \u2014 there might be a record.\n <\/p>\n![\"A](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2026\/07\/03-tcddowh-ec205-cropped.JPG\")
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