The Silurian Hypothesis: Could an Advanced Civilization Have Existed Before Humans?

Could a technologically advanced civilization have existed on Earth millions of years before humans, and if so, would we be able to find any evidence today? This profound question has been the focus of a unique scientific inquiry by astrobiologist Adam Frank and NASA scientist Gavin Schmidt.

The exploration began in 2017 when Frank, a professor at the University of Rochester, posed a question to Schmidt: "Can alien civilizations cause climate change?" Frank was investigating whether any advanced civilization harnessing vast amounts of energy would inevitably lead to planetary climate shifts, mirroring current human activities. Schmidt's surprising response, "How do you know?" sparked a deeper investigation into the possibility of a pre-human civilization leaving behind detectable traces.

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Can alien civilizations cause climate change?

This unusual scientific pursuit led to the formulation of the "Silurian Hypothesis" in 2018, named after a fictional advanced reptilian race from the TV series Doctor Who. The hypothesis is a thought experiment designed to explore whether evidence of a past technological civilization, which might have thrived millions of years ago, utilized energy resources, and subsequently vanished, could be identified. The scientists emphasize that this is a conceptual exercise, not an assertion that such a civilization actually existed.

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How do you know?

Atmospheric scientist Katharine Hayhoe, not involved in the research, noted that the hypothesis underscores the overall vulnerability of advanced civilizations. It raises critical questions about humanity's future, specifically whether every civilization reaching a global energy consumption scale is doomed to environmental collapse or if a sustainable path to long-term survival exists. Frank connects these questions directly to our present moment, stating, "We are pushing the planet into a completely new climate regime. We know it's happening, yet we still aren't doing what's necessary."

The inspiration for Schmidt's involvement stemmed from one of paleoclimatology's enduring mysteries: the Paleocene-Eocene Thermal Maximum (PETM), approximately 55 million years ago. During this period, Earth experienced an extreme warming event, with average temperatures rising significantly and vast amounts of carbon dioxide released into the atmosphere, causing widespread ecological disruption. The lack of a clear explanation for this event fuels the ongoing scientific curiosity about Earth's deep past and the potential for unknown phenomena.

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All these questions are directly connected to the moment we are living in today. We are pushing the planet into a completely new climate regime. We know it's happening, yet we still aren't doing what's necessary.