The Silurian Hypothesis and Long-Term Preservation: Could Pre-Human Civilizations Have Existed on Earth, and Where Should Humanity Archive Its Legacy?

This paper examines two interconnected questions fundamental to humanity’s understanding of its place in deep time:(1) Could technologically advanced civilizations have existed on Earth millions of years before humans, and would we be able to detect their remains?(2) Where should humanity preserve archives intended to endure for millions or even billions of years—on Earth or on the Moon? Drawing upon the Silurian Hypothesis proposed by Schmidt and Frank (2018), we analyze geological processes that erase evidence of past civilizations, exploring why the absence of “space junk” or technological artifacts does not necessarily preclude ancient industrial societies. We then evaluate Earth versus lunar environments for ultra–long-term archival preservation, examining current initiatives such as the Arch Mission Foundation’s Lunar Library. Our analysis reveals that plate tectonics recycle Earth’s crust every 200–500 million years, effectively erasing most surface evidence, while the Moon’s lack of atmosphere, tectonics, and erosion makes it a far superior repository for preserving human knowledge across geological timescales. This paper contributes to the fields of astrobiology, planetary science, and information preservation by synthesizing evidence for potential pre-human civilizations and establishing criteria for billion-year archival systems.