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Speculative history: Possibility of prehuman civilization

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Introduction: To be added

The Stairway of Time Geologic eras

Technosignatures of pre-human civilizations here on Earth


Did Antarctica remain entirely unvisited by humans until the early 19th century? History.Stackexchange.Com

Could an Industrial Prehuman Civilization Have Existed on Earth before Ours? Scientific American

Was There a Civilization On Earth Before Humans? A look at the available evidence. The Atlantic.

Technosignatures of ET life elsewhere in our solar system

THE BIG QUESTIONS Did Intelligent Space Aliens Once Live in Our Solar System? NBC News

Technosignatures of ET life elsewhere in our galaxy, outside our solar system

What is SETI?

Misconceptions about SETI


Could Solar radiation pressure explain ‘Oumuamua’s peculiar acceleration

Harvard Smithsonian Center for Astrophysics, 60 Garden st., Cambridge, MA, 02138
Accepted for publication in the Astrophysical Journal Letters


Research articles

The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record? Gavin A. Schmidt, Adam Frank

If an industrial civilization had existed on Earth many millions of years prior to our own era, what traces would it have left and would they be detectable today? We summarize the likely geological fingerprint of the Anthropocene, and demonstrate that while clear, it will not differ greatly in many respects from other known events in the geological record. We then propose tests that could plausibly distinguish an industrial cause from an otherwise naturally occurring climate event.

Prior Indigenous Technological Species, Jason T. Wright

One of the primary open questions of astrobiology is whether there is extant or extinct life elsewhere the Solar System. Implicit in much of this work is that we are looking for microbial or, at best, unintelligent life, even though technological artifacts might be much easier to find. SETI work on searches for alien artifacts in the Solar System typically presumes that such artifacts would be of extrasolar origin, even though life is known to have existed in the Solar System, on Earth, for eons.

But if a prior technological, perhaps spacefaring, species ever arose in the Solar System, it might have produced artifacts or other technosignatures that have survived to present day, meaning Solar System artifact SETI provides a potential path to resolving astrobiology’s question.

Here, I discuss the origins and possible locations for technosignatures of such a prior indigenous technological species, which might have arisen on ancient Earth or another body, such as a pre-greenhouse Venus or a wet Mars. In the case of Venus, the arrival of its global greenhouse and potential resurfacing might have erased all evidence of its existence on the Venusian surface. In the case of Earth, erosion and, ultimately, plate tectonics may have erased most such evidence if the species lived Gyr ago. Remaining indigenous technosignatures might be expected to be extremely old, limiting the places they might still be found to beneath the surfaces of Mars and the Moon, or in the outer Solar System.

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