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This question already has an answer here:

Say that billions of years ago, there was an intelligent homo sapien-like species that had advanced technology like that which we have today, and this species went extinct with the dinosaurs. Is it necessarily the case that there would be archaeological evidence of them? Is it possible that we wouldn't know such a species or its technology existed?

If it makes things easier, we can assume all members of the species lived in roughly the same area.

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marked as duplicate by Hohmannfan, o.m., Community Aug 30 '16 at 19:21

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • $\begingroup$ Am I correct in rephrasing your question as "In what way could advance technology and culture have existed billions of years ago, where modern scientists would not be aware of it today?" $\endgroup$ – Nex Terren Aug 30 '16 at 17:56
  • $\begingroup$ @Nex Not just the tech, but the civilization that built it, too. $\endgroup$ – user21719 Aug 30 '16 at 17:59
  • $\begingroup$ Okay, just wanted to clarify for anyone who might read this that it's figuring out how it would be possible, not estimating if it's probable. $\endgroup$ – Nex Terren Aug 30 '16 at 18:00
  • $\begingroup$ How many billions? As far as i understand Earth is only like 5 billions years old. $\endgroup$ – Mołot Aug 30 '16 at 18:06
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    $\begingroup$ If you like those kind questions, commit on the "What if..." project on Area51 :D $\endgroup$ – EngelOfChipolata Aug 30 '16 at 18:11
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I'm going to use modern humans as an analogue of how Cretaceous humanoids interacted with their environment.

It would be probable given 7 billion of them that there would be evidence of them in the fossil record. It's possible that one of these fossils would have a ceramic or metallic implant that would survive the fossilization process. Even if no evidence of the implant remained there would be indicators like missing bones from a hip replacement that would have some serious implications of technology to a paleontologist studying the remains.

Then there's the effect that modern humans are having on the geological record. There is a chance that some of our largest megaprojects would still be detectable in 147 million years.

The Antarctic ice sheet is too new for it to contain evidence of air pollution.

Probably the most detectable evidence would be an increase in radioactive isotopes in the geologic record from when the humanoids went nuclear to their extinction.

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Not unless the predecessor technologists were about as populous and industrious as we are.

We have made major, major changes to the composition of our planet. There are innumerable novel compounds that didn't exist on our planet at all until we synthesized them, and they've changed the nature of the planet. There is a movement within the geological sciences to dub the post-industrial period of Earth's geologic history the Anthropocene because of the radical changes we've made to our planet, which will be plain to see in the geological record for as long as our planet has an examiner to examine it. The idea that the oceanic ecosystems are in a possibly-irreversible process of collapse is almost universally regarded as true in the scientific community.

This is because there are so many of us doing so much, consuming so many resources, and producing so much waste. It's possible to imagine a brighter civilization that controlled its numbers and advanced its science and technology more responsibly. Perhaps a small tribe of technologists (Tesla's timelost children?) characterized by no exposure to other tribes (no external security concerns) and internal harmony (few internal security concerns) would be able to reach the information age without radically transforming their host planet... but it seems kind of unlikely. Our technological history doesn't really suggest that such a thing is possible. Particularly before the era of industrialization and capitalism (in which innovation seems to center on creating novel problems for which you can be paid for managing), innovation occurred to solve proximate problems. The level of social harmony necessary for a tiny population to innovate radically and quickly undermines any particularly strong motivation for doing so. If wild fruit trees produce a bountiful, nutritionally complete, and delicious diet year-round in your habitat, you'll never want for the science of baking, refrigeration, or even necessarily a wheelbarrow.

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  • $\begingroup$ Have to disagree with much of this...on this time scale, continents move across the globe and land rises and sinks, glaciers crush everything, and the cycle repeats. If all humanity died today, we'd leave 10 incomplete fossils at best...our buildings and technology don't fare much better $\endgroup$ – Twelfth Aug 30 '16 at 22:52
  • $\begingroup$ All the continental drift in the past and future history of Earth won't erase the perfluorooctanoic acid and countless other novel compounds that came on the scene within the space of 150 years because humans were doing chemistry. The geologic record will show that things got very weird very quickly, whether they remain so indefinitely or not. $\endgroup$ – SudoSedWinifred Aug 31 '16 at 2:06
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As I mentioned in my answer to this question: https://worldbuilding.stackexchange.com/questions/46959/earth-nukes-mars/46964#46964, the give away for previous high tech civilizations would be radioactive isotopes.

If they had nuclear power or technology, they would have produced many non natural radioactive isotopes, as they decay predictably over millions or billions of years we would be able to measure the amounts of various isotopes, similar to how carbon dating works and tell that some non-natural nuclear reactions were happening long ago.

In terms of actual physical artifacts, things survive, that's how we know about dinosaurs and other ancient life via fossils. The obvious place to look for artifacts of an advanced civilization is in space, but micro-meteors and other space debris would actual cause wear, and most orbits decay or drift in the time frames your talking about, but say finding a lump of refined metals or other non natural material (polymers alloys etc.) would definitely be an indication of ancient advanced life.

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Finding a piece of their technology that soft-landed on the moon would be a good proof. Other than solar wind and meteorites, there's no erosion up there.

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  • $\begingroup$ I had worded it as a rhetorical question: now rephrased. $\endgroup$ – John Feltz Aug 30 '16 at 19:04
  • $\begingroup$ Yeah, it is ok. $\endgroup$ – Hohmannfan Aug 30 '16 at 19:09