We think we're the first advanced earthlings -- but how do we really know?

Imagine if, many millions of years ago, dinosaurs drove cars through cities of mile-high buildings. A preposterous idea, right? In a compelling thought experiment, scientists wonder how we would truly know if there were a past civilization so advanced that it left little or no trace of its impact on weiter …

Source:: https://www.sciencedaily.com/releases/2018/04/180416124327.htm

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