True, though not reliable evidence. The problem in this case is defining what counts as even circumstantial evidence, and what counts as misleading false evidence. Without any non-circumstantial evidence to provide an outside context for our judgements of mythology, there's no way to tell what's based on reality (and to what degree) and what's just made up.

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"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
"The Mayan symbol for "book" looks a lot like a triple hamburger, but I've never seen them claiming it as proof the Mayans had Big Macs." - KaiYeves
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort