Interesting, isn't it? Stars decay, form planets, and lifedust. This gives the chemical and biological unity of the universe. The same elements are present on the other side of the universe as they are in the solar system. Spectroscopy shows this.
Thus far, we can't detect the biological features of extrasolar planets, but we can detect the bigger planets, and that's fascinating.
Imo, it's evident that advanced (human-like) civilizations have detected us long, long time ago, probably from the moment Earth's fortunate bioforming. Just as we are now taking small steps in the exoplanetary field, exponentially advanced civilizations must be doing this since ages, and thus must have detected us, long before our young technological era.
Ergo, one should assume that the Earth must have been visited - at least once - and even more... Extraterrestrials must have played a certain role in the Earth's biological evolution. Wouldn't we garden a young, fructile planet?
There is good evidence for antique visits. The same saucer-shaped UFO's that we've been photographing since the '50s are painted on classical paintings and tapestries. No doubt about that.
Compare
these(Argentinia, 1970's) to
these(15th century).
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