I don't think it's farfetched to assume that extraterrestrial lifeforms do in fact exist.
I think it's more farfetched that, by way of sheer hubris, we have come to the forgone conclusion that we are completely alone in a universe where there are many equally as inhabitable planets that we know of and others that we've yet to discover as they are far beyond our reach.
What I personally have never seen is actual evidence that would be firmly convincing. The pentagon's most recent video depicting an aircraft that moved in ways that we could not explain certainly added fuel to the idea that we are not alone.
After all the shit we've seen and experienced this year alone, nothing would surprise me at this point. If alien species were to present themselves tomorrow, I'd simply accept the fact that it was bound to happen sooner or later.
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