We have no good reason to believe that aliens have ever contacted Earth. Sure, there are conspiracy theories and some rather strange reports about harm to cattle, but nothing credible. Physicist Enrico Fermi found this odd. His formulation of the puzzle, proposed in the 1950s and now known as "the Fermi Paradox", is still key to the search for extraterrestrial life (SETI) and messaging by sending signals into space (METI).
There’s a decent chance that while life is common, technologically advanced life isn’t - life evolved almost as soon as conditions allowed (on a geological timescale) but it took a lot of good fortune and time for humans to appear.
I don’t know, we’re not the only species that’s started using stone tools, for example. As far as I can tell species get more or less prehensile and intelligent over time fairly randomly, and it’s just a matter of diffusion for one to reach the capability of using technology.
I don’t know, we’re not the only species that’s started using stone tools, for example. As far as I can tell species get more or less prehensile and intelligent over time fairly randomly, and it’s just a matter of diffusion for one to reach the capability of using technology.