nerdygirl wrote:
But if there are aliens, we still have the same questions - where did they come from? Not just a question of where in space, but how they came into being in the first place...
You've got your questions confused.
Some folks respond to the question of "where did life on earth come from?" with "aliens planted life here". Those folks then have to explain how life on the home planet of the aliens started. And if they say that "life on THAT planet was planted by other earlier aliens, then ....
The OP is assuming that life evolved here on earth from the earth, and that life evolved on the other planet from that other planet, but that the other planet spawned an intelligent spacefaring species sooner (maybe because the planet formed earlier) than we did and that they visited us.
And gosh darn it! Theyre still at it! Abducting us! Mutilating our cattle! And vandalizing farmer's fields with graffiti!