That you can write—and I and others can read—your comment on Free Republic suggests that our planet has not been “wiped out.”
Unless the aliens were extraordinarily sloppy and inefficient (which would contradict their resource-gathering capability needed for interstellar travel), Earth’s resources and the elemental isotope distributions we see today are not “merely what’s left over,” but what this planet has had since the beginning, supplemented occasionally with some comets, meteors, and meteorites.
After the last ice age, there were about 30,000 humans left on the earth. That is practically the bare minimum for genetic continuation of the species.
I look at the western US and I see the results of a (*probably natural) cataclysm. The ground when viewed from the air shows a fast moving drainage of an ancient lake or ocean all the way down to Baja.
There have been multiple extinctions on the earth. I believe they are mostly naturally caused but there are stories from our ancient past that refer to more nefarious causes.
My mind is open. I enjoy reading all sorts of stuff. I am capable of discerning between fantasy, legend, and archeological facts. I am skeptical of aliens—mostly because of the know physics related to the distance traveled. But, it is sometimes fun to speculate.
None of the possibilities, if discovered real, is going to change whatever I decide to have for dinner.