I was drafting the first paragraphs of an "alien invasion" sci-fi
story last night.
Early this morning, while laying in bed deciding if I really wanted to
get up :)>, and so building a story outline, I realized what the
narrative the faux aliens could tell when they appear during the
tribulation period.
  They could say that several thousand years ago, they discovered a
large ape like species on our world. So, being the "good guys," they
decided to do genetic experiments, producing a hybrid species that is
now US!
   For a thousand years, they walked openly on Earth, helping us build
the first cities.
Then one day, a swarm of asteroids collided with the Earth, wiping out
everything and almost everyone. After that, they gave up on their
project, and have just been occasionally visiting since then.
   It certainly is a plausible story, a convenient half truth that the
lost world can and will buy.
   And yes, some version of that will make a good sci-fi story ...
Lewis B