Space Jockey's kick-starting civilization on Earth is a plot device from the Harvest script, or at least very similar too it, provided they don't just retread other Ancient Astronaut stories. In Harvest, it is insinuated that the planet being 'harvested' by the Space Jockey's may in fact be Earth, but it would have to be removed from the Derelict's plot, unless that crash is still present. Its very curious and this may be how Spaihts' ideas remained a prominent idea in the later drafts.
Where do you keep digging up these Alien Harvest inferences?!
There is NOTHING at all from the accumulated official information realeased so far that relates in any way to the Alien Harvest script! So far its looking like Shadow 19 was the blue print for the alien prequel.
All I can do in response to this question is restate.
In Harvest, the Space Jockey's are terraforming a planet that it is insinuated is Earth, and the android-hybrid character is the same person in both timelines.
That is not nothing. Time Dilation is also in Harvest, the cast is similar in gender and size, as is the Space Jockey, and the Derelict, and geez. No one is saying anything is certain. It's just a possibility. If you want to ignore the possibility, go right ahead. But I dont see any reason to. Its not a matter of like or dislike, if the possibility is reinstated, so why get so bothered by it?
Why ignore the similarity? It's not a small one, its a very big thematic similarity for both scripts to feature Space Jockey's terraforming Earth. Why overlook that similarity when we know so many changes have been made even if... Its the exact same situation as SHADOW 19. That script obviously isn't going to be this exactly. It would have to have been changed drastically to fit what we already know. We shouldn't ignore that script either. That doesn't make sense, especially since there have been so many redrafts. I mean, why is that any different than discussing the Alien 3 scripts that didnt get filmed?
The whole idea of these threads is speculation, at this point.