When did xenomorphs first exist?

There is the belief that the Engineers did not create the first xenomorphs, but rather they were trying to breed them on their ship as weapons in Alien. The creatures seen in Prometheus (the octopus-type ones, not the xenomorph at the end), were a different type of weapon they were trying to breed. Actually, I think it's a good theory that makes sense. There's an article outlining it that someone posted in another thread, you can find the article here: http://thewertzone.blogspot.in/2012/06/filling-blanks-tying-prometheus-to.html?m=1

AVP isn't canon, so they're ignoring it, not forgetting it. But, the space jockey with the burst chest carrying the egg cargo from Alien is older than the engineers in Prometheus, so even in the canon universe, the xenomorph already existed, in familiar form. The one we see at the end is some kind of clumsy step toward the known finished product created via the black goo rather than naturally arising from the normal life cycle. Or heck, maybe that's just what a baby queen looks like, and that explains why it is so much larger than what we're used to seeing freshly born.

AVP means NOTHING in this whole mythology, ymisofine...ignore ANYTHING from those films...

So I read another thread that discussed the idea that the eggs and xenomorphs that Ripley has to deal were an ancient, and natural version (meaning they were bio-engineered, they were just sort-of gathered by the space jockeys for use as a weapon) and that the vases and new, Prometheus xenomorph is an advanced refinement of that weapon. So the timeline would be Ripley xenomporhs are millions of years old (also based on some line from Alien about the space jockey being fossilized) and the new one is only about 2000 years old. I'm sort of partial to this idea (especially the egg to vase part) but it does seem like that Ripley xenomorphs are a bit more of an efficient killing machine...however we haven't seen the new one grow up. And maybe it is just a baby queen (the queen did have that sort of hood that her primary jaws rested under).

sorry, weren't bio-engineered.

also, there's the mural and the sort of temple room which looks like it could be a sort of shrine to the origin of the new weapon...but what's up with that green rock?

Thanks for the feedback guys. Its all very interesting.

I don't think the 'proto-xeno' at the end of Prometheus was a Queen. The Queen that grew inside Ripley in Alien3 bursted through her chest in the same worm-like form as Kane's passenger in Alien. The proto-xeno was shown bursting out of the engineer as fully-formed which leads me to believe it's a different type altogether. Possibly a lesser-evolved version.

To keep the storylines sorted out maybe we need one set of threads/posts for Prometheus/Alien and another for anything else related to Alien/Predators/Prometheus. I am having enough trouble trying to grasp details and overall themes in the former without considering the AVP world. I would say when I think of xenos I sort of lump all of the alien creatures(are they entities yet?) in Prometheus all together not quite sorted out. That is not fair because of how each is portrayed in the movie.or how they transformed Fifield/Holloway/Millburn. As far as the Deacon name it contiues a religious theme in my book and somehow is a link to the Alien movie world