To introduce the world of alien organisms into terms of how the humans know of them in the universe of Alien.
We find from what Harry Dean Stanton said, the reality of the Alien take place in a part of outer space where mysteries surrounding ancient cultures and strange organisms might prevail in the way that we have heard of the yeti, the Loch Ness monster and UFOs
He thought that probably lot of strange things have been found across space and it wasn't a big deal.
It still becomes strange for the Nostromo crew to wake up in the middle of outer space and have to deal with a strange alien spaceship on a remote planetoid somewhere.
- Harry Dean Stanton:"Well. we just figured the crew was more familiar, on a mundane level with alien creatures. We figured that they had been heard of and talked about. It wouldn't have been all that new to us. From my point of view anyway,aliens had been discussed in the world in which we worked. Probably a lot of weird things had been found, so it wasn't that big a deal. Of course it's strange, but I think the crew viewed aliens like we view the Yeti or the Loch Ness monster. And UFOs for example, look at the attitude we have towards that." (Alien collectors edition p45)