Others?

atleast mother new about the location of the aliens, so sure to believe they met some before or atleast shows they knew it was there. so someone was there before. would be interesting to know how many different type of aliens are already known will the nostromo was sent off. but at the end of the day, why they didn´t really discuss things i reckon is that ridley and his crew didn´t have anything else in mind than kayne and getting him back to the nostromo and i think aswell the screen writers, ridley and because the movie is decades old, that people didn´t pay too much attention to so little details like people do today. so it didn´t come mind....

There are 18 known alien races currently on the planet Earth so I suspect more would be known by the time the events in Alien occurred.* *-This according to a friend of mine that couldn't pull himself away from the water-pipe.

how many of those are classified as illegal aliens?

And how many are taxi drivers?

David Wilcock and David Icke included?

Excellent point Vertigo.

In Aliens, there is a suggestion that the colonial marines are used to get ridden of "bug infestations". But to stick with the canon, I was ever under the impression that Mankind never encountered extraterrestrial life in the "alien" universe, or at leat, not intelligent life. Ash actually says that "Muther never saw anything like this" when they encounter the derelict. But I agree that there is some ambiguity in the movie and in the script, probably deliberate. I don´t remember if the novelization gives some clue. I once had it, but sadly I lost the book.

Ah, yes. The "Is this another bug hunt?" quote from one of the marines during Apone's briefing. One possibility is that as the humans colonized planets, they brought along stow-away life-forms (like what happened with rodents and snakes coming across in ships and upsetting ecosystems here on Earth). The nastiest stow-away, however, was the one that humans carried....new germs (bugs?) wiping out indigenous homo-sapiens that had no immunity. Take head-lice. During space-travel, the lice "could" grow larger, and on planets with gravity less than 1.0, that average sized New York cockroach could become something like that large crab in Jules Verne's "Mysterious Island". Who knows what can happen in space or on a newly colonized planet. Plus we can discount that some planet "may" have had non-intelligent indigenous life. Thoughts?

@centrosphere I agree that the scripts appear ambiguous, because starting from your same assumptions I'm led to believe that in the Alien universe (especially Alien and Aliens) mankind has come in contact with several examples of ET life, to the point that it's not a major concern. In Alien "they have never seen anything like that before" can mean that none of the other alien species/crafts encountered so far look like the derelict. In Aliens, during Ripley's debriefing they refer to the fact that they have never encountered that particular species before, but never openly deny that alien species exist. When the marines see Ripley the first time one says "She saw an alien once" and the answer is "I'm impressed" (which could mean "So what?", but also "Here's another nut" I concede). Then there's the reference to Arcturians and finally the "Bugstomper (We endanger species)" markings, which can be indeed a reference to space lice infestations but having marines specialised in disinfestation of vermin seems a bit too overkill. Or it could be pure banter.

I'm surprised no Predator fans piped up on this thread.