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I watched all movies of the Alien series and I'm still unsure about the origin of the Aliens.

In the first movie it somehow got onto the Nostromo spaceship. Then in "Aliens vs Predator" there is something about the Predators keeping Aliens just to hunt on them.

I am confused. Where do the Aliens come from?

Alien Warrior

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up vote 5 down vote accepted

We don't know. James Cameron never wrote a back-story for them.

The shortest answer is that there's no canon explanation for their origin. The writer; James Cameron never created a back-story for the xenomorphs, content that each movie should stand on its own merits as this interview shows;

"Daniel Line asks more questions about the derelict which, as a writer, I could provide plausible answers for, but they're no more valid than anyone else's. Clearly, the dental patient was a sole crew member on a one-man ship. Perhaps his homeworld did know of his demise, but felt it was pointless to rescue a doomed person. Perhaps he was a volunteer or a draftee on the hazardous mission of bio-isolating these organisms. Perhaps he was a military pilot, delivering the alien eggs as a bio-weapon in some ancient interstellar war humans know nothing of, and got infected inadvertently."

If you want to go into more depth, there is an extensive speculative commentary on Aliens Wikia regarding the origin of the "xenomorph" aliens that Ripley and others encounter in the Aliens Franchise movies.

In brief, there's no in-universe description of where they came from, nor have we seen either their genesis as a biological weapon, or as a naturally evolved species on their own planet.

We do know from the film Alien that they weren't native to LV-426 and in the film Prometheus we see them being experimented on genetically (which definitely lends credence to the suggestion that the alien pilots seen in Alien and Prometheus were intending to use them as a bio-weapon) but that's about it.

There's also no indication whatsoever that the Predators had any hand in their creation.

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The characters in Prometheus speculate directly about the likelihood that the building they discover is an Engineer military facility which was used to develop the xenomorphs as a biological weapon, intended to be deployed against Earth. While there's no canon "proof" that the aliens were created by the Engineers (as opposed to simply being appropriated and modified by them), I think the on-screen discussion about the possibility lends it heavy weight. – Brian S Feb 22 '14 at 12:13
@BrianS - I agreed with your point that without proof all there is is speculation. I'm not so sure you can jump from that to "they created the aliens", after all in Alien : Resurrection you find Ripley and various aliens inside a human genetic research lab. Aliens finding that facility could easily jump to the conclusion that we invented the aliens... – Valorum Feb 22 '14 at 12:34
Point of order: I move that Prometheus, both AVP, and Resurrection all be ignored as canon. Instead, they should be shot out of a cannon into a deep ocean trench. – John O Feb 22 '14 at 20:35
@JohnO - Along with jarjar – Valorum Feb 22 '14 at 20:49
Didn't one of the comics give them a backstory? I have a vague recollection of some such. – JdeBP Feb 24 '14 at 23:21

The Xenomorphs are almost certainly biological creations of the Engineers shown in the film Prometheus.


  1. Xenomorphs are able to reproduce inside of human beings - Without specific adaptations do so this seems to be impossible. And since they don't come from world where human beings are native, they cannot have evolved to break down the bio-chemicals barriers which separate organic species without some type of engineering.
  2. Xenomorphs are able to exist in Earth-like environments as demonstrated in the Alien Vs Predator portion the franchise - Unless they had been specifically adapted to this (which would likely have been a serious undertaking) this seems to be impossible that this would have been a natural occurrence.
  3. While the franchise never specifically states this, the Xenomorphs seemingly have only been found in areas where the Engineers have been present - Given the remote possibility that they evolved on either LV-426 or LV-223 (the planet and moon from the Alien/Prometheus franchise) then their existence should not have been a "surprise" to the humans which encountered them

While it is possible that a race of beings could have evolved to predate upon human beings or been biologically adapted to do so, it is more likely that such a being would be created to do so rather be a naturally occurring entity. Given the Xenomorphs proximity to the Engineers a reasonable inference can be made that their existence is the result of Engineer bio-technology experiments.

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I'm upvoting because I think your answer is mostly correct, in that the Xenomorphs were biological creations of the Engineers. However, your first point is a little weak, since there are instances of Xenomorphs gestating in non-human mammals as well as Predators.… – Doresoom Jul 28 '15 at 15:27
Without specific adaptations do so this seems to be impossible... they're Aliens with acid for blood. Who knows what their physiology is capable of? – Daft Jul 28 '15 at 16:34
Seems like Aliens are able to exist in almost any type of environment, as opposed to being specifically adapted/engineered to Earth-like ones. – Andrew Mattson Jul 12 at 15:20

If you've played Alien vs. Preditor, the videogame, at the end, the human race learns about the xenomorph home world location, but you can't tell where because the language on the computer is the preditor writing.

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Is the video game considered canon for this franchise? – Aegon Jul 12 at 13:35

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