Xenomorphs from series is known for their ability to enhance their host DNA by absorbing/altering DNA to give birth to a new type of creature.

  • alien hugs dog so it creates a dog-alien "runner" (alien³) and ripley says

"I haven't seen one exactly like this before, it moves... differently."

  • alien facehugs human, drone happens (aliens)
  • alien meets predator, predalien is formed (aliens versus predator 2)

Why don't they do it on their own kind? Because they are perfect already?

Maybe they try and they have 10th concentric mouths(mouth opens, another mouth bursts, it opens, another mouth bursts, it opens, until 10th mouth bites meters away from alien)? Even more acidic blood? Then normal aliens fear and attack these so these can't live?

Maybe simply they need more DNA to complete missing parts in their own but can't take their own?

Maybe because their acidic blood stops chest-bursters bursting chests?

Why didn't Weyland Yutani try this? Why own people? They could try with an elephant or some octopus?

Reddit says adult xenomorph simply chews facehugger. What if facehugger is the one seen on the new movie that is a lot bigger? (not covenant2017, the movie before that)

  • Related discussion on another site; What would happen if a facehugger impregnated a xenomorph?
    – Valorum
    Feb 9, 2017 at 21:51
  • I shall look at it thanks Feb 9, 2017 at 21:55
  • 3
    probably the same reason you wouldn't procreate with a close family member, genetic diversity
    – DForck42
    Feb 9, 2017 at 22:40
  • @DForck42 you said family, I said kind/branch. Think like worms living in whales but they are procreates with their own kind. Feb 9, 2017 at 22:54
  • so, it looks like parasitic worms, which the face hugger egg thing resembles a bit, DON'T procreate, rather they produce eggs that are then discarded via waste and then consumed by another animal
    – DForck42
    Feb 9, 2017 at 22:58

1 Answer 1


I don't know of an explicitly stated canon answer (though I haven't watched/read every Alien franchise work), but I don't think any special or unusual mechanism is required to explain this.

On Earth, predators have a 'search image' - criteria for what looks like viable prey. They don't indiscriminately attack every living thing. While the facehuggers apparently have a pretty wide range of potential targets, that doesn't make it necessarily unlimited. There have to be some limits so that they don't randomly attack rocks, machines, trees etc. - presumably one of those criteria is 'not another xenomorph'.

If the question is how they can reliably distinguish xenomorphs when these come in different forms, the regular alien, predalien, and runner/dog-alien all share common features like the weird head/jaw shape and the bone/chitin-like skin. Plus maybe they smell the same (does a facehugger even have eyes?)

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