Alien life cycle

I bet this has been discussed before, but Search didn’t turn up any hits…

OK: here’s the life cycle of an Alien (from the movie of the same name):

  1. Queen lays eggs.
  2. Egg remains dormant until a potential host walks by.
  3. Facehugger leaps out of egg and attaches to host, and deposits egg? larva? in host.
  4. Chestbuster emerges from host, messily, and grows into full-grown alien.

This is so weird.

First – it’s almost like there are 2 different species involved: species A gives birth to species B, which gives birth to species A.

Second – what would the evolutionary advantage be of having a 3 step growth process, with dormancy periods in the middle?

Third – is there anything remotely like this in the real world?

Tapeworms? Eggs which can remain dormant for quite some time, IIRC, passed around between mammalian hosts. However, tapeworms as adults don’t really live outside a host’s intestines; in fact they don’t have a true digestive tract of their own and absorb food that we’ve already broken down “for” them.

How about parasitic wasps? The female implants an egg in a host insect of some kind. Inside, the egg eventually hatches, then the larva devours its host and eats its way out.

And remember, there doesn’t have to be an evolutionary advantage for some characteristic to exist - there just have to have been no significant disadvantages that outweighed the current method.

To be picky, step 3 should read “Facehugger leaps out of egg and attaches to host, and deposits embryo in host”.

Yeah, it’s weird. But it makes for a good sci-fi premise with the overall goal of being scary. As to your questions,

Kind of. The facehugger exists solely as a vector to deliver the parasitical embryo to a host. However, since the alien queen lays the egg which contains the facehugger which contains the embryo, it’s hard to posit that they’re separate species.

An alien queen laying eggs that hatched into warriors doesn’t make as scary of a movie as eggs that hatch into another kind of alien that deposits an embryo inside of you that will kill you when it is born. It admittedly looks overly complex from a reproductive standpoint. However, if I’m gonna defend this, I’m gonna find a way.

Having eggs remain dormant until a viable host is nearby ensures that overpopulation will not occur and that the species will not need to compete with itself for an ecological niche. Furthermore, it allows an egg to exist in statis indefinitely and reassert the species at a later date on its own. If a hive is exterminated but one egg is left behind, that egg can ultimately generate a new hive given a sufficient supply of hosts.

Furthermore, by containing only a delivery method for the embryo, the egg itself need not contain the nutrients necessary to grow the embryo; rather, only enough for the facehugger to hibernate. The host provides the nutrients for the embryo.

Placing an embryo inside a living host can spread the species geographically, in that a mobile host can move to a new area before birthing the alien, potentially in a location that was unaccessible before. (Space station, et cetera.)

And it makes for a good movie.

There are some wasps that lay their eggs in prey. Spider wasps, for example:

I can’t think of a real-world equivalent to the queen-egg-facehugger-embryo process, though.

In real life, jellyfish have a polyp stage and a medusa stage, both with different ways of reproduction. cite

Insects are a perfect example of organisms that have very different body plans and ecological niches during different life stages.

Insects typically have:

  1. Egg
  2. Larva
  3. Pupa
  4. Adult

This is comparable to the alien life cycle. The aliens lay eggs. The eggs hatch into facehugger larvae. The job of the facehugger is to find a host that will provide the nutrients while in the pupal stage. When the pupal stage is over, the new adult rips free.

Typically in insects the larval stage concentrates on eating, while the adult stage concentrates on mating and laying eggs. Aliens are a little different.

However, we still don’t know how a queen’s eggs are fertillized, or what causes an egg to develop into a queen instead of a warrior, or if there are other castes we haven’t seen. Maybe these are developed in the comics and novels, but not not in the movies. But if Aliens follow a social insect pattern, it could be that unfertillized eggs develop into warriors, while fertillized eggs develop into Queens and males. Or it could be that the warriors are actually males, or it could be that there are no males.

Lemur, I don’t think metamorphosis is a good analogy. The 4 steps you cite all occur to a single individual; without getting too anthropomorphic, I think you could safely say that the “identity” of the bug hasn’t changed, just their physical form. In the alien, though, the facehugger is not the same thing as the chestbuster: the facehugger is dead, while the chestbuster is scuttling around.

You’ve obviously given this some thought, lno. I like that. :slight_smile:

To have used the wasp model in the movie, a full-grown alien would’ve had to grab Kane, ram an ovipositor down his throat*, and then send him on his way. A very different script; I think I like the existing one better. More suspense & surprise.

*[gratuitous MST3K reference] “…but I’m not an alien…”[/GMR]

There’s also a difference in the source material for your aliens:

In Alien there was no queen. The lifecycle was never fully detailed except in the director’s cut that showed:

  1. Egg
  2. Facehugger (who impregnates host)
  3. Chestburster
  4. Adult
  5. Egg

The adults would attack whatever they could find, immobilize them and coat them with alien slime which would start to break down the victim. The victim’s own biological material would be converted and the end result would turn into an egg containing another facehugger, and the cycle would repeat.

Like I said, this is only in the director’s cut, but you can see this process there when Ripley finds Brett and Dallas towards the end of the movie. Dallas is being slowly enveloped and digested by alien material and incoherently begs for Ripley to kill him. Brett’s much further along, with only his disfigured head sticking out from the top of the egg. In a way this life cycle makes more sense because it’s self-perpetuating.

Of course, when James Cameron wrote *Aliens *all he had to go on was what was in the theatrical release as far as the alien life cycle and it was incomplete. So he came up with the Queen and made the logic work for his movie.

But in the Alien mythos, the aliens themselves might be a biological weapon created by the owners of the derelict spaceship on LV426, created to do as much damage as possible. If that’s the case, evolution doesn’t factor in at all, and the aliens can be as creepy and improbable as they need to be. :slight_smile:


ez, I like this model – it does make more sense.

I’d heard about the director’s cut, and the scene with Dallas; but I thought it was more along the lines of the victims in Aliens, who are stuck to the walls while their chestbursters grow to maturity.

It also explains something I’d heard (somewhere, in the past 26 years…): that the eggs in the alien spacecraft are related to the fate of the alien crew. As you explain, each egg would be what’s left of one crew member.

Since you want to be picky, think about this: when the facehugger attaches itself to Kane, Kane falls unconscious. Even if he hadn’t been unconscious, you could hardly expect him to stagger back to the space ship by feel with that creature completely covering his eyes. It seems to me that this is a very poor method of spreading the species geographically.

I am intrigued by the idea that the aliens were a bioweapon developed by an unknown race in a (perhaps) long-forgotten war. This probably makes the most sense. The aliens would be developed for one purpose and one purpose only: to annhialate every living creature (with a face) on a given planet. Especially if the developers had no intention of inhabiting those planets themselves, but simply as a way to rid themselves of potential economic rivals.

My question has always been as to how the “birthed” version adds about 200 pounds of bodyweight in about a day without eating any of the carbon-based life forms available. All the people and cats are still around. Now THAT’S some interesting biology.

The human infecting stage of Schistosoma parasites comes close. Called a cercaria, it is a little swimmer roughly half body and half tail. If it finds a host in the water in the few days it is viable it penetrates the skin by wriggling vigoruosly and releaseing secretions that soften up the skin at the point of penetration. During the process it sheds its now unnecessary tail and leaves it outside the host.

Pretty effective little guys - some 200 million people are infected wordlwide.

  • Tamerlane

Damn it, I wanted to say this.

Oh well, I should add that Cameron did know about the previous life cycle type. But the problem with this is the lack of a specific goal in the movie. With a queen xenomorph you have something to go for, a boss, a headquarters.

I’ve seen some sources (such as the original Alien vs. Predator comic book series) claim that only some eggs will hatch into Queens; most eggs will simply hatch into warrior drones, and cannot perpetuate the species on their own. Is this canonical w/r/t the movies?

I’m sorry, but this strikes me as silly. How would the slime know how to convert the victim’s biomatter to form a new egg?

The father of the whole Alien mythology, Dan O’Bannon, did indeed base the whole facehugger/chestburster thing on the spider wasp. He loved the almost unbearably goulishness of another species using you for an embryonic host (and while keeping you alive!)

Oh, you know, its like, smart slime, or something!

It is a little hard to accept (which is why, I think, both Scott & Cameron didn’t mind leaving it out). You could say that its more than just slime, and that it doesn’t so much convert you into an egg, but just uses you as food while it grows into one.

And when nobody’s looking the alien uses magic fairy dust…

How does a single cell grow into a full human being?

Simple answer: a wizard did it. :slight_smile:

All good points. Some non-movie sources try to address this, hypothesizing situations where a male alien drone will mate with the female queen, being killed in the process, but fertilizing a ‘queen’ egg.

Well, Kane did awaken after the facehugger dropped off, albeit only a few hours before the breakfast scene. And the impregnated colonist in Alien: Resurrection had, likely, a few hours of ambulatory movement before his birthing. It’s a poor method, and likely slower than an alien drone carrying an egg to a new location, but it’s an additional method nonetheless.

The only indication we have is the queen embryo implanted in Ripley in Alien[sup]3[/sup]. It leads one to believe that only specific eggs carry facehuggers that carry queen embryos. However, non-movie material (the Leading Edge Games rpg, for instance, along with some comic books and other sources) mention how a drone can undergo a metamorphosis in an area without a queen so as to begin the formation of a new hive.

I’ve never really liked Ridley Scott’s take on a cocooned person becoming another egg. The alien lifecycle from Aliens seems nice and tidy and plausible enough; the ‘smart slime’ just feels like it’s pushed a little too far into handwaving-science-fiction. Part of the appeal of the universe, to me, is that it’s not very high-tech compared to other standard space movies. No warp drives, no phasers, no teleporters, just guys with ballistic guns, flamethrowers, improvised spears and nets. Of course, this is a personal line that I’ve drawn, and someone may think that hypersleep chambers and motion detectors are too sci-fi for them…

The explanation of the derelict spaceship in Alien and Aliens (director’s cut) that I like best is that they were transporting alien eggs for reasons unknown to us, and the safeguards they put into place failed, and aliens infected the ship, killing the crew and pilot, causing it to crash on LV-426. The eggs looked like they were in a cargo chamber - perhaps the ‘haze’ was supposed to keep them from opening, or maybe it was an impenetrable force-field that weakened over the months/years/centuries since the ship had crashed, or…

What can I say? I’m a sucker for this franchise, as I posted in the AvP movie thread. :slight_smile:

What are you telling me for? Call up Dan O’Bannon and Ridley Scott! :slight_smile:

Seriously, I didn’t have any trouble with it. As Maud’dib pointed out, we all come from a single cell. The slime, or whatever it is could carry genetic material, like a virus. It could break down the cells of the victim, like mold perhaps, and reorganize itself according to its own DNA to make an egg. And it does make the alien a lot more self sustaining and harder to eradicate. Instead of needing a queen to make a hive, all it takes is one adult and a lot of hosts.

Out of curiosity, did you think the 1982 version of The Thing was silly?


IIRC from “The Book of Alien” the designers deliberately wanted to make the alien’s reproductive system different and bizzare because it was, well, an alien. They wanted to make something that was completely removed from anything humans had experienced. Don’t get me wrong – I LOVED Aliens and her royal highness, but a queen her hive is something any kid with a backyard is familliar with. I give 'em props for trying to do something other than taking an earth critter and giving it big teeth. That kind of creativity in science fiction is often lacking.


Incidentally, you can dl the deleted scenes on the web. I don’t think they’re edited and remastered like in the Director’s Cut, but its worth seeing for completeness if you can’t get ahold of the DVD.


What did the aliens live on before humans happened to show up in their sector of space?