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The Alien (Xenomorph)

The following is a highly speculative theory regarding the evolutionary history of the alien creatures and their natural hosts, as well as the nature and conditions of the alien homeworld. These speculations are based on the following assumptions; that the alien evolved on a planet and was not created de novo by another species in its current form, that the alien and its homeworld have been shaped by physical and evolutionary forces which are similar to those in effect on our own world, that the alien is not the dominant life form on its homeworld, existing instead as part of a complex ecosystem, and that the homeworld is as diverse with life forms and potential habitats as is our own. The information used as a basis for this speculation comes solely from the ALIEN, ALIENS and ALIEN3 films.


The Alien Species
Life Stages, with images
Homeworld Speculation

The Species

Important common features of aliens taken from the 3 films:

  • Host dependent reproduction
  • Dual stage metamorphic life cycle
  • Metallo-silicate exoskeleton
  • Endoskeleton in juvenile form
  • Growth-stage mediated shedding of skin
  • Low pH blood
  • Increased speed & strength (relative to human standards)
  • Large curving crania of varying morphology
  • Internal mouthed tongue
  • Carnivorous external teeth
  • Air sac bellows in the juvenile form
  • Articulated limbs and tail in all life stages
  • Varying number of limbs and digits in different life stages
  • Predatory or greater intelligence
  • Copious production of "slime"

Presumed common features observed in some subset of the films:

  • Presumed sociality and communication (i.e., the hive was not a fluke)
  • Internal pressure greater than 14 psi
  • Body temperature equals ambient temperature
  • Can "breathe" underwater
  • Nest built in hot area

Some or all of these features may be due to the adaptation/modification of the organism to its current lifestyle as a space faring parasitic species. In the case of modification, it would be most parsimonious to assume that the aliens were intended for use as biological weapons. This theory assumes that the creatures found in space are adapted or modified to living in this habitat, and focuses on estimating their possible ancestral forms and the state of the ancestral homeworld. It assumes that any modifications and adaptations have been made using pre-existing characteristics, so that the ancestral creatures posses similar characteristics. The creatures found in space are referred to as "modern" in the following discussion.

To avoid confusion between discussions of various theorized species and their respective life cycles, the life stages have been specified as follows:

[1] Egg released from queen. (maturation phase - this period might occur in "utero")
[2] Egg matures. (dormant phase - length of this phase is indefinite, until Host signals are detected)

[3] Egg releases crawler, follows host signals, secures breathing orifice. (implantation phase - 24 hours)
[4] Crawler implants embryo in host breathing system and dies. (gestation phase - 1 to 10 days)

[5] Chestbuster emerges from host.

[6] Chestbuster stage undergoes a series of instar-like transformations until the imago is achieved.

[7] Queen-imago creates egg.

The life stages encompassing the egg and crawler are referred to as JUVENILE, and those encompassing the chestburster and imagoes are referred to as ADULT.

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Life Stages


Eggs are initially created inside a queen alien and enter the world (after being queued in her extended abdomen) via slimey tube to stand on their own (indicating that there is a definite "up" side and "down" side to the egg). The egg itself is a leathery object "'s full of leathery objects; like eggs or something..." Kane (Alien), translucent and approximately 2.5 feet tall. According to a scene that was cut from ALIEN these eggs could also be "constructed" by a regular alien "infecting" an organism (which would undergo some sort of metamorphosis) however, this concept was not supported (nor denied) in ALIENS and ALIEN3. It is important to note that this method was the originally intended method of the designer of the Alien, H.R. Giger.

ALIEN3 eggs - the egg in ALIEN3 was smaller than we had previously seen and it was more bulbous.


Face Huggers

Hibernating inside one of these eggs is a parasite, commonly referred to as a face-hugger. When a viable host is brought near a closed egg (either by curiosity, or being cocooned and held in place) it triggers the "contents" of the egg to come to life. The egg opens and the face-hugger launches out at the organism and attaches itself by wrapping a long "tail" around its victim's neck and using long spider-like legs (like a spider, the face-hugger has 8 legs) to firmly grip the organisms head. The face-hugger controls the amount of oxygen its host receives and puts the victim in a comatose state while it reaches down the host's throat and lays an egg. In order to ensure that the job can be completed with little outside interference, the face-hugger has concentrated acid for "blood" (a possible self defence mechanism) and can strangle its host with its tail "'s not coming off without tearing his face off with it." Dallas (Alien). After the egg is planted in the victim's body, the face-hugger leaves the host (who will soon re-gain consciousness and have no recollection of the implantation) and dies. "...he's got an outer layer of protein poly-saccarides, has a funny habit of shedding his cells and replacing them with polarized silicon which gives him a longer resistance to adverse environmental conditions." Ash (Alien).


Chest Burster

The alien begins its life by bursting from the chest of its host. At this stage in its development it has a small cranium, tan-colored skin and is susceptable to fire.

ALIENS chestburster - Unlike the one in ALIEN this chestburster had arms.

ALIEN3 chestburster - This chestburster was different from the ones in ALIEN and ALIENS; it was more "mature looking" immediately after its birth. Specifically, unlike the chestbursters of the previous movies, this one had legs.



Alien (Warrior)

As the chest-burster matures, it sheds its skin (similar to a snake), its cranium becomes elongated and it has a hard, dark (black/green) outer shell (exo-skeleton). The mature alien has concentrated acid for "blood" and a higher tolerance to fire. As indicated in ALIENS the alien creature does not "show up" on infra-red scanners which would indicate that it does not emit heat. One distinguishing feature of the alien is that it has two mouths, one inside the other. According to H.R. Giger, the inner mouth is in fact the alien's "tongue" (it is such a vicious creature that even its tongue is dangerous). Another interesting feature of the alien is that it does not have (what we would perceive to be) "eyes".

ALIENS alien - these aliens only had 3 fingers as opposed to the 6 fingered creature in ALIEN. Aliens in this movie had a "ribbed" cranium unlike the smooth cranium of ALIEN.

ALIEN3 alien - This alien is different than the previous ones we've seen; it tends to move around on all fours at times and ensures that the unborn queen alien is kept safe. It's possible that the aliens copy some of their host's DNA in order to help them adapt to the new environement that they'll be born to (this concept was in an old draft of the script for ALIEN), so this alien would be different because it came from a dog. Also, we have seen relatively few aliens. If you imagine what a whole planet full of them would be like, there might be a variety of different kinds: warriors, workers, messengers, etc...

ALIEN RESURRECTION alien - These aliens have a darker appearance. They definately have a high form of communication which is best seen when the three aliens talk to each other in the cage in which they are locked up. In this scene we also find out that aliens do have the intelligence to sacrifice one of them to open up doors that would otherwise be kept shut. They also are seen swimming. Their agility under water is higly evolved. They are also portrayed as highly intelligent strategic planning creatures: they form alien egg-filled traps for humans. They also don't need the queen alien that much to figure out what to do, as in ALIENS. These aliens are far more smart than in the previous movie.


Alien Queen

ALIENS Alien Queen - little is known about her. From ALIEN3 we know that a queen alien can be born in the same way as a regular alien. Some things that we do know about the queen: she has a much larger cranium than the usual alien and is slightly taller (approx 2-3 feet). The queen has the ability to create and lay eggs (through the use of the extended abdomen) and she has the ability to survive without the extended abdomen (for an unknown amount of time).

ALIEN RESURRECTION Alien Queen - This queen has the ability to procreate with a womb instead of an abdomen. It also created a nest which is less resin-like and more flesh-like. The womb opens up with a slit which runs all over the 'stomach'. The alien that emerges is full-grown and is largely human. The queen also seems to be more attached to the womb than the one in ALIENS, and is slightly deformed. Her arms are shorter and stick backwards from the first joint. The nest she makes also does not need humans like in ALIENS. In this movie the facehuggers are there to create drones for the nest, but the true birthing takes place in the womb. The queen does not seem to be able to create eggs anymore.

Alien Child

ALIEN RESURRECTION alien child - In the last movie we get to see that the alien species can mix its appearance with the appearance of humans and vice versa. The alien queen is able to retrieve information from the body of the Ripley-clone. It grows a womb, in which a new alien grows which is part alien and part human. It seems most of it is human, due to the appearance of the creature and the urge it has to see Ripley as its mother and not the creature that gave birth to it: the new alien queen.

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Homeworld Speculation

(assuming that the aliens are not entirely subterranean)

The homeworld has a higher atmospheric pressure and possibly a greater gravity than terrestrial standards. It has oceans which are of a very low pH and most likely an atmosphere of similar low pH. The EM spectrum incident upon the homeworld is significantly different from terrestrial standards, lacking "visible" wavelengths. This might indicate that the planet's orbit is very large, that it is extremely overcast or that it orbits a weak sun. In this case, the ecosystem might be based on geochemical and geothermal systems. Geothermal activity might also provide a relatively high ambient temperature. The acidic nature of the aquatic and atmospheric environments might also be due to extensive production of hydrogen sulfide and other "high energy" compounds via geochemical activity. A high level of volcanic and tectonic activity might be maintained by tidal forces stemming from planetary and stellar bodies in the system.

An ecosystem not based on photosynthesis would require radically different energy production schemes. Such an ecosystem might be founded on thermo- and acidophilic microorganisms. Larger autotrophs might incorporate endosymbiotic versions of these microorganisms. Vegetative "plants" would be found around areas of geothermal and geochemical activity, both on the surface and on the floor of the oceans. Other organisms might exploit the difference in pH and temperature at the boundary between aquatic and terrestrial environments. If volcanic activity were responsible for the overcast nature of the atmosphere, incident light might be used by photosynthetic organisms high in the atmosphere. Thermophilic photosynthesizing organisms might also be found near lava flows. Areas free of volcanic activity would be dead zones, possibly inhabited by hibernating organisms awaiting an increase in ocean level or the occasional lost creature.

Extensive tectonic and volcanic activity might result in habitats subject to frequent change. A geothermal habitat might be replaced by a geochemical or volcanic habitat, or might be flooded. If this were the case, organisms would have to be either extremely adaptive or mobile in order to survive.

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Variation in the surface morphology of the head seems to indicate a sensory function. Lone adults have uniform smooth reflective heads, while adults functioning in a nest have distinct anterior and posterior head sections; the posterior region being covered in a ribbed pattern with a sagittal crest, and the anterior region being characteristically smooth with a pair of pits on either side of the head. This morphology in social organisms may be used in sonic and chemical communication. That this ribbed pattern is visible in the neck regions of the lone adult may indicate that the smooth reflective surface of the heads serves as a canopy covering more complex structures.

This smooth canopy is reminiscent of the smooth surfaces of the queen's headpiece sheath. This sheath is comprised of at least three independent pieces, the largest of which possesses several overlapping flanges. Various sized holes are visible between these flanges, and the entire sheath may serve as a production organ for chemical signals. In the transformation from imago to queen-imago (see the discussion of ancestral types below), the adult canopy may develop into the sheath. Once this transformation has been accomplished, the new queen would issue chemical signals destroying the canopies of any nearby adults.

If the ribbed structures beneath the canopy corresponded to modest versions of the signal production organs beneath the queen's sheath, and were used for communication between nestmates, the canopy might serve to isolate a lone adult from foreign signals. Canopied adults would in effect be "deaf" to most nest signals. If all nestmates are progeny of the same queen, then the canopy destroying signal produced by a particular queen might be genetically specified. A canopied adult which found itself near a foreign nest or a foreign queen would not be susceptible to that queen's signals, and would develop into a queen. An adult which found itself near a related nest or queen would lose its canopy and join the nest. A dead queen would be replaced by a young canopied adult. It could be assumed that an uncanopied adult would be utterly subservient to the commands of a queen, in which case it might be possible for one queen to kill another and steal the uncanopied members of the nest. The canopy must allow limited communication, as a valid queen must be able to order its destruction. Possibly, canopied adults would be capable of identifying hosts harboring embryos as well, and could act to protect related embryos and possibly destroy unrelated ones.

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