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History of the Xenomorph

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The lifestyle of Internicivus Raptus suggests it would have evolved in a fecund environment like a jungle. Only an environment with a very large and constant supply of available prey would be able to sustain a species like I. Raptus. If dropped into anything less than an extremely rich ecosystem I. Raptus would quickly use up all available resources and die out. The low metabolism is also consistent with a warm climate. However, the ability to endure cold and enter frozen suspended animation suggests an extremely cold climate.

This can be reconciled surprisingly easily by postulating that the climate I. Raptus’s planet of origin is characterized by alternating periods of heat and cold. A likely model is a planet with a highly elliptical orbit, alternately carrying it very close to and very far from its sun (perhaps it is actually a moon of an eccentric gas giant that orbits within the life zone, like one of the RL planets of Upsilon Andromedae). The prolonged intense sunshine of the planet’s periastron “summer” would support luxuriant tropical growth and a very rich ecosystem. During the long apiastron “winter” the temperature would plunge. This would present a quandary for animals. They would need to be very well adapted to heat to survive the broiling summer and very well adapted to cold to survive the freezing winter. Nor would migration be an option: unlike Earth’s axis-determined seasons, the orbit-determined seasons of I. Raptus’s homeworld would be planet-wide.

For small plants and animals a likely solution would be to have generational cycles tied to the seasons: they would die in winter and leave behind seeds and eggs that would grow and hatch next spring. For larger plants and animals hibernation would probably be a popular option; just drop your leafs or fatten up and sleep through the long cold months (imagine it, this planet would have deciduous tropical forests!). Large animals that braved the long cold winter months would need particularly tricky adaptations. On Earth many animals have seasonal coats that are shed in spring when they become too hot. Some animals on I. Raptus’s homeworld may well have taken this a step further, alternating between a low-energy summer metabolism and a high-energy winter metabolism that they could switch between in response to environmental stimuli. A prolonged day/night cycle, which would also create extreme temperature fluctuations, may have also helped push animals toward such a development. Transplanted to other environments this would translate into great resilience to adverse temperatures, such as I. Raptus displays.

This would be a seasonal ecosystem, dying back in fall and coming back to life in spring. Spring on such a world might be characterized by fierce demographic warfare between competing species. For plants and animals on such a world success would lie in growing and reproducing as fast as possible as soon as the spring thaw comes; claiming as much trophic space as you can before a competitor can squeeze you out. In the context of a rich but seasonal ecosystem characterized by such competition I. Raptus’s tendency to increase as quickly as resources will permit with no eye to sustainability makes sense.


OK, so we’ve established a plausible scenario for Internicivus Raptus’s homeworld, but still, what could produce a species like this, especially its weird reproductive process?

Let’s take a trip through space and time, to Internicivus Raptus’s homeworld tens, maybe hundreds of millions of years ago. During this time nothing like the I. Raptus we know would have existed. But if one looked in the treetops during this period one might notice great balls of organic matter held together with slimy, resinous material, like giant bird’s nests. The material of these nests is a superb natural insulator; protection against the heat of the day and the cold of night. These are the hives of a small eusocial arboreal predator that lives on arboreal fruit and leaf eaters, bird-analogs, and their eggs, as well as the occasional fruit and other plant material when opportunity presents itself or food is scarce. The food is gathered by small armies of males. Sometimes one will capture a particularly impressive meal and bring it alive back to the queen for consumption. Its reward was a chance to mate. In winter, when temperatures plunge below freezing, the trees lose their leaves, and food becomes scarce the creatures hibernate, their bodies becoming icicles to be thawed by the warmth of the returning sun in the spring. In the cold of night they simply ramp-up their metabolism, a significant advantage as it allows them to hunt and gather at night, though it comes at a significant cost in energy. The queen lays eggs during the year, fertilizing itself from a spermatheca in which it saves the gametes of the males who bring it the best prizes. The creatures are highly intelligent, as arboreal creatures in challenging circumstances often are. They have enough foresight to stockpile food in their nests, including some of the live trophies, which are cocooned in the nest’s walls to be killed and consumed at leisure. During the spring some of their surplus eggs hatch, including a special egg that contains a new queen. The young are spider-like creatures that descend to the forest floor and walk off to find a new tree where they can molt into a second instar, then gorge themselves and quickly grow into adult size. They have evolved an interesting defense against predators: their blood contains a precursor compound that, upon contact with air, reacts to form a short-lived but extremely potent acid. Any creature that tries to feed on one finds itself missing its lower jaw after the first bite. These are the humble ancestors of the terrible Internicivus Raptus.

At some point, something pushed these creatures out of the trees. Perhaps a climatic event or mass extinction temporarily destroyed the forests. Perhaps a predator evolved a countermeasure to their acid blood. In any case, something pushed the ancestral Raptus to build its nests on the forest floor. There it became an opportunistic predator-scavenger. Its body adapted to function better on the ground. Freed from the need to stay light enough for branches to support its weight it was now free to become bigger and stronger. Its new lifestyle still provided it with a wide variety of challenges, so it had good incentive to retain and increase its intelligence. Like the earliest human ancestors, it would have adapted to life on the ground by becoming an upright biped, explaining why the modern Internicivus Raptus has a similar stature to humans despite having a totally different lifestyle. Like its arboreal ancestors it would have continued the behavior of males vying for a chance to mate by bringing live prizes to the queen. With its increased size and strength one species among the new prey that came within its reach was a particular large herbivore. This herbivore also hibernated in winter, but it had evolved this ability independently, and its hibernation was more like that of a bear; its metabolism slowed down, but it didn’t stop, and as a consequence it had to eat profusely to fatten itself up during the summer. This development would set the stage for the transformation of this creature into the Internicivus Raptus we know today.

This immense, fatty beast would form a significant food source for the hive, especially if it was captured in autumn, when it was bloated with food. If left alive until other food had been consumed it could extend the activity period of the Raptus into the winter months. The Raptus could hibernate to survive the cold and lack of food, but winter may have held other dangers. All those animals hibernating in winter would have amounted to a massive amount of defenseless meat, and it seems certain that some predators must have evolved to exploit this resource. The ancestral Raptus’s acid blood probably at least partially constituted a chemical warfare defense against such predators; a Raptus slaughtered in its winter slumber would have quickly had its revenge, as the predator died a horrible death as the acid-precursor thawed in its digestive tract. But it’s also logical to think that, sooner or later, some such predator may have developed a countermeasure to it. By decreasing its hibernation time the proto-Raptus would have decreased its risk of being slaughtered in its winter slumber. A selection pressure would have been established for the Raptus to seek out this herbivore and bring as many as possible into the hive as a food store for the winter. Eventually it could eliminate the need for winter hibernation entirely in all but the hungriest years. The adaptations that served to allow survival during the chill of the long nights would have served well to let them survive the winter, so long as food was assured. No longer need the Raptus fear devoured in its sleep.

With this herbivore being vital to the Raptus’s lifestyle in this way, the Raptus might have begun to make use of it in other ways. The Raptus’s larval offspring may have adapted to use the still-living herbivores as a food supply, attaching themselves to them and consuming their blood like giant ticks. Eventually they may have extended this lifestyle into endoparasitism. At first this might have taken the form of premature molting, followed by the molted young either burrowing into the body or crawling down the creature’s throat. Gradually, this was refined into the familiar facehugger implantation process we know.

This would have been a significant evolutionary advantage to the Raptus. The huggers could implant the cocooned herbivores in the autumn and winter, and the chestbusters could be synchronized to emerge when the herbivores began to come out of hibernation in the spring. By conserving the implanted herbivores all winter the Raptus could be assured of a population explosion each spring, allowing them to fill up their ecological “space” while rival predators were still just beginning their own spring round of reproduction. The Raptus now had a significant evolutionary leg-up over its competitors. This change in lifestyle was not without a price, however, namely greater difficulty in founding new hives. Remember that at this stage in the Raptus’s evolution the emergence of the chestbuster was tied to the metabolic changes in the prey-herbivore as it emerged from hibernation; facehuggers that left the colony would find their implanted parasites widely dispersed by the time the chestbusters emerged, and the queen and drones would have to wander considerably to find each other. The solution to this was a modification in the “royal” facehugger causing it to carry a male and female parasite. They could infect two herbivores in the same herd and the male would emerge first, and would guard and then fertilize the female. This would reduce genetic diversity greatly, but it was presumably worth the trade-off. This created the conditions for the emergence of a third drone caste of sterile males. The drones and males apparently evolved divergently, with the drones retaining bipedalism while the males evolved for greater speed, becoming the quadrupedal “Runner” form encountered on Fiorina 161. This may be because a bipedal creature would have difficulty keeping up with the herd, and hence the queen-host, so the males would have needed speed. The drones, on the other hand, hunted the herbivores by ambush, and did not need to be able to keep up with them, so there was no pressure for the species as a whole to abandon its relatively primitive and awkward bipedal stance.

This situation could have continued for quite some time, but at some point something disrupted it. The prey-herbivores started to die out. Perhaps it was due to the evolution of a new type of vegetation than outcompeted the one the prey-herbivore relied on for food, perhaps the Raptus itself hunted them to extinction, but whatever it was it killed them off, but not fast enough to also quickly kill off the Raptus that relied on them. The Raptus was forced to adapt. It was by now too committed to its parasitoid reproductive cycle to go back to conventional reproduction, and there were presumably no closely related species it that it could easily switch to. The Raptus’s solution was to evolve to be able to parasitize off a wide variety of animals, instead of relying exclusively on one species.

This was a great milestone in the evolution of Internicivus Raptus, marking the beginning of its transformation into the creature encountered on LV-426. Like most species that reproduced in a parasitoid manner, its population levels had previously been tied to the population of the prey-herbivores. Now that it was free to exploit a wide variety of animals as chestbuster hosts it could reproduce almost without restraint. The only limiting factor on its numbers were now food supply, gross supply of large animals in the area, egg-laying rate of the queen, and the ability of the drones to capture a suitable supply of prey. The population of the Raptus would have exploded. The constant pressure to fill up as much trophic space as possible during early spring would have pushed the queens in the direction of pumping out as many eggs as possible, causing the population to rise further. Very quickly, the Raptus would have become the dominant predator on the planet. Without serious competition from rival carnivores it could afford to need more food, and hence to become bigger and stronger. It ceased to be a “wild dog” and instead became a “lion”, increasing dramatically in size and strength. Needless to say all this was probably a disaster for its competitors and prey. Internicivus Raptus undoubtedly drove many species into extinction by competition and overhunting, and its ecological impact on its homeworld may very well be comparable to that of early man. Only prey species that reproduced quickly or were too big or otherwise dangerous for a pack of drones to take down are likely to have survived. Today it is probably the apex predator on its homeworld, and undoubtedly the most successful one, combining intelligence, strength, high reproductive rate, and a high level of organization. Ash was not exaggerating all that much when he characterized it as a perfect animal.


Internicivus Raptus’s arboreal origins are inferred from its quasi-humanoid form and the fact that it has crude but well-developed grasping hands, despite the fact that it has never been observed to use tools. Such traits only make sense in a creature that was once a climber. The excellent climbing abilities it demonstrates in the films is more evidence for this. The I. Raptus drone has a generally similar body plan to a human, so a not too dissimilar evolutionary history of descent from tree-dwelling to ground-dwelling would make sense.

Evidence for the acid blood not actually having a low pH in the creature’s body can be found in Alien Resurrection. The Ripley-hybrid uses hemoglobin (we know this because her blood is red) and probably many other human proteins (melanin, for instance, since she’s not an albino), which would almost certainly not last long in a bath of concentrated industrial strength acid, yet her blood has the same acidic qualities. There are also many other factors pointing to I. Raptus physiology not being profoundly alien enough for such phenomenally low pH blood to be viable, such as the fact that they use DNA, can presumably live on foods such as may be found in the Nostromo’s stores, and can parasitize off humans despite the fact that our blood should be like Draino to such an organism (in fact all this makes them a lot closer to us biochemically than a true alien probably would be, perhaps some form of panspermia is at work in Alien universe). Concentrated acid blood is problematic on a very fundamental level since it would destroy virtually any long molecule, so it does not seem very likely to be a necessary aspect of the creature’s physiology. On the other, as was pointed out in Alien, it makes a wonderful defense mechanism, and perfect sense as a chemical weapon against predators.

There has been speculation that Internicivus Raptus can survive on inorganic carbonates such as stone, which it would dissolve with acid secretions (see Anchorpoint Articles), but I see no compelling evidence for this unlikely ability. If Internicivus Raptus could get most or all the nourishment it needed from rock it would not have gone to all the evolutionary trouble of becoming an efficient predator, and it would not need teeth, which it obviously has. Its rapid growth in Alien can be easily explained by it raiding the ship’s food stores. As for AvP, it seems only logical that the Predators would have left food for their hunt animals. I do infer a relatively wide diet however, based on its ability to derive nourishment from human food stores, which would probably mostly be unappetizing to a strict carnivore.

The idea of a Raptus “king” is invoked as an alternate, more evolutionarily plausible, explanation for the Runner alien in Alien 3. So where were the kings in Aliens, A:R, and AvP? In Aliens the answer is probably just that it was there and we never saw it. Alternately, I. Raptus queens might practice sexual cannibalism, like praying mantises. As for the one in AvP, that can easily be explained by the queen having a spermatheca-like organ in which it preserves sperm, similar to that found in some insects on Earth, so that it would only need to mate once. The queen in A:R was obviously a mutant, so that can probably be dismissed.

The Predalien is more difficult to explain without invoking the dreaded “they take on the characteristics of their hosts” concept, and I can’t even begin to imagine how such an ability could have evolved. One possibility is to simply dismiss as a random mutant; a freak like the ones in A:R, but this reeks of desperation. Another possibility is that it is an artificial ability, introduced to the “domesticated” Raptus stock maintained by the Predators in order to make them more challenging opponents, which is not present in natural Raptus stock and may or may not have been present in the Raptus stock represented in the LV-426 derelict. This is probably the better option; it allows us to admit the obvious without accepting the premise that Internicivus Raptus must be a wholly artificial lifeform without a natural history.


Now that we’ve worked out a possible natural history for Internicivus Raptus the obvious question is how it came to be on LV-426. We know that the Predators hunt Internicivus Raptus for sport, so this suggests one obvious possibility. But the derelict ship on LV-426 was not a Predator ship, or at least its pilot was clearly not a Predator. So what did his race want with a hold full of Raptus eggs? One theory is that they were bioweapons, though I have always been dubious about this. While Internicivus Raptus is certainly a magnificent predator it would not pose a very serious threat to a properly prepared modern military (although presumably with some modifications it might, as it supposedly would have been worth billions to Weyland-Yutani’s bioweapons division).

It seems likely that the derelict’s builders (sometimes referred to as the “Space Jockeys”) had contact with the Predators, since they both acquired I. Raptus somehow. The most likely scenario is probably that the Predators acquired their Raptus stock from the Space Jockeys. One might imagine a scenario like this. The Space Jockeys found Internicivus Raptus’s planet of origin many millennia ago. Upon learning of Internicivus Raptus’s unusual nature they determined that the Predators might find them interesting to hunt. Apparently Raptus hunting quickly became all the rage with the Predators, and the Jockeys no doubt profited handsomely, providing the Predators with drone eggs for their hunts, either collected from the Raptus homeworld or bred from their own captive stock. Of course, their profits would have depended entirely on the Predators never acquiring a fertilized queen of their own, and since we know the Preds had access to at least one as of AvP the trade probably dried up long ago. But at some point before that there was an accident on one of the cargo ships, the crew was forced to set down on LV-426, some facehuggers got loose, and… well, you know the rest. Alternately, perhaps the LV-426 derelict was a Predator ship and the pilot’s species was a slave or subject race of the Predators.


The Predators seem to share some rather interesting characteristics with Internicivus Raptus, that seem to suggest they may come from rather similar planets. They are both rather implausibly tough animals, suggesting evolution in a quite hostile “green hell” environment. Like Internicivus Raptus the Predators have characteristics that would seem to indicate origin in a hot environment (their notorious love of heat), yet they are able to function just fine in Antarctica with an apparent minimum of protective clothing (presumably the film studio decided Predators bundled up like polar explorers just wouldn’t look very threatening), suggesting they too possess a variable metabolism that can be supercharged in response to cold. It seems a bit of a coincidence that the two species would both come from very similar planets (although, in fairness, given how many eccentric gas giants there are among real life known exoplanets, worlds something like the one that produced Internicivus Raptus may not be all that rare). Could it be that they actually evolved on the same world?

While there are some interesting similarities between Internicivus Raptus and Predators (they both have green blood, for instance) there are very great morphological differences, suggesting they come from very different evolutionary lineages. Internicivus Raptus has an exoskeleton, the Predators do not. Internicivus Raptus has no eyes, the Predator does, although they do not function like our eyes, seeing in infrared rather than visible light wavelengths. Internicivus Raptus lacks the distinctive Predator jaw configuration, indicating a divergence going back farther than the first creatures with movable jaws. Yet Earth also has its land dominated by two very divergent lineages of animals: insects and vertebrates. It doesn’t seem beyond possibility that a planet could have two competing lineages of large land animals. One might envision a scenario in which the decimation of its host species which first compelled I. Raptus to diversify its hosts was part of a general mass extinction that wiped out most of its order of life, setting the stage for the Predator’s distant ancestors to take over. In this case Internicivus Raptus would be a survivor from an earlier era on the Predator homeworld, like crocodiles are on Earth. It would certainly explain the importance of Internicivus Raptus to the Predators: I. Raptus would have probably have been the early Predators’ greatest natural enemy. One of the first great projects of an emerging Predator civilization would probably have been the systematic destruction of the nests of Internicivus Raptus. Internicivus Raptus would undoubtedly have featured prominently in early Predator mythology and cosmology; if this theory is correct one wonders if the hunts they carry out today might not actually be religious rituals, like the Mayan’s ceremonial ball games. They certainly seem to incorporate elements that one would not normally associate with simple sport hunting (the “duels” at the end of the first and second films, the ritualized scarification with the blood of the first Raptus killed seen in AvP, the cop being allowed to live at the end of Predator II).

Of course, it this theory is correct we must explain the Space Jockeys. Perhaps, as was already pointed out, the pilot of the derelict was a slave or subject race of the Predators. Alternately, perhaps the Predators were once a slave or subject race of the Space Jockeys, and later gained their independence one way or another.

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