Xenomorphs: How a Universe of Alien Biology Continues to Evolve Today
The Alien franchise has had ups and downs, but without fail, the films paint a beautiful biological mosaic.
Whether or not you’re a fan of sci-fi horror, it’s hard to avoid the cultural permeance of the franchise — and above all else, it’s the creatures that have made the biggest splash. The xenomorph has appeared in seven (soon eight) blockbuster films and over a hundred comics, novels, and videogames spanning the last 40 years. It’s kind of a big deal.
And as with Star Wars, Dune, and countless other sci-fi epics, the Alien universe has been chronicled at length by fan communities eager to explore and extrapolate the depths of this universe in immense detail. And to be frank, the xenomorph is worthy of the research — it’s the ultimate hunter, one that perfectly preys on all our fears as movie-goers. As described by Roger Ebert in his look back at the 1979 original:
I disagree, but let’s move past it.
There are few individual creatures that deserve more praise, both as film icons and as pinnacles of speculative biology. But this post isn’t about what the xenomorph is or how it operates as a predator. Rather, I want to look at how this creature and its franchise keep changing the rules of the game. Just as Alien (the franchise) has evolved over the last 40 years, and as we’ve learned more about the xenomorph, so has the interpretation of its life history.
How does that biology — and especially how it’s matured over time on screen— impact how we viewers experience the ‘verse. So without ado, let’s jump back to the beginning.
This, ladies and gentlemen, is the chestburster! One of five life stages of the xenomorph species, each more iconic than the last. I’m not going to run through the full scope of each stage — there are better in-depth sources for that — but I want to highlight a few bullets to make sure we’re all on the same page. The biology here is amazingly robust, and I wouldn’t be surprised if this post spawns a few more in the same vein. Xenomorphs are just that cool.
And beginning with the chestburster, there’s an obvious point to start with: xenomorphs are parasitic. And not just parasites… but parasitoids, which are defined by killing the host they inhabit(ed). Parasites are some of the most fascinating creatures around, and not to mention woefully underrepresented in in science fiction, so when we finally see one that reaches pop-culture acclaim — let’s celebrate with analysis.
Parasitism (more often than not) is an evolutionary advantage on two fronts: first, it’s an easy way to find free food. Once you land yourself a home, you’re basically set for life as long as that host stays safe and warm and fed, day in and day out. Until it gets sick and dies at least, but more often than not parasites don’t actually kill their hosts. Chestbursters and other parasitoids are exceptions, but we’ll get to that.
Secondly, and more importantly, parasitism is key for curbing population fluctuation. When resources get low and a host species slows down their own reproduction, parasites will be immediately responsive. It’s a very effective type of feedback loop, which are critical for species that live in ecosystems with rare or unpredictable resources. In deep space, this evolutionary strategy actually makes a great deal of sense.
Parasitoids are slightly different — these species will often kill a host in order to provide food for new babies that hatch and mature inside a decaying body. It’s still a feedback loop, but one more common for predators that will be able to rapidly respond to population growth in their prey. The life strategy of xenomorphs is actually remarkably similar to that of parasitoid wasps that live, amazingly, here on Earth. Some creators of the franchise have even acknowledged the similarities, but the connections with insect life don’t stop there. Like most types of ants, bees, or wasps, xenomorphs are a eusocial species, meaning that the animals live in colonies with queens that oversee reproduction and drones that handle the nitty-gritty tasks, like fending off predators or gathering food.
On the topic of reproduction though, and in stark contrast to these insect similarities, xenomorph eggs will also exhibit dormancy and stay in stasis until a host disturbs the nest. Much like the real-life examples of parasitism, dormancy is also a means of population feedback — although one much more common in plants than in animals. Again this makes perfect sense when considering that the alien species may be stranded in deep space for long periods with little access to resources.
The rest of the xenomorph anatomy is a grab-bag of adaptations that make the creature the perfect predator. Armored skin, bladed tails, acid spit, double-jaw… they add up to the ideal hunting machine. Greusome.
All this adds up to tell a perfectly succinct evolutionary narrative, although it’s worth noting that other theorists have offered conflicting backstories which are each genuinely valid and exciting in their own way. As for my interpretation of the evidence: xenomorph eggs lay dormant in space until disturbed by a host species, which the parasitoid larval stage uses to find nutrients and protection quickly before maturing into a top-tier killing machine. The animals can live socially with a queen and large-scale reproduction, but are also solitary predators that are fiercely territorial.
It’s like if wolverines and bees had a child, but that child lives in deep space.
Given this information, xenomorphs are swarm predators that are optimized for insanely rapid periods of population growth, followed by long phases of dormancy. Actually this tells us a lot about what it’s like to be a predator in deep space — food is hard to come by, so when you stumble on a meal, you chow down fast. It helps to be the perfect apex predator too; that way, no matter what type of meat you find, it’ll provide a hearty meal.
That’s what the old movies used to suggest. At least, until Prometheus.
A new drop of evidence in our bucket of data. The movie asks a lot of questions that (many authors would argue) remain unanswered, but regardless of the fine details, it casts a few broad strokes that dramatically changed the context of our hypothetical alien ecology.
And actually, that’s a wonderful thing to see happen.
In Prometheus, we’re informed that the xenomorphs did not actually evolve naturally at all. They were engineered by a distant humanoid race to be a planet-killer, more similar to a nuclear bomb than a wolfpack or beehive. This extreme degree of artificial selection isn’t something we’ve seen in our own biology, at least not on such scale. Humans have bred dogs and veggies to incredible lengths; in theory, the engineering of a superpredator wouldn’t be outside the realm of possibility.
Now we analyze the species a bit differently: a bioweapon engineered to perfectly eradicate a species. The dormancy and parasitism no longer just suggest a patiently waiting predator with scarce food supply; now we know it’s designed as a time-released weapon that incorporates its host’s DNA to develop into a perfect hunter. Aim the xenomorphs at a planet and pull the trigger, nature will do the rest.
Everything we “knew” about xenomorphs changed on the extension of the franchise in 2012, but as I said at the start of this post, I’m not trying to advocate that any single interpretation of the biology is right or wrong. If anything, the study of Alien has become a closer parallel to what real-life evolutionary ecology is actually like.
Just as with real science, new evidence is a constant variable in the equation. Daily research by ecologists into ants or apes or aardvarks may uncover a new element of their anatomy or behavior that fundamentally alters how we thought the species evolved. Look at how our understanding of dinosaur evolution changed at the discovery of a feathered tail just months ago. Or how new data on ant farming gives us a better look into their behavioral origins. Week by week, more information gets published that alters our existing understanding of lifeforms, their behavior, and the story of how they evolved.
And guess what? Our narrative changes. We modify and rewrite our evolutionary stories to fit in with the changing data we’re presented with. That’s science.
So the Alien xenomorphs aren’t just another example of how biology on screen paints a secret story, but also how that story is a hypothesis prone to change. If anything, because the Alien story appears inconsistent and tangled and, at times, even contradictory… it’s the most accurate portrayal of biology I’ve seen in film.
And as these movies continue to get produced, I look forward to seeing how the stories continue to evolve. Throw another wrench in the equation, Ridley Scott. Make it more fun for the rest of us.
