Alien (xenomorph)

Aliens as walking libraries of adaptation

Let us think about Aliens now – one of the most ingeniously designed fictional creatures ever. One their stunning piece of biology is the complicated lifecycle they undergo, but even more exciting is their ability to adapt by ‘taking’ traits of the hosts at the parasitic larvae stage. “Perfect organism” – that’s how they’re called in the movie, and I bet, referring to this particular superpower.

Widely accepted explanation of this ability is the horizontal gene transfer. In other words, a larvae can access the genome of its host and steal its DNA fragments. Need human-like hands – let’s steal the genes responsible for them; need speed of a dog-host – no problem, let’s just steal the corresponding DNA.

The ability for horizontal gene transfer is not unknown among the Earthly organisms. In particular, bacteria are capable to steal DNA fragments responsible for antibiotics resistance from each other. The question is: do aliens act alike?

And unfortunately, they absolutely don’t. Such an explanation of the Aliens’ adaptability is absurd at very least. One of many examples when popular culture has taken a random scientific fact and twisted it all the way around. Why horizontal gene transfer has nothing to do with aliens?

  • For a light start, different aliens are born from the same host. Compare the alien from the original “Alien” movie and an alien from “Aliens”. They look totally different and have different abilities. Yet both are “born” to humans. Partially, it’s merely a redesign – we’re talking about movies, after all, and special effects evolve. However, the aliens in two movies are indeed of different “types” – that’s the official canon of the series. The original alien is called “Drone”, and the aliens from the sequel are “Warriors” (plus one Queen, of course).
  • Bacteria steal particular genes responsible for particular proteins. It’s simple. But in case of Aliens, we’re talking about complex traits. Take our hands, for example: perhaps 2/3 of our entire genome take part in the expression of hands. Look how complex they are and how many unrelated structures are unified within them. Additionally, human and alien hands are non-homologous: they are somewhat similar, but have different origins and structure. Just like the wings of birds and butterflies. The genes responsible for wings in butterflies could correspond to the genes that in birds are responsible for guts or something. The same in insects and mammals: legs of both classes have nothing in common at all, develop absolutely differently and are coded by non-related genes. The fact that we have four limbs but insects have six doesn’t mean that insects’ genome has “six times of what we have four times”. Human hand is bone, muscles, blood vessels, skin. To express our hand, one has to express those four systems in the first place. Yet an alien can acquire sort-of human hands, but preserve its alien exoskeleton, vascular system, and absolutely unhumanly looks. Even better example: take an alien born to rhino from expanded universe. Rhino’s horn is concrete hair, part of its skin, yet in the alien the horn is merely a protrusion of its exoskeleton. Rhino’s and alien’s horns have nothing in common, no matter how alike they look. Literally not a single common gene. Just like fish gills and monkey lungs: idea is somewhat similar, but the essence is heaven and hell.
  • Assuming that aliens do indeed steal the traits from their hosts, then… where are those traits? Seriously. I get it: the movie is made for people, and in our eyes humans are smart, erect and hand-efficient creatures, while dogs are quadrupedal, agile and woolly beasts. But from, say, a bug’s perspective, both humans and dogs are four-limbed, hairy, live-bearing monsters with horizontal mouth, muscular tongue, red blood and endoskeleton. Where are those in the aliens? Live-bearing and hair are defining qualities of mammals, yet aliens never get them, but some subjective minor stuff like… hm… dog’s agility.
  • While expressing complex traits (such as hands), it’s not genes that matter most, but the tools to read those genes. The human genome can be used to create a human only inside human cell, surrounded by all necessary organelles and molecules. Otherwise, DNA is just a meaningless molecule.
    In fact, not only aliens can’t have those tools – they don’t have DNA at all. Alien lifeform, guys, that are in fact not organic, but silicate. Our DNA is both incompatible with and meaningless to the aliens: like trying to use a door of a real car with a rocketship build out of LEGO bricks.

So what’s the real explanation?

Here we go. Aliens’ biology most likely is this: all those traits that we witness in different aliens are already written in aliens’ “DNA”. There already is everything necessary to express hands, horns, wings, fins and anything that we’ve seen so far. I imagine alien’s genome thousands of times longer than ours. It’s a walking library of useful genes and traits, and it’s body is plasticine. And it’s number-one imperative on the larvae stage is to choose which of those archived traits must be brought up. It’s a soldier that is about to choose his equipment for a lifelong military mission.

To do so, it must study the things around:

  1. Egg stage. We’ve seen that alien eggs are complex and can react on hosts walking nearby. Which means they have their own receptors, feelings, and can perceive information about their environment. Are there other eggs around? Are there other aliens? What animals walk nearby? What’s the climate? Perhaps, it can even communicate with other aliens. Is there something that the current queen wants to be made of me?
  2. Facehugger. Who’s I’m attached to? What’s happening around? Are there other animals? Are they trying to remove me?
  3. Chestbuster. Now, inside of the a body, our alien can learn thoroughly about its host. What’s it breathing? What’s its metabolism? What does it feed on? Is it strong? Large? Fast?

Alien observes, and then it chooses the best traits from its library. Those that are the most vital under the circumstances it has learned about. It has thousands of hand variants to choose from: grappling, swimming, small, large. And it takes to choose just one set, the best for the conditions it is about to be born to.

For example, what could be the observations of the alien from the original movie:

When I was an egg, there were other eggs around, but no adult aliens. Then I attached to a human, who was the first organism to walk by in centuries. There are other people around, not many of them. When I got into the body, I found out that humans have large brains, erect posture and grappling hands.

In result, the alien never became a queen – there were heaps of eggs around already, no need to procreate. There were no other aliens around though, so it had to prepare for the expansion of the hive. That’s how we got the drone – the alien capable of building the hive and capturing new hosts (shown in deleted scenes and expanded universe). It’s barely armed, because humans are physically weak and never acted really aggressively (e.g., tried to destroy other eggs). Most importantly, its posture and hand are human-like, meaning that it won’t screw up when it has to, say, open a door – it’s about to be born to the human world after all!

It steals nothing, just selects the best set from the vast assortment it already has. Takes everything into account:

  1. What’s with the hive now?
    – Is there a queen? If not, then maybe it’s time to become one.
    – Maybe the hive is at war, then it’s a good idea to become one of the heavily-armed forms that we’ve seen in expanded universe:

    Crusher and Ravager - two heavily-armed Alien forms.

    Crusher and Ravager – two heavily-armed Alien forms.

  2. What’s with the environment?
    – If temperature is high, then it makes sense to express heat-resistant exoskeleton.
    – If gravity is strong, then it makes sense to be smaller.
  3. Who’s the host?
    That’s the most important part. Yes, aliens are born similar to the hosts, even without gene stealing. But how? On one hand, aliens grow to hunt down animals similar to their own host. On the other, they are born to survive in the host’s world. For example, an alien is born from fish. If it happened to be inside of fish, then it’ll likely be born to its natural environment, which is water. Obviously, it turns fins and hydrodynamic bodyshape on – how else will it survive and hunt other fish? From large animals, large aliens are born (e.g., a rhino alien from a rhino). Again, the same reason: it will be born to the environment where hundreds of rhinos like the host probably dwell – it doesn’t make sense to be small among them. Aliens from humans are born with grappling hands. That’s a great choice: they’ll be born to typical human environment, say, on a spaceship, and will have to interact with the same things that we do. Of course, they don’t know what doors or tools are, and don’t entirely understand what surprises the environment has for them. Hence… it makes sense to be like their hosts. If the host survived in the environment, then the alien like it will too. “If you don’t know what’s right and wrong, do what others do.”

Indeed, aliens are magnificent creatures. Millions of bodybuilds in one. We just better not let them on Earth, but Elen Ripley does the job well


Further reads

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