From a scientific point of view, it's not difficult to come up with a monster. Monsters don't have to be realistic or believable. They just have to be frightening. They look frightening, they do frightening things, and there doesn't need to be any scientific thought behind the matter. Monsters don't need to make us believe in monsters. Monsters are designed to make us fear monsters. If you put most monsters to the test of evolutionary science, they fall apart. And that's perfectly okay, because monsters are oftentimes creatures best left trapped in the pages of a good book.
What differs the science fiction alien from the traditional monster is often believability and scientific plausibility. Creating a believable alien takes a little research, because science fiction stories are often not about aliens, but are stories with aliens in them. While good horror can be about a spider that appears as a clown, a good science fiction story leaves us looking up at the sky and wondering where those aliens are. Unlike monsters, we can believe aliens exist after reading about them.
Science fiction is about what can be, and in order to create a believable alien, you'll need to start by looking at what already is. Let's take a look at life as we know it, so that we might create life as we don't know it.
Definitions of Life
If you were to go out looking for an alien, what would you be looking for? How would you recognize a living thing if you saw it? Do you expect little green men or a single cell? Believe it or not, the scientific community hasn't fully committed to a definition of life, but the most popular traits of a living organism are the ones you may remember from the fogginess of grade school. I don't need to reinvent the wheel here, so I'll just use the list from Wikipedia. Deal with it.
- Homeostasis: Regulation of the internal environment to maintain a constant state; for example, electrolyte concentration or sweating to reduce temperature.
- Organization: Being structurally composed of one or more cells — the basic units of life.
- Metabolism: Transformation of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
- Growth: Maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
- Adaptation: The ability to change over time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's heredity, diet, and external factors.
- Response to stimuli: A response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is often expressed by motion; for example, the leaves of a plant turning toward the sun (phototropism), and chemotaxis.
- Reproduction: The ability to produce new individual organisms, either asexually from a single parent organism, or sexually from two parent organisms.
Viruses fall outside of this list, since they can evolve and multiply like living things, but don't metabolize anything and require other cells to replicate, making them "questionably alive." But besides that, this list isn't a bad definition of life, right? It seems to fit pretty much everything here on Earth.
...which, of course, is the problem. Every living thing on Earth shares a remarkably similar genetic code, and the vast majority of theories agree that all life evolved from a single source on this planet (whether or not the source actually originated here). These traits define life on the only source we've ever known, which is like saying you know what music sounds like even though you've only ever heard a single song.
That's not a fault of science, but rather a result of our inability to account for variables we haven't encountered on our little blue planet. Which variables, you ask?
Alien Biochemistry
In general, life on Earth has adapted to the Wal-Mart brand of chemicals. Everything making up life here is cheap and abundant in the galaxy, so when we look for life on other planets, we're usually looking for environments similar to Earth. But they aren't the only chemicals in the universe, and if we take into account hypothetical substitutes for our essential Earthly chemicals, then you'll notice how significantly we have to expand our classification of "habitable planets." Let's take a look:
Water: An incredibly simple chemical that does some really neat stuff, such as lower in density when it freezes (as opposed to almost every other known substance). Water is the solvent (soup broth) in which our bodily chemical reactions take place. Everything on the planet needs at least a little water to survive, and because of how life evolved here, nothing can replace water.
However, not everyone is convinced that life can only exist using water as a solvent. Isaac Asimov pointed out that ammonia is pretty similar to water in most of the ways that matter for organic reactions, and theorized about life forms that use ammonia as a biological solvent. It's not as good as water in places like Earth, but in environments where water is scarce or at temperatures that would turn water into ice, ammonia could hypothetically serve as a ready substitute.
Oxygen: Oxygen is important for respiration, which is how our body breaks down food and nutrients to make energy. Perhaps you know from personal experience that if you go too long without oxygen, you die in a few minutes. Even plants need oxygen to perform respiration, so it's got to be a pretty important component of life, right?
Well, not if you're a certain type of microorganism. Even here on Earth, there are organisms that can survive perfectly fine without oxygen using a process called anaerobic respiration. Now, this is a far less efficient method of producing energy than aerobic respiration, and the only organisms that can survive for long using anaerobic respiration tend to be microscopic and have low energy requirements. But we can say with certainty that oxygen would not necessarily be a requirement for alien life.
Carbon: You've probably heard that we're made of carbon, and perhaps you know that the definition of "organic" is "containing carbon." Carbon is such a big deal due to the element's rather rare ability to form four separate bonds, allowing carbon to serve as a backbone for immensely complicated compounds, such as those necessary for a living organism. Carbon is the dark part in the middle of the structure below:
There are a few other elements which are capable of forming four bonds and therefore could theoretically replace carbon, but only silicon can remain somewhat stable while doing so. Silicon forms the basis of non-carbon life in many science fiction stories, but has a lot of drawbacks compared to carbon, mainly that silicon is bigger, which in chemistry limits its ability to bond as creatively and dynamically as the smaller carbon atom. In fact, even though silicon is far more abundant on Earth than carbon, the latter element makes up all life, which probably is a galactic hint that silicon isn't an evolutionary favorite. Considering that carbon is the fourth most abundant element in the universe and a major component of stars, it seems unlikely that extraterrestrial life would bother using anything else.
So what do aliens look like, then?
There are two trains of thought when it comes to how aliens would develop, and they both follow theoretical evolutionary pathways.
1) They look like us.
Let's assume for a moment that Earth is a fairly rare bird in the galaxy, and life can't exist without the resources and environmental specifications found here. Life would then only develop on Earth-like planets that have liquid water, plenty of oxygen, a temperature range between 0-40 degrees Celsius, and so forth. Any planet not meeting this criteria would fail to develop life.
In such cases, we could reasonably expect life to look like it does here on Earth. Evolution allows the development of the best-surviving body types for any particular organism. So if life is developing in similar conditions to Earth, then evolution would favor characteristics similar to what works on this planet as well. We could expect symmetry, and legs and eyes on animals, chloroplast-like structures in plants, and so forth. The organisms might still look pretty strange, but they would be familiar at the same time. We would probably know right away that we've found extraterrestrial life.
Keep in mind that certain fictional body types don't exist here on Earth because of natural biological limitations, and these limitations should be true for any Earth-like planets as well. For instance, the reason we don't see giant sea monsters like those found in Cloverfield or Godzilla is because of how difficult it would be to sustain even a single creature of that size from a diet of tiny fish. The blue whale, for instance, has to consume around 8,000 pounds (3.6 metric tons) of krill per day. Basically, the more Earth-like your planet, the more Earth-like your creatures should probably be.
2) They're unfathomably different from us.
Going back to what I said earlier, the only basis we currently have for defining life is what we can find on this planet, and how life evolved in the environments and with the resources found here. But many scientists don't rule out the possibility of life evolving in completely different circumstances with completely different building materials. And this is where a science fiction author can get truly creative, because now you can create a living organism that is so alien, we might not even realize it's alive.
For instance, what if an alien life form appeared to only live for a fraction of a second? Time is relative, after all, and though a lifetime and reproduction cycle of milliseconds might be difficult for us to fathom, there isn't much from a scientific point of view which would prevent this theoretical creature from existing. What about a creature that lives in the middle of a water cloud in space? Space is the most hostile environment imaginable for humans, and it's difficult for us to imagine a life form that could survive in a vacuum, but could it be possible?
If you want to create a truly unique, weird alien that survives in unfathomable environments or by unknown biological methods, then you're only limited by your creativity. The main thing to remember is that creatures look the way they do because of evolution, so your alien should be adapted to survive in the place it came from.
How can I come up with interesting aliens?
Luckily for us, aliens are nothing more than unfamiliar evolutionary products resulting from bizarre environments, and if you look carefully, you'll find plenty of bizarre environments right here on Earth. Bizarre environments produce bizarre creatures. Since guessing at fictional evolutionary pathways isn't an exact science, my suggestion is to look at one of the strangest environments on the planet: the deep sea.
I have a horrible phobia of sea critters. It's not the fish that scare me, but rather the things that live under water that we can't see. I recently had a nightmare about Charybdis, because that's the kind of person that I am. But I feel somewhat justified, because the deep sea is a relatively isolated place that doesn't see much sunlight, and produces some really terrifying creatures, such as the angler fish, goblin sharks, and (*shudder*) the giant squid.
Chances are you aren't writing your aliens to resemble sea monsters, but what's important here isn't what they look like. Focus instead on how creatively these guys evolved. For instance, angler fish produce their own light, which attract prey, and have one of the most bizarre mating strategies we see in the animal kingdom.
So it's a thought experiment. Look at Earth's environment, then look at your fictional planet. Figure out what the differences and similarities are between the two planets. When you create your aliens, match the adaptations to the similar aspects between environments, and diverge in the places where your environment is different than Earth's.
Let's try one together.
Say your hero is flying around a gas planet, and you want to add a bit of life to the environment. A gas planet is remarkably different than Earth, but we can say that both planets have an atmosphere, both planets must have nutrients, and both planets have at least one sun that's providing a constant source of energy to the planet.
Now we have to start thinking about what kind of evolutionary adaptations would be needed for an animal survive there. I'm going to imagine a jellyfish-like creature, which has the ability to inflate and float in the gaseous atmosphere, since gas planets don't have solid ground. I know it needs to eat in order to be alive, so I'd imagine that it consumes nutrients from the air, inhaling like a giant, inflating stomach, absorbing the nutrients, and then "exhaling" the waste back out. Its reproduction would need to take place in the air as well, so how about something akin to pollen, where gametes are sprayed into the air and caught by receptive partners? Of course, the randomness of this process would make finding a designated female in the population difficult, so perhaps my aliens are sequential hermaphrodites, like many sea animals.
There. Without a huge amount of effort, I've managed to create a floating bag of an alien that lingers in a completely alien environment, yet is fairly believable because I ensured that it has ways to fit all the definitions of life. It may not play a huge part in my story, but it certainly makes that random gas planet feel far more alive, doesn't it?
Alien Intelligence
It may seem strange that I've talked so much about aliens, and yet dedicate only this short section to alien intelligence. The reason is twofold.
First, the development of human intelligence is rather a mystery to us, evolutionarily. There are several theories out there, but so far, we aren't really sure how we ended up being the only animals with the capacity to study our own brain. True sentience is a unique evolutionary trait on Earth, and the only reason we have it is because of our highly-developed brains. So if you give any animal an advanced brain capable of language and reason and empathy, you have the capacity for intelligence. Scientifically, there's no reason your space dragon or space jellyfish can't also develop advanced intelligence, as long as you ensure there is some sort of complex nervous system, whether in the form of a brain or something more creative.
Second, as I mentioned in my evolution article, human intelligence has given us the ability to control our environment, which means we can somewhat control our own evolution. Sure, that can be in the form of genetic engineering, but even the simple fact that we can sit inside of a room instead of out in the snow has fundamentally changed our evolutionary pathway. When you create intelligent aliens, you can build them from an evolved template, but realize that even basic technology such as shelter and language will affect evolution. A lot of how an intelligent alien looks and functions depends entirely on how technologically advanced you've created them to be.
Do you think aliens actually exist?
Yes, absolutely. I've never seen any, and I don't believe in ghosts, or people who can talk to the dead, or telekinesis. I believe in aliens because, when you consider the scope of our universe, the idea that we are alone out here is insanity.
Understand that in our own solar system, we are but one of two different planets (including Mars) within the habitable zone around our star. Our lone, unremarkable star is only one among at least two hundred billion in our galaxy, many with their own planets, and many of those planets within the habitable zones of their stars. And even this mind-boggling picture is only a speck of dust in a cosmic ocean, because there are hundreds of billions of galaxies in our universe, each containing hundreds of billions of stars, each star containing its own solar system.
If this is difficult for you to picture, then you might understand why even a rare event like the formation of life would be, in a universe filled with such a vast number of stars, perhaps even a common occurrence. Life, and even intelligent life, could litter this universe.
So yes, I believe in that vastness where we are so unimaginably tiny, there are alien animals and plants on other planets, and alien authors writing alien columns about aliens. And maybe, some alien science fiction author is imagining a hypothetical alien race made up of muscely bipeds covered in hair and only just beginning to realize that there is so much more to the universe than the tiny floating blue pebble where they began.
Do you have an idea for my next science-themed article? I'm taking suggestions! Drop me some topics in the comments, and if I like it, and feel that I either understand or can research it well enough to explain it, your idea can be the next IMOS article. Also, feel free to call me out if you spot an error anywhere; I'd rather have a perfect article than a reputation for being perfect.
About the author
Nathan Scalia earned a BA degree in psychology and considered medical school long enough to realize that he missed reading real books. He then went on to earn a Master's in Library Science and is currently working in a school library. He has written several new articles and columns for LitReactor, served for a time as the site's Community Manager, and can be found in the Writer's Workshop with some frequency.
