Tag: aliens

Creating aliens is fun and all, but why do we do it? Mostly, it’s because those aliens are going to have some role in our stories. And what kind of organism plays the biggest role? For most, that would be the intelligent kind.

Sentient aliens are the ultimate goal, thanks to a lifetime of science fiction. Yes, the discovery tomorrow of indisputably alien bacteria on Mars would change the entire world, but we’re all waiting for the Vulcans, the Mandalorians, the asari, or whatever our favorite almost-human race might be.

Mind over matter

It’s hard to say how plausible sentience is. We’ve only got one example of a fully intelligent species: us. Quite a few animals, however, show sophisticated behavior, including dolphins, chimps, octopuses, and so on. Some are so intelligent (relative to the “average” member of the animal kingdom) that authors will draw a line between sentience (in the sense of feeling and experiencing sensation) and sapience (the higher intelligence that humans alone possess). For aliens, where even defining intelligence might be nearly impossible at the start, we’ll keep the two concepts merged.

A sentient alien species remains a member of its home biosphere. We’ll always be evolved from our primate ancestors, no matter what the future holds. It’ll be the same for them. Their species will have its own evolutionary history, with all that entails. (Hint: I’ve spent quite a few posts rambling on about exactly that.) The outcome, however, seems the same: an intelligent, tool-using, society-forming, environment-altering race.

We don’t know much about how higher sentience comes about. We don’t even know what it means to have consciousness! Let’s ignore that minor quibble, though, and toss out some ideas. Clearly, intelligence requires a brain. Even plants have defensive mechanisms activated when they feel pain, but it takes true brainpower to understand what happens when inflicting pain upon another. Sentience, in this case, can be equated with the powers of reasoning, or an ability to follow logical deduction. (Although that opens the door to claiming that half of humanity is not sentient. Reading some Internet comments, I’m not sure I would disagree.)

Other factors go into making an intelligent alien race, too. Fortunately, most of them default to being slightly altered expressions of human nature. Sentient aliens usually speak, for example, except in some of the more “out there” fiction. Even in works like Solaris, however, they still communicate, though maybe not always through direct speech. Now, we know language can evolve—I’m writing in one of them, aren’t I?—but it was long thought that humans were the unique bearers of the trait. Sure, we had things like birdsong and mimicry, but we’re the only ones who actually talk, right? Attempts at teaching language to “lesser” animals have varied in their efficacy, but recent research points to dolphins having at least a rudimentary capacity for speech. That’s good news for aliens, as it’s a step towards disproving the notion that language is distinctly human.

What else do humans do? They form societies. Other animals do, too, from schools of fish to beehives and anthills, but we’ve taken it to new extremes. Sentient aliens probably would do the same. They may not follow our exact trajectory, from primitive scavengers to hunter-gatherers to agrarian city-states to empires and republics, but they would create their own societies, their own cultures. The shapes these would take depend heavily on the species’ “upbringing”. We’re naturally sociable. Our closest animal kin show highly developed social behaviors—Jane Goodall, among others, has made a living off researching exactly that. An alien race, on the other hand, might develop from something else; imagine, for instance, what a society derived from carnivorous, multiple-mating, jungle-dwelling ancestors would look like.

Likewise, the technological advancement won’t be the same for aliens as it was for us. Some of that could be due to basic science. An aquatic species is going to have an awful time crafting metal tools. Beings living on a higher-gravity world, apart from being generally shorter and stouter, might take much longer to reach space, simply because of the higher escape velocity. A species whose planet never experienced an equivalent to the Carboniferous period could be forced far sooner into developing “green” energy.

Differences in advancement can also stem from psychological factors. Humans are altruistic, but not to a fault. We’re basically in the middle of a spectrum. Another race might be more suited to self-sacrifice (and thus potentially more amenable to socialist or communist forms of organization) or far less (therefore more likely to engage in cutthroat capitalism). Racial, sexual, and other distinctions may play a larger or smaller role in their development, and they can also drive an interest in genetics and similar fields.

Even their history has an effect on their general level of technology. How much different, for instance, would our world be if a few centuries of general stagnation in Europe—the Dark Ages—never occurred? What would the effects of “early” gunpowder be? Aliens can be a great place to practice your what-ifs.

The garden of your mind

We are sentient. We are sapient. No matter how you define the terms, no other species on Earth can fit both of them at the same time. That’s what makes us unique. It’s what makes us human.

An alien species might feel the same way. Intelligence looks exceedingly rare, so it’s stretching the bounds of plausibility that a planet could hold two advanced lifeforms at the same time. On the other hand, science fiction is often about looking at just those situations that sit beyond what we know to be possible.

One or many, though, aliens will always be alien to us. They won’t think just like us, any more than they’ll look just like us. Their minds, their desires and cares and instincts and feelings, will be different. For some authors, that’s a chance to explore the human condition. By making aliens reflections of some part of ourselves, they can use them to make a point about us. Avatar, for example, puts its aliens, the Na’vi, in essentially the same role as the “noble savages” of so many old tales. Star Trek has Klingons to explore a warrior culture, Vulcans for cold, unassailable logic, and hundreds of others used for one-off morality plays.

Others use aliens to give a sense of otherworldliness, or to show how small, unimportant, or deluded we humans can be. Aliens might be a billion years older than us, these stories state. They’d be to us what we are to trilobites or coelacanths…or the dinosaurs. Or if you want to take the view of Clarke and others, a sufficiently advanced alien would seem magical, if not divine.

Whatever your sentient aliens do, whatever purpose they serve, they’ll have thoughts. What will they think about?

We’re a few parts into this series now, and we still haven’t discussed what aliens look like! It’s time to remedy that. Here, we’ll look at alien physiology and body structure. From cells to organs to “the surface”, we’ll see what goes into making something seem alien, yet plausible.

On the inside

A lot of the earlier parts go into making aliens. After all, they are organisms evolved in and adapted to a specific environment. That’s going to affect their nature. If you’ve ever watched some of those David Attenborough nature shows, then you probably know this already. Fish that live deep in the ocean tend to be flatter. Desert plants have ways of capturing and storing water. Humans lost most of their body hair, while gaining the larger brains that enable us to write (and read) posts like this.

Physiology, of course, is about more than just appearances. It’s also about how the body works. And that’s a complicated matter. We, as humans, have a bunch of organs, almost all of which have to function just right. Some have redundancy—we can live without one lung, or one kidney. Others, like the heart, brain, or liver, are alone; notice how many of those have extra protection. And then there are a few that don’t really seem to be of any use. We can get by just fine without tonsils, for instance. I do. And the appendix literally does more harm than good, having the sole purpose of occasionally becoming inflamed or worse.

Other complex organisms have organs, too. Some of them have different sets of them. Ruminants (like cows) have multiple stomachs, for example. Birds, being egg-layers, have extra equipment for that purpose. And so on.

But the systems that organs control are fairly general. Those things an organism must do will often have dedicated systems. In addition, there will be a few other “support” systems to make these work. So let’s look at what’s biologically required of us, and we’ll see how that translates to aliens.

Intake

Everything living requires some sort of energy input. For us, that comes in the form of food, water, and air. We need all of these to run the chemical reactions that create life as we know it. So does everything else. Thus, we’ve got a mouth that’s front and center, our universal access point for input. So do most other animals.

Plants are a little different. They don’t need to “eat” in the same way we do. Much of their energy input comes from photosynthesis, a different kind of reaction using sunlight as the power source. But they still require water, and they still need air. (And that includes some oxygen, not just CO₂.) So you won’t see plants with mouths, except in the case of carnivorous plants—and most of those instead use a trapping mechanism.

As for aliens, the situation depends on evolutionary history and environment. If your aliens eat and drink, then they’ll have some equivalent to a mouth for that purpose. After the mouth, there’s the digestive tract, where nutrients are extracted from the food. While it won’t necessarily be human-like, it has the same function as ours, so it might be somewhat similar to something on Earth.

Output

Not everything is digestible. The leftovers are mostly useless to us, so there’s no point keeping them around. Thus, our bodies get rid of them, in the form of waste. Animal waste, including human, does have its uses (e.g., as fertilizer or fuel), but it’s mostly just that: waste. Because we don’t want it inside us, we’ve got a system to get it out.

For solid waste, of course, we’ve got a dedicated part of the body. Liquid waste (urine) gets mixed in with other parts, however, in a bit of evolutionary parsimony: we’re not going to use both functions at the same time, so it wouldn’t hurt to let one organ do two unrelated jobs. Other organisms, including aliens, might not do this, which is okay unless you’re really into that sort of thing. Excretory systems, in an advanced, sapient species, may develop cultural taboos, too, but that’s a subject for a later post.

Reproductive

The sole reason to live, from an evolutionary perspective, is to reproduce. At its core, that’s why sex is enjoyable—if we didn’t like it, we wouldn’t do it as much. And so it stands to reason that reproductive organs have a lot of cultural significance attached to them. But they’re also interesting from a biological standpoint.

As stated above, human reproduction overlaps with excretion, but that’s not necessarily a given in aliens. What is, though, is that they’ll reproduce. And it’s likely to be sexual reproduction, not the asexual style used by, say, bacteria. Sexual reproduction requires at least two parents (possibly more, as in the recent news about three-parent IVF), but that gives it the benefit of better genetic mixing. By taking genes from two sources, organisms have a better chance to resist a bad mutation. That’s not the only upside, but it’s one of the biggest.

The internal part of reproduction has its own intricacies. For mammals and many other animals, only one parent actually contains the reproductive machinery. Males can impregnate, but females give birth. It doesn’t have to be this way. Other species on our planet show hermaphroditism (some or all members have both sets of reproductive organs). Another possibility, though harder to make work, is more than two sexes. And then there are odder methods. An alien race could be all females, but some can temporarily express “maleness”. Or the males could carry eggs for a period of time.

Just as important as the organs at work is the way reproduction happens. Are babies born live, as in mammals? Do they hatch from eggs? How many are born at once? For this one, humans are mostly one-at-a-time, but multiple births aren’t exactly rare. Other species, especially those that lay eggs, have larger litters or clutches.

(Oh, and before you ask, it’s astronomically unlikely that we’d be compatible enough with an alien race to reproduce with them. Half-human hybrids, though great for storytelling purposes, are not the hardest of science.)

Senses

Organisms must experience the world around them, if for no other reason than to obtain food and find a mate. For that purpose, we have our senses: sight, smell, taste, touch, hearing. Each one has a use, and each has developed over the ages.

Evolution determines which senses are present. The ecological niche of a species is a good indicator of what its sensory capabilities will be. Cave-dwellers often have poor eyesight—if they even have eyes at all. Carnivores might have heightened senses of smell to track prey, while scavengers may have weakened taste. Here, the best guideline is reasoning: think of what your aliens would need where they live—or, if they’re highly advanced, where they originally came from.

Exotic senses can exist, within reason. Echolocation is popular in Earth animals, especially those without a good sense of sight. An herbivore living in a dangerous area might develop better peripheral vision. Hearing in the infrasonic and ultrasonic is perfectly valid for aliens, as are infrared and ultraviolet sight. Some birds seem to have sensitivity to magnetic fields. About the only things that aren’t possible are those that, well, aren’t possible. Like psionics, or seeing X-rays.

Each sense is going to have at least one organ behind it. We’ve got eyes, ears, the nose, the tongue, and the skin. Others are possible, though. Whiskers, antennae, suckers, tails, and anything you can think of can go towards the sensory system, if you can give it a good reason for being there.

Body plans

The outside of the body—what a species looks like—is probably more important from a storytelling point of view.

We humans have a distinct body symmetry. Left side looks like right, and we’ve got a lot of double organs, like lungs, eyes, and ears. And most animals are the same way. There might be small differences, such as fish with both eyes on the same side of the head, but those tend to be exceptions that prove the rule. This bilateral symmetry isn’t the only option. Starfish, for example, show a radial body plan: arms sticking out from around a center. Many plants aren’t really symmetrical at all, instead opting for a kind of “fractal” body plan.

Another thing we, as animals, have is segmentation. You might recall from science classes long ago that our bodies are divided into three segments: head, thorax, and abdomen. The head is where the brain lies, while the other two make up the body proper. And each of those segments has a pair of limbs (it’s a pair because of that bilateral symmetry). If we had another segment, say between the thorax and abdomen, we might have a second pair of legs (like a centaur) or arms (like Goro from Mortal Kombat). And if we kept growing new end segments as we aged, we’d be literal human centipedes!

Interesting minutiae

That covers the most important parts of an organism’s physical body. There are plenty of other systems (circulatory, nervous, endocrine, etc.) that will likely have counterparts in an alien race, but they follow much the same logic as those mentioned above.

Some other bodily things to think about include:

• Defenses: Some organisms have evolved methods to defend against predators…or each other. Some plants are poisonous. Many snakes are venomous. Cacti and porcupines are both covered in sharp and pointy armor, while turtles and snails opt instead for hard shells. If your aliens were very recently not near the top of the food chain, then they’ll likely have their own ways of protecting themselves.

• Pheromones: Human pheromones are mostly mythical, but a lot of animals do have them. They’re used to attract mates, mark territory, or as a further defense mechanism. Aliens could have them, as well, although they likely wouldn’t have any effect on us.

• Vestigial organs: Evolution rarely discards that which is no longer needed. If it’s not actively harming the reproductive process, it’ll likely stick around far past its expiration date. That’s what happened with the human appendix, and it’s possible for an alien species, too.

• Blood: It’s a staple of sci-fi that aliens don’t always have red blood. Sometimes, theirs is even toxic to us. Both cases result from using a different chemical mix than our iron-based hemoglobin. So if you’re looking for a hard-science excuse for green blood, that’s where you’ll want to start.

Conclusion

I could go on for hours, but this post is long enough already. Again, the best way to create aliens is to think about them. Environment affects appearance. Ecology matters. Inside and out, an alien race is beholden to its environment. If it isn’t, then it’s only a matter of time before it becomes so. But we, as worldbuilders, can work backwards: make what we want, then create the world to justify it.

Everything that lives lives somewhere. All organisms exist in an environment of some sort. It may not necessarily be what we think of when we hear the word “environment”, but that’s merely our human bias creeping in. Animals live in a specific environment. So do plants. So do extremophile bacteria, though theirs and ours have essentially nothing in common. Aliens, too, will be found in a certain environment, but which one is very dependent on their evolution.

The nature of Nature

For a long time, scientists and philosophers wrestled with the question of how much an organism’s environment affects its life, the so-called “Nature vs. Nurture” debate. We know now that there is no debate, that both have an impact, but let’s focus on the Nature half for now.

We, as humans, live mostly in temperate and tropical climates with moderate to heavy rainfall. We’re adapted to a fairly narrow band of temperatures, but our technology—clothes, air conditioning, etc.—augments our ability to survive and thrive in more hostile environments. Indeed, technology has let us travel to nearly lifeless regions, such as deep, dry deserts like the Atacama, the frozen wastes of interior Antarctica, and that most deadly environment of all: space.

But puny little us can’t live in such places. Not by ourselves. Other organisms are the same way, and they don’t have the benefit of advanced life-support machinery. So most of them are stuck where they are. Look through history, and you’ll see numerous accounts of wild animals (and indigenous people!) being captured and returned to an explorer’s homeland, where they promptly die.

Now, evolution’s very premise, natural selection, says that the most successful organisms are those best adapted to their environment. Thus, for an alien species, you want to know where it lives, because that will play a role in determining how viable your alien is. An aquatic animal isn’t going to survive very long in rain-shadow desert. Jungle trees won’t grow at 60° latitude. And the list goes on.

Components of an environment

A few factors go into describing the kind of life that can exist in a specific environment, or biome. Most of these boil down to getting the things life needs to perform its ultimate goals: survival and reproduction. For instance, all kinds of life require some form of energy. Plants get it from sunlight and photosynthesis, while animals instead eat things. The environment serves as a kind of backdrop, but it’s also an integral part of an organism’s survival, which is why life’s goals are better suited by becoming more adapted.

On a more useful level, however, we can look at a biome as an area having the following characteristics in about the same quantities:

1. Temperature: Most species can only live effectively at a certain temperature. Too low, and things start to freeze; too high, and they boil. On Earth, of course, water is the primary limiting factor for temperature, though truly alien (i.e., not water-based) life will be constricted to somewhere near the range of its preferred chemical. (Not to say that freezing temperatures are an absolute barrier to life; penguins live just fine in subzero temps, for example.)

2. Sunlight: This is the “energy” component I mentioned earlier. Assuming we’re dealing with a surface-dweller, sunlight is likely going to be the main type of incoming energy. That’s especially true for plants or other autotrophs, organisms which produce their own food. As any horticulturist knows, most plants are also highly adapted to a certain amount of sunlight. They’ll bloom only when the day is long enough, for example, or they’ll die if the nights grow too long, even if the temperature stays just fine.

3. Proximity to water: I was going to label this as “precipitation”, but that turns out to be too specific. Water (or whatever your aliens use) is a vital substance. Every species requires it, and many absolutely must have a certain amount of it. If they, like plants, can’t move, then they must rely on water coming to them. That can fall from the sky as precipitation, or it can come across land in the form of tidal pools, or just about any other way you can think of.

4. Predators and prey: If you remember old science classes, you know about the food chain. Well, that’s something all life has to worry about, if you’ll pardon the anthropomorphizing. Predators adapt to the presence of certain kinds of prey, and vice versa. Take one away, and things go out of whack. Species can overrun the land or go extinct.

Humans get away with a lot in this. Once again, that’s because of our intelligence and technology, and it’s reasonable to assume that a sapient alien race would overcome their own obstacles in much the same way. But everything else has to limp along without the benefits of higher thinking, so other species must adapt to their environment, rather than, essentially, bringing their own with them.

Great upheaval

All environments are constantly in flux. Climate changes, from season to season or millennium to millennium. Rainfall patterns shift, oceanic currents move, and that’s before you get into anything that may be caused by humanity. Then there are “transient” changes in environment, from wildfires to hurricanes to asteroid impacts. These can outright destroy entire habitats, entire biomes, but so can the slower, more gradual shifts. Those just give more warning.

When the environment changes beyond the bounds of a species, one of two things can happen. That species can adapt, or it will die. History and prehistory are littered with examples of the latter, from dodos to dire wolves. Adaptation, on the other hand, can often give rise to entirely new species, distinct from the old. (For an example, take any extant organism, because that’s how evolution works.)

An alien race will have its own history of environmental upheaval, entirely different from anything on Earth. A different series of major impacts, larger tidal effects from a bigger moon, massive solar flares…and that’s just the astronomical effects. Aliens will be the result of their own Mother Nature.

That’s where they become different. Even if they’re your standard, boring carbon-based lifeforms, even if their “animal” kingdom looks suspiciously like an alternate-color version of ours, they can still be inhuman. On Earth, one branch of the mammalian tree gave rise to primates, some of which got bigger brains. On another world, it could have been the equivalent of reptiles instead. Or birds. Or plants, but I’m not exactly sure how that’d work. One thing’s for sure, though: they’ll live somewhere.

Whether life is made from DNA, some sort of odd molecule, or binary data, it will be subject to evolution. That’s inherent in the definition of life. Everything living reproduces, and reproduction is the reason why evolution takes place. Knowing the how and the why of evolution can help you delve deeper into the creation of alien life.

How it happens

For life as we know it, evolution is the result of, basically, copying errors. DNA doesn’t replicate perfectly; there are always some bits that get flipped, or segments that are omitted or repeated. In that, our cells are a bit like an old record or CD player, skipping at the slightest bump. Sometimes, it knocks playback ahead, and you don’t get to hear a few seconds of your favorite song. Other times, it goes back, replaying the same snippet again. It’s the same for a strand of DNA.

Mutations, as these genetic alterations are called, happen for a variety of reasons. Maybe there was a glitch in the chemical reaction that produces the DNA replication. Perhaps a stray bit of radiation hit a base molecule at just the right time. (Digital organisms would not be immune to that one. Programs can crash due to bad memory, but also from cosmic rays—interstellar radiation—hitting the components. And as our processors and memory chips get ever smaller, the risk only increases.) Anything that can interrupt the reproduction process can be at fault, and there’s almost no way to predict what will happen on the base level.

Most of the time, these errors are harmless. A single base being swapped usually doesn’t do much by itself, although there are cases where they do. Our genetic code has builtin redundancy and error correction mechanisms to prevent this “drift” from causing too much harm. Single-celled organisms have a little more trouble, as they don’t have billions of copies of their genes lying around. They tend to bear the brunt of evolution, but it can be in their best interest, as anyone who knows about MRSA can attest.

A few larger errors (or a compounding of many smaller ones) can cause a greater change in an organism. That’s where natural selection comes in. Species adapt to their environments. All else being equal, those that are better adapted tend to reproduce more, thus ensuring their genes have a higher likelihood of passing on to further generations. Thus, evolution acts as a sort of feedback loop: beneficial mutations ensure their own survival, while harmful ones are stopped before they can get a foothold. Neutral mutations, however, can linger on, as they have little outward effect; its these that can give a species its variety, such as human hair and eye color.

How you can use it

Assuming current theories are anywhere close to correct, all life on Earth derives from some microbial organism that lived three or four billion years ago. Through evolution, everything from dogs to sharks to apple trees to, well, us came to be. There are a few open questions (What was that primordial organism? Is there a “shadow” biosphere? Etc.), but that’s the gist of it. And that tells us something important about alien life. If it exists, it’s probably going to work the same way. The Grays of Planet X, for example, would be related to everything native to their homeworld, but not to the aquatic beings of Planet Y. (Unless you count panspermia, but that’s another story.)

That does not mean that all life on a planet will look the same. How could it? A quick glance out your window should show you anywhere from ten to a thousand species, none of which are visibly alike, and that’s not counting the untold millions that we can’t see. Gut bacteria are necessary for life, and their also our ten-billionth cousins. Nobody would mistake a dog for a dogwood, but they both ultimately come from the same stock. So try to avoid the tired trope of “everything on this planet looks that same”.

On the other hand, the vagaries of evolution also mean that life on one planet probably won’t look like life on another. Sure, there may be broad similarities (physiology will be the subject of the next part of this series), but it’s highly unlikely that an alien world will have, say, lions or bears. (However, this doesn’t necessarily apply at microscopic scales, as there are fewer permutations.)

Classification

For worldbuilding, you’ll likely be most interested in the species level. That’s how we define humans, as well as many of the “higher” animals. We’re Homo sapiens, our faithful pets are Canis familiaris or Felis catus, and that nasty bug we picked up is Escherichia coli.

But closely related species share a genus, and this might be something to keep in mind, especially if you’re creating a…less-realistic race. Unfortunately for us, genus Homo doesn’t have any other (surviving) members; the Neanderthals, Homo erectus, and the “hobbits” of Flores Island were all wiped out millennia ago. But that doesn’t mean your world can’t have multiple intelligent species that are closely related. They can even interbreed.

Higher levels of classification (family, order, etc.) are less useful to the builder of worlds. The traits that members of these share are more broad, like mammals’ method of live birth or the social patterns of the hominids. Really, everything above the genus is an implementation detail, as far as we’re concerned.

Adaptation

Now, back to natural selection. Species, as I’ve already said, adapt to their environments over time. We can see that in animals, plants, and any other organism you care to name. Fur changes color to provide camouflage, beaks alter their shape to better fit in nooks and crannies. Blood cells change to protect against malaria—but that leaves them more susceptible to sickle-cell anemia.

If an organism’s environment shifts, then that can render the adaptations useless. The most dramatic instances of this are impact events such as the one that killed the dinosaurs, but ice ages, “super” El Niños, and other climate change can destroy those species that find themselves no longer suited to their surroundings. And species are interconnected, so the loss of population in one can trigger the same in another that depends on it, and so on.

Apex

Much of this is background material for most aliens. The ones that are most interesting to the public at large are those that are intelligent, civilized. Like us, in other words.

We are not immune to natural selection. Far from it. But we have managed to short-circuit it to a degree. People with debilitating disorders can live long lives, potentially even reproducing and thus furthering their genetic lines. Adding to this is artificial selection, as we have performed on hundreds of plant and animal species. That’s how domestication works, as much for a wolf as for a grapevine. We take those individuals with the most desirable qualities and work things out so those are the ones that get to reproduce. It works, as attested by the vast array of dog breeds.

So aliens like us—in the sense of having civilization and technology—won’t be as beholden to their environment as their “lesser” relations. They won’t be bound to a specific climate, and they’ll be largely immune to the small shifts. Does that mean evolution stops?

Nope. We’re still evolving. It’s just that the effects haven’t really shown themselves that much. We’re taller than our ancestors, for example, because taller men and women are generally seen as more attractive. (A personal data point: I’m 6 feet tall, a full 12 inches taller than my mother, and my father was 5’8″. Not that that seems to make me any more attractive.) We live longer, but that’s more a function of medicine, hygiene, and diet, not so much genetics. Parts of us that have evolved relatively recently include Caucasian skin and adult lactose tolerance.

If our species continues to thrive, it will continue to evolve. One sci-fi favorite is space colonization, and that’s a case where evolution will make a difference. It won’t take too many generations before denizens of Mars have adapted to lower gravity, for instance. People living on rotating stations might learn to cope with the Coriolis forces they would constantly feel. It’s possible that there may come a time when there are living humans that cannot survive on their original homeworld.

And the same may be true for aliens. As an example, take Mass Effect‘s quarians. In the third installment of the series, they can (if you play things right) return to their homeworld of Rannoch. But centuries of living as space nomads spoil the homecoming, as they find themselves poorly adapted to their species’ original environment. A race of many worlds will discover the same truth: evolution is unceasing.

What is life? At the most basic level, we’re not entirely sure. We’ve got a lot of good theories that accurately explain most of life’s inner workings, but there are quite a few loose ends. We don’t, for example, truly know how life began, nor do we know if it exists on other worlds. (Not that we don’t have a few candidates elsewhere in our solar system: Mars, Europa, Enceladus, Titan…)

All life on Earth works in about the same way, however, and we’re pretty sure we know how. It’s all based on the same fundamental building blocks, the same chemical and biological processes—processes that are not the only way to do things. When you get right down to it, we have more in common with the smallest bacteria than we probably would with any extraterrestrial, unless you invoke some sort of higher principle. As of yet, that’s uncalled for, considering we have a total biosphere sample of 1, but who knows?

The way it is

Earthly life is based on carbon. There’s no question about that. In fact, carbon is so important to life that it’s a requirement for a chemical compound to be called organic. (Think about that the next time you see “organic salt” for sale. Table salt is mostly sodium chloride, NaCl. No carbon there.)

Carbon is a great element for life, as countless astrobiologists and writers of science fiction have discovered over the years. It’s very stable, and it’s good for forming long “chain” molecules, or polymers. It readily bonds with lots of other molecules, and the compounds made from that are…interesting, to say the least. Things like carbon dioxide, sodium bicarbonate (baking soda), hydrogen cyanide, and, of course, ethanol.

But life is more than carbon. We also need a solvent, and nothing works better than plain old water. It’s perfect as a medium for the biochemical reactions necessary for life. Water has a relatively large liquid region (0°C to 100°C, or 32°F to 212°F), and it’s a fairly simple compound (H₂O). It’s essentially neutral, so it doesn’t affect the reactions as much as other liquids might. Oh, and it covers about 70% of our planet’s surface, so there’s that.

Other elements find their way into Earth life besides carbon, hydrogen, and oxygen. Nitrogen is a big one; percentage-wise, there’s more of it in the air than there is water on the surface, so life would be silly not to do something with it. Phosphorus, despite its volatile nature, is relatively stable once it’s bonded to a bunch of other atoms, and it’s the backbone of adenosine triphosphate (ATP), one of the most important complex molecules at the cellular level. Calcium is needed for our bones. Iron is what makes our red blood cells, well, red. Sulfur, potassium, sodium, magnesium, and a dozen or so other elements are all vital for us and most other life as we know it.

On Earth, as we know, life is made from DNA. We all know the double helix that is its form, and some might recall the scene in Jurassic Park explaining DNA and the genes made from it. From another point of view, DNA is like a computer program: a series of “instructions” that make a blueprint for life. But from a biochemical standpoint, it’s nothing more than four moderately complex molecules organized on a pair of polymer chains. These four nucleic acids bond in pairs across the chains; strictly speaking, only one chain is necessary, as in the similar (but single-stranded) RNA.

One of DNA’s functions is to encode which higher molecules are needed where. These large polymers are proteins, and they’re made up of smaller parts called amino acids. In the genetic code (on our planet, at least), three nucleic acids in the DNA chain represent an “instruction” for an amino acid. We use about twenty of those. So do dogs. And trees, mushrooms, and any other “complex” life you can think of. Bacteria use a slightly different set, but even their genetic code is built around the same twenty.

To a chemist, that’s life: a bunch of molecules acting and reacting, bonding with each other, splitting apart. What makes it unique is the fact that it can do this in such a way that it perpetuates itself. Life, once it gains a foothold, will reproduce as long as it can. That’s why the “life on Mars” debate is so polarizing: if life did exist on Mars for any serious length of time, then it would have spread all over, and some evidence should be relatively easy to find even after a billion years.

True, there’s a difference between any old kind of life and the sentient, sapient species we expect when we think of aliens. But life like that didn’t spring fully-formed. By all that we know, it had to come from somewhere, and it likely came from the same place that every other living thing on its planet did. (One hypothesis, however, argues for a shadow biosphere, a whole set of lifeforms unrelated to anything we know, yet still living all around us.)

The ways it could be

The four basic elements of organic life—carbon, oxygen, nitrogen, and hydrogen—are everywhere. They’re common here, and they would be in just about any hospitable world you could imagine. Life would almost be expected to use them. Carbon, because of its polymerization qualities, is the best backbone of the four. Hydrogen and oxygen make good compounds, notably water, but also—when bonded to carbon chains—sugars and carbohydrates. Those may sound like dirty words to a health nut, but we can’t live without them (in moderation). Nitrogen isn’t of much use on its own, but throw it into molecular compounds, and it’s suddenly great.

For “life as we know it”, those four are the big ones. It’s the trace elements that will be in different concentrations. Phosphorus and calcium are important for us because of their chemical properties; it’s not entirely unreasonable to imagine alien life using them for the same purposes. The rest, though, are fair game. It’s possible that alien organisms could find ways to use elements and compounds that are toxic for us, such as heavy metals (lead, mercury, etc.).

All life on Earth is based on DNA (or its precursor, RNA), but that’s not a given. Rather, the form isn’t a given. Complex life does need some way of replicating, something resilient, resistant to random mutations, yet easily formed from common materials. Chemists have created a chain of peptides that can hold nucleic acids. And those nucleic acids don’t have to be our familiar four. Xanthine, for instance, is chemically related to adenine and guanine, and it’s found throughout the body.

Even if you have DNA, even if it functions the same way as ours, that still doesn’t mean you’re Earthly life. A simple bit of multiplication shows that there are 64 possible ways to code amino acids. But we barely use a third of that space. Most amino acids have multiple, redundant encodings, probably for added security against mutations. Mix up some of those encodings or add different options for amino acids, and you’ve got a whole new way of life.

Another option to look into is chirality. Amino acids are peculiar molecules; they can appear in one of two forms that are identical in composition, but slightly altered in shape. Chemically speaking, they’re called isomers, and life on Earth overwhelming prefers a specific shape for them. But “opposite” amino acids could be the basis for life on a different planet. That life might be otherwise terrestrial, but utterly incompatible with our proteins, enzymes, and so on. (Mass Effect used this idea in a couple of places.)

More alien

As much as any kind of life can be considered common, most alien aficionados expect ours to be so. Carbon, water, and DNA/RNA work. We’re living proof of that. Anything that uses those will be “like us”, at least at the most basic level. But can we change even that?

The problem with designing an alternate biochemistry is that it’s entirely hypothetical, and it will remain so for the foreseeable future. That hasn’t stopped some from trying, and they’ve come up with a few ideas that are scientifically possible, if not necessarily plausible.

Silicon is the favorite of sci-fi, and it also has its proponents in “serious” scientific work. Looking at the periodic table and the very ground beneath your feet, you’d think it was ideal. It’s a heavier analog of carbon, able to form polymer chains by bonding with itself, with hydrogen and oxygen and a few other molecules attached to the sides. But its added mass renders it less common, less stable, and less…free. Silicon doesn’t have the same breadth of possibilities as carbon, and many of its more interesting compounds aren’t suitable as the basis for life. Still, it does have some potential, though it would take an entirely new subfield of chemistry to explore that potential.

Sulfur, as a core element, is another possibility. It can form long chains like carbon, and it’s a bit more common than silicon. But its downfall is again in the “organic” chemistry. Those long chains are all linear. They don’t branch, and branching carbon chains are responsible for the vast array of organic molecules we know today. That doesn’t mean sulfur-based life is impossible, but it doesn’t look like it could become complex. On the other hand, sulfur can be—and is—used instead of oxygen in some lifeforms. (Bacteria that do this on Earth are used to create hydrogen sulfide, H₂S, the sulfuric analog of water.)

Metallic life could use any of the more common metals as a basis. We haven’t explored much of this sort of chemistry, but titanium and a few other metals are potential candidates, particularly in high-temperature, high-pressure environments. Apart from the practicalities of using a heavier, rarer element, the lack of knowledge on this subject is what keeps us from positing “metallo-organic” life.

Arsenic is mostly poisonous for Earthly life. The very reason why it’s toxic is the same reason why it could be a potential alternative for life: it’s in the same atomic class as phosphorus. It reacts with many of the same molecules as phosphorus, “competing” with it. That’s what makes it harmful to us, but other life could use it in something like DNA. That was actually the working hypothesis for a strain of bacteria found a few years ago in California. (That claim has since been discredited.)

For solvents, authors both serious and fictional have devised a host of possibilities beyond “just add water”. Ammonia could work, but only at much lower temperatures (or higher pressures) than on Earth. And ammonia is flammable, so oxygen-breathing organisms would find it problematic, to say the least.

Another option, one that has a few scientists awfully excited, is methane. It’s a very simple hydrocarbon (CH₄), it’s fairly abundant in the universe, and—under the right conditions—it’s pound-for-pound as effective as water. Methane also has the bonus of being related to bigger hydrocarbons like ethane, some of which could also be used by life. Imagining a “sea” of liquid hydrocarbons isn’t even that hard. We’ve got three of them in our solar system: Titan’s Kraken, Ligeia, and Punga. And there are indications from that moon of something that could be life-related.

The list of also-rans is long, and getting longer all the time. In addition to ammonia and methane, people have imagined life using as solvents everything from hydrogen sulfide to peroxide to silicon dioxide, AKA glass. All of them have their drawbacks, usually coming from the range of temperatures where they are liquid. But don’t let that stop you from trying.

Finally, there are a few ideas that are even more “out there”. Clouds of Venus? Sure. Charged dust inside a plasma sitting in space? Yeah, that could work. Life on a neutron star? A bit harder, but we can work something out. None of those would resemble life as we know it, though. Indeed, we might not even recognize them as living, although they would fit every definition.

Next time

So…life is complex, you see. This was only a basic overview of one aspect of it, and it’s one of the longest posts I’ve written. And truth be told, most writers won’t need any of it. Unless you want to be wild and weird, you’ll probably stick with something Earth-like: carbon, water, DNA, etc. And that’s okay. You can still make great aliens while staying inside those borders. Such life is far easier to see as alive, too, although it will almost certainly resemble nothing on our planet. (And forget about eating it. The proteins and enzymes and such will probably be completely different.)

In the next part, we’ll switch from biochemistry to actual biology, as we look at evolution and how it makes possible the variety of life in a biosphere. Aliens, like us, will evolve. They may not have genes like we do, they may not reproduce in the same way, but they’ll evolve. Next month, we’ll see how and why.

Is there anything more “sci-fi” than an alien? Sure, some of the best science fiction stories are wholly concerned with humanity, but the most popular tend to be the ones with aliens. Star Trek, Star Wars, and any other franchise beginning with the word “star” are the best illustrations of that point, but it’s easy to see anywhere you look. Aliens are all over the place, in movies, TV, video games, books, and every other creative media you can think of.

But there are aliens and there are aliens. In earlier days of TV and movies, for example, most aliens were typically just actors in makeup, which severely limited their appearance to the humanoid. Modern video games have returned to this state, mainly because of the cost of 3D modeling. (In other words, if everything is close enough to human, then they can all use the same base model.) Books were never under this sort of pressure, so authors’ imaginations could run wild. Think of Larry Niven’s two-headed, three-legged Puppeteers, for instance.

Looks, however, aren’t everything. In visual media, they’re a lot, but for the written word, it’s more about how an alien thinks, acts, sees the world. It’s how aliens are characterized. In harder sci-fi, it’s even about how they exist in the first place.

This series of posts, if I may be so ambitious, will cover all of that. I’ll probably only write about one of these a month, each covering a small part of the topic. As has become my usual pattern, we’ll start with the broader strokes, then fill in the details later on. Along the way, I’ll try to keep a balance between the hard worldbuilding bits and the space-opera fun. Because aliens are both.

First, though, let’s cover the basics.

What we know

This is an easy one: nothing. At this point in time—unless something has happened in the three weeks since I wrote this post—we don’t know if aliens exist. (Ignore fringe theories for the moment.) We really don’t even know if they can exist. All we have are theories, hypotheses, and speculation. In other words, a perfect breeding ground for the imagination.

Of course, we’ve worked out the basics of how astrobiology (life outside of Earth) would work. We can confidently say that a few old theories are wrong, like the fabled canals on Mars or jungles of Venus. But what we don’t know is a vast field. Are we alone? The premise of this whole series is that we are not, but we can’t yet be sure. Are we the first intelligent life in the universe…or the last? Did life arise on Earth, or did it spread here from elsewhere?

Today, in 2016, we simply cannot answer any of those questions in a rigorously scientific manner. Thus, it falls to us creative writers to fill in the blanks. How you do that will depend on the expectations of your genre and medium, but also how deep you wish to delve.

Forks in the road

We have a few different ways to play this. Some will work better than others, obviously, and some will resonate better with different segments of your audience. So this is our first big “branching point”, the first decision you’ll have to make.

The hard way

Here, “hard” doesn’t mean “difficult”. Well, it kinda does, but not in the way you think. No, this is a reference to hard science fiction, where the object is the most realistic and plausible scenario, based on as few “miracles” of technology, biology, and the like as possible. Yes, that does make the creation of aliens more difficult, because you have to think more about them, but the results can be amazing.

Hard SF aliens are best suited to written works, if for no other reason than they’re the least likely to be humanoid in body or mind. (We’ll see why in a later post.) Those visual media that have tried to build aliens in this harder style tend to make them incomprehensible to mere humans, or they focus on the ramifications of their existence more than their appearance. But hard sci-fi is often seen as too boring and too “smart” for movie and TV audiences, so there aren’t very many good examples.

The easy way

Now, this time I’m talking about difficulty. In total contrast to the harder style above, many works opt to make their aliens to fit the needs of the story, with varying degrees of care for their actual plausibility. In a few cases, they can be made to illustrate a concept or explore a particular section of human psychology. (Older Star Trek series often did both of those.) This might be termed the space-opera method of alien creation.

Obviously, this is more palatable for visual and interactive media, because space-opera aliens tend to fall into the category of Humans But. In other words, this type of alien race can be described as, “They’re humans, but…” Maybe they’re all women, or they have catlike features, or they’re overly aggressive. They could have multiple differences, but they’re still largely human at heart. What makes them special is how they are different from humanity.

Examples of this style aren’t hard to find at all. They probably make up the majority of aliens in fiction. Why? Because they’re easy. Easy to create, easy to visualize, easy to characterize.

The PPC way

For our series, we’ll take a hybrid approach, if only because we have so much ground to cover. I’ll spare you the highly technical intricacies of biology and biochemistry, but we’ll certainly be going deeper into those fields than the shoulder-pads-and-forehead-ridges crowd. The idea is to keep suspension of disbelief while still allowing for a good story. (Honestly, the hard sci-fi approach only really makes for one good story: discovery.)

Likewise, I’ll assume you’re the best one to know what sort of character you need, so we won’t really cover that too much. We’ll probably touch on the psychological aspects, but those are most definitely not my specialty. And we’ll try to make something more interesting than humans in makeup.

Where we go from here

As I said, this series will probably be something close to monthly, but I already have the first few posts planned out. Again, these mostly cover things from a higher level. The finer details will be in the nebulous future.

Here’s what I have so far:

1. This introduction
2. Biochemistry, DNA, and alternative forms of life
3. Evolution and genetics
4. Interaction with the environment
5. Physiology
6. Intelligence, sentience, and sapience

These won’t be the only posts, and they likely won’t even be consecutive. If I come up with something that I think needs to be said, I’ll say it, no matter what the schedule reads. But these six are a good start, and they outline the main areas I feel should be covered.

Remember, we’re making “softer” aliens out of “harder” stuff. That’s why you don’t see a post dedicated to characterization, or one specifically focusing on appearance or mating rituals. Those can come later. (If you’re worried at the lack of language as a topic, also remember that a third of the site is dedicated to exactly that. I will be writing “alien languages” posts, but those will show up on Fridays.)

So that’s it for the intro. Come back soon for the real start to the series. I’ll see you then.