I love alien characters, always have. On any given Star Trek, my favorite character is always one of the aliens. Characters who think in a unique way which I couldn’t possibly understand are reliably intriguing to me. Oh, that guy’s from another planet? Tell me everything, worldbuild his family structure and his planetary government and his cellular metabolism. I am never going to stop being curious about that guy!

Star Trek has a bit of a reputation, though, for the “forehead of the week.” That is, aliens who are different from humans in some barely-noticeable quirk that was easy for the makeup department to do, and we learn next to nothing about their society before moving on. That reputation isn’t entirely deserved. Are there plenty of boring, under-imagined aliens? Sure. But the Vulcans, Klingons, and Ferengi get more complexity, which I really love to see. Each one started with a single quirk (logic, warfare, greed), but they developed into fully-fleshed species after enough time on the show.

One weird quirk

To think about what an alien race would need, ask yourself this: what is humanity’s forehead of the week? What’s our one weird quirk the rest of the galaxy knows us for?

Immediately the obvious answer is that we don’t have one—we’re a complicated, often self-contradictory species! The second answer is, it really depends on what the neighbors are like. You don’t know what stands out about yourself till you’re standing in a lineup.

But let’s just say, for the purpose of argument, that humans are famous around the galaxy for being extremely promiscuous. Other species have sex for reproduction only, or don’t have it at all, and humans are the ones who keep trying to ask everyone out.

Weighing our society against that one stereotype, we can see a few things.

The quirk isn’t universal: plenty of humans aren’t promiscuous, though it may be hard for our galactic neighbors to tell if not many of us go to space. If the first batch of astronauts was horny enough, that reputation would follow us forever, universally true or not.

The quirk has affected our cultural institutions: we have tons of societal workarounds for the fact that people are going to have sex all the time, even in situations where they shouldn’t. It affects family structures (we raise kids with our sex partners, is that weird?), direction of technological development (we have dozens of ways to prevent pregnancy), even the kinds of jokes we tell.

The quirk affects individual instincts: most humans experience the desire for sex frequently. Celibate humans are often struggling against their nature all the time. The small minority that doesn’t desire it is treated like something’s wrong with them. Maybe space would be a haven for them, a place where they can get free of our cultural scripts about sex.

The quirk experiences shifts over time: there have been cultural eras that tried very hard to enforce monogamy and eras where people had sex more freely with whoever they wanted.

And we’re a lot more than just one quirk; we have all the things every species would have to have: an economy, a government, different religions, different regions. Imagine an alien meeting you and saying, “Oh, I’ve met a human before, I know all your customs” and then starting to speak Japanese. You might be a bit offended! Japan and the US might not seem different to them, way out across the galaxy, but they’re different enough that not all customs would hold true.

All of these are things a truly intriguing species has. For every difference they have from us (and there doesn’t have to be just one), there should be far-reaching effects on society and on the way individuals think, too. And every society we see should be complicated and in flux: different attitudes, changing customs. Giving them this level of development helps them feel like a real species, as complex as humans while entirely strange.

Alienation—literally

One of the ideas I find most fascinating is the concept of cultural misunderstandings much vaster than those you get between humans. Humans from different cultures can fall back on basic facts about human nature: laughter, food, love. But could we understand the basic drives of an alien? Maybe you’ve been living alongside Xrrt from Jupiter for years and get suddenly blindsided by his assumption that you two are life partners because you accepted his gift of fruit four years ago and have lunch with him every day. And explaining the misconception doesn’t help because he feels something about you and the things you’ve been doing together that you can’t experience or relate to.

The place I’ve seen this done best is the Foreigner series by C. J. Cherryh. She doesn’t bother to give her aliens, the atevi, any tentacles or extra eyes. They look like bigger humans for the most part. But they’re so drastically different inside that it takes a lifetime of training to be able to communicate with them at all without starting a war.

The atevi have instincts about numbers that humans can learn, but never really understand. Why is the vase okay when it has three flowers in it, but when you take one out, it’s suddenly infelicitous? Nobody knows, but you still have to keep track. An error could give serious offense.

The atevi also have instincts about loyalty which drive their society and relationships more than romantic love does. They have tons of literature about how somebody thought their loyalty was to one person, but at the last minute it turned out to be to someone else, and our human hero can’t understand why the whole opera house is in tears over it. Also, he’s not really sure that loyalty is the right word, he just knows it’s asymmetric and doesn’t have anything to do with sex.

Besides the great worldbuilding, she does a tremendous job setting the mood. Her hero is the one human who can talk to the atevi, so he lives among them, but in a state of perpetual alienation and confusion. Things happen around him he doesn’t understand; he has to be careful not to be used as a political pawn in a system of government no one will ever explain. When I read those books, they really transport me to a different world, make me feel what it would be like to be surrounded by aliens.

Pointy ears or pseudopods?

Now, I’ve talked so far about alien culture while ignoring alien biology. Often, especially in TV, it’s easier to use a rubber forehead as a kind of symbol, so as to focus on the interior differences. In real life, you’d probably have a way easier time interacting with a sassy tentacle blob than a humanoid that didn’t understand humor.

I’ll leave the technical biology to a later post, but let’s talk about why you’d choose a humanoid or a tentacle blob.

You might choose a humanoid if you don’t want biology to be a focus of your book, or you want the characters to experience the uncanny valley of a thing that looks human but isn’t. Inner differences are more striking when the outsides look mostly the same. 

It’s also just plain easier to write about a humanoid, because you can use common references with your readers. “He held out a hand” is just easier than “He extended a pseudopod, which was twenty inches long and covered with purple suckers.” The weirder your aliens, the more often you’ll have to pause and describe what they’re doing. Instead of “He smiled,” you might have to write “He exuded the aroma of cut grass, which was a sign among his species that he was happy.”

On the other hand, if you choose something weird that you invent for the story, you get the fun of creating it: tentacles, exoskeletons, biblically-accurate eyes, really anything you want. That will take up page space, but as a reader, I enjoy those parts a lot, so I won’t be complaining. You’ll also get to consider how the aliens’ physical differences affect the way they act within the book. Do they need a special seat on the spaceship? How do they express emotions without eyes and a mouth?

And that biology can also lead you to your cultural quirks. A species that reproduces by budding is obviously going to have a very different culture. If everyone is venomous, how do they deal with playground fights on the homeworld? A creature that uses photosynthesis would be confused and possibly disgusted by our habit of eating.

You can’t mess this up

One of the best things about writing aliens is that it’s basically impossible to mess up. It’s your alien! If you say it has purple antennae, it does. And they can act the way you choose, as well. Did an editor write, “These motivations don’t make sense!” on the margins of your first draft? Boom, make her an alien; those motivations make sense to her.

Of course you can still end up using implausible biology. But even there, there’s a lot of scope for the imagination. We’ve never seen an extraterrestrial life form, and thus we have no real idea of what’s possible out there. Readers regularly suspend their disbelief for aliens even if they won’t for your tech. Because on what grounds can they say they’re wrong? Did they check every alien in the galaxy? Checkmate.