Not all science fiction involves aliens. When a story, TV show, or movie does, however, one of the most devastating criticisms is that its aliens are “humans in rubber suits.”
Exception: fictional aliens who are intentionally humans thinly disguised. In Pierre Boulle’s novel Planet of the Apes (the premise of the movies differed quite a bit), the aliens—intelligent apes and unintelligent humans—were clearly allegorical. (I won’t argue if you consider this book mainstream literature in a rubber suit. Its “science” was atrocious, even when it was published in 1963.) Throughout the Cold War, SFnal aliens were often stand-ins for one or both sides of that Earthly conflict. There are many other alien-for-human substitutions/parables.
But what about when the author wants true aliens?
What makes aliens alien? Here’s what works for me.
Don’t make them two-armed, two-legged bipeds. A look around Earth says there’s nothing special about that anatomical configuration (except the reduced FX budget for the video version). At least add a tail.
Give the aliens one or more senses humans don’t have, and maybe remove or diminish a sense we take for granted. Earth life offers such examples as echolocation (bats), infrared/heat sensing (pit vipers), electric-field reception (sharks), and magnetic-field reception (many migratory birds). Show how the aliens’ world view is affected by the additional (or missing) senses.
Get them off Earth, if only in flashbacks. These are aliens, evolved in an alien environment, so let’s see how that environment shaped them. We see great variety across Earth, of course—differences from Earth should lead to differences from terrestrial life. Parallel evolution and Panspermia can only be tortured so much.
And most important: give them behaviors—both culturally and psychologically—that relate to their environmental, physiological, and evolutionary context.
Here are some of my favorites SFnal aliens:
The “Tines” in Vernor Vinge’s A Fire Upon the Deep. They live on an Earthlike world, but in every other way they are alien. The individual biological unit is something like a dog—and unintelligent. Intelligence emerges from a small pack, its units communicating by ultrasound. Cooperating muzzles and jaws must substitute for hands. As units die, the nature of the collective intelligence changes—or may fade away. Tines can’t congregate too closely, lest the intra-mind communication of one pack be scrambled by the intra-mind communications within other packs.
Gaia, the world-sized intelligence of John Varley’s Titan series.
Puppeteers, the two-headed, herd/herbivore-descended, cowardly manipulators of Larry Niven’s Known Space. (Full disclosure: sometimes I write Known Space books with Larry, with Puppeteers taking a prominent part in the collaborations.)
My personal blog, SF and Nonsense has an ongoing series of (irregularly scheduled) posts on the alien-aliens topic, including mentions of some of my own contributions.
Alien aliens: a way to know we’re not in Kansas any more.
Edward M. Lerner worked in high tech for thirty years, as everything from engineer to senior vice president. He writes near-future techno-thrillers, most recently Fools’ Experiments and Small Miracles, and far-future space epics like the Fleet of Worlds series with colleague Larry Niven. Ed blogs regularly at SF and Nonsense.