This is the first part in a series. Follow the links for the different parts: II, III, IV
Note:Personally, I do not believe in macro-evolution. I am a Young-Earth Creationist, and that is my own personal conviction which I have come to after years of personal study and reflection, and much debate with people of views across the board. No two people believe the same thing, and that’s ok. All that said, even if I don’t personally believe in it, Evolution is a very useful idea for dynamic brainstorming for ideas in science fiction. It is hard to think up things that an intelligent designer would create (but hasn’t), but it’s easy to think up things that could evolve, given different environments. That is why I say, in this case, that regardless of what you believe about the origin of the actual universe, or whether or not you intend to have Evolution play a role in your story’s universe, the idea of macro-Evolution by natural selection can be very useful in helping you think up unique ideas for alien life forms.
“Whenever you invent an alien creature, you should invest a great deal of effort in determining why, in evolutionary terms, its unusual features would have developed. Not that you have to figure out the exact mechanism of evolution – we’re still arguing about that in the real world! – but you do have to think about why the alien’s unusual features would have survival value.”

The idea behind this is that anything weird or unexpected about a creature should have a purpose sure, you could just slap some huge, moth-like feelers on the otherwise human-looking alien, but what are those actually for? Does this species have to commonly rely on scent instead of sight to find food, or do they actually function like TV antennae and pick up (and transfer) radio waves? While I’m asking, why do they otherwise look human? These are the sort of questions you should be asking yourself when you think about what your aliens look like, but let’s not get ahead of ourselves.
- Is it similar to earth? (use these sparingly and with good reasons; can intelligent life only exist on earth-type planets? This is an entirely possible answer, and would make a good plot point)
- Is it a harsh planet? (What makes it harsh? Poisonous atmosphere? High-pressure Atmosphere? Very thin atmosphere? Very hot surface? Very Cold? Full of predators? Sparse of food?)
- Is it a favorable planet? (Is it lush and plentiful? Is it rural or urbanized?)
- What kind of landmasses or bodies of water are there? (is it mostly land or mostly water, or some balance of the two? This could be anything from a water planet with island chains, to a mountainous ball of rock with only oasis and an equatorial jungle.)
-Would it be better to be small or large? Nimble or tough?
-Would they need to run? Climb? Burrow? Fly?Are they safe enough to be weak, or does living in this world make them strong? Are they constantly fighting or are they relatively peaceful?-Do they have any natural weapons/defenses? (Claws, teeth, horns, bony plates, venom, acid, etc.)
Alternately to this sort of inductive method, you could try to think up what kind of real-world animals might survive in your world, and mix and match to come up with something strange and unique:
Have broad, open plains or savannas and extremely high winds? Perhaps some kind of cross between an elephant and a turtle would be both heavy enough and aerodynamic enough to resist those winds.

As you can see, the possibilities are endless, but these kinds of questions come a little easier if you think of them in terms of what might evolve. While you’re thinking about these questions, don’t settle for the quickest answer- keep questioning your ideas, not letting it get by without thorough examination. How can it be better? Is this anything new? Research and make sure that you’re not accidentally copying someone else’s idea.
Feel free to turn this whole process on its end and think of the creature first if it works better for you, and once you get an idea, keep working at it until it’s crafted into something that is truly yours.
Well, that’s all I’ve got for the first step. Next week we’ll talk about creating your own alien societies for these newly-crafted creatures.
Until then, what are some of your favorite aliens? Let me know in the comments below!
ET comes to mind first..likable..cute..harmless, but my fav was in an old movie with Dennis Quaid and I think was called Enemy Mine.. 1985
Excellent movie and characters and I would recommend to anyone
Chris
Favorite aliens… Literary or non-literary? Growing up and watching Star Trek with the family I have to say I always loved the Vulcans…but oddly enough I never really thought of them as aliens. Then I started watching Stargate. The Asgard are pretty cool.
I think Out of the Silent Planet was the first book I read that had aliens in it. I loved the Hrossa. And since I am an Orson Scott Card fan, the buggers were an interesting alien race.
Using evolution to generate (and check) your aliens is excellent advice. The next step, and one too often omitted, is thinking through their world ecologically. How many times, even on the usually well thought through Star Trek, have we gone to a planet that has no ocean and no organic life, but has a breathable atmosphere! Guess what: not possible. The only reason is that the costume people are too lazy to break out the space suits. Or George Lucas putting what look like humongous herbivores in a desert (Tatooine). What do they eat there? How do they grow so big, eating food of this kind? Hmmm. (By the way–if you don’t have an ocean, you aren’t going to have a rain forest. Just sayin’.)
In contrast, the best example I know of this being done right is Frank Herbert’s original Dune. It’s all in Tolkien’s essay “On Fairie Stories,” by the way. Got to give your world an “inner consistency of reality” if you want us to fully embrace it. This post is a good start in that direction.
Anne McAffery’s Pern comes to mind. Well thought out including orbital dynamics, although I’m not enough of a mathmetician to know if they would actually work. Real dragons with a purpose! Not really aliens, though.
I like the Membari from Babylon 5 and the Ewoks from StarWars! I also have to admit a fondness for Tribbles…
The Hoka were pretty cool, too… I wonder what would happen if a Hoka met an Ewok…
* Minbari — sorry, my alien spelling is not so good 😛
My sister told me about this blog, and this article in particular. Thanks for this article, it will come in very handy as reference material while writing my sci fi epic saga.
A suggestion: focus on how your sapient, tool-using race came to be so. If they have arms, where did those arms come from? If evolution is right, humans came from primates, who’s arms were used for swinging between branches, thus they developed powerful and flexible grasps. As IQ started going up, using these for tool-use (as seen in some primates already) developed more flexibility and versitility. If you’re doing salamander-men from swamp-land, how did their hands become hands? Maybe early salamanders needed to dig around in the mud? Are the hands shovel-shaped? Are the bones designed to bear more weight in certain directions? How did the arm muscles and joints develop to support this? How did it impact the posture of a no-longer quadrapedal creature?