I've been wanting to make an alien planet for a while, and though I don't want it to just be an 'earth but everything is wacky colored' type thing, I honestly do not have the patience to simulate millions of years of evolution. yes, this planet will have special circumstances that the animals will 'evolve' to live in, but how do I design these creatures without spending weeks on speculative evolution, and still have them fit where they are?

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    $\begingroup$ Make it a colony world with plants, animals and microlife imported from Earth. Then just evolve those well established life forms to survive in whatever conditions your planet brings to the game. Instead of millions of years of natural evolution, now all you need to do is a few hundred years of genetic engineering. Then, as an author afterthought, change the colonial origin to natural, Leave all your new animals and plants in place, just remove the genetic scientists and colonists. Same results with a lot less work. $\endgroup$ Commented Aug 5, 2020 at 19:56
  • $\begingroup$ How different do you want this alien planet to be? Obviously, the more different the more time you will need to spend designing it. Or are you looking for ideas of how life forms could be different yet viable from Terran ones? $\endgroup$
    – llywrch
    Commented Aug 5, 2020 at 21:07

2 Answers 2


Design the creatures how you want them to be first, and then bother yourself with how they evolved later - if you bother yourself at all with that.

A seminal work in sci-fi is The Forever War. It features a species of psionic, green, tripod "teddy bears". Why are they tripods? Why are they green? How are they psionic? Joe Haldeman never elaborated on that. The creatures appear for two or three pages, and even then only briefly.

The Forever War won the Hugo, Nebula and Locus awards. Each of these is to sci-fi books what oscars are for movies.

If you really must explain stuff, then dark planets make for good hearing, low gravity gives you good jumpers yada-yada. If you really, really want to go into speculative evolution, then probably the story you want to write is the speculation itself. This is a niche of sci-fi with its own cult followers.

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    $\begingroup$ This is the correct yet heretical idea (for Worldbuilding, anyways). The number of people in a typical audience who even notice that, given the location of the mountain range and the sea, your lush rain forest ought to be a desert, or that it doesn't make sense for your alien to have feathers AND fur, are vanishingly small. I might be bothered by the nonsensical cleavage patterns of the rocks in your sci-fi landscape, but most people don't care. $\endgroup$
    – Jedediah
    Commented Aug 6, 2020 at 1:18

Your best option seems to be to identify which main unique traits you want for each creature, determine where they live, then research our own animals which live in a similar habitat to have a better idea on how they'd look like.

This might seem like your "earth but everything is whacky colored" problem, but here's the problem regarding biology: there's no such thing as copyright in nature, so a specific trait or body plan which is advantageous for a creature can and likely will evolve multiple times in species which originally had very little in common. This occurrence is called "convergent evolution" and has happened several times here on earth throughout history, with flying squirrels and sugar gliders being a very good example (both look very similar, but one is a marsupial mammal while the other is a placentary mammal).

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So in essence, it's all about identifying the similarities between your world's habitats and those found here on earth, thus seeing what would likely be similar in your own creatures and then determine traits which evolved differently from creatures on earth. Of course, you can still have creatures completely unlike anything that's ever walked on our planet, but know that the existence of creatures which look similar on the outside is far from unrealistic or a sign of a lazy job, and the sheer amount of different creatures and traits on our own planet just shows how you don't have to worry about creating an entire evolutionary graph for them to look real (without genetics and the studies in biology, I doubt anyone would ever believe you, a cat, an ostrich and a dinosaur all came from a fish with stumpy leg-like fins).

Regarding reference for what you might be looking for, "subnautica" and "james Cameron's avatar" are both good examples of this process, having many creatures which look a lot like some of our own animals, but they're not quite the same due to a vastly different ancestor and due to having unique traits which their own variations in the environment selected as more advantageous. The game "the Outer worlds" are also good reference on how to combine different traits of creatures we have on earth to create something that looks pretty unique and alien-like.


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