Towards a taxonomy of cliches in Space Opera (2016)
&gt; Because primates are a universal deterministic outcome of evolution on all worlds<p>In all fairness, if you think of the constraints required for a species to become space-faring, you&#x27;re going to be hard-pressed to make it work with an organism which isn&#x27;t at least a bit like us.<p>1. You can&#x27;t be a marine organism, because developing advanced technology requires combustion, and water isn&#x27;t something you want to be carting into space with you.<p>2. You need a musculoskeletal system which can support a large brain. For non-marine organisms, this implies something with a big head on top of an upright stance.<p>3. Having a surplus of limbs is contraindicated for large organisms. Large limbs are expensive to build, and larger organisms are more constrained by gravity than surface tension, which makes multiple limbs less useful.<p>4. You need appendages for manipulating tools, and voices to debate and share ideas.<p>5. To develop non-trivial intelligence, you need to be multicellular, and multicellular organisms need to be able to reproduce. So, there is probably going to be sex involved, along with all the complexity that goes along with that, such as sexual competition and selection, caring for the young, and all the politics that arise from these kinds of interactions.<p>Putting these constraints together, you don&#x27;t have too many options for aliens which are both realistic and interesting enough to build a story around. Your aliens are either:<p>* Bipedal politickers.<p>* Robots.<p>* Not capable of building something we would recognize as technology or civilization.