It occurred to me the other day that many fictional alien species conform to a small number of body plans: humanoid, insectoid, feline, robot, and reptilian.
There's a huge amount of creativity in appearances and cultures, admittedly, but most races out there fit one of those body plans. The Wikipedia list of fictional aliens is a good overview, for the above and other body plans, though it's definitely not complete.
I realize there are reasons why most aliens are humanoid or nearly so. It's easier to sympathize with something that looks human. It's easier to conceive of aliens based on familiar Earth species. It's easier to put make-up on an actor than to deal with CGI, or it was until recently. Still, why doesn't more science fiction push the envelope? Why don't we see more unusual body plans? It's not as though we'd have to create entirely new physiologies, though we need those too. Earth has a whole host of creatures that have been underutilized in science fiction, including a few with proven intelligence.
Sharks, for instance, are ancient. They have cartilage instead of bone. They sense electricity and have an excellent sense of smell. They have problem-solving and social skills. There are documented cases of parthenogenesis. They're built for predation and we're already conditioned to cast them as villains.
Octopuses, corvids, parrots, and dolphins also have intelligence, or at least use tools and solve problems. Ravens can mimic sounds and have a wide range of calls, often for social purposes. Parrots are capable of communicating with humans. Dolphins have proto-language as well and are highly social. When was the last time you saw them (or parrots, or octopuses, or sharks) cast as aliens? Well, except for Hitchhiker's Guide to the Galaxy…. Other possible species include: horseshoe crabs, trilobites, rabbits, elephants, slime molds, moss, bacterial hive-minds, and marsupials, including monotremes.
And as I mentioned above, we need more entirely new physiologies too. Species that don't match up with the Earth life we're familiar with, or even with our extremeophiles. If we make the environment first, the species second…
One possible environment, close to home: the diamond oceans of Uranus and Neptune. This would be a hot, high pressure place to live. There probably wouldn't be a lot of gas mixed into the diamond, let alone oxygen, so either the aliens wouldn't breathe, they'd use a system like photosynthesis where they'd break down carbon for energy, or they'd be like whales, surfacing to breathe hydrogen, helium, or methane (those being the abundant gases). The aliens would almost certainly be carbon-based, and would consume other carbon-based life for energy. They'd likely evolve something like fins or flagella to propel themselves. Maybe they'd use jet propulsion.
There's no reason why these aliens couldn't evolve intelligence or even civilization, though I doubt they'd achieve buildings as we know them, because short of building on the solid-diamond floes, there'd be nothing solid, and the caps probably wouldn't be all that stable. I can see floating structures tethered together, however, provided the aliens had something to build with. Perhaps after millennia of them using these structures, they'd adapt to them, becoming more amphibious than aquatic or losing the flippers and gaining something more like hands. Or perhaps not.
I have no idea what first contact will look like when we make it. The realistic version, of us finding microbes on Mars or one of Jupiter's moons, lacks a certain something, though I'll be pleased when it happens. But wouldn't it be great if we ran into alien blue jays or giant platypuses or sentient hammerhead sharks?
An earlier, rougher version of this essay was posted on my blog, Specnology.
This post originally appeared on Science In My Fiction.