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The Implausibility of Popular Sci-Fi Aliens

Introduction and Biology


If you are a fan of science fiction, you have probably encountered many aliens already, be they in the pages of a book, or on the screen in movies, TV shows and video games.

But just how ‘alien’ are these aliens, and how plausible are they? This three-part article series will investigate some of the most iconic alien species portrayed in popular science fiction, and compare them to some of their lesser known, but more interesting counterparts. 

Part one: Biology

We will start with Star Trek, in all of its many guises. Regardless of the incarnation, be it The Original Series, The Next Generation, DS9, Voyager, Star Trek: Enterprise, Discovery, the earlier movies, or the JJ Adams reboots, they all suffer from the same trope; most of the aliens were ‘Humans with bumpy heads’.

The major races, the Vulcans, Klingons, Romulans, Cardassian, Bajorans etc. are all guilty of this. They all look essentially human. Indeed, in Star Trek IV: The Voyage home, Spock was able to disguise himself as a human with a simple headband covering the tops of his eyebrows and ears. 

Video by These Are The Voyages

Granted, the design of the main species in the original series was largely due to budgetary constraints. It was far cheaper to apply make-up and use simple prosthetics than to create a full body suit, or to use animatronics. TOS Klingons did not even possess their later characteristic bumpy heads. Instead, they resembled a space-faring version of the Mongol Golden Hoard. A simple shave and costume change would render them indistinguishable from a human.

Video by SkaIathrax

The same budgetary constraints, twinned with the need to be accessible to a mass market, are probably the source of many of the show’s other contrivances.

For example, all the main alien species appear to speak perfect English, without a trace of an accent. What’s more, they appear to understand our idioms and figures of speech. Considering people from different parts of the same country can have difficulty understanding each other’s accents and dialects, this seems unlikely.

Non-neurotypical people, for example, those on the autistic spectrum, also have difficulty with this. Since the brain of an alien species is unlikely to be the same as a human’s, it is likely they too would have difficulty understanding our idioms, and vice versa.

The ‘Universal Translator’ is the in-universe explanation given for this ease of communication. But how does this work exactly? We do not hear the computer translating anything being said. Nor does it account for why the alien’s lips sync perfectly with the English we hear.

Most importantly, it does not explain how it is able to translate alien speech in first contact scenarios. Logic dictates that even the most advanced computer would need to have the equivalent of a digital dictionary of the alien’s language to translate from first.

In reality, breaking the language barrier would likely be a long and difficult process. Frankly, Star Trek’s UT has as much credibility as the comedic Babel Fish, and the Babel Fish was not meant to be taken seriously.

Video by BBC Studios

Again, scientifically this is highly unlikely. Even our closest living relatives, Chimpanzees and Gorillas, cannot replicate human speech. The fact that they can be taught to communicate via sign language suggests they possess the mental capacity for simple non-verbal language, but they are physically and mentally incapable of speaking. This is due to the physical differences in their brains, mouths and larynxes. It is likely that the differences between humans and an alien species would be far greater.

An alien species may ‘speak’ in frequencies that are inaudible to humans, such as ultrasound and infrasound. Imagine if half the syllables used were outside the range of human hearing. This would make communication very difficult. It might sound something like this; “The ra.. in.. ..ain fa… mo…. on t.. pl….” (The Rain in Spain falls mostly on the plane.)

It is of course entirely possible that an alien species may make noises from somewhere other than their mouths. For example, most insects make noises by rubbing their legs against their bodies and wing cases.

It is reasonable to assume that many alien species will possess sound detecting organs of some sort, considering how many times such organs have evolved independently in unrelated phyla.

An example of a plausible translation device is ‘the squeaker’ used by the Vasudans in the FreeSpace video game franchise. When communicating with you, you first hear their guttural speech, which consists of sounds that no human could replicate—then a computer-generated human voice. The slight delay between the Vasudan talking and the translation adds credibility to this. Presumably, this works both ways, with the squeaker changing our higher pitched sounds into something the Vasudans can understand.

Video by Gergination

Humans, Vulcans, Klingons etc. all appear to breathe exactly the same atmosphere, and at the same atmospheric pressure. We all walk around each other’s ships, home worlds and colonies without any breathing equipment, pressure suits, or the need to decompress. Considering the effects that even a small change in atmospheric pressure, or chemical make-up, can have on the body, this is scientifically unlikely.

Presumably, we are all resistant to each other’s pathogens as well, since none of us need to wear HAZMAT suits, or even basic medical masks.

Babylon 5 made some attempts at addressing this. There were parts of the station set aside for aliens with different atmospheric environments, which were partitioned with airlocks. A human entering these areas would require a breathing apparatus. Likewise, these aliens needed to use their own breathing apparatus when moving about the human areas of the station. 

Humans about to enter 'the alien sector' in Babylon 5: The Gathering

However, these aliens were, for the most part, minor players on the galactic stage, and were rarely seen. The main species, such as the Minbari, Narn and Centaurai were all as guilty of the ‘human’s with bumpy heads’ trope as Star Trek. This was likely done for convenience, and relatability, as viewers might find relating to, and empathizing with, a truly alien species difficult.

Incidentally, according to the blu-ray extras, this is why the 'prawns' from District 9 were portrayed as humanoid with expressive faces, and why the child prawn was made to look cute. Earlier concept art depicted them as far less humanoid, but it was felt that most audiences would struggle to empathize with something so totally alien.

The main species of Star Trek and Babylon 5 appear to share the same dietary requirements, as we are all able to eat each other’s food, and drink each other’s drinks, with no ill effects. Considering how seemingly innocuous foods can prove fatal to even related species, this is highly unlikely. For example, raisins, onions and chocolate are lethal to dogs, but harmless to us, and we are both Earth-born mammals. The dietary requirements, and tolerances, of a truly alien species are likely to be very different.

This similarity appears to carry over to the different species’ internal anatomy and physiology as well, since we all appear to have easily recognizable structures and organs. There are differences of course. We are told that Klingons have no tear ducts, but have two spines. Vulcans have green blood due to their haemoglobin analogue using copper as opposed to iron. Again, the anatomy and physiology of an alien species is likely to be very different. Consider how different from each other an octopus, a human and a lobster are. It is likely an alien species would possess an anatomy and physiology equally different, if not more so.

By far the most unlikely aspect of the humanoid races of Star Trek is that they all share the same life cycle, to the point that the different species are capable of inter-breeding successfully. Quite apart from any taboos that might be associated with this, and the small problem of ‘compatibility’ between the species’ reproductive organs, the chance of alien species being genetically compatible is near zero. For an example, most mules, which are the result of a pairing of a donkey and a horse, are infertile, despite both being in the same genus (Equus).

Spock, well known for being half human-half Vulcan appears to suffer no ill effects or dwarfism, nor does he display hybrid vigour, all of which are traits associated with hybrids. Whether Spock is fertile remains to be seen. This is made all the more implausible by Vulcans possessing copper-based blood, which suggests their physiology is as different from ours as a Horseshoe crab's, even if their gross morphology is similar.

Spock's chest wound is leaking blood. Green blood. 

The implausibility of all the above was recognised in The TNG episode ‘The Chase’, where it is revealed that an ancient, and presumably extinct, humanoid race seeded our part of the galaxy with their DNA. This provides an in-universe explanation as to why there are so many humanoid races in the Milky Way, and why they are so similar. This is, of course, a ‘retcon cop-out’, and does not hold up to scrutiny. 

Video by AJLaw98765

If the seeding was relatively recent—say in the last million years or so, this would have been obvious to any geneticist, or even paleontologist, since the results of introducing alien DNA into an established ecosystem would be pretty obvious. It would result in drastic changes in the species that came after this seeding, which would result in a missing link as deep as a chasm. The fact we share so much DNA with other primates clearly shows we are descended from a common ancestor.

One sci-fi franchise that got this right was the Homeworld video game series. The protagonist race, the Kushans, realised they were not native to Kharak, the world they lived upon, when they discovered genetics. Their genomes, and that of two species of quadrupedal pets—which might be cats and dogs—were unlike any other life form on the planet. This discovery led them to realise they had been exiled from their true home world of Hiigara thousands of years ago. 

Video by GOG.com

But what if the TNG progenitor humanoids had seeded their DNA early on when life was just starting on the various planets? Then all life on those worlds would have a similar genome, right?

Theoretically yes, but there is a huge problem with this, the problem being the equally huge amount of time that has elapsed since then. This vast time-frame would allow evolution to diverge greatly from this initial starting position.

The chance of evolution on multiple worlds all resulting in essentially the same outcome is effectively zero. Many scientists believe that if we were to turn the clock back on Earth to the unicellular age and let evolution take its course, it might go down a very different path. The lifeforms that would inhabit the world billions of years later, in our present, might be totally unrecognisable to us.

For example, bone has only evolved once—in the so called ‘bony fish’. All phyla that possess bones since then, i.e. fish, amphibians, reptiles, dinosaurs, birds and mammals are all descended from this group.

What’s more, our crossing of an airway with an esophagus has only occurred once, again in this same lineage. Therefore, the chance of that happening multiple times, on multiple planets, is next to zero. 

Incidentally, we inherited this design flaw from our early ancestors, since the first vertebrate jaws appeared in fish, and those jaws evolved from their gills. This is why for most vertebrates the feeding and breathing apparatus are linked, and why we are at risk of choking on our food.

As an aside, this invalidates the concept of the ‘Facehugger’ from Alien being a ‘universal parasite’, since it would only be able to impregnate something with the same eating and breathing set up as a human. Ridley Scott’s retconning to make the Xenomorphs the creation of a human-created android actually makes more sense. They are compatible with humans, because they were made with human hosts in mind.

Video by Philippe Pelletier

Very few popular sci-fi TV shows or films appear to have given thought to the evolutionary history of these aliens, and why they are the way they are. For a species to make sense now, you must first know where it came from.

Sometimes this lack of thought results in aliens with ludicrous biologies. For example, the aliens from Signs die if exposed to water, despite clearly operating at temperatures where water is liquid. The Ocampans from Star Trek Voyager can only have one child per lifetime. This is less than replacement levels, so they would become extinct very quickly.

If you have made it to the end of this article then well done, and thank you; you are a trooper. There was a lot to cover, and there are many other examples that could have been included, but I think I have taken up enough of your time today already. What other ridiculous alien biologies have you encountered on page or screen?

In the next article we will take a look at the boring or implausible alien societies in popular sci-fi. See you all then. 

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