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Movie monsters and astrobiology

11 May 2010

I have a problem: I like sci-fi movies.  This might not qualify as much of a problem, but I’m a little bit picky. I demand some kind of thought when it comes to movie monsters and alien lifeforms.  More often than not, as soon as a monster/HILF appears, I sigh in disbelief, curse the creators for ruining another perfectly good film/TV show and switch off.   So, what are they doing wrong?  On closer inspection the issue can be split into two sub sections: ‘amazing’ monsters and ‘humanoids’.

The ‘amazing’ monster problem


This is where the film/TV show makers let their imagination run wild, and the creature end up being the result of a brainstorming session starting with the phrase “Wouldn’t it be cool if..”.  This almost always results in a monster that has counter-adaptive traits and lack any sense of place in the alien ecosystem.

A perfect example would be the giant asteroid worm in ‘Star Wars: The empire strikes back’.  It’s a huge creature that lives inside caves in small(ish) asteroids.  Problem one: how can it survive in a vacuum and in absolute zero temperatures?  Problem two: with those big teeth it is obviously a carnivore – so what could it possibly hope to catch and eat in a desolate asteroid (and don’t say ‘space ships’)?  It doesn’t fit into its surroundings – it’s just a ‘wouldn’t it be cool if..’ scenario.


On the other hand, the creature in ‘Alien’ has a complex and fascinating life cycle which alternates between parasitic and carnivorous stages.  It has clearly taken inspiration from the insect world, with its molting phases, exoskeletons and dual jaws, but brought into the macro-fauna scale.

It’s not without it flaws though. Firstly, as a parasite, how is it possible for it to use the human body for cultivating its ‘pupae’ and hatch into the ‘adult’ stage, when it never encountered humans (or even mammals) before?  Almost all parasitic lifeforms are highly specialised to use only a small group of closely related hosts.  Secondly, after hatching and breaking through the rib cage of the host (ouch!) the tiny alien somehow molts into a 7 ft monster in less than a few hours.  Where did it get the matter to build that body?  Did it eat the walls of the space ship?


‘Humanoids’ or para-humans is my pet hate.  They are usually just actors dressed in vaguely Roman clothes and feature one or more of the following: pointy ears, odd nostrils, bumpy bald heads, fangs, patterned or oddly coloured skin.  This is probably mostly due to budget constraints (actors + makeup = cheap), but I also believe it is to make it easier for us to identify and sympathise with an alien life form.  What ever the reason, sci-fi films and TV shows are littered with humanoids.

Convergent evolution in dolphins, sharks and ichthyosaurs.

Now there is such a thing as convergent evolution, where two not closely related creatures take on a similar form under the force of natural selection.  Compare a shark with a dolphin: both have hydro-dynamic bodies with smooth skin, fins/flippers to steer with and a powerful tail fin to propel themselves with. And since they both feed mainly on fish they also have plenty of sharp teeth for catching prey.  There was even a third group of animals a while back with almost exactly the same traits: the ichthyosaurs.  All three groups of animals look more or less the same even though one is a fish, another a mammal and the third a reptile.

But closer examination show that they are all related in so far that they are all vertebrate animals – they all descend from a single predecessor who had a spine protecting its central nervous system, an internal skeleton onto which muscles were attached, a single heart powering a closed circulatory system, a jaw with teeth, a digestive tract with a stomach, gall bladder, liver and a pair on kidneys. It also featured single pairs of eyes, ears, nostrils and frontal fins.  In other words the basic body plan of a fish.  So apart from the fact that dolphins and ichthyosaurs descend from land animals, they all share the same basic body plan.  In addition, the rules for being a successful aquatic predator are quite simple – you need to be quick, strong and have sharp teeth.  This will result in similar appearance over and over again.

Yeah, right...

Our human evolutionary history is a different story.  Many of our distinctive traits are the result of chance and/or distinct adaptations to previous environments.  Five fingered hands? That’s just because 300 million years ago a fish that became our ancestor happened to keep five boned fins that later became feet (and our hands).  Opposable thumbs? That’s only because our primate ancestors used them for climbing trees.  Forward pointing eyes (ie stereo vision)?  That was necessary for judging the distance when jumping between branches.  Colour vision?  Again, our ancestors needed colour vision to find ripe (ie coloured) fruit hidden in the green canopies.  Bipedalism? Ah, now it’s getting interesting.  This could be the result of abandoning the trees and populating the grassy plains that appeared around 7-8 million ears ago.  Being bipedal would have given us better view looking over the tall grass, and would also have freed up our arms to allow us to carry food long distances.  Lack of fur?  Perhaps this was an adaptation to moving across grassy plains in intense sunlight.  Being hairless would allow us to sweat and have the sweat evaporate quickly to get rid of excess heat.

That's more like it.

High intelligence?  This is the big one.  Why would we evolve such complex (and expensive) brains, that also puts the mother at risk during birth due to the big head?  And if it is such a  great thing to have, why doesn’t every other animal also have one?  One answer could be that as an early ape, we happened to live in medium-sized groups, who needed to cooperate on a high level to be able to survive.  Our cousins the Chimpanzees, Gorillas and Orangutans lack the same level of intelligence only because they stayed in the forests and didn’t have to deal with this new and dangerous environment.

So, unless an alien species has gone through almost exactly the same evolutionary history (vertebrate fish with bone based fins, arboreal fruit eaters, deforestation and exposure to new dangers and challenges) there’s no chance at all that they’d look anything like us.  Bipedal?  Sure, why not.  Bilaterally symmetric body plan?  Probably.  Highly intelligent?  Ok, it’s possible I guess.  But blue humans with pointy ears?  Never gonna happen.

4 Comments leave one →
  1. Andrew Lawrence permalink
    11 July 2010 13:31

    While i have less difficulty with some of the similarities between alien races than you do,( i largly put it down to poetic license and the distinc lack of non-human actors available for the role) my biggest pet hate is the ability for two sentient races from different worlds to be able to procreate.

    Its one things to fudge a few small details, but this is garingly, slap-in-the-face, obviously, and very very basically wrong at the most fundamental level.

    Its as if they have stopped even trying.


    • 11 July 2010 13:57

      Very true. Unless they are VERY closely related it just wouldn’t work. Not even a horse and a donkey can create viable offspring and the are obviously quite closely related.



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