I remember as a child I liked to watch a lot of nature programmes that my mother would record for me off the television (recorded on VCR, anyone under about 30 will be bemused to know!). One of the ones that fascinated and horrified me featured the tale of a parasitic wasp that captured a caterpillar, paralysing it with its sting. It then laid eggs in the body of the caterpillar which hatched and ate their hapless victim alive. Gruesome!
Of course, this is the obvious reason why a lot of SF (particularly films) like to feature alien biology as being parasitic. They suck you in (pun intended) with that element of horrified fascination – and you can get a lot of mileage out of that (if not necessarily high-quality drama). It’s not like there aren’t plenty of horrible examples of parasites – here’s a relatively cute cartoon video, with only some nasty pictures, but there’s plenty worse to search for if you have the stomach for it. I still recall that parasitology practical in my second year pathology module with horror…not least because the entire room smelt of, well, poo.
The gruesome wasps were of course one of the inspirations behind Alien, one of my all-time favourite films. The film is stuffed with metaphors for sex, rape and birth (although probably anyone who has given birth probably notices the birth thing more…), but interestingly the director, Ridley Scott, said that:
“It has absolutely no message…it works on a very visceral level and its only point is terror, and more terror.”
Ah, visceral, such a great word – and a key one. This is pure Body Horror – as, indeed, a lot of horror is. These bad aliens don’t just invade, blow up your cities and kill you – they take over your body. Being bodily creatures, that squicks us. Badly.
What’s even worse is when some of them take over your mind. Again, this isn’t without precedent – a lot of parasites change the behaviour of their host organisms. Mice infected with Toxoplasma, for example, lose their fear of cats, because the parasite’s goal is to infect a cat, it’s next host. Stargate’s Goa’uld are snake-like parasites that completely take over the body and the mind – the personality “running” the body is that of the alien. This might have been more horrifying if most of the Goa’uld weren’t pantomime villains often played for laughs as well.
Far more interesting were the rebel Tok’ra – still Goa’uld, but ones that did not suppress their host and shared the body equally, meaning that you effectively got two people for the price of one. Symbiosis, in other words, as was also seen in Star Trek’s Trill, although here the personalities merged. Unfortunately the series under-utilised these rather interesting characters, and favoured the hugely boring Jaffa, which carried the larval Goa’uld, and were a frankly cliched noble warrior race. I don’t know about you, but I could definitely do with fewer noble warrior races in my fandoms.
Of course, both these examples are hugely unrealistic. Parasites are highly specialised, usually adapted to infect either only one species, or a few at different stages of their lifecycle (e.g. the malarial parasite infecting both us and mosquitoes). It’s vastly unlikely that an alien species would ever successfully manage to parasitise something from another planet, like us, so rest easy in your beds. (I grant you the Alien xenomorphs were implied to be engineered biological weapons). One of the key problems a parasite has is to evade the host’s immune system from attacking it. Another is reproduction – how are you supposed to meet parasites of the opposite sex when they are stuck somewhere inside another host body? For this reason, many are hermaphrodite, and self-fertilise. Why then does the Alien xenomorph have a queen, only one individual in a colony capable of reproducing (and whose job it is to do little else)?
The whole xenomorph “biology” setup is a weird mash-up of ideas. You have the facehuggers, which hatch from eggs and have to find hosts, which lay another kind of egg down the (human) host’s throat. That then hatches as a chestburster which grows into a bigger adult version of itself that attacks and often kills future hosts, but is supposed to bring them back to the queen so they can be cocooned, ready for the eggs that the queen has laid. It’s taken the idea of the parasitic wasp and the idea of a beehive and produced something completely biologically implausible. Again, I think this is for maximum squick factor. You don’t just get the parasites, you get big monsters stalking you (bringing out a lot of primal childhood fears of something big and scary eating you), and finally one huge and terrifying dragon at the centre of it. You have to love it. I can only think that Stargate adopted the queen system because of Alien, and not because, well, they thought it through at all.
It’s not the only type of parasitism you can encounter of course. John Wyndham’s Midwich Cuckoos exhibited a form of brood parasitism in which human women became pregnant with and later raised as their own children, non-human aliens (very like cuckoos, which lay their eggs in other birds’ nests). It’s a more insidious form of societal takeover in this case, not so much a biological one, although it is possible that the humans would later be supplanted by the aliens if they do not necessarily require human hosts.
This starts treading into the territory of aliens altering our society, as opposed to our bodies. Here, the concept of organisms being interlinked and inter-dependent in ecologies, inspired by the Gaia hypothesis, and the rise of environmentalism, led to parasitism and symbiosis being used as tools to explore human relationships with other species in general. Indeed, the Encyclopedia of Science Fiction notes that:
…Exotic biological relationships are transformed into metaphors applicable to social relationships (or vice versa), relationships between humans and other intelligent beings or even, in a psychological sense, relationships between humans and their environment. This is, of course, a totally unscientific use of scientific ideas, but it can be very effective as a literary device….Thus, for example, the hive-mind becomes in SF not so much a mode of social organization pertaining to insect species as a metaphor for considering possible states of human society. Similarly, symbiosis becomes symbolic of an idealized relationship between humans, or between human and other beings.
Indeed, if you don’t get body horror, you get a kind of social horror, like the hive mind of the Borg. Yes, I know this isn’t strictly parasitism, but it is essentially being invaded and taken over by an alien, and it manages to work in that other type of “other” to fear, machine-based life, in a creepily effective amalgam of the two. Oh, and they have a queen as well. Why do they have a queen? Maybe it’s something to do with the linking of fears about communism and “mindless worker drones” (although communist societies shouldn’t, theoretically, have a monarch at the top). Maybe, at the end of the day, modern humans just have to believe that somebody has to be in charge. Or that lots of aliens evolved from something like bees and wasps.
Those nature programmes have a lot to answer for.