Something so seemingly elementary as defining what it is that makes humans unique should not plague us, but here we are. The task is infinitely laborious, and this only enflames our desire to find intelligent life somewhere out there in the universe. Even some skewed form of intelligent life on earth might do the trick. For what is a definition without some comparison? It’s no wonder that the struggle to conceptualise humanity permeates throughout film. It’s a powerful medium for expression and exploration, and a place to face our fears. But what do our fears say about us?

Take a look at two of film’s most overused monsters, zombies and vampires. The undead are often made more terrifying by a lack of understanding in how the transformation occurs – an invisible foe, robbing individuals of their humanity. The latter involves a soul-piercing moment of finality, an ultimate loss of innocence if not of life. Each of them is near human, at least in appearance, but so vitally monstrous. The upcoming horror remake of The Thing utilises an alien that can take the form of anyone it touches to terrify the audience, somewhat akin to Invasion of the Body Snatchers (1956). The German word doppelgänger refers to this very sort of malevolence: an often evil duplicate of a person, their foe and foil.

Like a terrorist or spy, the mysterious and unknown get under our skin because of their near-familiarity. We know the dark thoughts that sometimes go through our own heads, and we can only imagine how far something wicked and unscrupulous might go. Look back at Solaris (2002), a film documenting how well we do not understand humanity and what should be treated humanely. District 9 (2009) takes a much more direct approach, showing us how humanity might decide to treat something that is near-human. That is, they regard them not as humans but as extra-terrestrials, experimenting on and mistreating this race of “prawns”.

Could it be that anthropomorphised monsters are just easier to make? How could filmmakers hope to successfully depict emotion, create tension, or simply stay within budget if they tried to create convincing non-human threats? The complexities of creating something inhuman can be greater than those of creating something with no semblance of humanity. Look at films that do not deign to show the monster. Or those that actually do manage to create something unmistakably exotic, as in the aptly named Monsters (2010) and Alien (1979). They struggle, but to serve other purposes.

The inhuman gives us an opportunity to explore the mundane in a novel light. The Doctor, of Doctor Who fame, always had a soft spot for us humans, suggesting that we had an indomitable spirit, even if we could also commit acts of unthinkable cruelty. Who better to tell us that than an outsider?

Science fiction naturally takes the spotlight in this conversation, and anthropomorphised monsters and aliens are a microcosm of what purpose the genre serves as a whole. Science fiction changes one or many elements of reality, and represents what we see everyday in a new light. Rooms are scary in the dark and people aren’t attractive when they’re eating, but imagine what each is like when gravity is reversed and everyone talks like they’ve got a stuffy nose. Vampires and Klingons take the concept of human and humanity and apply a different history or biology to them, but only enough to make us think about ourselves. This, them, that. They’re all us.