I have the Darwin in me to blame for my disinterest in horror films. Really, let's think about it for a moment. Why do all these ghosts, phantoms, demons, and other supernatural beings want to kill the horny teens, or the hikers lost in the woods, or the new homeowners? What is in it for them? They certainly do not want to eat their victims. We have never seen on the screen a ghost frying a human hand or heart. But the usual reason something kills another thing is precisely to make a meal out of it. The late French philosopher Gilles Deleuze soberly described being eaten as a "bad encounter." The animal having the relations that define its individuality consumed by another animal (or microorganisms) is just having a bad encounter. Why should this be scary?
But there are also good encounters. Such an encounter is obviously not bad for the animal that's eating; the food satisfies it and gives it the energy to fuck and reproduce itself, which, after all, is the whole meaning of life. So how does an evil demon fit into this circle of good and bad encounters? Does it have a stomach like a lion? And if you are unlucky enough to be eaten by a lion, you do not say to it: "What an evil thing you are!" You instead understand that the animal has a problem (it is hungry) and you are the solution (food). This is how the universe happens to work. It's really, as the hit men in Mafia films often say, nothing personal.
My unrepentant Darwinism is the reason that the one horror film I really, really love and watch over and over is Alien. The monster is, yes, an alien, but it is definitely biological. It is not from hell or some obviously supernatural place but from another planet, where it must have evolved like all living things evolved on Earth. The alien, which is black and has super-sharp teeth, is a multicellular organism with what appears to be an exoskeleton. It also has blood.
Released in 1979 and directed by Ridley Scott, Alien is about a seven-crew commercial hauling ship that, on its return trip to Earth, is required to respond to a distress signal from a strange and dark planet. Two of the workers on the Nostromo—Parker (Yaphet Kotto) and Brett (Harry Dean Stanton)—are not at all happy about this operation. To begin with, it's not their job; they are workers on a commercial spaceship, not a rescue spaceship. They also do not want to talk about "systematic signals" that could indicate intelligent life. That shit is for the scientists; their main concern is, to use the words of Parker, "the bonus situation." The two are informed that it is in their contract to investigate signals.
Eventually, three workers fly down to the cold planet and discover a derelict and alien spaceship that has a bunch of weird eggs on it. One of these eggs opens and some kind of creature leaps out and attaches itself to the face of one of the investigators, Kane (John Hurt). All three return to the Nostromo, and the thing on Kane's face is examined in a medical room. It has a tail, fluid sacs, and legs like a spider. Eventually, the thing lets go of Kane's face and dies. Kane seems fine, and the crew has dinner before resuming the trip back home. But as they are eating, a mean-looking creature bursts from Kane's stomach and flees into the depths of the spaceship. The little thing quickly grows into a big monster and begins killing the crew members one by one.
The economic realism of Alien (the workers worried about contracts, better pay, bonuses, and so on) is matched by the biological realism of the alien (the perfect organism). In fact, the first part of the movie is essentially Marx in space, and the second part of the movie is Darwin in space.
It can even be argued that Alien is not really a horror film but a science-fiction drama about a crew that has a really bad encounter in space. Indeed, the members of Nostromo could just as well have had a good encounter while investigating the mysterious signal. The eggs found on the alien spaceship might have turned out to be as edible and nutritious as the eggs on Earth. It was only the crew's bad luck that the alien they discovered happened to be better at decomposing them than they were at decomposing it. The universe takes no sides in such matters.