A Quiet Place didn’t feel the need to spend time on lots of exposition, and was probably all the better for it. The film doesn’t really tells us much about the creatures at all. However, director, co-writer and co-star John Krasinski actually did flesh out their backstory during the pre-production process, as revealed in a chat with ‘Empire’:
“They are absolutely aliens. They’re from another planet. Where I developed the idea of them and what I wanted them to look like was most alien movies are about takeovers, agendas, they’re a thinking alien creature, and for me this idea of a predator, this idea of a parasite, this idea of something that is introduced into an ecosystem was interesting.”
“The idea behind all that is they’re definitely aliens and they’re an evolutionarily perfect machine. So the idea is if they grew up on a planet that had no humans and no light then they don’t need eyes, they can only hunt by sound. They also develop a way to protect themselves from everything else so that’s why they’re bulletproof and all these things. I had to make it make sense. I needed the rules of the monster to adhere as tightly to the rules of the family. The family, we had set up all these incredible rules, and I needed the monster to not just be convenient.”
“And the other idea was the armor is also the reason why they were able to survive kind of the explosion of their planet and then survive on these meteorites, because they’ve evolved to be bulletproof. Until they open themselves up to be vulnerable, they’re completely invulnerable.”
Thanks to Collider for the transcription.