What is the symbolism of Caleb's scars?

The placement of his scars can't be purely coincidental. What is the symbolism, and significance of Caleb's scars?

It's part of Garland's plan to misdirect the viewer and keep them off-balance and subvert their own expectations based on what they have seen in previous movies that explored similar subjects.

There’s lots of misdirection in the film, one of them is to associate Ava constantly with a kind of innocence, to put her above suspicion. And little nudges. I know everyone’s watched Blade Runner so I know everyone is going to be thinking, “Oh she’s not the A.I. he’s the A.I.” And I push them towards little scars on his back and little moments to sort of nudge you in that direction. Also moments to make you not look over there, like that rather childlike, almost nursery chimes that you attach with her. It was like a kind of game doing that whilst also having a big conversation about misdirection within the film. There’s a whole thing within the film about misdirection, look over here so you don’t look over there and that’s happening to the audience at the same time. Hopefully!

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I started work as a novelist and there are some similarities between that and screenwriting. There are some differences, too. When you write a book, you can’t assume that every reader has read every book that you allude to. In film, you pretty much can. I could say that there are allusions or uses of things like Blade Runner or say, Apocalypse Now. In the case of Apocalypse Now, I’m pretty sure that everyone watching this film has seen it, but they wouldn’t necessarily have read Heart of Darkness [the novel based on the production of the film]. In the case of Blade Runner, I was assuming that people had already seen it. I thought I made a pretty fair assumption. I’ve seen it several times. To the extent I was aware I was using it, it had to do with things like misdirection. I would assume that a similarly literate audience would catch that quite quickly. Like the test on which Caleb questions if he is a machine or not or Oscar is a machine. I knew audiences would [make assumptions] and they’re nudged to go there in the way that Domnhall Gleeson’s character has strange symmetrical scars on his back. Gently nudging the audience in that way will result in misdirection, covering up what’s actually going on in the film. The twist in some respects is that there is no twist.

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Ava is clearly the AI. Her mechanical body parts are exposed early on and Oscar himself states that she was built by him. However, we as the audience are led to automatically assume both Caleb and Oscar are humans. Remember, we are given very little info on Caleb and Oscar's lives prior to them meeting each other. What little info is given is mainly for setup.

The little knowledge we have on Caleb is important. It is a test to answer the question, "how do we know if someone is human?" How convincing is Ava if you didn't know she was an AI? How do we know we're not an AI with fabricated memories? Caleb knows Oscar is a genius with a hidden agenda and plans for Caleb. It's the bare amount of info that leads to Caleb's paranoia over his own existence.

The scars, they're meant more for the audience to ponder the same question. Does this scar prove his humanity? Can we trust the story about the scar? It's the sort of misleading tactic the director employs throughout the film to toy with how little we as humans understand what makes us human.