The Shimmer doesn't destroy—it refines.
It takes your DNA and asks: what if you were optimized? What if every inefficiency was smoothed away, every weakness rewritten by exposure to perfect information about what you could become?
That's not contamination in the biological sense—it's alignment in the worst way possible. The system works exactly as designed, improving everything it touches until improvement becomes indistinguishable from annihilation. But the film's actual argument lives in Lena's final act. After the lighthouse, after Kane dies, after she understands what the Shimmer is—she lies to Kane's handlers about her contamination.
The camera holds on her face as she claims she's clean. She isn't. She knows she isn't, but she decides this information, this truth, cannot be transferred. Watch the interrogation scene. The handlers already suspect her, they have technology, they have authority—and still, she lies, not because she's protecting herself, but because she understands something they don't: if she tells the truth about her contamination, the response will be worse than the Shimmer itself. Eradication. Quarantine. The logic of biological threat escalates from refinement to elimination.
This is what the film nailed before the field even had language for it—not the monster, but the choice to let it spread because transparency becomes the actual weapon.
Go to 1:39:20 in Annihilation—Lena's interrogation with the handlers—and watch not the dialogue but the microexpressions. Notice when she chooses lying. Then read 'The Vulnerable World Hypothesis' by Nick Bostrom to understand what Lena actually realized about information hazards.
Alex Garland's director's commentary on the Criterion Collection release discusses how the film's ending was deliberately designed to be ambiguous about whether Lena is still contaminated, but he never directly addresses why contamination itself isn't framed as a threat in the final scenes—suggesting the filmmakers intuited something about the nature of the problem without fully articulating it.