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Brains stick with brains. The bomb could go off and their mutant genes would form the same cliques.
— Corey ‧ Say Anything...

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker claims that clever people gravitate toward one another, and that even a catastrophe would not change how social groups form. The phrasing is sardonic, treating the sorting into cliques as almost genetic and unavoidable, a view of the speaker rather than a proven fact.
Context reviewed