carcinization
Many different lineages of crustaceans keep converging on the crab form over time, a process which has been named "carcinization". When a trait or body form keeps re-evolving independently, it's usually a sign that it's a pretty effective way for an organism to be. People on the internet learned about this and then extrapolated to say that not only are many crustaceans fated to become crabs, but maybe everything alive will one day adopt the claw! We're going to wait and see what happens...
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