Crabs have evolved five separate times—why do the same forms keep appearing in nature?

Charles Darwin believed evolution created “endless forms most beautiful.” It’s a nice sentiment but it doesn’t explain why evolution keeps making crabs. Crabs belong to a group of crustaceans called decapods, literally “ten footed”, since they have five pairs of walking legs. Some decapods, like lobsters and shrimp, have a thick, muscular abdomen, which is the bulk of the animal that we eat. With a quick flick of their abdomen lobsters can shoot off backwards and escape predators. Crabs, by contrast, have a compressed abdomen, tucked away under a flattened but widened thorax and shell. This allows them to scuttle into rock crevices for protection. Evolution repeatedly hit upon this solution because it works well under similar sets of circumstances. Five groups of “crabs”,,, >click to read< 14:10

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