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TagDoug Johnson

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Crab close up, Cuba

If We Find Life on Exoplanets, Some of It Might Be “Crabs”

Over millions of years, many crustaceans gradually grew to look more and more like crabs, a process called convergent evolution

The earliest crablike creatures are thought to date from about 365 million years ago (the Late Devonian period). But the odd thing is that many creatures that did not start out looking like crabs have, over tens of millions of years, grown to look like them. A good many lobster-like decapods (= they have ten feet) began to look like crabs (carcinization). Possible causes include greater mobility (some crabs can climb trees), easier hiding in narrow spaces, and less temptation for predators (no juicy tail). Biologists call this process convergent evolution — life forms converge on the same solutions to their problems even if they are not closely related. So we might ask, if we find life on other planets,…