Now, at Popular Mechanics, readers are learning about convergent evolution. The process of turning into a crab is called “carcinization.”
That crabs (both “true” and ersatz) have so densely but separately evolved the same form is highly unusual, even in a world full of these examples of strong parallel and convergent evolution. “The fact that a crab-like habitus did not evolve solely in ‘true’ crabs but also several times independently in the Anomura makes this process ideal for evolutionary research,” the researchers explain.
It’s not just superficial shape that unifies the five evolved crab forms. The paper details neurological commonalities, shared circulatory systems, and more, while also detailing the organ and systems that differ in shape and size.
Moreover, the crab-shapedness of the groups can make it hard to trace what came about from interacting internal systems as opposed to, well, the crab shell…
Caroline Delbert, “Animals Keep Evolving Into Crabs, Which Is Somewhat Disturbing” at Popular Mechanics
So they share these qualities without common descent? Hmmm.
Here’s the open-access paper from 2017.
See also: Evolution appears to converge on goals—but in Darwinian terms, is that possible?
Hat tip: Philip Cunningham