If you are like me, perhaps you have been wondering (or worried about) what exactly the future holds for us humans. It is easy to get caught up in thoughts of eventual doom and gloom, especially with climate change, political infighting, and economic downturns. While humanity is guided by many different belief systems that give us strength during tough times, there is only one thing that is for certain. My guiding light. My teacher. My sage and guru. One ring to rule them all. It’s crabs.  

What do I mean exactly? Well, there is an evolutionary phenomenon, known as carcinization, which states that non-crab-like crustaceans, across multiple evolutionary lineages, have evolved over the last 300 million years to all take on crab-like forms.  

The Sally Lightfoot Crab seen on rock edifices on the tidal pools of the Galapagos Islands.

Ask an evolutionary biologist why this happens and the answer is not so simple. We all recognize that the round and flat thing with pinchers that lives in or near a body of water is a “crab”. However, scientists would actually say that there is a big distinction between all these crabs. We all recognize that spider crabs, hermit crabs, snow crabs all have a similar body shape and plan that makes the human brain lump these organisms into the same category. These forms actually represent something else entirely – known as convergent evolution. 

There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone circling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.

Charles Darwin, On the Origin of Species 

Think about all of the things you know that have wings. A few examples that come to my mind right away include insects, bats, and birds. All of these organisms have wings that help them to fly for a variety of reasons. The smallest bat on earth might be called the Bumblebee bat, but we know that it is not actually an insect, right? This basically sums up the ethos of convergent evolution. Organisms can evolve certain body forms to meet their needs in environments that might be similar or evolve certain traits for similar purposes. In the case of birds, bats, and insects – flight became an advantageous trait at some point in history, resulting in all of these different lineages of organisms having this similar trait. These animals do not have a recent shared ancestor with wings but they evolved in environments where wings were helpful or advantageous. The same is true with “crabs”.  

Somehow, somewhere, evolution decided that the most perfect form of existence for a crustacean to manifest was the crab. The National Science Foundation has even given some scientists at Harvard and Florida International University the funding to explore why this phenomenon occurs. Their paper, published in 2021 in the journal BioEssays was titled: “How to become a crab: Phenotypic constraints on a recurring body plan.” The paper proposed several different hypotheses for further investigation into why this carcinization phenomenon occurs. While the journey that crustaceans take to become a crab could be inspired by numerous positive or negative constraints in the environment, there is something about the locomotion and body plan of a crab that aids in its evolutionary success. The authors of this study, however, end with saying that more research into understanding this phenomenon is desperately needed.  

PBS Eons does a great job of summarizing lots of concepts from evolution – including this great video on carcinization!

For now, let your mind be at ease as you imagine a world without conflict or problems. A world where your carapace and pleon slowly begin to merge into one. A world where carcinization is the true and purest form of existence. A world more perfect and beautiful. A world where you are a crab.  

If you are inspired to learn more about crabs or convergent evolution, check out some of the resources I have included below, some of which are found in the KCKPL collection: 

Credit: Ev Shmev (Facebook Group: Wild Green Memes for Ecological Fiends)