Convergent Evolution and Carcinization

When unrelated species of animals or plants have common features, evolutionary biologists call it “convergent evolution.” There are many examples, such as:
* Dolphins and bats use echolocation to find food.
* Titan arum and rafflesia plants use putrid odor to attract pollinators.
* Nightingales and humpback whales sing similar songs just for beauty.

Those are only a few of the vast number of examples that scientists explain as convergent evolution. You can probably think of others. For example, bats, birds, and insects all have wings, but they are not related. In addition, unrelated venomous or poisonous creatures often wear bright colors as a warning, for example, snakes, frogs, and insects. Usually, the convergent features of various animals and plants serve an obvious purpose for the species’ survival.

Perhaps the most repeated convergence appears in the crab-like body shape. A crab has a flat, rounded shell and a tail that tucks under its body. Evolutionary biologists say that body plan has “evolved” at least five times. Scientists even have a name for this phenomenon. They call it “carcinization,” but they can only guess why it happened.

The result of carcinization is that many unrelated crustaceans resemble crabs. As a result, we often call them crabs even though they are not true crabs. A familiar example is the so-called king crab. Crab-shaped animals come in a wide range of sizes and live in various habitats, from the oceans to the mountains. So, with these creatures living in diverse ecosystems, scientists have difficulty explaining why they evolved the same body plan. Some suggestions include the tucked-under tail providing greater safety from predators or the body shape allowing them to move sideways.

We have a suggestion of why the crab shape, or carcinization, shows up in so many different crustaceans. Rather than convergent evolution, the common traits can be explained by a common Creator. That would explain why these creatures have the DNA building blocks for crabbiness – oops, I mean crab body shape.

— Roland Earnst © 2023