As you may have heard via a barrage of internet memes, evolution can't get enough of crab-like forms. The body shape of crabs has arisen on many separate occasions in natural history, in a phenomenon known as ' carcinization '. However, one feature sets true crabs ( Brachyura ) apart from their lookalikes: their near-exclusive, characteristic sideways walk. "Sideways locomotion may have contributed significantly to the ecological success of true crabs," says behavioral ecologist Yuuki Kawabata