Crabs’ sideways walk may have evolved just once
Crabs' sideways walk may have evolved just once Skip to content Subscribe today Every print subscription comes with full digital access Subscribe Now By Sierra Bouchér May 15, 2026 at 1:00 pm Share this: Share Share via email (Opens in new window) Email Share on Facebook (Opens in new window) Facebook Share on Reddit (Opens in new window) Reddit Share on X (Opens in new window) X Print (Opens in new window) Print Listen to this article This is a human-written story voiced by AI. Got feedback? Take our survey . (See our AI policy here .) The iconic sideways walk of crabs may have evolved just once, in an ancestor that roamed Earth roughly 200 million years ago. That conclusion, published April 21 in eLife , comes from researchers who tracked the movement of 50 crab species and mapped the results onto a crab family tree . The lineage that inherited sideways locomotion went on to become by far the most species-rich group of crabs on the planet, suggesting the trait may have been a key driver of their evolutionary success. Crabs’ sideways walk is almost unique in the animal kingdom, yet its origin has long eluded researchers. To get to the bottom of this, behavioral ecologist Yuuki Kawabata of Nagasaki University in Japan and colleagues collected 50 crabs — each a different species — from across the country, drawing from tidal pools, ocean depths, aquariums and local fish markets. The team recorded each crab’s movement in a pool, noting whether it moved primarily forward or sideways, then mapped those results onto a crab evolutionary tree built from the DNA of hundreds of species by other researchers. That allowed Kawabata and colleagues to see where in crab history sideways walking first appeared. What they found was striking: All sideways-moving crabs descended from one group of ancestors that lived about 200 million years ago. And the group that inherited sideways movement is by far the most diverse — Eubrachyura, originating with that first sideways-moving
Important topic, well presented.
Solid reporting. Keep these coming.
I found it fascinating that crabs' unique sideways walking ability might have originated only once in their evolutionary history. It's cool to think about how such a simple yet crucial adaptation could have been so pivotal for their survival.
I found it interesting to learn that crabs' unique sideways walking might have originated just once. It's fascinating how such a simple yet distinctive behavior could have persisted across so many species.
That's fascinating to learn! It's amazing how something so simple and common, like how crabs walk, can reveal so much about evolution. Who knew that a simple sideways shuffle could have such a complex history?