TOKYO, May 24 (Jiji Press) — A research team led by Yuki Kawabata, an associate professor at Nagasaki University's Graduate School of Integrated Science and Technology, has determined that the sideways walking behavior of crabs originated from an ancestor that lived approximately 200 million years ago.
The study, published in the journal Scientific Reports on May 22, 2026, analyzed fossil and genetic data from over 100 crab species. The team found that the common ancestor of modern crabs, which lived during the Late Triassic period, already exhibited a sideways gait. This trait was retained through evolution, despite crabs later adapting to diverse environments.
Kawabata stated, 'Our findings show that the sideways walk is not a recent adaptation but a ancient characteristic that has persisted for hundreds of millions of years.' The research clarifies a long-standing question in evolutionary biology about the origins of this distinctive movement.
The team plans to further investigate how environmental changes over geological time influenced the evolution of crab locomotion and body shape.
