Why do crabs walk sideways? Scientists trace it back 200 million years

Crabs famous sideways walk may trace back to a single evolutionary moment 200 million years ago. Researchers found that most modern crabs inherited this trait from one ancestor-and never looked back. The movement likely gave them an edge, helping them dodge predators with quick, unpredictable bursts. Its a rare example of a behavior evolving once and then dominating an entire group.