Fish are masters of coordinated motion. Schools of fish have no leader, yet individuals manage to stay in formation, avoid collisions, and respond with liquid flexibility to changes in their environment. Reproducing this combination of robustness and flexibility has been a long-standing challenge for human-engineered systems like robots.
Having no real hierarchy is extremely rare in the animal kingdom. Ants and most other insects have their queens. Herds of elephants are led by the oldest female. etc