In 1948, three Japanese scientists embarked on a long-term study of wild Japanese macaques (Macaca fuscata) on Koshima Island. Their strategy involved leaving food, including sweet potatoes, on sandy beaches to observe the monkeys’ behavior. Among these macaques was an 18-month-old named Imo, who unwittingly sparked a remarkable change.

In September 1953, Imo did something extraordinary. Instead of wiping the sand off her sweet potato with her hand, she washed it in a river. Her innovative approach to problem-solving caught the attention of the scientists.

Imo’s intelligence was not confined to her. She taught her siblings and even her parents to wash their food. This behavior transfer from offspring to parents was an unusual occurrence in nature. Imo’s creativity didn’t stop there – she began dipping her washed potatoes into the ocean before eating them, revealing a preference for the taste of salty potatoes.

The impact of Imo’s actions went beyond her immediate family. Gradually, the entire troop adopted the potato-washing behavior. By 1962, an overwhelming majority of monkeys over two years old on Koshima Island were washing their food.

Imo had fundamentally transformed their community.

Hirata, S., Watanabe, K., & Kawai, M. (2001). “Sweet-potato washing” revisited. In T. Matsuzawa (Ed.), Primate origins of human cognition and behavior (pp. 487-508). New York, NY, US: Springer-Verlag Publishing.