Koshima macaques

Koshima macaques are presented as a community transformed by the innovations of one young female, Imo. Their adoption of her methods for cleaning food makes them a case study in how individual discoveries can become collective knowledge: the group’s contribution was not necessarily to invent the useful behavior, but to recognize and spread it through imitation.

Imo’s innovations

In the early 1950s, Imo, a one-year-old female macaque on the Japanese island of Koshima, began washing sweet potatoes in a creek before eating them. Within a few years, the practice had spread so widely that it was difficult to find a macaque on the island that did not wash its sweet potato.

Imo later applied a second practical innovation to wheat. Researchers sometimes gave the macaques wheat on the beach, where it became mixed with sand. Imo discovered that throwing a handful of the mixture into the ocean separated the two: the sand sank and the wheat floated. Within a few years, most of her fellow macaques were using the method and benefiting from it.

Imitation as collective judgment

The account initially seems to challenge the idea of group wisdom: if one exceptional animal found the solutions, the macaques’ success might appear to be the work of an individual rather than a crowd. The book locates the collective achievement elsewhere. Imo originated the practices; the group’s wisdom lay in imitating her and allowing useful behavior to spread.

This example distinguishes generating solutions from choosing among them. Invention may begin with an individual, while the adoption of an invention can be a collective process. The macaques’ response turned two discoveries into shared practices, showing how imitation can distribute the benefits of knowledge beyond the individual who first uncovers it.

The value and limits of copying

The Koshima example makes imitation a means of rapid cultural transmission. A community can adopt a useful practice without every member independently rediscovering it; in that sense, behavioral change can proceed faster than waiting for change across generations. The book presents this as a way a community can become better fitted to its circumstances through social learning.

Imitation is not beneficial without qualification. The account of Koshima supports the value of copying a practice that works, while the broader argument stresses the importance of stopping to learn independently when the gains from doing so become substantial. Following others regardless of the result can harm group welfare. The macaques’ significance therefore lies not simply in copying, but in the collective spread of useful innovations.