Slime Mold Solves Mazes

Lacking a brain or even a single neuron, the organism Physarum polycephalum demonstrates a remarkable form of decentralized intelligence. This giant, single-celled amoeba navigates its environment by extending a network (Review) of tube-like tendrils. When a tendril encounters a food source, the organism reinforces that pathway by pulsing more of its cellular material through it. Simultaneously, it retracts any tendrils that prove to be dead ends or inefficient routes. This simple yet elegant process of strengthening successful connections and pruning failures allows the slime mold to perfectly map the shortest possible path through complex environments.

This ability was put to a fascinating test by a team of Japanese and British researchers in 2010. They arranged oat flakes, a favorite food of the slime mold, on a plate in a pattern that mimicked the major cities and stations surrounding Tokyo. The Physarum was placed at the "Tokyo" location and allowed to explore. In just over a day, the organism had grown a network connecting the food sources that was strikingly similar in its efficiency, reliability, and cost-effectiveness to the actual Tokyo rail system, a marvel of human engineering. This natural optimization algorithm has inspired scientists to explore new models for designing resilient communication networks and efficient transportation routes.