Opened in 1927, Tokyo’s subway lines arrived in their current conformation after nearly 80 years of planning by hundreds of city planners and engineers. Recent research published in Science has shown how a simple mold is capable of reaching the same conclusions by redesigning the entire network in just 28 hours.

It is called Physarum Polycephalum, and it is a yellowish-colored mold, a single-celled organism that arises and proliferates in cool, moist environments, showing an incredible ability to solve complex network analysis problems. Indeed, it manages to orient itself and move through mazes, not only efficiently, but also by expending the least amount of energy.

In the experiment, researchers at Hokkaido University, led by Toshiyuki Nakagaki, arranged oatmeal in a pattern that mimicked the pattern of major cities around the Japanese capital that could be reached by the same trains. Left free to act, the mold initially began to move, but more importantly to grow exponentially, and within the first 10 hours it touched the major cities surveyed, seemingly reached at random.

The mold then reorganized itself from an expanding to a branching structure and rewrote the Tokyo metropolitan system. Over the course of 28 hours, it was able to make a new configuration that was more viable and practical than the existing one, tracing the most efficient path to connect all the affected points.

The behavior of the Physarum Polycephalum demonstrates how such a malleable system can be useful for creating networks that need to change over time, such as short-range wireless sensor systems that would provide early warnings of fires or floods. Because these sensors are destroyed when a disaster occurs, the network must redirect information efficiently and quickly.