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How a Brainless Slime Mold Recreated the Tokyo Rail System

What's the best way to design a new subway network or road system? It might be using slime mold. Yes, slime molds—the single-celled, brainless organisms that you might have seen covering a log on a hike in the woods—happen to be excellent urban planners.

For over a decade, researchers have been studying how slime molds spread out to look for food via the most efficient paths. When the mold finds something to eat, the path to that spot gets stronger, not unlike the way a line of ants will zero in on a picnic sandwich. Scientists in Japan decided to see how the mold would navigate the Tokyo area, and set up a "map" with oak flakes—slime mold's favorite food—marking local cities. Within a day, the mold had essentially recreated the Tokyo rail system, finding the same paths that it took teams of engineers years to plan.


Researchers have also used slime molds to recreate highways in China, the United States, Canada, the U.K., and Spain, noting that sometimes the mold discovers a slightly more efficient route than the humans did.

Though reports on this research started coming out a few years ago, I haven't seen cities using slime molds in actual transportation planning yet. Who will be first to add slime mold to the urban planning department?

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