A single-celled organism with no brain redesigned Tokyo's rail network from scratch
Researchers placed a yellow slime mold, Physarum polycephalum, onto a map of Tokyo with oat flakes marking the positions of major stations, and watched it grow a network connecting the food sources. Within about a day, the slime mold had pruned its initial sprawl down to a network strikingly similar in efficiency and redundancy to the real Tokyo rail system, one engineered by human planners over decades.