Slime Mold, Network Designer

In an experiment reported in the New York Times on Tuesday (Jan 26), slime mold uses design principles very close to those devised by humans. The slime mold is a unicellular being that spreads itself out in search of food and then links to food sources via tiny tubes. In the experiment, researchers placed food sources at the some position relative to the slime mold as the surrounding cities are to Tokyo. Within 24 hours, the slime mold had linked the food sources in a pattern similar to that of rail links among Tokyo and nearby cities. Reporter Henry Fountain writes, “The researchers found that the slime mold network was as efficient as the rail network, it tolerated breaks in the connections just as well, and it was created at reasonable cost to the organism.” The image at left, copied from the paper, shows the mold (yellow blob), food sources (white dots), and tubular connections (thin white lines) at 0, 5, 8, 11, 16, and 26 hours of activity.  This is considerably less time than it took engineers to design the railway system. Scientists have already created a mathematical model to replicate the simple steps–call them algorithms–that lead the slime mold to create this kind of pattern. How similar are human networks?