Network Engineering and the Slime Mold:

I’ve written a fair bit – in my book, in a couple of articles here and here, and on this blog from time to time – about the extraordinary development of the new science of networks, an amalgam of research in biology, physics, systems engineering, mathematics, sociology, and other disciplines, all focused on unraveling the laws governing the growth and development of networks. So here comes a wonderful illustration of some of the connections that these researchers are uncovering, in this week’s issue of Science. A team of researchers at Hokkaido University in Japan investigated the network-creation behavior of the slime mold, an extraordinary createure that grows on forest floors in the form of an interconnected network of tube-like tendrils which transport nutrients around the organism. The researchers put out a bunch of oat flakes (a favorite slime mold food) on a platform in a pattern replicating the distribution of population centers in and around Tokyo, Japan, and then plunked the mold down in the middle and let it get to work. The idea was to see what kind of network the mold would build, connecting the various food sites together.

And lo and behold, the network of tendrils the mold — an organism, incidentally, without anything remotely resembling a “brain” — came up with bore a striking resemblance to Tokyo’s actual existing rail network. As a report in The Economist put it, the slime mold “had not simply created the shortest possible network that could connect all the cities, but had also included redundant connections that allow the creature (and the real rail network) to have resilience to the accidental breakage of any part of it.” It’s quite astonishing. The Shortest Viable Network problem is mathematically quite daunting — engineers have any number of algorithms that attempt to produce the right pattern of links and connections, but it’s a tricky, difficult business. But somehow, the most primitive organism imaginable seems to “know” how to solve the problem. Fabulous! How do they do it? Good question!