In 2009, scientists unleashed an amoeba-like blob on to Tokyo, and watched as it consumed everything in sight. In less than a day, the blob had spread throughout the entire city, concentrating itself along major transport routes.

Fortunately for the citizens of the great Japanese metropolis, the blob did its work on a model. Flakes of oats stood in for the major urban zones and the scientists involved were no B-movie villains. Rather, they were biologists studying the sophisticated behaviour of a slime mould, an oozing blob of goo that performs feats of apparent intelligence despite being completely brainless.

The slime mould Physarum polycephalum spends most of its life as a yellow mat, sliding among the leaf litter in its search for food, such as bacteria and fungal spores. This mat is a gigantic single cell, called a plasmodium, which forages by sending out dozens of tendrils from a central mass. The branches of this living network grow and shrink, emerge and vanish, according to what they encounter.

Without a brain, Physarum makes decisions by committee. The plasmodium is a single sac but it behaves like a colony. Every part rhythmically expands and contracts, pushing around the fluid inside. If one part of […]