How Brainless Slime Molds Redefine Intelligence @ Scientific American.

Inside laboratories slime molds have effectively re-created Tokyo’s railway network in miniature as well as the highways of Canada, the U.K. and Spain. When researchers placed oat flakes or other bits of food in the same positions as big cities and urban areas, slime molds first engulfed the entirety of the edible maps. Within a matter of days, however, the protists thinned themselves away, leaving behind interconnected branches of slime that linked the pieces of food in almost exactly the same way that man-made roads and rail lines connect major hubs in Tokyo, Europe and Canada.

In other words, the single-celled brainless amoebae did not grow living branches between pieces of food in a random manner; rather, they behaved like a team of human engineers, growing the most efficient networks possible.