Samir Patel of Archaeology Magazine writes a report on how the Romans might have designed their transportation network:
… Physarum polycephalum, consists of a single large membrane around many cell nuclei, and has drawn the attention of a wide range of scientists because of its uncanny ability to solve almost impossibly complex computational problems.
It’s a fascinating sentence: impossibly complex recalls a previous discussion of free will. If a problem not solvable through mathematics is solvable through some other means, what does this say about the strictly mechanistic view of the universe when mathematics cannot resolve problems directly resolved by the Universe? Does the slime mold prove free will? Well, as usual I’m probably a little too far out on a limb here, but I do find the idea of a slime mold solving difficult computational problems to be fascinating. It’s difficult to make a brain think in new ways, but perhaps the visual image of a slime mold solving problems may spark new ways of thinking about certain classes of problems.
Through rhythmic contractions of its membrane, called shuttle streaming, the slime mold grows out in search of food. If you put a P. polycephalum into a maze with two food sources in it, over a few days the organism will grow toward the food sources and retract from everywhere else except the shortest path between them. Mathematicians and network analysts call this the “shortest path problem.” When presented with additional food sources, the slime mold forms ever more complex and efficient networks. These “Physarum machines,” as they are known, may help in the understanding of communication, road, and transport networks, which also, over time, come to balance complexity and efficiency.
The new study applied the power of a Physarum machine (and a computer program that simulates its behavior) to landscape-scale archaeology, specifically Roman roads in the Balkans. Researchers placed a P. polycephalum in a petri dish containing 17 little bits of food representing 17 urban centers in the Balkans from the Roman imperial period. The slime mold “imitated rather spectacularly the two main military roads of the area, the Via Egnatia [across Macedonia] and the Via Diagonalis [from central Europe to Constantinople],” says archaeologist Vasilis Evangelidis of the Hellenic Ministry of Education. This was a test case, but future experiments with P. polycephalum might reveal previously unobserved patterns in complex networks of human settlement, trade, and migration.
I wonder if, and how, they simulated geographical features as well.
