Are Cities Like Human Brains?

Scientific American highlights a recent study which finds real similiarities (via Mark Thoma):

There’s the obvious analogy: neurons are like highways. Neurons are channels that carry information in the form of electric signals from one location within the brain to another, while highways are channels that transport people and materials from one location within a city to another. Cognitive scientists Mark Changizi (web,  twitter) and Marc Destefano (web,  twitter) think that the analogy goes deeper, though: “from the perspective of the city as a whole, the materials and people that highways transport are crucial to the large-scale function carried out by the city, and are, in a sense, signals – that one signal is electric and the other physical may not matter in regards to the fundamental properties governing them.” And that’s not all. They argue that the organization of city highway networks is driven over time by political and economic forces, rather than explicitly planned based on principles of highway engineering – which means that city highway systems may be subject to a form of selection pressure similar to the selection pressure exerted on biological systems. Cities themselves are also under selection pressure to connect with other cities via highways and roads – an inaccessible city can’t survive. Cities are also an appropriate model for comparison with the brain, as they lie on land: a sheet-like structure, just like the cortex.
“Nearly half of Earth’s 6.6 billion people now live in cities,” they write, “and cities are becoming ever larger and densely populated. The proper functioning of a city requires that people and materials be quickly moved throughout it.” City populations tend to increase over time, and at a faster rate than city surface area, meaning that an efficient highway system must continually evolve from pre-existing systems. Cities are starting to sound more and more like brains. Is it possible that city highway systems and the mammalian cortex follow similar scaling laws? If so, it could be that the organization of the brain is just one instance of a more general type of structure found in nature. Changizi and Destefano collected data from 60 cities in the United States, across a wide range of geographic locations and population sizes.

The story goes on to comparing ratios of brain structures to total brain surface area and ratios of city infrastructure to city surface area.  They are amazingly similar.  Overall, it is pretty interesting.