This should provide a sufficient amount of "whoa" for the day: mathematically speaking, how are elephants and big cities the same? A: both cities and elephants have developed a similar level of efficiency in the distribution of resources and transportation.
Geoffrey West of the Santa Fe Institute and his colleagues Jim Brown and Brian Enquist have argued that a 3/4-power law is exactly what you'd expect if natural selection has evolved a transport system for conveying energy and nutrients as efficiently and rapidly as possible to all points of a three-dimensional body, using a fractal network built from a series of branching tubes -- precisely the architecture seen in the circulatory system and the airways of the lung, and not too different from the roads and cables and pipes that keep a city alive.
(thx, john)