There is a "near-universal presence of modularity in biological networks as diverse as neural networks -- such as animal brains -- and vascular networks, gene regulatory networks, protein-protein interaction networks, metabolic networks and even human-constructed networks such as the Internet."
It turns out that by adding a cost to adding more links, simulations of evolution soon evolve modularity.
In my chapter Getting to the Hayekian Network, I suggest different purposes for different network architectures. The modularity argument contributes to this, suggesting that any time you have a complex network, you will find radical decentralization through the creation of modules.
Further, this suggests that the evolutionary psychologists are on to something in positing the brain to be constructed of modules. One still needs to address, though, the presence of "general intelligence" in humans. How those modules are connected and communicate matters.