If I had access to a genetically identical infant, before its aware mind had formed, and I transplanted its brain into my own (suitably expanded) skull, could I grow a larger, coherent, brain? Would the younger neurons give me neuroplasticity? Would this increase my ability to learn? Would people who had undergone this procedure be more prone to schizophrenia -- which I think of as multiple minds trapped together in one brain and body?

If cities are more economically productive than separate villages, because they increase communication among people... well, how much higher-capacity a communication channel than brains literally wired together? You can do better than bike lanes, people.