According to this article by The Economist, human neurons are distant relatives of tiny yeast cells, themselves descendants of even simpler microbes. Yet they are organised in structures that are capable of astonishing feats of creativity. How did the world get from bacteria to Bach, from fungus to fugues?
The story is one of Darwinian natural selection: of complexity emerging gradually as beneficial mutations are preserved and harmful ones weeded out.
Initially, memes spread in human populations like viruses, selected simply for their infectiousness. Some were useful, however, and the human brain adapted to foster them: genetic and memetic evolution working together. Words and other memes gave humans powerful new competences–for communication, explicit representation, reflection, self-interrogation and self-monitoring.