New Scientist hat einen langen, sehr ausführlichen Artikel über die Evolution des Gehirns, von der Bildung des ersten Neurons bis zum Menschenhirn (und darüber hinaus spekulieren sie am Ende, ob Krähen, wären die Dinos nicht ausgestorben, heute so intelligent wie Menschen wären). Sehr spannend!
The story of the brain begins in the ancient oceans, long before the first animals appeared. The single-celled organisms that swam or crawled in them may not have had brains, but they did have sophisticated ways of sensing and responding to their environment. "These mechanisms are maintained right through to the evolution of mammals," says Seth Grant at the Wellcome Trust Sanger Institute in Cambridge, UK. "That's a very deep ancestry."
The evolution of multicellular animals depended on cells being able to sense and respond to other cells - to work together. […] So almost from the start, the cells within early animals had the potential to communicate with each other using electrical pulses and chemical signals. From there, it was not a big leap for some cells to become specialised for carrying messages.
These nerve cells evolved long, wire-like extensions - axons - for carrying electrical signals over long distances. They still pass signals on to other cells by releasing chemicals such as glutamate, but they do so where they meet them, at synapses. That means the chemicals only have to diffuse across a tiny gap, greatly speeding things up. And so, very early on, the nervous system was born.