There was a story on NPR's
Morning Edition a couple weeks ago concerning the underlying grid structure of the brain and how it could explain the evolution of the brain. That story might provide you with some references to research further:
Morning Edition: How Your Brain Is Like Manhattan
You can read the transcript/synopsis and listen the audio of the story. The story is based on an article in
Science and it mentions a five-year study by NIH, the
Human Connectome Project, an effort to map out the neural pathways of the human brain.
Two other
Morning Edition reports, from 20 May 2011 and 09 Aug 2010 respectively, are:
Mammals Smelled Their Way To Bigger Brains
From Primitive Parts, A Highly Evolved Human Brain
In line with that second story is Carl Sagan's book,
The Dragons of Eden (1986) in which he described the human brain as being a reptilian brain (the limbic system with basic drives, including "fight or flight" response) topped by a mammalian brain (the cortex with more expanded emotions and nuturing behaviors and greater ability to learn) topped by a human brain (the neo-cortex with rational thought), with each part still handling the tasks and functionality of those of our ancestors.
As I said, just a few leads to help you get started.