The source of our concept of self, the seat of the soul if you're that way inclined, is one of the great mysteries. What is it about humanity which allows us to feel that we are conscious, to have a sense of ourselves? In 2000 Edge.org posted an essay by V S Ramachandran entitled "Mirror Neurons and imitation learning as the driving force behind the "Great Leap Forward."" He was referring to the great leap that humankind has made, far outstripping the rate of progress of any other observed species. The essay was about the so-called "mirror neurons." In experiments on apes, it was found that specific groups of neurons fired whenever the apes performed voluntary tasks such as button pushing or reaching out for food. This is not particularly interesting in and of itself; the interesting part is that a small subset of these neurons fired when the apes merely watched other apes performing the task. Ramuchandran speculated that the presence of these mirror neurons in humans permitted us to learn by imitation, sparking the great leap which allowed the sharing of knowledge about how to replicate useful events which would otherwise have occurred only once.
Now, nearly 7 years later Ramuchandran has extended the theory in the new issue of Edge. He speculates that it is these very neurons that allow us self awareness by allowing us to imagine ourselves performing an action as if we were someone else. That is a gross oversimplification, so if you have any interest at all I would suggest that you read the full text of his surprisingly concise essay.