What the heck is our lizard brain?

We all have a lizard brain.  It is part metaphor and part science.  Scientifically speaking, it is two almond-shaped amygdala located deep in our heads that form a sort of mini-brain.

This mini-brain seems to take over when we are afraid, mad, aroused, hungry or out to get someone.  It is very primitive.  It has served to keep us alive as a …