When ancient Roman seers conducted their magical rituals, they would face north. East--to the right--represented luck and positive omens. The west--to the left--was the dark realm of the dead. The Bible tells of the good sheep who, on Judgment Day, will find comfort at the Savior's right hand, while the sinners at his left will be condemned to eternal damnation.
The division between right and left, between good and evil, persists in today's idiomatic expressions: a left-handed compliment is really no compliment at all; someone with two left feet is clumsy on the dance floor. Yet someone's right-hand man is always there for him. We vilify the left, thanks to centuries of derision by the right-handed majority. Across cultures, righties outnumber lefties nine to one. What causes such a glaring disproportion? The answer lies between the hemispheres of the brain.