Most humans have a clearly dominant hand (usually the right one). What is the lowest form of life that shows such a preference or dominance? Why are most people right-handed?

Birds, which have neuronal populations in the left hemisphere that regulate their song production, are the lowest phylum with a convincing laterality or dominance. The reason for dominance—-its evolutionary or survival advantage—-is unknown.

There are many theories to account for the existence of dominance, but none of them really makes much sense.