Legend has it that the Etruscans began the wishbone tradition. They believed chickens had fortune telling powers, so in the event that a chicken was killed and consumed for a meal, the sacred collarbone was saved and left to dry in the sun. Tribe members were allowed to make a wish while stroking the drying bone.
The Romans took many of the Etruscan customs as their own and since everyone wanted good fortune, they fought over the bones, breaking them. The tradition eventually was passed on to Europe and America.
It is said that the phrases "I need a lucky break" or "I never get a break" come from being the loser in this tug of chicken bone contest.