A new genetic study shows that "musical ability is linked to gene variants that help control social bonding. The finding adds weight to the notion that music developed to cement human relationships. Musical aptitude evolved because musical people were better at forming attachments to others: "Think of lullabies, which increase social bonding and possibly the survival of the baby."
I dunno about lullabies, but I do know the guys who learned to play guitar in high school definitely had an advantage with, er, relationships.