We love our iPods and stereos, but what evolutionary purpose does all of this music serve? The Shakespearean idea that "music be the food of love" is popular among experts, who say music aids courtship and therefore human survival. Another theory says music replaced another social activity: grooming. When tribes grew too big for everyone to groom everyone else, humans started singing to keep the group together.
A Harvard language theorist dismisses these, and calls music an accident. Like "cheesecake," he says, music arose to sate an appetite nature couldn't. Now we're hooked, and can't stop listening—or eating. "What all of these hypotheses have in common is the ability of music to manipulate the emotions, and this is the most mysterious part of all," the Economist reports.