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Q: Why does music have a hotline to our emotions? What is the evolutionary advantage of this?
Philip Le Riche, via email

David Robson, BBC Future feature writer, answers:

Who hasn't ever felt a song pulling at their heartstrings? Whether it is the feeling of euphoria in a club, or a lonely cry to a heartbreaking ballad, music can cut us to the core, expressing emotions more eloquently than words ever can.

But as our reader, Philip, points out, the reasons for this are far from obvious. "It's clear to me the appeal of rhythm, and I get all the stuff about anticipation, surprise and fulfilment of expectations. These all help to explain why music is interesting - but why it moves us at such a deep level remains a mystery to me," he explained in an email to the BBC Future team.
Is music just "auditory cheesecake", or does it have a deeper meaning?
Posing this question puts Philip in good company. Even the father of evolutionary theory, Charles Darwin, was stumped by our musical faculty, calling it one of "the most mysterious with which [humankind] is endowed". Some thinkers, such as the cognitive scientist Steven Pinker, have even questioned whether it has any particular value at all. In his view, we like music because it tickles some of the more important faculties, like pattern recognition. By itself, he says, it has no value - it is mere "auditory cheesecake".

Yet if that were true, human beings across the world would be spending an awful lot of time on an activity that has absolutely no inherent value. If you think you're obsessed with music, consider the BaBinga people from Central Africa, who have elaborate dances for almost every activity, from gathering honey to hunting for elephants. The anthropologist Gilbert Rouget, who lived with them in 1946, found that sleeping through the ceremonies was considered one of the greatest crimes. "It cannot be more clearly stated that singing and eating are equally necessary to stay alive," he wrote. For this reason, many people (including myself) struggle to believe that music was simply a small, incidental soundtrack to the human story of evolution.

Fortunately, there are alternative theories. One popular idea was that music arose from "sexual selection": like the peacock's tale, it's a sexy display that makes you stand out from your rivals. The evidence is thin, however: a study of 10,000 twins failed to show that musicians were particularly lucky in bed (though Mick Jagger and Harry Styles may disagree).

Others have proposed that music emerged as an early form of communication. Certain motifs in music may, in fact, carry some of the signatures of the emotional calls made by our ancestors; upwardly rising, staccato sounds tend to put us on edge, while long descending tones seems to have a calming effect, to give just two examples. Such patterns of sound seem to carry a universal meaning shared by adults of different cultures, young children, and even other animals. So perhaps music built on associations from ancient animal calls, helping us to express our feelings before we had words. As a form of "protolanguage", it could have even paved the way for speech.
When you move in synchrony with another person, your brain starts to blur its sense of self
What's more, music may have helped gel human societies as we began to live in bigger and bigger groups. Dancing and singing together, seems to make groups of people more altruistic, and to have a stronger collective identity. According to cutting-edge neuroscience, when you move in synchrony with another person, your brain starts to blur its sense of self. It is almost as if you are looking in the mirror: you think they look more like you, and that they share your opinions. And as you'll have found with your own toe tapping, music is the best way to get people moving together.

Although it may heighten the impact, active participation in music is not absolutely necessary for these benefits: as we recently explained at BBC Future, simply listening to a song that produces pleasant musical frisson (also known as "skin orgasms") can also increase altruism. That's comforting for people like me, whose musical life revolves around their sofa and iPod.

With increased solidarity and less in-fighting, a group may then be better equipped to survive and thrive. This is perhaps most extensively illustrated by the BaBinga's "musicking". As Rouget, the anthropologist, wrote: "The engagement seems to be paired with a certain self-effacement, as each individual becomes one with the body of singers". But music's role as a social glue can also be seen in work songs sung by slaves, sea shanties among sailors, and soldiers' chants. Music, it seems, really does bond us closely.

Lying at the heart of our relationships in this way, it makes sense that music would tug at the heartstrings, helping us to create an emotional connection. Each culture may then build on this rudimentary instinct, creating their own musical lexicon of certain chords or motifs that come to be associated with particular feelings.

Whatever its early origins, today we can't help but associate certain music with the most important events in our lives. It is the soundtrack of conception, pregnancy, births and funerals, and everything in between. No wonder we all imbibe such a heady cocktail of feelings and memories whenever we hear our favourite tunes.