One of the advantages of working on a PhD is that you get to do a lot of reading and re-reading. I find the re-reading more interesting than the initial reading as I get to read the article or book in a different way, with a different level of depth and understanding.
This happened recently when re-reading a chapter in Peretz and Zatorre's (2003) The Cognitive Neuroscience of Music that considered arguments for and against the idea that music is an evolutionary adaptation. The author David Huron's primary conclusion was that the evidence—though not strong—suggests there could be an evolutionary adaptation for music, primarily because music fits the essential criteria (i.e. it is old, it is ubiquitious, etc.).
The challenge, though, is to try and determine why. What is it about music that makes it adaptive? Huron summarizes some of the major evolutionary theories that have emerged:
As an aside, what's interesting about reading through these theories knowing what I do about music and brain and behavior function is that overlaps do exist, even in modern society. Remember mix tapes? Back when I was a kid, giving someone a mix tape was an expression of love ("courtship behavior"). And when you're a pre-teen and teenager, who is your celebrity crush? More often than not, it's a rock star or pop singer (New Kids on the Block for me. Joey was soooo cute. I even had the sleeping bag...).
Those examples were just for the first theoretical possibility listed above. There are more overlaps. You walk into almost any preschool and you will find music. Music may help with transitions between activities, it may help with learning (the alphabet song, anyone?), it may be used to develop fine motor skills ("Itsy Bitsy Spider" is the classic example). And what about those family vacations that required a long car ride (think pre-iPods, video games, and DVD players)? One common method to pass the time, hopefully without driving everyone nuts, was to sing (I have a cousin who learned all the words to the theme of the TV show Beverly Hillbillies when he was 3 years old thanks to a daily 2-hour commute with my aunt).
So there is overlap between these speculative theories and modern human behavior. But there's still not enough evidence to pinpoint which theory might explain why music evolved. What is Huron's favorite theory? He settles on a social bonding-based theory.
According to Huron, this theory has emerged from an evolutionary theory of language development advocated by Robin Dunbar, a "grooming and gossip" hypothesis which acknowledges that there is safety in numbers and that grooming helps to form alliances that support protective group living. However, the problem with grooming is that only two people can be engaged in the activity at a time, the "groomer" and the "groomee." If a species develops language, though, you can engage in "vocal grooming" with more than one person at a time. It supports close interpersonal interactions, thus supporting the development of these alliances and social bonds with other members of the group.
How does music fit in? Huron claims that music has some advantages over language. One, singing is louder than speaking, thus you can reach more people by singing. Two, music can engage an entire group of people, either through focusing their attention, through coordinating a group motor activity (e.g. dancing), or through synchronizing the mood of a group. Three, there is evidence of some hormone-based music and social bonding connections. Listening to music can lower testosterone, resulting in less aggression and, subsequently, more group cohesion. There is also evidence that music can cause oxytocin release, which is also implicated in both infant-caregiver and peer-group bonding.
Of course all of this is specualtive at this point. In fact, there are some who argue that music may have evolved before language.
But part of understanding and improving human behavior is knowing where we have come from, which is why this line on inquiry, no matter how complex, is important and compelling.
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Huron, D. (2003). Is music an evolutionary adaptation? In I. Peretz and R. Zatorre's The Cognitive Neuroscience of Music (pg. 57-75). Oxford: Oxford University Press.