The short answer to this question is that no-one really knows. It’s an enormous question, with a huge amount of active research being pursued in its name.
The long answer, however, is much more rewarding, and stumbles fittfully from ‘why’ to ‘how’ and back again. If you’ve been to any kind of concert (except maybe classical, or experimental jazz) you’ll have realised that humans, probably including yourself, are exceptionally good at recognizing rhythmic sounds and clapping along. If only for a few bars. We are, in fact, so adapted to this process that if there is a “syncope” (a missed beat) in the music, people will still tap or clap along: Your brain will expect that missing beat, and act accordingly.
Your brain works by means of chemical and electrical signals and we can record the mass result of those electrical signals by placing several electrodes on top of your head. This is a relatively easy, cheap and common technique called electroencephalography (EEG), the recording of electrical activity along the scalp, and with it we can tell something about the functioning of the brain. If there is a syncope, or a beat missing, you can record a negative peak in the electrical signals, indicating that the brain was expecting that beat. Interestingly, this feature of our brain is even found in two-day old babies. So right from the beginning humans have a sense of rhythm. Songbirds also have a sense of rhythm, so it is not unique to humans. But monkeys do not appear to have it!
So why, and how, do we (humans, birds) appreciate music? There are several theories about this. Evolutionary psychologists, such as Steven Pinker, think it is a by-product of functions in our brain which were evolutionary meant for language processing. In this case it would be a sort of recent enhancement of our language centres in the brain. However, new research (since 2003) has shown that the structures that handle language in the brain are not necessarily the same as those that handle music.
Your brain is separated into two hemispheres, left and right, which offers some distinct evolutionary advantages, including parallel processing of tasks. In addition, for large swathes of the human population, some tasks are largely carried out in one hemisphere to the exclusion of the other. For 95% of right handed people, language tasks are mostly carried out by the left hemisphere of the brain. But, and this is a big ‘but’ considering the question at hand, although speech perception is an overwhelmingly left-brain activity, pitch and tonal perception are right-brain activities. And for good reason: Dealing with fast, rapidly changing information, as when making out a series of words with swift vowel and consonant shifts, or a drum beat with the potential for syncopy, seems to be the preserve of the left hemisphere. Tracking complex changes in frequency and categorising it appropriately (‘spectral’ information), as when following the chord progression of a piece of music, is the domain of the right.
In some individuals one or both of these networks of activity have been disrupted, whether through trauma or since birth. When those individuals are gracious and brave enough to become the subject of scientific study, we discover that some lesions impair musical ability while preserving recognition of speech, voice, and environmental sound, while others preserve musical ability while impairing recognition for speech and non-musical bangs, whistles and clatters. In some cases (of right brain damage) melodic components of music are spared while rhythmic patterns are destroyed, and in others (of left brain damage) the opposite is true.
Except (as above) in the cases of some kinds of classical and jazz, music is a combination of both rhythm and melody. It would seem that there are distinct neural networks for processing of intervals, and contour, and scale structure. Musical pitch, melody, harmony, rhythm, tempo, meter, and duration are all accomplished by distinct neural circuits that are distributed throughout both left and right hemispheres of the brain. What is important here though, is that some of those circuits are thoroughly indepent from our ability to communicate verbally. Rest assured, it is entirely possible to be born without an ounce of musical talent, but to have no particular problem with any kind of language. And what’s more, where they are present, the musical predisposition of infants suggests that basic levels of musical understanding are either innate, or acquired very early on.
So, if understanding music is at least partly distinct from our urge to communicate, why do we have those circuits at all?
The dominant theories are relatively simple: Sex, and community. Darwin, in his racey volume “The Descent of Man and Selection in Relation to Sex”, suggests that music in humans might fulfil the same function as it does in birds. For several species, female birds are increasingly turned on as the complexity of their suitors’ ballads unfolds. With each successive generation males engage in a musical/sexual arms race to outperform each other, with very real neurological consequences, in order to converge, inevitably, on the avian equivalent of Bryan Adams, or Tom Jones.
Geoffrey Miller, an evolutionary biologist, found that with or without hand-claps, the musical output of jazz musicians changes as they get older. Post-puberty sexual dynamos of the jazz world have the most rapidly increasing output, peaking, so to speak, in young adulthood. Jazz-mothers and Jazz-fathers meanwhile, occupied with the demands of rearing their Jazz-children, whether through a lack of imperative or just time, or sleep, or all three, are less productive. And the same appears to have been true for 19th century classical composers. No doubt, there are many musicians who are in it largely for the first term of the holy trifecta, which only ends in rock n’roll. As with so many things, the greats did it first.
Lastly, there is a less sexy, but more controversial theory. Animals, particularly birds, have been known to engage in the grooming of prospective partners and play-mates far beyond the call of duty. The obvious explanation is that it’s enjoyable for both individuals, and that it’s a form of bonding that allows extended families to socialise more effectively. Dr. Robin Dunbar points out the seemingly obvious truth that you can’t groom everyone, all the time. As human tribes expanded past the point where we could spend quality time with each other en masse, a form of “remote grooming” would become necessary. Despite the creepy name, Dunbar’s theory is that between individual, one-on-one dates and the group size at which human language really came into play (around 140 individuals), music, dance, and other forms of performance bridged the gap, allowing us to become cohesive, socially well adapted and effective clans of humans. Which is to say, the kinds of groupings that would evolve language in the first place.
Did language or music come first? It’s currently impossible to say. Why do we enjoy music and rhythm? Because they’re as natural to us as talking to each other.
-V, O, & D
Want to read more? Check out Prof. Honing’s page on Musical Cognition:
And some podcasts from Prof Isabelle Peretz:
And the Heart Of The Beat: