Charles Darwin argued that music evolved as a way to attract lovers, and a study claims to support his idea. But how strong is the evidence, asks Phil Ball.

Humans have been making music for at least 40,000 years. The earliest known instruments are flutes made from hollow animal bones. What is less clear is why we make music.

One of the most enduring theories was put forward by Charles Darwin, who suggested that, as with bird song, it’s all about sex. “Musical notes and rhythm”, he wrote in The Descent of Man, “were first acquired by the male and female progenitors of mankind for the sake of charming the opposite sex.”

Now evidence appearing to support Darwin’s hypothesis has come in the form of a study by psychologist Benjamin Charlton of the University of Sussex in Brighton, England. In his experiment, he found that women’s sexual preferences for composers changed during their menstrual cycle, and that they preferred composers of more complex music – who might be construed as more capable mates – at the most fertile point of the cycle.

The study’s controversial claims have already proved irresistible to headline writers. But how credible is the notion that making music is all about sex?

Let’s start at the beginning: what’s so special about music? First, all known cultures have had music – even those that have lacked a written language. It is as close to a universal human trait as you could hope for.

Second, music – unlike, say, cooking, farming, talking, raising a family – doesn’t obviously have any benefit. Of course, we love it, it makes us joyful or transports us into tears, rapture and dance, but it bears no obvious, tangible evolutionary advantage.

There is no shortage of ideas for why it first emerged among our ancestors. Some think that music began as a way of fostering social cohesion, a ‘tribal’ role that still persists today. Others say it began in the sing-song of mother-to-infant communication, an exaggeration of tones called ‘motherese’ that people all over the world practice. There are also those who think that music and language were once merged into a composite form of communication dubbed ‘musilanguage’, from which music split as a vehicle of the emotions while language became all about semantic meaning.

Survival of the sexiest

Darwin’s notion of music as an agent of sexual selection remains a favourite, not least because it has his name attached. He regarded sexual selection as an adjunct of natural selection: it was ‘survival of the sexiest’, regardless of whether the sexual attributes had any other survival benefits. According to this view, skill at singing and making music functioned like the peacock’s tail: useless, even an impediment, but attention-catching.

It is conceivable that such sexual displays do offer honest clues about genetic fitness. The male peacock might be saying “I’m so ripped that I can survive even when encumbered with this absurd thing.” Likewise, a musician able to make complex and beautiful music might be displaying his or her (but usually his) superior cognition, dexterity and stamina. By this logic, falling for a skilled musician makes good evolutionary sense.

The link between sex and music might seem indisputable. Rock and pop stars are famously surrounded by gaggles of sexually available fans at the height of their fertility, and no one made the guitar more explicitly phallic than Jimi Hendrix. And it’s not just a modern or rock and pop-based phenomenon: performances by Franz Liszt, the Hungarian pianist, composer, and conductor, also had women swooning, and a study published in the year 2000 reported that, in classical concerts, there were significantly more women in the seats nearer the (predominantly male) orchestras than in the back rows.

There’s also anecdotal evidence to suggest that music performance quality declines after sex. For example, Miles Davis attested that musicians are often celibate before big concerts, to retain their edge. And in case you’re thinking that being a musician didn’t do much for the survival prospects of Hendrix, Jim Morrison or Kurt Cobain, bear in mind that – as Darwin himself pointed out – some male birds drop dead from exhaustion when singing in the breeding season. It’s worth the risk for the sake of becoming a sexual beacon (and after all, Hendrix did father three children).

A sexual-selection origin of music might also help to explain the apparent impulse towards diversity, creativity and novelty, for many male songbirds also develop large repertoires and variety in an effort to produce the most alluring mating signal. And doesn’t the excess of the peacock’s tail – the result of a well-attested runaway tendency in selection of sexual characteristics – seem to speak to the towering stacks of amplifiers and speakers, the pyrotechnics, the outrageous costumes? In short, mightn’t it explain the phenomenon that is Kiss?

But part of the problem with Darwin’s idea is it is just too alluring, inviting evidence by anecdote. Songs in pre-literate cultures are by no means the tribal equivalents of ‘Let’s Spend the Night Together’. Those of the Australian Aborigines, for example, express the singer’s feelings as a member of the community. Most Western music in the Middle Ages was practised by supposedly celibate monks. And in some African societies, musicians are regarded as lazy and unreliable, and so poor marriage material.

Hard scientific evidence for sexual selection in music is been scant and equivocal. If women do pick sexual partners on the basis of creative or artistic traits, one would expect changes in their preferences during peak fertility. A study in 2006 did find that apparently creative men were favoured at this time.

Cycle of attraction

So what does the latest study add? Charlton reasoned that the complexity of a male composer’s music might be considered an indicator of his creativity and capacity for learning complex behaviour, and so this too might affect female sexual choice. He has previously found that ovulation doesn’t seem to affect women’s preferences for complexity of music per se. But what about the composers themselves?

Charlton divided his group of 1,465 adult women survey participants into those at low and high risk of conception at the time of testing, based on what they reported about their reproductive cycle. He played them several short melodies, composed for the experiment, of varying degrees of complexity. First he asked some of the participants to rate the melodic complexity, to ensure that they could do this reliably.

Next he asked a different group which of the supposed (male) composers of a pair of melodies of different complexity they would prefer as a short- or long-term sexual partner. A significant number showed a greater preference for the composer of the more complex piece – but only in the high-conception-risk group, and only as a short-term partner.

Now, numbers are numbers: it seems that something connected to the reproductive cycle was indeed changing preferences in that situation. But what? The findings, Charlton says, “support the contention that women use (or ancestrally used) the ability of male composers to create complex music as criteria for male choice.” That would in turn suggest that musical complexity itself arose from an arms race in which male musicians increasingly strove to prove their prowess and woo a mate.

Yet while Charlton’s findings are intriguing, they are far from conclusive. For example, the most complex music, according to some measures, is Indonesian gamelan, which is among the most social, devotional and non-sexualized of all world music.

There is also little evidence to suggest that music has displayed a steady trend towards greater complexity. And it is very hard to untangle a listener’s preferences for a composer from their preferences for the actual music. The latter in general shows a peak of ‘preferred complexity’, beyond which preference declines. As the Beatles’ music got steadily more complex, for example, their sales declined.

And this is even before we get into the murky issue of how cultural overlays will colour the assumptions that women might make about fictitious composers, based on a tiny snippet of ‘their’ tunes. More work required, then – or in other words, if music be the food of love, play on.

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