erhaps animals other than humans also communicate with sounds, but we are unique in our profligate employment of the trick. A murder of courteous crows will caw to warn each other of an approaching fox. We add to the warning caw the soothing coo, the admonishing cluck, the terrible tsk, the haughty hmph, the snobby shish, the ha! and the oh! and the eewwww. We chatter, chide, plead, pontificate, whine, whisper, and do so much more than merely warn.
A songbird outside the window at my back, a common myna, protests. She must have read over my shoulder the boast I made in the previous paragraph and taken umbrage. I have no words to describe the impressive range of sounds she just made, and that, I think, was her point.
Fine then. It is not the sounds we make that make us unique, but the assembly of these sounds into syntax. Take that, Ms. Birdy!
On the subject of songbirds, the evolution of the syrinx (the bird vocal organ, comparable to the mammalian larynx) into a music box was driven, it seems sure, by sexual selection. Birds sing to attract mates, and the better singers succeed. A similar process probably accounts for our vocal cords. Our ancestors sang love songs to each other before they spoke!
Darwin said as much:
[W]e may assume that musical tones and rhythm were used by our half-human ancestors, during the season of courtship, when animals of all kinds are excited not only by love, but by the strong passions of jealousy, rivalry, and triumph. …We must suppose that the rhythms and cadences of oratory are derived from previously developed musical powers.
He imagined that “before acquiring the power of expressing their mutual love in articulate language,” our ancestors “endeavoured to charm each other with musical notes and rhythm.”
We are not the only apes that sing. Our cousins the tree dwelling gibbons are renowned for their singing. Because gibbons are territorial and may only glimpse gibbons outside their families on rare occasions, they must come to know each other by their songs. Young gibbons in search of love serenade potential mates across the leafy expanses of their jungle habitat. These passionate troubadours fall in love with each other’s voices before convening physically to consummate their love. But the story of gibbon singing gets more interesting still. The crooners and divas then enter lifelong, monogamous, co-dominant relationships. And how are bonds between mates strengthened over the course of their lives together?
By singing duets. Each morning in rainforests throughout southeast Asia, gibbon couples transform their jungles into colossal concert halls.
The singing is often started by the female when she calls out a few short notes to begin the song. But she is then silent while the male sings. When she is ready to join in, she signals her readiness to go into her series of great calls by first giving a call of short, monotonous, repeated notes. Then she opens her mouth to the fullest and sings out the great calls. The male stops singing entirely[.] The female is in full song. Her calls swell in volume and finally reach a climax in pitch, in intensity, and in rapidity that goes on for twenty seconds or so. They are repeated every two minutes. Gradually she finishes her song and the male calls again to finish off the duet.
The point of these duets is partly to declare their territory to other gibbons, but is also related to pair bonding. A study of siamang gibbons in zoos revealed that “duetting activity was positively correlated with grooming activity and behavioral synchronization, and negatively correlated with interindividual distance between mates.” Gibbons whose duets are better coordinated have closer relationships, hinting as to the purpose of their songs.
(If you’ve never seen the Mad TV skit “You Are the Love of My Life,” please find it on YouTube. The skit is about an emotional pop ballad with a very simple and repetitive message. I think gibbon duets must have much the same message.)
In addition to their songs, Gibbons make a range of other sounds:
A gentle hoo-hoo is given if the gibbon is in dense vegetation, just to keep in touch with other family members. It hoos with much more violence and loudness if it is upset. Then there is a glug-hoo at the first sight of food, such as ripe figs or other fruits. This is a throatier and higher call than the usual hoo and seems to indicate much pleasure. A low, sad little hoo sigh or bleating sound is the one a young animal gives if it is in trouble or separated too far from its parents. Grunts and squeals are given by young animals when playing. A squeak with a facial grimace is an apologetic gesture a young juvenile will give if it feels its parents are annoyed with it. A prolonged loud hoo-hooing is given when one animal is about to move aggressively toward another. This happens when one adult meets another on the territorial border, for instance. A prolonged screech is given when one male is about to chase and try to catch and bite an intruder. The great call of the female is the most overwhelming and loudest of all the calls, and when she gives it all the other gibbons fall silent listening to her performance.
When gibbons feel certain emotions they use their voices to make certain noises. Other gibbons attach meanings to those noises, and in this way gibbons are able to talk to each other. A gentle hoo-hoo means I’m over here. A glug-hoo means I’ve found good food. A bleating sound means I’m scared, please help me. Self-expression becomes communication.
What do I mean by self-expression? I mean the instinctual urge to put a voice to one’s feelings, to advertise one’s current state of being. Communication is a side effect, and it is probably because of the accident of communication (which offers obvious advantages to those animals that learn the trick) that the urge to vocalize feelings is naturally selected. But the need a gibbon feels to hoo does not depend upon other gibbons being nearby, and so a desire to communicate is not actually what drives gibbon vocalizations. Gibbons seem to experience an instinctual need to express their emotions out loud.
Perhaps we humans are similar to gibbons, and for that matter to songbirds, in this way.
But what about syntax! Doesn’t that separate us from other animals?
Yes, praise be to our vaulted syntax. But rather than patting ourselves on the back for the complexity of our vocal patterning, and priding ourselves on how we, once again, are the only animal in the world that does such-and-such, we might benefit from opening our ears to the conversations of crows, the duets of gibbons, and the musical dramas unfolding between common mynas. What we do is fundamentally similar to what they do. Like them, we put our passions – our love, longing, anger, fear, and ecstasy – to music. This is the essence of speech. Syntax is a thin layer over a musicality that is ingrained deeply within us. We are singers, and talking is evolved serenading.
-  You’ve likely heard of a pride of lions. But have you heard of a cry of hounds, a parliament of owls, a shiver of shark, a knot of frogs, or a hurtle of sheep? Poetic names for groups of animals date back to the 15th century (many listed in a book published in 1486 called The Book of Saint Albans). A “murder” is a poetic name for a flock of crows.
-  Soon after I wrote this, I discovered it wasn’t true. According to a paper published in June 2011, researchers at Kyoto University discovered that the Bengalese finch possesses the ability to discriminate syntactic rules, indicating that “passerine songbirds spontaneously acquire the ability to process hierarchical structures, an ability that was previously supposed to be specific to humans.” See http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.2869.html ↩
-  The Descent of Man by Charles Darwin, See http://www.darwin-literature.com/The_Descent_Of_Man/21.html ↩
-  Gibbons by Patricia Hunt, p49. ↩
-  Gibbon Song and Human Music from an Evolutionary Perspective by Thomas Geissmann, See http://www.gibbons.de/main/papers/pdf_files/2000musicevol.pdf ↩
-  Gibbons by Patricia Hunt, p46-48. ↩