Changing Calls

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If humans hadn’t lost a small tissue in their voice box millions of years ago, humanity would have lacked the ability to produce an Elvis Presley, a Whitney Houston or a Rob Halford, according to a new study on non-human primates and the evolution of human speech.

Researchers recently studied the voice box – scientifically known as the larynx – of 43 species of apes and monkeys, reported New Scientist. For their study, they used magnetic resonance imaging (MRI) or computed tomography (CT) scans on dead or anesthetized animals in the first such large-scale study of primates.

They discovered that all the primates had a “vocal membrane,” a tiny extension of the throat’s vocal cords that gives them coarse, irregular and louder sounds.

The team said that when some of the anesthetized creatures would let out calls – while waking up or stimulated to do so – the primary source of their sounds would derive from vibration and collision of the vocal membranes, as their vocal cords were in motion less often.

Unlike their distant relatives, however, humans don’t possess these vocal extensions. Instead, our vocal cords – which are flaps of tissue in the throat – vibrate as air is expelled from the lungs, allowing us to make “voiced” sounds, as opposed to breathy ones.

The researchers suggested that humans lost these membranes and also experienced changes in the brain that allowed them to develop speech. If they still existed, humans would sound like an individual with laryngitis.

Still, some scientists pointed out that many apes and monkeys can produce quieter and more controlled noises, noting that the “alleged limiting effect (of vocal membranes) … seems exaggerated.”