Our ancestors speak out after 3 million years

Listen to simulations of our ancestors' first sounds

YOU may think humanity's first words are lost in the noise of ancient history, but an unlikely experiment using plastic tubes and puffs of air is helping to recreate the first sounds uttered by our distant ancestors.

Many animals communicate with sounds, but it is the variety of our language that sets us apart. Over millions of years, changes to our vocal organs have allowed us to produce a rich mix of sounds. One such change was the loss of the air sac - a balloon-like organ that helps primates to produce booming noises.

All primates have an air sac except humans, in whom it has shrunk to a vestigial organ. Palaeontologists can date when our ancestors lost the organ, as the tissue attaches to a skeletal feature called the hyoid bulla, which is absent in humans. "Lucy's baby", an Australopithecus afarensis girl who lived 3.3 million years ago, had a hyoid bulla; but by the time Homo heidelbergensis arrived on the scene 600,000 years ago, air sacs were a thing of the past.

To find out how this changed the sounds produced, Bart de Boer of the University of Amsterdam in the Netherlands created artificial vocal tracts from shaped plastic tubes. Air forced down them produced different vowel sounds, and half of the models had an extra chamber to mimic an air sac.

De Boer played the sounds to 22 people and asked them to identify the vowel. If they got it right, they were asked to try again, only this time noise was added to make it harder to identify the sound. If they got it wrong, noise was reduced.

He found that those listening to tubes without air sacs could tolerate much more noise before the vowels became unintelligible.

The air sacs acted like bass drums, resonating at low frequencies, and causing vowel sounds to merge; Lucy's baby would have had a greatly reduced vocabulary. Even simple words - such as "tin" and "ten" - would have sounded the same to her.

Observations of soldiers from the first world war corroborate de Boer's findings. Poison gas enlarged the vestigial air sacs of some soldiers, who are said to have had speech problems that made them hard to comprehend.

De Boer's study provides clear evidence supporting the idea that the need to produce complex sounds to communicate better made air sacs shrink, says Ann MacLarnon of the University of Roehampton in London. More sounds meant more information could be shared, giving those who lacked air sacs a better chance of survival in a dangerous world.

De Boer found that air sacs also interfered with the workings of the vocal cords, making consonants trickier. Only once they had gone could words like "perpetual", requiring rapid changes in sound, be produced.

What, then, might our ancestors' first words have been? With air sacs, vowels tend to sound like the "u" in "ugg". But studies suggest it is easier to produce a consonant plus a vowel, and "d" is easier to form with "u". "Drawing it all together, I think it is likely cavemen and cavewomen said 'duh' before they said 'ugg'," says de Boer.

Listen to simulations of the vowel sounds with and without air sacs:

a without an air sac.

a with an air sac.

? without an air sac.

? with an air sac

y without an air sac

y with an air sac.

Journal reference: Journal of Human Evolution, DOI: 10.1016/j.jhevol.2011.07.007

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