What did man’s earliest ancestors sound like?
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.
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.
I bolded that last paragraph for emphasis. The whole article is very cool, but I found that paragraph particularly fascinating. Click through to hear the recordings used in the study.