The Unique Gift of Human Speech

We're so enamored with products like Siri and Alexa because they can speak to us and the more human the better. Yeah, the google AI assistant caused quite a stir when it made a restaurant reservation that sounded just like a person because it injected 'ums' when it spoke. We remain the only species on earth that can speak and process words. A fascinating article in the magazine 'Scientist' explores this most human of all characteristics.

Evolution allowed for changes in our vocal tract and in our brains that made speech possible. Our lungs provide something called acoustic energy in dispelling air. Then the manipulation of that air to produce defined sounds is possible with help from the diaphragm and the intercostal and abdominal muscles. Air is then released through the larynx, the structure that contains the vocal cords and the supralaryngeal vocal tract or SVT.

The SVT includes the oral cavity and the pharynx which is at the top of your throat. Interestingly, the anatomy of the human SVT evolves as a child develops. After birth, the tongue is flat and resides in mostly the mouth. Eventually the tongue grows into the throat and the oral cavity shortens to allow us a greater range of sounds.

Meanwhile, development of neural networks in the brain allow us to produce, process and understand sounds. A protein called FOXP-two has been shown to be instrumental in allowing speech. Only human and direct human predecessors, Neanderthals and Denisovans have a form of this protein. Amazing that one small change in anatomy gave us this tremendous ability.