Los humans we are the only species known to use the language, that combination of sounds that form words and that, in turn, complete structured sentences with a complex meaning. Despite being an everyday skill, its origins still raise many questions. To trace its beginnings, researchers often use a comparative approach, pitting the vocal production of other animals, particularly primateswith that of humans.
There is usually the perception that evolution has tended towards the sophistication of the organs, making them increasingly complex. However, a new study published in ‘Science’ suggests that, in the case of language, it was simplicity that made the difference: the loss of vocal membranes, air sacs and the simplification of the larynx allowed us to create an entire range of sounds that today form our speech.
Human vocal production is based on the same acoustic and physiological principles as vocal production in other terrestrial vertebrates: air from the lungs drives the oscillation of the vocal cords in the larynx. However, human speech has several distinctive features: the fluctuations of our vocal cords are much more stable, and the abrupt frequency transitions commonly seen in most other mammals are much smoother. This feature, combined with improved neural control, made it possible to develop a wide range of sounds that enable speech and spoken language.
So far, identifying the evolutionary adaptations that gave rise to human speech has been a challenge. This new research, led by Takeshi Nishimura -a researcher at the Center for the Evolutionary Origins of Human Behavior at Kyoto University- used magnetic resonance imaging and computed tomography to examine the larynxes of 29 genera and 44 species of primates: all possessed a vocal membrane that is totally absent in the humans.
With these data, Nishimura and his team developed anatomical and phonal models to compare the acoustic effects of the vibration of this membrane and, sure enough, its lack resulted in a more stable vocal source, like ours. That is to say, the simplification of the organs allowed us to be able to speak. Complexity is not always synonymous with evolution.