Teleology & evolution: Vocal cord development (Introduction)

by David Turell , Friday, June 17, 2016, 01:19 (3082 days ago) @ dhw

These organs are amazing instruments with a huge range of sound, and it appears we are not using all of it!-http://phys.org/news/2016-06-pitch-range-vocal-cords.html-"It's absolutely amazing how nature has created a compound, laminated string to cover a pitch range that is difficult, by any stretch of the imagination, to cover with one string," Titze says.-***-"At birth, vocal cords are composed of a uniform, gel-like material. As the vocal cords mature, fibers develop within the gel, eventually forming a multilayered, laminated string. Imagine a set of guitar strings glued close together with gelatin.-"Fibers throughout the vocal cord layers are linked together, however, so that while some layers may be under different amounts of tension than others, the layers do not vibrate independently of each other. Returning to our guitar-strings-in-gelatin analogy, when one string is plucked, the entire gel-fiber set shakes along with it. The muscles in the larynx further modulate the sound the cords produce, lengthening and shortening the cords to change the pitch.-***-"Titze's investigations into vocal cord structure also reveal something more primitive. Titze says that vocalization evolved to help primates communicate over long distances by using high and loud calls. Modern human speech communication, however, does not make much use of the wide pitch and loudness range of the mammalian larynx.-"That capacity is still inherent in our vocal cords, he says, but so much of our communication is electronically modulated and amplified, with even professional singers aided by microphones, that our vocal cords are rarely put to their full use.-"'If you never stretch your vocal cords and never do high pitches or loud voice, eventually the ligament will atrophy into a simpler structure and you won't have that range available to you," Titze says.-***-"Despite the complexities of the vocal cord structure, Titze says he was surprised at how well the model of a simple vibrating string explained the cord's range. "Most people would laugh at using a simple vibrating string model for something as complicated as a 3-D, nonhomogeneous tissue structure," he says. "But the string model does an incredibly good job of explaining this range of frequencies.'" -Comment: We have been given an amazing organ in the vocal cords, more capacity than we need. A good question is why they have all of this capacity when not required by evolution? Perhaps given as an extra complex design?