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Oral Cavity’s Supposedly “Lousy” Design Is a Key to Human Speech

oral cavity

It’s a staple for Darwinists who compile lists of human anatomical features supposedly demonstrating “unintelligent” or “botched” design. We’re constantly told that the design of the human larynx, trachea, and oral cavity is poor because it allows for choking on food.

The point is made by the snarky Centre for Unintelligent Design, which lists “The ease with which we can choke” as an example of “unintelligent design,” and by Wikipedia. On the “Argument for poor design“ page they include this under “Fatal flaws” in human anatomy:

The existence of the pharynx, a passage used for both ingestion and respiration, with the consequent drastic increase in the risk of choking. 

In a conversation with Edge on “Unintelligent Design,” anthropologist Scott Atran complains, “Humans are more liable than other animals to choke, as they attempt to simultaneously coordinate eating, breathing and speaking.” RationalWiki adds, “Drinking and laughing at the same time — makes the drink come out of the person’s nose. Or potentially choke the victim of such a lousy design.” And so on.

The design does come with an increased chance of choking, but it’s also something that allows us to speak as we do. An interesting new article at The Scientist goes into some detail. From “Why Human Speech Is Special,” by Philip Lieberman:

In On the Origin of Species, Darwin noted “the strange fact that every particle of food and drink which we swallow has to pass over the orifice of the trachea, with some risk of falling into the lungs.” Because of this odd anatomy, which differs from that of all other mammals, choking on food remains the fourth leading cause of accidental death in the United States. This species-specific problem is a consequence of the mutations that crafted the human face, pharynx, and tongue so as to make it easier to speak and to correctly interpret the acoustic speech signals that we hear.

At birth, the human tongue is flat in the mouth, as is the case for other mammals. The larynx, which rests atop the trachea, is anchored to the root of the tongue. As infants suckle, they raise the larynx to form a sealed passage from the nose to the lungs, allowing them to breathe while liquid flows around the larynx. Most mammalian species retain this morphology throughout life, which explains why cats or dogs can lap up water while breathing. In humans, however, a developmental process that spans the first 8 to 10 years of life forms the adult version of the SVT [supra-laryngeal vocal tract]. First, the skull is reshaped, shortening the relative length of the oral cavity. The tongue begins to descend down into the pharynx, while the neck increases in length and becomes rounded in the back. Following these changes, half the tongue is positioned horizontally in the oral cavity (and thus called the SVTh), while the other half (SVTv) is positioned vertically in the pharynx. The two halves meet at an approximate right angle at the back of the throat. The tongue’s extrinsic muscles, anchored in various bones of the head, can move the tongue to create an abrupt 10-fold change in the SVT’s cross-sectional area….

As it turns out, the configuration of the adult human tongue’s oral and pharyngeal proportions and shape allow mature human vocal tracts to produce the vowels [i], [u], and [a] (as in the word ma). These quantal vowels produce frequency peaks analogous to saturated colors, are more distinct than other vowels, and are resistant to small errors in tongue placement. Thus, while not required for language, these vowel sounds buffer speech against misinterpretation. This may explain why all human languages use these vowels. [Emphasis added.]

So Darwin and his latter-day followers may complain about the design of the oral cavity but they’d have a harder time doing so (and being understood) if it weren’t for this instance of “poor design.” Note that “all human languages use these vowels,” an indication that this is no negligible feature for clear communication. And speech, of course, is arguably the keystone of humanity’s exceptional status in the world of life.

None of which, of course, is to make light of the peril of choking. But to put things in perspective, according to the National Safety Council, “5,051 people…died from choking in 2015,” which works out to 0.0018 percent of all deaths in the United States, and of those “2,848 were older than 74.” (See here and here.) There is no doubt some relationship to the prevalence of age-related conditions like Alzheimer’s disease. As an article for The Conversation points out, “The result is that millions of brain disease patients are at risk for inhaling food and saliva into the lungs, leading to death by pneumonia or even choking.”

That having been said, the design of the human oral cavity looks more like a trade-off than a botch. As Evolution News has put it, “Trade-offs are compromises made to optimize the highest design goal.” They are not errors but necessary features of design in a material world.

Photo credit: CarlottaSilvestrini, via Pixabay.