This makes it harder for them to make a wide variety of sounds, and thus, human-level language.
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It’s happened to all of us: you’re in the middle of a conversation, and for some reason, you take a weird breath and suddenly, you’re having a coughing fit. Why is it so easy for us to end up hacking up a lung, just because of our own saliva? Like, that feels like the kind of flaw that evolution should have gotten rid of by now.
As it turns out, those coughing fits are part of a trade-off that happened over the course of millions of years. And what we got in return for some awkward moments was a critical thing that makes us, well, us: the ability to produce complex sounds and spoken language.
Every time you go to swallow something, it kicks off a complex series of movements in your mouth and throat. When something gets pushed to the back of the mouth with the tongue, it enters the pharynx, which is the part of the throat directly behind the mouth. That’s where the swallow reflex begins, which causes several small but important motions to occur.
The timing of these motions has to line up for you to swallow without choking. Since this reflex requires the epiglottis to cover up the airway temporarily, your breathing has to pause for just a couple of seconds to protect the windpipe while you swallow. But if you breathe in anyway, or say, start to laugh while you’re mid-swallow, you can end up choking something that should have gone down the esophagus.
We can see the differences between human and chimpanzee anatomy by comparing our throats’ anatomy to other, less chatty mammals, including our closest living relatives. Humans have much flatter faces than chimps do, which affects the proportions of everything else down the line. Our flat faces also came with changes to the mandible, or jawbone, giving our tongues more space to move around. Our tongues are also rounder than chimpanzee’s tongues, and we can do more precise movements with them than our ape cousins can.
So we know why choking happens in us. But why haven’t we evolved out of it by now? As it turns out, all those awkward moments are an evolutionary trade-off that enables us to do something pretty crucial: talk. Chimps have air sacs in their throat which enable them to produce loud, fast, and high-pitched calls to one another. However, these same sacs prevent them from making the complex vocalizations needed for verbal language. Humans, on the other hand, have a more capable mouth and throat, allowing them to make a greater variety of sounds and thus develop speech. Despite the risk of occasionally choking, the advantages of talking were so important for our survival that it is worth the risk.
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