The larynx drop and its role in speech / choking risk

Factual Questions
1

I was having a rather frustrating experience at stackexchange biology, where I asked the same question and got booed out of any proper answers for not ‘doing enough research’. What’s maddening is that from the bits of info they spared, I feel I’ve come really close to the answer, yet can’t confirm it (partly because the nature of such Q&A site doesn’t allow active bouncing of ideas). So here I am, resorting to SD. I’ll try to summarize all the things I’ve learned till now, please correct me if there’s misinfo in any steps:

  • In a summer course I followed, it was revealed that “(paraphrased) at birth, the larynx is situated up high, and as the infant grows, it drops gradually. Which makes speech easier and also chokes likelier.”
  • Apparently, choking can be divided into 2 categories of water and food, both are relevant to the problem in different ways.
  • This picture demonstrates the anatomy of adults on the left, apes and supposedly infants on the right. Let’s call the crossroad where the airflow meets the foodflow, well, “crossroad”.
  • When animals drink water, the reddish larynx in the pic will move even higher upwards (yuck), forming a sealed, continuous airway to allow breathing while drinking. I imagine it as connecting 2 hoses by tightly inserting 1 inside another and the ends. Water will flow around the tube because the crossroad’s space is quite bigger than the tube’s diameter => animals can never choke on water.
  • But when animals eat, any tube will block the foodflow, therefore the larynx stays in its place. Instead, another gadget called epiglottis will flap down and completely cover the airway. (Big) chunks of food coming through the crossroad will only serve to push it close more tightly, so the airway is always safe from foreign bodies. Yet this also explains why animals can choke on food: if the fish is too big, it could be stuck right at the crossroad, and the animal would die of oxygen deprivation.
  • Enter humans. As we developed languages, somehow a dropped larynx is more advantageous. It being lower is said to “leave space for an echo chamber”. While it’s true physically, I doubt its practical purpose. Many ape species are recorded & filmed to have a wide voice range when they vocalize. Even an infant human with her heightened larynx can produce quite a range. So I contest that the dropping only serves to make our voices more bassy, not “helping speech easier”. In fact, most of our phonemes result from other articulating organs doing their work, and what differentiates humans from apes & animals is not the voice box being able to vibrate. As for why more bass voice is more preferred, I have no concrete ideas. Help?
  • Humans lost the ability to connect the hoses and form a sealed tube, so both when we drink and eat, we use the epiglottis to cover out airway. However, since water is a liquid, it can enter our lungs even if there’s a small slit, i.e. when the epi can’t do its job perfectly => humans have increased risk of water choking. But it has nothing to do with the dropping of larynx, because even at infant stage, we already can’t form the sealed tube anymore. In other words, infants are at the same risk of water choking as adults.
  • When it comes to eating, theoretically we can do better, because solid chunks of food might help the epi close more effectively. But because we’re social animals, (some of us) tend to talk while dining, especially those who want to jump at others’ mouth when the others are speaking and they themselves are swallowing. This leads to conflicting commands to the poor epiglottis, and in desperation it lets stuff into our airway => humans may have an even more increased risk of food chokes.
  • So, back to the original lecture, now it seems the dropping of the larynx, technically, neither makes ‘speech easier’ and ‘chokes likelier’. Or very, very little. Is my conclusion wrong? Is the logic flawed at some point?
  • That leads to the question of why the larynx doesn’t appear way down in infants in the 1st place. Perhaps since this is a very recent development in our evolutional history, it doesn’t have time to progress in utero? Like our tails, which appeared then shed, but did it in time before birth.
  • Which leads to a related question. Why do we even have crossroads? Is this an error in our proto-ancestor that, if we have the chance for a grand re-design, we’d not let happen?
2

No you weren’t. You were informed of the standards for questions at the site:

Consequently, questions that show little or no prior research effort are off-topic on this site as are “homework” questions unless you have shown your attempt at an answer.

and given advice for improving your question:

Please edit your question and tell us where you’ve looked for answers, what you do know about the topic, and where exactly you still have questions.

This is good advice for asking a question anywhere.

In this case for instance you could have included that your fourth point, about animals being able to drink while breathing comes from another biology stackexchange answer you were pointed to and which quotes no sources. I think it is wrong.

Here’s why: Mind you, I’m no anatomist, vet or doctor. But as can be shown in anatomy drawings of almost all tetrapods, we eat or drink with the lower opening (mouth) and breathe through either. But it’s the upper pipe that leads to the stomach, and the lower that leads to the lungs. I’m referencing directions in a non-upright vertebrate here because it makes the directions consistent for opening and pipe.

There’s no simple way for one pipe to connect to “its” opening to form a continuous tube and the other remaining open, and I find no evidence that a complicated way exists in other animals. I do however find evidence that bad science has been published on infants drinking and breathing at the same time and that it has had staying power despite being false:

I think it likely that the same misconception is prevalent about animals. And the cause is likely that it is easier, when the choking risk is lower, to quickly alternate drinking/swallowing and breathing and this has been misinterpreted as doing both at the same time. But in general tetrapods cannot drink and breathe at the exact same time. One exception is snakes, and they haven’t evolved a way to link up a nose (which they don’t use to breathe) and the airways, they’ve simply moved the opening to the airways to the front of the mouth. There might be other oddball tetrapods with other anatomical quirks allowing breathing and swallowing at the same time, but it is not standard.

So why do adult humans choke so easily? I suspect one part is that we have a large vertical volume of shared air/food space where gravity is pushing the food or liquid onto the epiglottis. Try to speak or breathe while that space is filled and gravity will push the food and liquid back against the air and potentially into the airway when the airflow stops and before-while the epiglottis is being pushed shut again. With the epiglottis further up-forward in the airway that space is reduced and there is less risk of food or liquid with significant pressure behind it being present around the epiglottis.

In addition, as mentioned in one of the answers in the previous question you were pointed to, humans make a habit of mixing their consumption of food with conversation, which involves breathing, and don’t always time the commencement of speech right.

I’ll leave the question of how the lower larynx helps with speech to someone else.

3

That could be the root of the problem at SEb. In the field of linguistics, there’s a thing called Gricean maxims, in which one should assume that her interlocutor is genuine, telling the truth, and telling everything he knows. But on SEb, the default assumption is that if someone can’t show scientist-level of knowledge and research method, along with a bunch of evidence, then he’s either lazy or is using the site to do his ‘homework’, or both. That bias right from the start makes cooperation difficult.

Let me try using that mindset to evaluate your answer:

  • Your only cited evidence is on infants, and it has nothing to do with how animals drink or eat. In fact, it actually reinforces my notion that infants have the same risk of choking as adults.
  • When it comes to animals, you finding no evidence “that a complicated way exists in other animals” doesn’t mean it doesn’t exist. Maybe it could help if you edit your post and tell us where you’ve looked for evidence?
  • Now it turns out that both your answer and the answer I relied on have no (animal) citations. We’ll use another type of heuristics to judge which is more trustworthy. On 1 hand, you admitted that you’re not any type of professional. On the other, the linked answer has many upvotes on SEb (which is supposedly a professional site based on their high standards), and was written by someone with 8628(!!) points, 53 medals, and was revised by the author herself to maybe reflect most updated information. I think it’s pretty clear which carries more weight.
  • Therefore, your guess that animals quickly alternate between gulping and breathing in unfounded. Furthermore, your claim that tetrapods can’t drink and breathe at the same time is once again lacking any citations. Some images or videos of their anatomy in action would be appreciated.
  • Your hypothesis about gravity, while sounds intuitive, can be seriously questioned in practice. Astronauts swallow in microgravity without any problems. It’s been demonstrated on Earth that if one does a handstand, he can still swallow against gravity. I guess that is because, in fact, our pipe are really small but elastic, thus making any bit of food a relatively big chunk when compared with resting diameter. So food will actually be stuck in our pipe regardless of how strong a gravity is, or which direction it’s pointing. Instead, it’s the very act of swallowing - an undulating pulsation of the muscles around the pipe - that causes food chunks to move. Thus, with gravity out of the way or playing a negligible role, the larynx being up or down doesn’t affect the risk of chokes.

As you can see, that stuff above can feel pretty quarrelsome, yes? I could have said something like “Yeah yeah, I also found it weird to have the hoses connecting, hence the Yuck in the OP. The gravity theory is interesting, could you point to any articles mentioning it?”, but then I might sound lazy… What I’m trying to get to is something like ‘common sense’. It assumes the best in people and urges one to do their best to reciprocate. Without such mindset, a constructive conversation that facilitate ideas and collaboration will turn into heated arguments and attacks, or worse. Just look at my question at SEb having a negative score and no official answers, and I still believe that’s an unwelcome reaction to ‘outgroups’, i.e. “booed”.

I also believe SD is different. But this has been derailed. What do you think of the above (larynx) points?

4

You thoroughly misunderstand both the nature of and the intent of the advice you were given. The point isn’t to determine who is being lazy or trying to do homework, it’s that answering such questions often involve a decent amount of research and work, and that work can be reduced drastically if the question asker presents their current knowledge and understanding and how they obtained it.

And I’ll respond as if you hadn’t started both your original post and this one with such adversarial statements.

Your question is about humans and how they compare to animals. Infants are obviously relevant. As is the existence of possibly wrong information in the scientific literature on ability to drink and breath at the same time in the human animal.

I acknowledge in a later paragraph that there could be complicated ways to connect them in other animals, along with the information that snakes have airways the extend into the mouth and opens up “in front” of the throat. If this had been a scientific article I would likely have made sure this statement was closer to the other, to avoid confusing the casual reader.

And you are free to ignore my answer. Someone being a prolific and popular SEb poster doesn’t mean they can’t mess up though.

It’s not a guess, it’s a deduction based the anatomy in question. The epiglottis exists to block the airways when swallowing. Apart from in snakes there’s no evidence of tetrapods having a way to keep the airways open while swallowing.

This is true. Peristalsis is involved in swallowing and gravity is not a necessity to swallow. We evolved from animals with much more horizontal movement of the food after all. But gravity is why humans are able to, for instance, shotgun a beer. Relax your throat and the liquid just drops down.

This doesn’t follow. It could be true, but the orientation and/or length of the pharynx is the main difference between animal and human throat physiology and it’s not unreasonable to posit that it’s involved in increasing choke risk. I couldn’t find any information about the frequency of astronauts choking on their food in the first few pages of search results. Apparently the existence of peristalsis is so little known that everyone would rather ask how astronauts can swallow without gravity.

5

It could be worse, you could not have a hard palate. Makes it hard to breathe and chew at the same time. But animals made do without one for quite some time (and many still do).

Complex speech is such a recent development it’s going to take a while to “fix” the larynx situation.

6

I am a vocal major, so I do know a bit about larynx position and resonance. One thing that is drilled into us is that a relaxed, lower larynx position is vital for “vocal protection,” i.e. preventing vocal fatigue and damage from louder and continual use of our voice.

We’re also taught about resonance and how it allows us to sing louder and more clearly with less effort. And that you can increase resonance with a more “open throat,” i.e. a lower larynx position. Though you do also use the nasal resonance as well.

So my hypothesis would be that we evolved our lower default larynx because of how much we talk, how often we have to yell, and how important it is that our vocalizations remain clear, not having to change too much when they get louder. When I listen to most other animals that can make a lot of sounds, it seems they have different sounds if they’re louder or softer. And I notice that baby cries sound different based on loudness.

This is just a guess, of course. But it could explain the idea that our lower larynx is more useful for speech sounds.

7

Yeah, if I were strictly a rationalist and applied their ‘Bayesian inference’ (I’m not sure I totally know what that phrase means) then I’d give that answer a big weight and yours smaller. But my common sense points out that getting 2 hoses tightly fit inside each other is a hard process that requires precision, and it feels xenomorph-y alien. So I actually favor your proposal a bit more. I note that there’s a lack of in-action media evidence for either.

Nice example. Yet, I want to point out that it only proves the case for liquid, which can flow in all but the tiniest pipe diameter. I’ve never heard of anyone shotgunning pizza, likely because it’s impossible.

True - that’s what I did too! But when I dived deeper to confirm, there’s actually no definitive evidence of such, like this thread is proving.

Also, there’s a problem with the ‘quick alternate between gulp & breath’ theory. If we accepted that both humans and animals use the epiglottis for both drinking and eating, then it’d make sense that we can also do the fast alternate. But we can’t.

Sorry, but I’m not confident I can follow. Could you elaborate? The way I’m understanding your comment, it’s like this: “humans have hard palate, but animals don’t. Hence whenever they chew, they’re essentially holding breath. Humans in the far future will have either low larynx at birth, or somehow decreased choking risk.”

This is interesting. Does that mean we should keep a bassy voice whenever we have to talk loud and for long?

Is the stuff you were referring to, what they call ‘registers’?

…
So, combining all the ideas till now, here’s my take: the larynx does drop to make speech easier (and clearer, which is an important distinction). But that biological change doesn’t necessarily lead to an increase in our choking risk. Instead, it is our social nature that makes us more vulnerable to chokes.
If the theory holds, then the only salient puzzling question remaining is: why don’t infant have lower larynx? I can think of 2 hypotheses:

  • Speech is so recent, DNA couldn’t incorporate it fast enough during pregnancy. So it has to progress as we grow up to be ‘complete’.
  • We have been ‘actively’ encoded to have higher larynx at birth and lower as adults, implying that there must be a benefit. About that, my current train of thinking is: a higher larynx don’t help as much with the risk of choking as with the handling of such incidents. See: infants and adults have about the same risk; in fact, infants choke all the time. But having a higher larynx is beneficial in that, when the incident inevitably occurs, they will have a relatively longer tube to deal with the liquid. In other words, milk will face a longer time before it can reach the lungs and cause damage - meanwhile, we activate the coughing response right when we detect something post-epiglottis. Besides, a longer tube also means we have a longer air column at use, to expel the foreign bodies more effectively. When infants grow up, they develop language skills, so the larynx has to drop to facilitate speaking. And by that time, although the tube is relatively shorter, in absolute terms it’s actually longer, so everything’s alright.

What do you guys think?

8

It’s not intended as proof. It’s an illustration of why your “gravity plays no role” argument is wrong. It’s unreasonable to think gravity only influences liquid, though it’s obvious it has a less dramatic effect on a food bolus.

The food or liquid that ends up in the airways is most likely to be food or liquid that is already present in the larynx when the epiglottis is opened by exiting air. Clearing the larynx of food before breathing is an obvious risk reduction event. A smaller larynx obviously clears faster.

9

My post is very clear. Your misunderstanding is way out there. You could click the link, you know.

10

A more resonant voice or a lower larynx has nothing to do with the actual pitch of the voice. So, no, you shouldn’t add bass to your voice. The actual physical process you need to make your voice more resonance is tricky to describe in text form, and you really need feedback to make sure you’re doing it right.

The best advice I’d give you reducing speaking fatigue is to try to reduce tension from the throat on up, even as you get louder.

11

Really? But when I put my fingers on the throat and vocalize low-to-high pitches or vice versa, I notice my larynx goes up & down all the time. The fact that adults have deeper voices than kids also happens to coincide with the larynx drop.

12

That’s just a bad habit. A very common bad habit, but a bad habit nonetheless. It’s one of the things that a voice teacher will teach you not to do. In fact, raising your larynx when going up actually cuts off your upper range significantly. You want your larynx to be stable, and singers spend a long time learning how to do that. (This is actually a key part of “breath support.”)

You actually need to stretch your vocal cords to make them thinner so the pitch goes higher (like tightening a guitar string), and you need the extra space to be able to do that. It’s counterintuitive, which is why people often need help learning how to do it. (But do note that this is not all there is to it.)

It is true that the larynx drops at puberty (even for “female” voices). But that’s not what drives the voice change. That is caused by the actual vocal folds getting thicker. The larynx just drops to give them more room to freely vibrate and resonate.

You can prove this to yourself, if you’d like. Hold a comfortable pitch with your voice, and then manually (but gently) move your voice box with your hands. You’re raising the larynx, but the pitch doesn’t change. (That said, this shouldn’t be something you do often.)

13

If I move my larynx the pitch changes, but I believe you when you say it’s habit, as I can do the opposite. If I hum a high pitch I can gradually lower it while holding my larynx in place.

Fascinating!

14

I agree, that’s cool. Though when I try to hold my larynx in place, I sound really weird.

Is that why those who are about 25 or more aren’t really considered candidates for music school (because their habits have rooted too deep)? Is breath support beneficial for virtually everybody? And the golden question, I think: can we practice it without a trainer, only sources on the internet?

And an overarching question remains: why do we even have the food pipe intersecting with the air pipe?? There seems to be no benefits whatsoever.

15

There often isn’t any “why” in evolution. If it doesn’t hinder survival or reproduction, there’s nothing to select against it. Many mammals, birds, and lizards all have the same arrangement.

In an animal with a long neck, sharing a single pipe for air and food does have a survival advantage. Having two pipes means twice as much tissue for those parts of the anatomy, which means a slightly higher food intake is required to feed those tissues. If you have two otherwise identical creatures, the one with two pipes will starve to death before the one with a single pipe.

16

[quote=“longtry, post:14, topic:969175, full:true”]
I agree, that’s cool. Though when I try to hold my larynx in place, I sound really weird.

It’s never too late to get vocal lessons or learn an instrument. We had people over 25 in my classes at college.

Breath support is good for everyone, yes. Uses outside of singing include learning how to speak for long periods of time, how to correct vocal problems, learning control, and so on. And, yes, there are tons of online resources about it. I would consider it safe to learn. You see, breath support is about learning to hold back the breath with your breathing muscles, and not your throat. The actual problem when learning to sing is trying to manipulate the voice without breath support.

I’ll recommend this video that covers a pretty widely known technique. And if you’re interested, he has other videos on breath support, and singing in general.

And, yes, he teaches singing without actually hearing you. But he also tries to teach you what to listen for, how to know if you overdid it, and relatively safe exercises you can do that can help. It’s not a replacement for a proper teacher, but it’s probably the best attempt I’ve seen at doing it. And he doesn’t claim he will teach you to be some amazing singer this way.

17

Wow, that’s deep, thank you @BigT . I only get it after watching the video. Though he doesn’t mention the larynx at all, I guess it will appear in his other breathing support lessons.
If I often experience a mild ‘hoarseness’ of the throat after talking for about 30mins in a louder and higher tone than usual, is it a clear sign that I have some of the problems you listed?

In case of humans, we have almost 2 separate pipes. The shared length is comparatively short.

I read somewhere that the reason we have contralateralization in the brain (left hemisphere controlling right body) is perhaps because at some point in the far past, our proto-ancestor turn its head 180 degrees. If that’s true, then it’d create a twist at the neck, resulting in the 2 (supposedly separate) pipes to wind around each other. It must be a waste of material, not to mention the difficulty of swallowing & breathing, so maybe after that it evolved to have the 2 pipes intersecting at 1 point, eliminating the twist.

18

Probably not, given that all vertebrates have a contralateral brain, regardless of how far they need to rotate their head.

I have read that it has something to do with developing stable symmetry. This isn’t my area of expertise though.

As for one pipe making it easier to rotate your head farther, you might be on to something there. That part of our anatomy probably developed back when we looked more like squirrels than anything else, and a squirrel-like rodent trying to survive in the ecological chaos of the world after that big rock came crashing down in the Yucatan Peninsula could definitely benefit from being able to look quickly around in all directions.

19

I started reading this topic because I have Parkinson’s Disease, which makes the voice quieter and more gravelly. It also makes it more likely that food and pills will go down the wrong pipe. I will soon begin physical therapy for the speech part. Rather than hijack this topic, I’ll probably start another about the Parky angle. of it.

20

I mean, perhaps the proto-species turned their head permanently according to the theory. idk, why the frick would it do that… So it sounds implausible for me.

Anyway you see fit, but in case you make a new topic, could you drop a comment here when it’s on? I’d like to hear the doctor’s opinion, if he has, about the larynx’s role.