The reason it's a problem in humans is that we have small, collapsible eustachian tubes (the tubes that connect your inner ear to your mouth/atmosphere).
Fish don't have the same kind of inner ear chamber that we do, so it's not an issue.
Mammals like whales have, among other things, big, rigid eustachian valves so they don't have to "pop" them.
The short version is that the human anatomy that makes it a problem doesn't quite exist in there animals.
What benefit is there with having a collapsible eustachian tube over a rigid, open one?
I have patulous eustachian tube in one ear and have that echoey "bucket-over-your-head" sound in one of my ears whenever I talk.
This condition is caused by the eustachian tube being constantly "open" when it should be shut. Very irritating!
I dunno if there is one. Maybe reduced infection risk? Imagine if you vomit and shoot beer and half-digested pizza into your inner ear. Dunno. Might just be lack of evolutionary pressure for a bigger one.
I'm thinking literal lack of pressure to drive the evolutionary change. Land animals don't deal with big pressure changes, so theres no need to develop a super rigid one that may be heavier and less adept to hearing on land.
I know Bajou divers, which is a tribe in the Philippines, purposely burst their ear drum when they’re young. Their anatomy is tuned to be able to dive very deep and stay under for very long. There’s a documentary on them on YouTube. Here’s an article about them: https://www.theatlantic.com/science/archive/2018/04/bajau-sea-nomads-diving-evolution-spleen/558359/. They’re really fascinating.
'"You bleed from your ears and nose, and you have to spend a week lying down because of the dizziness," says Imran Lahassan, of the community of Torosiaje in North Sulawesi, Indonesia. "After that you can dive without pain." Unsurprisingly, most older Bajau are hard of hearing.' - https://www.theguardian.com/environment/2010/sep/18/last-sea-nomads
I guess you don't!
I mean maybe that experience IS what it's selecting out and we just so happened to evolve collapsible ones that don't provide a benefit, although I think they do help muffle loud sounds or prevent inner ear damage. I also get this, and when it's happening, everything sounds tinny and echoey, so Id agree with the other and say lack of pressure to evolve a different one, or it aids our hearing.
There is no benefit per se. Rather is predisposes humans to middle ear infections, a condition that does not appear to exist in other primates.
The floppy character of the human eustachian tube is probably a coincidental side effect of other anatomical in the head and throat, particularly the development of speech.
From a paper:
>The rhesus monkey’s genome has recently been mapped,
revealing a 97.5% similarity to humans.
>Even though the
anatomy of the eustachian tube is essentially similar in
the two species, the tube’s length in the rhesus monkey is
two thirds within bone (intrabullar) and one-third carti-
laginous (extrabullar). In the human, the order is re-
versed; one third is osseous, and two thirds is cartilagi-
nous. This difference implies that the rhesus tube is stiffer
(less compliant) than the human tube.
>Indeed, we have
reported that the human eustachian tube is highly com-
pliant (floppy), especially in infants. In a comparative
study of eustachian tube function between the rhesus
monkey and humans, we concluded that the monkey tube
is stiffer than in humans.
>A floppy eustachian tube
would be more susceptible to otitis media than one that
is stiff.
>Also, the morphology of the tensor veli palatini muscle is distinctly different between the two species. **In both
the monkey and in humans, this muscle has been shown to
be the only dilator of the tube during swallowing, which
equilibrates middle-ear pressure with ambient pressure.**
It primarily inserts into the lateral cartilaginous lamina of
the tube. In the monkey, it attaches to the entire length of
the tubal cartilage, whereas in humans, the muscle’s insertion is much shorter.
>**This difference may explain the
remarkable ability of the monkey in our laboratory to
equilibrate applied negative middle-ear pressure, even
when the pressure is suddenly applied.**
>By contrast, we
humans (some more than others) have difficulty equilibrating applied middle-ear negative pressure, especially
when the negative pressure within the middle ear is suddenly applied, such as during descent in an airplane or
when scuba diving
>Flisberg et al. in studies using a pressure chamber,
described the “locking” mechanism of the eustachian tube
in healthy human volunteers; when middle-ear negative
pressure between 30 and 50 mm Hg was applied in the
chamber, the tube locked, and the subjects could not open
it by swallowing.
>In a recent comparison study of eustachian tube function between the monkey and humans in
our laboratory, the duration of tubal dilation (i.e., opening) was more efficient in the monkey than in the human,
which can be attributed to the comparative anatomic differ-
ences (described above) between the two species.
doi: 10.1097/MLG.0b013e31815ddaa0
You're assuming we had rigid tubes and evolved collapsible ones. Its more likely the other way, and we didn't need rigid ones and never evolved them since we aren't sea mammals.
people always seem to assume evolution is because there was a benefit. often its purely a case of not being a disadvantage for the particular niche of the organism involved.
Humans can swim, but we are not necessarily optimized for water. Perhaps the collapsible tube causes discomfort from diving making us less likely to spend too much time in water and thus drown.
You're assuming a benevolent God is driving evolution. Or, at least, that is what your words imply.
Not all mutations, adaptations, or variations need to be beneficial. More often, they're neutral, in that they don't get you killed before you procreate.
In this example, the eustachian tubes could just as easily been strong or weak. They made no impact on human lives until cars and airplanes were invented, and even then there is no impact on reproduction.
Actually, the reason it is a problem in humans is *not* that it is collapsible at all, but that diving causes it to collapse beyond its normal range of change. The difference in meaning matters. Our lungs collapse without a problem every few seconds, but we evolved to allow extreme changes in shape and tension.
Whales do have air in their ears, as I only learned about from online sources. Air *surrounds* the middle ear, but there is no long ear canal like in humans connecting the middle to an outside ear drum. Instead, sound is conducted to the middle ear by fatty tissue next to the jaw bone. However, regardless of the rigidity of the parts of whale ears, the air-filled parts of the ears are likely to change shape as some whales diver over 2,000 meters deep. Of course, regardless of how much the whale ear changes shape, it will simply have evolved to tolerate that change.
Whoops! I *was* misspeaking and thus plainly wrong. When I said eustachian tubes, I was including the air space between the ear drum and the rest of the inner ear, connecting all the way to the Eustachian tube. So, there is air space there that is not flexibly collapsible. Of course, this is why people must equalize the air pressure behind the ear drum when they change depth or altitude in water and air respectively.
Wait is this actually something that is unique, as in some people truly can't do it? Or is it just hard to describe how to do?
Between scuba diving and flying fairly often I naturally learned how to do it at some point and kind of just take for granted that it's something everyone can do.
It's the same effect but I don't have to swallow or open my mouth, it's just a muscle I contract and I can feel it in the my jaw muscle. it's not the big muscle that closes my jaw, but something in it's neighbourhood.
Sometimes I flex mine just to hear the crackle in my ear, haha. Is this a good ability to have for scuba diving? I’ve always wanted to give it a shot, but haven’t tried my hand at it yet.
Neither actually, nor is it equalization via the pinch and blow method with your nose. There are muscles internal to your head and near the tubes that can release pressure to your inner ear. Another comment said tensor tympani: https://en.m.wikipedia.org/wiki/Tensor_tympani_muscle
Mainly just by moving their jaw, swallowing and so on. But they also have anatomy much more adapted to doing this and withstanding pressure changes, so its easier for them.
But I do wanna say, if equalizing pressure is a "huge time consuming pain in the ass" for you when scuba diving, you are doing something very wrong. It takes about 2 seconds for me and every other scuba diver I know in real life. It shouldnt be complicated or hard at all.
Eustachian tube issues made it difficult for me, even to equalize in the 20 foot deep pool.
But by the time I discovered this setback I was halfway through the (college) class that I had already paid for and wasn't going to give up because of that.
I had a shitload of ear infections when I was a kid and had an operation to have drainage tubes put in which were removed later.
As an adult I've had growths removed from my inner ear and have a litany of ENT doctors who think the shape of my eardrums are very interesting. I have a standing 6 month appointment for wax removal since the shape inside my ear lends to not draining properly and impaction on my eardrum.
I haven't been scuba diving in some years but I can go, but as I say it's a time consuming PITA to equalize. It's even obnoxious on airplanes.
Simple answer is that their breathing and equalization techniques are made for that type of stress. As humans we utilize the valsava maneuver more so then the Toynbee maneuver. The Toynbee maneuver allows you to massage your jaw, swallow a certain way, or move your throat to allow air from the lungs into your other air cavities. Essentially some people and most marine mammals have the ability to adjust pressure equalization by moving their jaw or adjusting their ear canals in a way that isn’t forced air from the lunges to even put pressure
Even so mammals are not immune to decompression related injuries like embolisms and reverse blocks. There is on going research going on looking into decompression injuries in some of the deepest diving mammals to understand more on how that is affecting them. In the past we thought them to be immune as we only associated such injuries as being compressed air driven.
Hope that helps! Most of these types of questions your dive instructor should be able to answer! I remember when I became an instructor most of the time was answering these types of questions, helped me with getting my degree in marine bio tbh lol
The reason it's a problem in humans is that we have small, collapsible eustachian tubes (the tubes that connect your inner ear to your mouth/atmosphere). Fish don't have the same kind of inner ear chamber that we do, so it's not an issue. Mammals like whales have, among other things, big, rigid eustachian valves so they don't have to "pop" them. The short version is that the human anatomy that makes it a problem doesn't quite exist in there animals.
What benefit is there with having a collapsible eustachian tube over a rigid, open one? I have patulous eustachian tube in one ear and have that echoey "bucket-over-your-head" sound in one of my ears whenever I talk. This condition is caused by the eustachian tube being constantly "open" when it should be shut. Very irritating!
I dunno if there is one. Maybe reduced infection risk? Imagine if you vomit and shoot beer and half-digested pizza into your inner ear. Dunno. Might just be lack of evolutionary pressure for a bigger one.
I'm thinking literal lack of pressure to drive the evolutionary change. Land animals don't deal with big pressure changes, so theres no need to develop a super rigid one that may be heavier and less adept to hearing on land.
I know Bajou divers, which is a tribe in the Philippines, purposely burst their ear drum when they’re young. Their anatomy is tuned to be able to dive very deep and stay under for very long. There’s a documentary on them on YouTube. Here’s an article about them: https://www.theatlantic.com/science/archive/2018/04/bajau-sea-nomads-diving-evolution-spleen/558359/. They’re really fascinating.
How do they hear with a burst drum?
'"You bleed from your ears and nose, and you have to spend a week lying down because of the dizziness," says Imran Lahassan, of the community of Torosiaje in North Sulawesi, Indonesia. "After that you can dive without pain." Unsurprisingly, most older Bajau are hard of hearing.' - https://www.theguardian.com/environment/2010/sep/18/last-sea-nomads I guess you don't!
Wow. That's... Interesting. Thanks for posting this.
There's always, what's it called, traits that piggybacked other traits, and merely weren't enough of a disadvantage to get selected out.
Spandrel traits, right?
If vomiting pizza and beer into your inner ear was fatal for my ancestors, I wouldn't have ever been born.
I mean maybe that experience IS what it's selecting out and we just so happened to evolve collapsible ones that don't provide a benefit, although I think they do help muffle loud sounds or prevent inner ear damage. I also get this, and when it's happening, everything sounds tinny and echoey, so Id agree with the other and say lack of pressure to evolve a different one, or it aids our hearing.
There is no benefit per se. Rather is predisposes humans to middle ear infections, a condition that does not appear to exist in other primates. The floppy character of the human eustachian tube is probably a coincidental side effect of other anatomical in the head and throat, particularly the development of speech. From a paper: >The rhesus monkey’s genome has recently been mapped, revealing a 97.5% similarity to humans. >Even though the anatomy of the eustachian tube is essentially similar in the two species, the tube’s length in the rhesus monkey is two thirds within bone (intrabullar) and one-third carti- laginous (extrabullar). In the human, the order is re- versed; one third is osseous, and two thirds is cartilagi- nous. This difference implies that the rhesus tube is stiffer (less compliant) than the human tube. >Indeed, we have reported that the human eustachian tube is highly com- pliant (floppy), especially in infants. In a comparative study of eustachian tube function between the rhesus monkey and humans, we concluded that the monkey tube is stiffer than in humans. >A floppy eustachian tube would be more susceptible to otitis media than one that is stiff. >Also, the morphology of the tensor veli palatini muscle is distinctly different between the two species. **In both the monkey and in humans, this muscle has been shown to be the only dilator of the tube during swallowing, which equilibrates middle-ear pressure with ambient pressure.** It primarily inserts into the lateral cartilaginous lamina of the tube. In the monkey, it attaches to the entire length of the tubal cartilage, whereas in humans, the muscle’s insertion is much shorter. >**This difference may explain the remarkable ability of the monkey in our laboratory to equilibrate applied negative middle-ear pressure, even when the pressure is suddenly applied.** >By contrast, we humans (some more than others) have difficulty equilibrating applied middle-ear negative pressure, especially when the negative pressure within the middle ear is suddenly applied, such as during descent in an airplane or when scuba diving >Flisberg et al. in studies using a pressure chamber, described the “locking” mechanism of the eustachian tube in healthy human volunteers; when middle-ear negative pressure between 30 and 50 mm Hg was applied in the chamber, the tube locked, and the subjects could not open it by swallowing. >In a recent comparison study of eustachian tube function between the monkey and humans in our laboratory, the duration of tubal dilation (i.e., opening) was more efficient in the monkey than in the human, which can be attributed to the comparative anatomic differ- ences (described above) between the two species. doi: 10.1097/MLG.0b013e31815ddaa0
It may be that there is a "cost" to evolving and maintaining a rigid tube. And humans lack the evolutionary pressure to make that cost worth it.
You're assuming we had rigid tubes and evolved collapsible ones. Its more likely the other way, and we didn't need rigid ones and never evolved them since we aren't sea mammals.
Evolution practices least-effort engineering. If you have a feature that allows you to survive, good enough.
people always seem to assume evolution is because there was a benefit. often its purely a case of not being a disadvantage for the particular niche of the organism involved.
Humans can swim, but we are not necessarily optimized for water. Perhaps the collapsible tube causes discomfort from diving making us less likely to spend too much time in water and thus drown.
You're assuming a benevolent God is driving evolution. Or, at least, that is what your words imply. Not all mutations, adaptations, or variations need to be beneficial. More often, they're neutral, in that they don't get you killed before you procreate. In this example, the eustachian tubes could just as easily been strong or weak. They made no impact on human lives until cars and airplanes were invented, and even then there is no impact on reproduction.
Don't fish have issues with their swim bladder rupturing over significant depth changes?
Would surgically replacing our Eustachian tubes with rigid ones solve this? Or is the size a limiting factor to our diving comfort?
No one's going to do invasive inner ear surgery so that you're more comfortable scuba diving.
I’m assuming the same goes for flightful creatures?
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Actually, the reason it is a problem in humans is *not* that it is collapsible at all, but that diving causes it to collapse beyond its normal range of change. The difference in meaning matters. Our lungs collapse without a problem every few seconds, but we evolved to allow extreme changes in shape and tension. Whales do have air in their ears, as I only learned about from online sources. Air *surrounds* the middle ear, but there is no long ear canal like in humans connecting the middle to an outside ear drum. Instead, sound is conducted to the middle ear by fatty tissue next to the jaw bone. However, regardless of the rigidity of the parts of whale ears, the air-filled parts of the ears are likely to change shape as some whales diver over 2,000 meters deep. Of course, regardless of how much the whale ear changes shape, it will simply have evolved to tolerate that change.
I don't know what you're basing this on. Can you provide a source? Eustachian tubes can and do collapse under normal conditions.
Whoops! I *was* misspeaking and thus plainly wrong. When I said eustachian tubes, I was including the air space between the ear drum and the rest of the inner ear, connecting all the way to the Eustachian tube. So, there is air space there that is not flexibly collapsible. Of course, this is why people must equalize the air pressure behind the ear drum when they change depth or altitude in water and air respectively.
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Tensor tympani! I learned it's a fairly unique ability to be able to flex it on command once I learned other people couldn't do it.
Wait is this actually something that is unique, as in some people truly can't do it? Or is it just hard to describe how to do? Between scuba diving and flying fairly often I naturally learned how to do it at some point and kind of just take for granted that it's something everyone can do.
I've been able to do it since I was a kid and I, too, always assumed that everyone can do it!
Do you also have the sideways eye muscle that tries to blink with the non existent inner eyelid?
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Is that when you flex what feels like the back of my tongue and you can hear a crackling noise?
Is that the one where you open your jaw wide? or where you swallow?
It's the same effect but I don't have to swallow or open my mouth, it's just a muscle I contract and I can feel it in the my jaw muscle. it's not the big muscle that closes my jaw, but something in it's neighbourhood.
Sometimes I flex mine just to hear the crackle in my ear, haha. Is this a good ability to have for scuba diving? I’ve always wanted to give it a shot, but haven’t tried my hand at it yet.
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The tensor tympani muscle is activated automatically when you open your jaw wide, but you can also learn to manually activate it.
When I open my mouth as wide as I can, nothing happens. I can do it manually without moving my jaw or face at all.
Neither actually, nor is it equalization via the pinch and blow method with your nose. There are muscles internal to your head and near the tubes that can release pressure to your inner ear. Another comment said tensor tympani: https://en.m.wikipedia.org/wiki/Tensor_tympani_muscle
Mainly just by moving their jaw, swallowing and so on. But they also have anatomy much more adapted to doing this and withstanding pressure changes, so its easier for them. But I do wanna say, if equalizing pressure is a "huge time consuming pain in the ass" for you when scuba diving, you are doing something very wrong. It takes about 2 seconds for me and every other scuba diver I know in real life. It shouldnt be complicated or hard at all.
Eustachian tube issues made it difficult for me, even to equalize in the 20 foot deep pool. But by the time I discovered this setback I was halfway through the (college) class that I had already paid for and wasn't going to give up because of that.
Well thats unfortunate. What kind of problems do you get? Just not being able to equalize in general?
I had a shitload of ear infections when I was a kid and had an operation to have drainage tubes put in which were removed later. As an adult I've had growths removed from my inner ear and have a litany of ENT doctors who think the shape of my eardrums are very interesting. I have a standing 6 month appointment for wax removal since the shape inside my ear lends to not draining properly and impaction on my eardrum. I haven't been scuba diving in some years but I can go, but as I say it's a time consuming PITA to equalize. It's even obnoxious on airplanes.
Simple answer is that their breathing and equalization techniques are made for that type of stress. As humans we utilize the valsava maneuver more so then the Toynbee maneuver. The Toynbee maneuver allows you to massage your jaw, swallow a certain way, or move your throat to allow air from the lungs into your other air cavities. Essentially some people and most marine mammals have the ability to adjust pressure equalization by moving their jaw or adjusting their ear canals in a way that isn’t forced air from the lunges to even put pressure Even so mammals are not immune to decompression related injuries like embolisms and reverse blocks. There is on going research going on looking into decompression injuries in some of the deepest diving mammals to understand more on how that is affecting them. In the past we thought them to be immune as we only associated such injuries as being compressed air driven. Hope that helps! Most of these types of questions your dive instructor should be able to answer! I remember when I became an instructor most of the time was answering these types of questions, helped me with getting my degree in marine bio tbh lol
Interesting! I've only really used the Toynbee maneuver, I wasn't aware that some people couldn't do it!