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Comment by thaumasiotes | Hacker News Reader

This is why you chew your food.

Most frogs don't have teeth though.

https://i.pinimg.com/736x/c0/64/72/c0647299ff0863268d4adafd9...

I get this is a joke, but just bouncing off: don't humans mainly need to chew food because we have a terrible design and evolution put our lifeline of air intake in a tiny hole behind a flap right where we swallow food in a small, relatively inflexible tube and location?

No. It's true that other animals don't have the difficulty with choking on food that we do. But it's not true that other animals don't chew their food. You chew your food to make it easier to digest and so that it will fit down your throat.

And, if it's alive, so that it will be dead instead.

> But it's not true that other animals don't chew their food.

I didn't say that.

If you claim that humans chew their food because their throats are uniquely vulnerable to choking, you have also claimed that animals without such awkward throats don't need to chew their food.

Putting things another way, just a few minutes of observation are sufficient to demonstrate that running the air intake past the esophagus is so irrelevant to the purpose of chewing that the absence of that problem does not affect the behavior in any way.

Isn’t that logic in reverse?

No. The two claims are contrapositives of each other:

1. Chewing -> bad throat

2. Good throat -> no chewing

Bad throat -> chewing required.

Good throat -> chewing not required for that reason but possibly for other reason.

Chewing -> bad throat possible, but not required.

Not chewing -> bad throat badge not unlocked.

> If you claim that humans chew their food because their throats are uniquely vulnerable to choking, you have also claimed that animals without such awkward throats don't need to chew their food.

No, I haven't. That quite simply does not follow, at all. There is to much variation in the definitions and permutations of chewing, throat design, air intake design, types of foods eaten, and digestive systems to make that leap.

Cows and animals alike (ruminant) basically chew all day and they bring the food back from the stomach to chew it again. Otherwise they cannot get enough nutrients out of gras and co.

Quite a few animals chew their food multiple times for more effective digestion - cows for example. Plant fibers are notoriously hard to break down. Horses don’t and if you compare the digestion results, you’ll see a significant difference between horse dung and cow dung.

Besides the ruminants, there are also other animals, the best known being the rabbits, which are not able to reverse the direction of the food to bring it back from the stomach into the mouth, so after a one-way passage of the food through their bodies they must eat it again, to chew it for the second time.

Yeah. Horses are so inefficient at digestion that the largest breeds (such as Clydesdales) would starve to death in huge fields of grass. They can only survive by being fed copious amounts of grain such as oats.

Hmm. Do you have a reference for that? From what I have read, Clydesdales are fine on good pasture (hay in the winter), but they won't be able to do much if any work if they don't get additional feed. They would also likely not be as muscled as a horse with supplemental feed. A clydesdale raised on pasture only might also end up smaller, but they won't starve to death, assuming it is quality pasture.

I'm talking about a large breed raised on grain and then suddenly switched to pasture -- not one raised on pasture its whole life -- as you might see with a retired working animal. They may not literally starve to death, but they will lose a lot of muscle mass and may get sick and die from that, or may struggle to survive the winter.

Given a sample size of my dog, I believe chewing is only necessary for making bland food more delicious. The more yummy the food, the less my dog chews it - thoroughly chewing dry kibble and culminating in literally inhaling something like roast chicken.

Thus, it's because grass and weeds are bland and lacking in tasty fat that bovines and ruminants chew their food for so long and so many times.

Not really, no.

Carnivores vs. herbivores.

Also, it depends if something eats leaves (not very digestible, not very nourishing) vs fruit (very digestible, except the seeds, and highly nourishing).

Carnivores don't need to chew much.

Carnivores have shorter guts than herbivores.

>And, if it's alive, so that it will be dead instead.

For most animals, this is true I think. But frogs seem to be perfectly happy swallowing live prey whole. You can see videos of frogs eating live mice!

No. It's actually important for an effective digestion. Not just because smaller pieces are easier to break down, but because the enzymes in the saliva start the process.

Digestion is important but I think being able to breath is more important. Poor digestion won't kill you as readily as suffocation or pneumonia from aspiration. They, being protecting food from blocking or entering the trachea and digestion, both seem pretty important as part of the whole chewing system, so I don't think it's a plain "No". I should correct my original comment from mainly to one of the main reasons.

Do you know how snakes "eat"?

Chickens have no teeth, but they chew their food (the food is first stored in their crop, along with gravel, where it is "chewed" before passing to the stomach.)

Well, sort of, it's the gizzard that "chews" it, not the crop.

What does that have to do with humans?

breath /breθ/ -- noun: air that is drawn in and out.

breathe /briːð/ -- verb: the act of inhaling and exhaling for the purposes of respiration.

They are not the same word and they do not sound the same.

typo noun ty· po ˈtī-(ˌ)pō plural typos : an error (as of spelling) in typed or typeset material

--------

I know what the words mean.

Absolutely. But at least we (and all other animals with a secondary palate) can chew while breathing. I heard that before that has evolved it put a severe caloric disadvantage on the animals since one was limited in how much chewing can happen by the need to breath.

https://en.m.wikipedia.org/wiki/Secondary_palate#Evolution

> But at least we (and all other animals with a secondary palate) can chew while breathing

Interestingly, sprint predators such as cheetahs have to pause to get their breath back after a fast chase before they can eat their prey. In contrast, raptors such as falcons can eat immediately after a kill because they don't get out of breath in the same way. The avian respiratory system is actually quite different to ours, with relatively rigid lungs, separate air sacs to pump the air, and a one-way flow through the lungs, in contrast to mammalian lungs where the air goes in and out through the same pipe, and the lungs act as bellows as well as gas transfer devices.

I fail to see how we represent terrible design. Most animals our size need to chew food with their mouth, and of them I can't think of any more successful than us, evolutionary speaking.

The fact that our species is successful doesn't mean that every mechanism in our bodies is good. There are a lot of "design decisions" which could have been improved if they had gone through a review, rather than evolution.

One such example is the way our retinas are wired to the optic nerve on the inside of the eye, rather than behind, causing us to have a "blind spot" where the nerve fibres need to go back. In some other animals, particularly the octopus, the retina is wired the "right way", such that they don't have a blind spot.

Same for the design of our pharynx, larynx and esophagus. As mentioned in sibling comments, other animals suffer from choking much less, as compared to humans, where we have ~5k deaths/year from choking just in the US [0].

[0]https://www.statista.com/statistics/527321/deaths-due-to-cho...

Nor does it mean it is terrible. That is the kind of exaggregation I reacted on.

I guess you feel it's an exaggeration, but how? We put physical filters in front of basically anything we build that takes in air for the exact reason of it's bad to take in anything other than air for systems that only expect air.

Choking kills thousands of people every year and is the fourth leading cause in children under 5. According to this article (https://pubmed.ncbi.nlm.nih.gov/35099619/), aspirated pneumonia is even worse, especially for older people, who guess what, can't chew well.

And it's all due to the (apparently not terrible) design.

In order for you to subjectively label it terrible you need to present a bad outcome from the design. Evolutionary/objectively, it's not a bad design.

How do you define and measure evolutionary "success"? By what mechanisms is it achieved?

For a cross-species comparison, you'd usually measure evolutionary success in terms of biomass. More is better.

You don't. It is not even agreed upon that evolution optimizes <<something>>.

And even if you agree that evolution is an optimization process, attempts to define its objective function run into problems with tautology and circular definitions once you move beyond simple examples.

It is described by Dawkins et al.

More successful == gets to have more surviving offspring.

That is the TL;DR. He, she or it that has the most babies, wins.

I think we have to know the order in which these features occurred. As others pointed out, chewing has other benefits. Maybe evolution took advantage of chewing to change the air intake design for some other advantage.

I thought of this, as it could also be the other way around. As in, hey this food is already chewed because of the air intake design, resources can be allocated elsewhere instead of spending them on digesting. Or it developed completely differently I'm actually curious as to what the guesstimated order is.

Humans don't need to chew their food at all. If there is enough moisture, you can swallow most foods whole in chunks. Chewing is part of the digestive process (especially for plant material) to increase the surface area of the food. Even carnivores with huge throats and few or no molars can be observed chewing certain foods.

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