Speaker 1: Welcome to Stuff to Blow your Mind from how Stuffworks
Speaker 1: dot com. Hey, welcome to Stuff to Blow your Mind.
Speaker 1: My name is Robert Lamb and I'm Joe McCormick and
Speaker 1: Robert I got a question for you. What do you
Speaker 1: think is the most underrated body part on the human
Speaker 1: You could go in a lot of ways, right, you
Speaker 1: really can. I mean, certainly, we we tend to put
Speaker 1: more emphasis on the brain and the heart, and then
Speaker 1: of course throughout human history confused the two and the
Speaker 1: role they might play. Uh, you know, I think back
Speaker 1: to the the the ancient Egyptians and their idea that
Speaker 1: the heart was far more important than the brain, and
Speaker 1: the brain was just to be removed and discarded, whereas
Speaker 1: the heart had a privileged place in the funeral preparations
Speaker 1: of dead pharaohs. But of course it's impossible for us
Speaker 1: to underestimate the value of the heart and the brain
Speaker 1: now since we know them to be so important. But
Speaker 1: there are all kinds of body parts you have that
Speaker 1: you probably just don't stop to be very thankful for
Speaker 1: or think about very much, but they do you a
Speaker 1: lot of good. I think about the underrated facility of
Speaker 1: the toes. Yeah, yeah, to toes are granted toes maybe fetishized,
Speaker 1: as as can any part of the human anatomy. Oh no,
Speaker 1: I didn't mean that way. No, I mean they're like
Speaker 1: usefulness and balance and movement. Oh yeah, yeah, certainly, but
Speaker 1: but it's not something that we tend to attach our
Speaker 1: identity to. Whereas the brain. Yeah, I mean our podcast
Speaker 1: has had a brain on its logo in the past.
Speaker 1: You know, the heart has all these symbolic meanings where
Speaker 1: we want to attach our identity to them in addition
Speaker 1: to the functions that they play. But then there are
Speaker 1: parts of the body that we generally don't want to
Speaker 1: think about, and we don't think about unless they are
Speaker 1: giving us grief, unless there's something wrong with them, and
Speaker 1: then they become the center of our existence. Right. It's
Speaker 1: the same way that you never think about your internet
Speaker 1: connection unless it's not working. Right. There are parts of
Speaker 1: the body that you probably just never think about unless
Speaker 1: something's going wrong, right, or we go to great pains
Speaker 1: not to think about them. You know, we kind of
Speaker 1: have all these blinders up. Really, the part of many
Speaker 1: and animals anatomy that we're going to discuss here today
Speaker 1: the anus. The anus today it's anus science on stuff
Speaker 1: to blow your mind, right, and I I wanted to
Speaker 1: do this episode really since I guess that's when I
Speaker 1: really first found out about anus. Is. Yeah, I had
Speaker 1: no idea. I had no idea what it would happened.
Speaker 1: And then I read this, uh, this cool science paper
Speaker 1: and I was like, whoa, this is this is this
Speaker 1: is where it all comes from. This is this is
Speaker 1: the center of all the activity. I really appreciate you
Speaker 1: suggesting this topic because the anus turned out to be
Speaker 1: far more interesting than I had ever imagined it is.
Speaker 1: And that's what we're going to try and outline in
Speaker 1: this this episode. Now, we we do have to drive
Speaker 1: home since we are talking about the anus and there
Speaker 1: is there's just so much not not really. I don't
Speaker 1: think taboo is going to be a stumbling block for
Speaker 1: us here, but the anus is so tied into our
Speaker 1: our systems of humor, Like it is so giggle inducing.
Speaker 1: When you when you saw this title pop up on
Speaker 1: your your your your device or whatever program you used
Speaker 1: to listen to your podcast, you may have giggled at
Speaker 1: the prospect of listening to say in an hour's podcast
Speaker 1: about the anus. Yeah, you'll probably notice that we talk
Speaker 1: about biology a lot on the podcast. I've gotten to
Speaker 1: where it's extremely easy to talk about, say, the biology
Speaker 1: of sex, without making any jokes. That's something a high
Speaker 1: school or might not be able to do. But you know,
Speaker 1: when you talk about it enough, it's just an interesting
Speaker 1: subject on its own. Well, sexist is its humor appeal? Well,
Speaker 1: sex is one of these things. Sexual reproduction is a
Speaker 1: case where I feel like most people, at least, you know,
Speaker 1: most adults are capable of having both a humorous conversation
Speaker 1: about and a serious conversation about. You reach that point
Speaker 1: where you realize there is this entirely serious side to
Speaker 1: the discussion, and you can switch back from one and
Speaker 1: the other. But with the anus, there's it's almost gotten there. Yeah,
Speaker 1: it's almost all humorous, unless you yourself are are a
Speaker 1: proctologist or or or just a medical professional, or you
Speaker 1: have had to deal with health issues related to the anus.
Speaker 1: Otherwise it's just all the realm of body humor. Or
Speaker 1: maybe you're somebody who studies the evolution of the anus,
Speaker 1: which is something that we will definitely be touching on today.
Speaker 1: These questions about whence this hole in the backs of
Speaker 1: our bodies? Where does it come from? And what is
Speaker 1: it doing. That's not so much what is it doing
Speaker 1: that's pretty obvious, yes, but but the way that it
Speaker 1: does it, the way that it's come to do it,
Speaker 1: and just how how it functions. Uh, hopefully you will
Speaker 1: leave this this episode with a whole new respect for
Speaker 1: the anus of any animal. Okay, Now we wanted to
Speaker 1: start with an interesting fact, Robert, that you came across,
Speaker 1: actually a curious little book that you found on the internet, right,
Speaker 1: that's right. So I was casting about for some mythology
Speaker 1: related to the anus and we'll we'll get to some
Speaker 1: of that later on gods and so forth. Yeah, yeah,
Speaker 1: I figured, you know, it's always good to throw in
Speaker 1: a little mythology a few monsters when we can. And
Speaker 1: I was just plugging in different ancient cultures. I plugged
Speaker 1: in the ancient Egyptians to see what what was up,
Speaker 1: and I ran across this book, The herbal Lore of
Speaker 1: Wise Women and Warp Cunners The Healing Power of Medicinal
Speaker 1: Plants by wolf D. Storrel, and he points out that
Speaker 1: the doctors of ancient cultures were part of the priesthood,
Speaker 1: and for the ancient Egyptians, each physician was responsible for
Speaker 1: curing only one illness. So the pharaoh was attended by
Speaker 1: such specialist as the Royal Keeper of Pharaoh's left eye,
Speaker 1: the Royal Keeper of the Pharaoh's right eye, and then
Speaker 1: most importantly of all, perhaps the shepherd of the royal
Speaker 1: anus or the nerofoot. If I am reading that correctly,
Speaker 1: the Shepherd of the Royal anus. Now laugh, you may laugh,
Speaker 1: you may, but this is actually a kind of interesting
Speaker 1: because it's an early example of medical special realizations, something
Speaker 1: that we've seen again in the modern world. There are
Speaker 1: a lot of reasons that a pharaoh might have need
Speaker 1: needed to have a special attendant to problems dealing with
Speaker 1: their anus, because a lot of the problems you can
Speaker 1: have with your ans can be related to, say, certain
Speaker 1: types of over indulgent diet. Yeah, I mean just in general,
Speaker 1: there's just so many digestive ailments they can occur in
Speaker 1: one's life. You see this pop up in a number
Speaker 1: of different traditional practices, for instance, moodras. Are you're familiar
Speaker 1: with moodra's, I'm not sure. So this is a whenever
Speaker 1: you see someone in a yoga pose and they're making
Speaker 1: or they're a meditative state and they're making a particular
Speaker 1: little hand uh motions. They're holding their fingers together in
Speaker 1: a particular pattern. That is a moodra And I've read
Speaker 1: up on them in the past, and when you start
Speaker 1: looking at the different moods that they have them for
Speaker 1: different things, it's you know, it's about channeling energy and whatnot. Uh.
Speaker 1: But it seems like most of them are related to digestion,
Speaker 1: which which makes sense when you when you think about
Speaker 1: all the digestive ailments that can afflict an individual over
Speaker 1: the course of their lifetime. Totally, now the sky's storial
Speaker 1: that I want to say, this book does appear to
Speaker 1: be kind of in a liminal or less than totally
Speaker 1: authoritative space. I think this guy deals in some some
Speaker 1: kind of natural apathy areas and stuff. But it was
Speaker 1: curious and had some fun ideas in it. Yeah, he's
Speaker 1: he's not an Egyptologist or anything. But but I I
Speaker 1: have to point out that I did find this bit
Speaker 1: about the Shepherd of the Royal Anist backed up in
Speaker 1: some other works, including Medicine in the Days of the
Speaker 1: Pharaohs by dermatologist Bruno Hella and cardiologist Bernard Ziskins from
Speaker 1: two thousand five. Yes, I think that fact is well attested,
Speaker 1: but also I just wanted to follow up on this
Speaker 1: other idea. In his book, Storial argues that every culture
Speaker 1: has a primary external metaphor that it uses to understand
Speaker 1: medical insights, which is like a model through which to
Speaker 1: visualize health and human function. So for the ancient Mesopotamians,
Speaker 1: he says, this moll was the movements of the planets
Speaker 1: through the zodiac. For the ancient Indians, he says one
Speaker 1: of the models they used most often was the cycle
Speaker 1: of the seasons from spring to pre monsoon to monsoon.
Speaker 1: And for the ancient Egyptians, this model, he says, was
Speaker 1: the Nile River quote regularly cleansing and fertilizing the thousand
Speaker 1: mile long oasis. Just as the Nile flows from Nubia
Speaker 1: to the Mediterranean, so the elementary tract, also known as
Speaker 1: the digestive tract, flows from the mouth to the organs
Speaker 1: of elimination in the human body, bringing health and cleaning
Speaker 1: out impurities. Now, upon reading this, I couldn't help but
Speaker 1: notice that if this is true, what what he says
Speaker 1: about the you know, this metaphor of human health being
Speaker 1: the Nile River, the Nile River delta, which is this lush, fertile,
Speaker 1: agriculturally productive region that sustains the civilization around it. In
Speaker 1: the metaphor, the delta would be the rectum in the anus. Yeah,
Speaker 1: this reminds me of something that that I was thinking
Speaker 1: about researching this topic as well. Like we think about
Speaker 1: the the the track of digestion in the human experience,
Speaker 1: the linear experience of digestion, uh, And I wondered what
Speaker 1: extent uh that plays a role and just our understanding
Speaker 1: of time. When we were talking about time in our
Speaker 1: episode that this present moment we talked about comparing time
Speaker 1: to the river we see flowing past us and so forth.
Speaker 1: But here we have this river flowing inside us that
Speaker 1: is an even closer uh metaphor, that's that makes itself
Speaker 1: readily available. So you're thinking, maybe if we had evolved
Speaker 1: to have large brains, but to not have a one
Speaker 1: way digestive tract instead to have I don't know, one
Speaker 1: of these open sack mouths We're going to talk about
Speaker 1: more as the episode goes on, where you just sort
Speaker 1: of like eat and digest and poop all through the
Speaker 1: same one orifice and sack. Would that lead us to
Speaker 1: have a different conception of sort of the the order
Speaker 1: of things in history, and the meaning of structure and
Speaker 1: our lives. Yes, I, as we proceed here, I challenge
Speaker 1: anyone out there too imagine an alien life woman, intelligent
Speaker 1: alien life form with one of these sort of rival
Speaker 1: digestive systems, and imagine how that rival digestive system might
Speaker 1: impact their perception of time or the universe. Take up
Speaker 1: the challenge. Alright, Well, on that note, we should probably begin, uh,
Speaker 1: well at the beginning or at the end if you'd rather,
Speaker 1: by discussing just what the anus is and what it does? Yeah,
Speaker 1: what is your anus and what does it do? Uh?
Speaker 1: The anus? Of course I shouldn't giggle, should I know?
Speaker 1: I think a little a little giggling is uh just
Speaker 1: cannot be avoided thanks human culture. The anus, of course,
Speaker 1: as we all know, is the point of termination for
Speaker 1: the digestive system. It's the exit point for solid waste
Speaker 1: in the body. And I think one of the things
Speaker 1: we should regularly stop and be thankful for is the
Speaker 1: fact that we have an anus. It does one job.
Speaker 1: It is dedicated to the elimination of solid waste. There
Speaker 1: are lots of complex animals that are not like this. Um.
Speaker 1: We are going to talk more about some simpler animals
Speaker 1: that have like a single opening through which everything takes place,
Speaker 1: but even complex animals like birds, reptiles, amphibians, monitory ms
Speaker 1: do not have an anus, but a cloaca, which serves
Speaker 1: as a general purpose opening for solid waste, liquid waste,
Speaker 1: and reproduction, kind of a fusing of the different categories
Speaker 1: together exactly. So, if you imagine we had evolved from
Speaker 1: birds instead of mammals, we would probably still defecate, urinate,
Speaker 1: and give birth all through the same hole. Now, maybe
Speaker 1: if that was how we were, we wouldn't mind, But
Speaker 1: I don't know. I think most humans are probably glad
Speaker 1: that things don't have to be that way. Well, I
Speaker 1: think we should also be thankful that humans don't yet
Speaker 1: have the power to decide like where their waste elimination
Speaker 1: or if this will be and how it functions, because
Speaker 1: we would we put it down there. We'd probably put
Speaker 1: it down there on our heel, so we could discreetly
Speaker 1: defecate as far from the rest of our our body
Speaker 1: as possible. I have often wondered that same exact thing.
Speaker 1: Why doesn't defecation happen at like the end of a
Speaker 1: tale or something? Something farther away from you. But then again,
Speaker 1: why would it need to And once you've got a
Speaker 1: tale that you need to defecate through, what happens if
Speaker 1: it gets chopped off something? And that will come up
Speaker 1: in this episode. Hey, it has come up in the
Speaker 1: previous episode. Uh, there's it's the anus is important and
Speaker 1: therefore it really needs to be core and center to
Speaker 1: the the primary trunk of the body. Now, if you're thinking,
Speaker 1: come on, guys, or if you're not on board yet, right,
Speaker 1: you know you're thinking, like, how can we really do
Speaker 1: an episode on the anus? It's just a hole that
Speaker 1: stuff comes out of. What could there be to say
Speaker 1: about it? I would say that the anus is a
Speaker 1: surprisingly complex organ, uh, and so I think maybe we
Speaker 1: should look at its complexity and what it has to do. Indeed,
Speaker 1: so as we dive in here, I want to turn
Speaker 1: to the words of Mary Roach, who wrote a wonderful
Speaker 1: book several years back, Gulp Adventures on the Alimentary Canal.
Speaker 1: I've referenced this in other episodes. It's just a wonderful
Speaker 1: exploration of human digestion and some additional topics. For instance,
Speaker 1: there's a whole section in the book where she talks
Speaker 1: about the practice of smuggling things in one's rectum and
Speaker 1: sort of the science of that practice. But here's a
Speaker 1: here's a wonderful quote where she talks about the anus quote.
Speaker 1: Anal tissue is among the most densely innervated on the
Speaker 1: human body. It has to be. It requires a lot
Speaker 1: of information to do its job. The anus has to
Speaker 1: be able to tell what's knocking at its door, is
Speaker 1: it solid, liquid, or gas, and then selectively release either
Speaker 1: all of it or one part of it. The consequences
Speaker 1: of a misread are dire. They certainly are. Now. Yeah,
Speaker 1: though I wonder I've had this thought before. Okay, So,
Speaker 1: in modern polite society, you don't want to just whoop anytime, right,
Speaker 1: you know, you want to be able to control that
Speaker 1: for like cultural and privacy reasons, and maybe for some
Speaker 1: hygiene reasons. But if you imagine us living in the wild,
Speaker 1: what's the reason that you would need to be able
Speaker 1: to control when you poop? Why does that matter? Well,
Speaker 1: I mean, controlling when you defecate is really important because
Speaker 1: outside of the particular human concerns, this is an issue
Speaker 1: of hygiene but also survival. Being able to choose where
Speaker 1: and how you defecate. It's tremendously important and it entails
Speaker 1: everything from not pooping where you eat, to say, pooping
Speaker 1: in a place where you can easily hide the stuff.
Speaker 1: That we see this every day, or at least cat
Speaker 1: owners do with a litter box, that the cat wants
Speaker 1: to poop where it can hide its poop because it
Speaker 1: has this uh evolved necessity to disguise the scent of
Speaker 1: its of its activity. And then also sometimes you want
Speaker 1: to produce the right sort of round poop that will
Speaker 1: roll away from your body. This is apparently the case
Speaker 1: with with goats. If you've ever been to a petting
Speaker 1: zoo with a child, for instance, you probably noticed that
Speaker 1: the round poop is basically falling out of the goats
Speaker 1: at all times. And uh and and that he's round
Speaker 1: so that it can roll away. Is this kind of
Speaker 1: like when it comes out sort of like a spray
Speaker 1: of coffee beans. Yeah, just kind of like tumbling coffee
Speaker 1: beans and the pebbles. Yeah. And apparently the purpose is
Speaker 1: these things would roll away. It's self hiding poop. They
Speaker 1: don't have to bury anything at all. Now I'm curious
Speaker 1: about what you said about the idea that controlling when
Speaker 1: you defecate plays a role in survival? What what would
Speaker 1: the role in survival be? Well, I ran across a
Speaker 1: paper a few years back because from two thousand thirteen,
Speaker 1: The Control of Defecation in Humans and Evolutionary Advantage by
Speaker 1: Italian bowl experts UH G. Besati and V. Villainacci, And
Speaker 1: it breaks down the particular human side of this. Uh
Speaker 1: and this is something I've explored before when I was
Speaker 1: looking at the Monster or Science of the Googlies. You
Speaker 1: remember Googlies right before film. The cover was a little
Speaker 1: monster popping out of the toilet. Yeah, tagline taste, They'll
Speaker 1: get you in the end. But it made me think
Speaker 1: it's like, all right, well, humans are are vulnerable when
Speaker 1: they're on the toilet. All animals are vulnerable to some
Speaker 1: extent when they are defecating. So how does evolution plan
Speaker 1: to all of this? Well, in this case, the authors
Speaker 1: point out that human fecal matter would have certainly put
Speaker 1: early humans at risk from the apex predators of your
Speaker 1: So if you run a human fecal sample, modern or ancient,
Speaker 1: through complex gas uh chromatographic or mass us spectrometric analysis,
Speaker 1: you'll discover that quote, human feces are rich in volatile
Speaker 1: compounds likely to be identified by potential predators. So volatile compounds,
Speaker 1: what does that mean? Smell? Yeah, And as we've driven
Speaker 1: home before on the podcast, I think our human sense
Speaker 1: of smell is rather limited, like we're seeing in grungy
Speaker 1: black and white, whereas something like an apex predator or
Speaker 1: something like even our our pet dogs and cats, especially
Speaker 1: the dogs, they have an entirely different, like full color
Speaker 1: HD experience of things. Well, Robert, have you ever owned
Speaker 1: a dog. It's been a very long time. I've mostly
Speaker 1: been a cat owner my entire adult life. I think
Speaker 1: most people who have dogs will know what I'm talking about.
Speaker 1: Dogs love poop. They want to smell all of the poop.
Speaker 1: When I take my dog out on a walk, it's disgusting.
Speaker 1: Other people's dogs leave their poop on the sidewalk wherever,
Speaker 1: and he wants to go to all of it. And
Speaker 1: if you try to pull him away, like no, Charlie,
Speaker 1: you don't want to get into that, He's like no, no,
Speaker 1: I need to. Well, there's information there. There's there's information
Speaker 1: on a level that that that humans can barely grass.
Speaker 1: We just know it doesn't smell pleasant, or it certainly
Speaker 1: Lena doesn't look pleasant, but this is important environmental information
Speaker 1: to the dog, right right. So to take us back
Speaker 1: to the paper, then the idea is that while we
Speaker 1: are pooping, we're producing smells that advertise our vulnerability to
Speaker 1: potential predators exactly. And the full conclusion from the from
Speaker 1: the paper I think is rather great. They say, quote,
Speaker 1: we hypothesize that the voluntary control of defecation by our ancestors,
Speaker 1: together with greater brain volume, erect stature, opposable thumbs, and
Speaker 1: other changes, may have contributed to the successful march of
Speaker 1: hominids along the road of evolution. In fact, by deciding when,
Speaker 1: how and where to defecate may have several advantages in
Speaker 1: the complex prey predator relationship because spores are left in
Speaker 1: places undetectable by predators, or there are no fecal tracks
Speaker 1: who sent maybe easily individualated by prey genius. So we've
Speaker 1: we figured out evolutionarily speaking, that you need to know
Speaker 1: when to poop, because if you just poop anytime, you
Speaker 1: may be squandering opportunities or putting yourself in danger exactly.
Speaker 1: So let's break down how that actually functions biologically, though, Like,
Speaker 1: what is the actual biology of pooping. Okay, So the
Speaker 1: first step is six to eight times a day a
Speaker 1: peristaltic muscle contraction, called a mass movement, squeezes the contents
Speaker 1: of the colon along the path. Yeah, and peristalsis is
Speaker 1: the word for a wave of muscle contraction and relaxation
Speaker 1: that travels down the length of a tube inside the body. So,
Speaker 1: if you've ever run your fingers down the length of
Speaker 1: a sausage casing to squeeze the sausage out, or if
Speaker 1: you've ever tried to push the last bits of icing
Speaker 1: out of a piping bag, you have roughly simulated peristalsis
Speaker 1: on that on that tube. I want to say, this
Speaker 1: is also akin to how an earthworm moves, right, It's
Speaker 1: kind of this. Uh. This wave a wave of muscle
Speaker 1: contraction running down the length of of a cylindrical object,
Speaker 1: And in the sense of a hollow tube, that cylindrical
Speaker 1: object has its contents continually pushed down the length of it.
Speaker 1: So what happens next. The material pushes against the rectum
Speaker 1: wall with enough pressure to trigger the stretch receptors, and
Speaker 1: this triggers the defication reflects now. This entails a simultaneous
Speaker 1: contraction of the rectal wall muscles and a relaxation of
Speaker 1: the anal sphincter. Little known fact people actually have. I
Speaker 1: had no idea until last night. Two anal sphincters. Did
Speaker 1: you know you have to? No? No, I just thought
Speaker 1: there was the one. No, You've got to The internal
Speaker 1: anal sphincter is involuntary, so it holds up everything until
Speaker 1: a certain threshold of rectal wall stretching is reached, at
Speaker 1: which point it automatically says, okay, time to open the gate.
Speaker 1: But then you've still got the external anal sphincter. And
Speaker 1: this is what's under conscious executive control, perhaps for the
Speaker 1: reasons hypothesized by the researchers we were just talking about.
Speaker 1: It's like in a submarine movie when they're gonna launch
Speaker 1: a nuclear missile. Yeah, you have to have like both
Speaker 1: the key individuals push the button at the same time
Speaker 1: because otherwise there will be disastrous consequence. Right, I've got
Speaker 1: the missile key. Al right. So yeah, this is where
Speaker 1: human choice enters the picture. Uh A, poop your own
Speaker 1: adventure book, if you will, So you might choose to
Speaker 1: bear down, and this will raise the pressure on the
Speaker 1: rectum walls to prematurely trigger deification. So this is again
Speaker 1: part of the choice. It's not only the idea of
Speaker 1: the well I'm not getting ready to go yet inner sphincter.
Speaker 1: I'm going to go seek a spot behind a bush.
Speaker 1: You can also say, actually, I'm ready now, let's go
Speaker 1: ahead and expedite this process. But again, likewise you can
Speaker 1: hold it back. But the larger and more liquid the load,
Speaker 1: the harder this is. Roacha quotes so one gut expert
Speaker 1: in gulp as saying, quote, not even the sphincter of
Speaker 1: Hercules can hold back water. I just I like that
Speaker 1: by the sphincter of Hercules. I like the idea that
Speaker 1: since Hercules is very strong, like he's got big muscles
Speaker 1: on his arms and legs and back, he must also
Speaker 1: have an especially strong sphincter muscle. Of course he would.
Speaker 1: I mean, just if you have the blood of God's
Speaker 1: running through your body, if you're a hybrid of of
Speaker 1: humanity and deity, like, why would the why would the
Speaker 1: anus be off limits? Why would that be untouched by
Speaker 1: by the I corps. I want to hear from the
Speaker 1: health and wellness experts out there in the audience, if
Speaker 1: you know this fact does muscle training actually make your
Speaker 1: sphincter stronger? I want to know. Uh. Interbook Roach also
Speaker 1: quotes physician Robert Rosenbluth who says, think of it, no
Speaker 1: engineer could design something as multi functional and fine tuned
Speaker 1: as an anus. And then he points out that to
Speaker 1: to call someone an anus or another crude word for anus,
Speaker 1: that you're ultimately quote really bragging them up. Yeah, it's
Speaker 1: saying like you are a fine tuned specimen. Nature made
Speaker 1: you perfect. Yeah. And this comes back to the idea
Speaker 1: of the shepherd of the anus. I think because when
Speaker 1: we were talking about this in an email chain yesterday
Speaker 1: before we recorded the episode, it was brought up, well,
Speaker 1: there's only one anus, why would you need a shepherd.
Speaker 1: A shepherd tends to a flock of sheep, and I
Speaker 1: would wondering, Well, maybe the scenario here is more than
Speaker 1: the anus is the shepherd, because the anus controls what
Speaker 1: comes in and out. It has such a vital role.
Speaker 1: It's kind of like the shepherd. It's the well, the
Speaker 1: shepherd is the gatekeeper. Yeah, it is the shepherd of poops,
Speaker 1: the gatekeeper of fecal matter. Yeah. Alright, Well, on that note,
Speaker 1: we should probably take our first break, and when we
Speaker 1: come back, we're gonna talk a little bit about mythology
Speaker 1: and monsters before we descend into the world of anal evolution.
Speaker 1: Than all right, we're back now. If you have been
Speaker 1: listening to the show for a while, you've probably listened
Speaker 1: to our episode on the Cuteness Monster Spectrum we discussed
Speaker 1: back in October, where we talked about monsters, especially monsters
Speaker 1: from Japanese folklore that combine elements of cuteness and horror
Speaker 1: and monstrosity. And one of those monsters we talked about
Speaker 1: was a little water dwelling demon called the Kappa. Oh yes, Now,
Speaker 1: the cap will hang out in the river and if
Speaker 1: you get too close, so pull you in and drown you.
Speaker 1: But it gets more interesting than that, Michael Dillon Foster
Speaker 1: writes in a paper called the Metamorphosis of the Kappa
Speaker 1: from Asian Folklore Studies in uh he writes the following quote.
Speaker 1: Not only does the Kappa have a penchant for pulling
Speaker 1: both children and adults into the water, but it often
Speaker 1: does this in order to steal the liver, a feet
Speaker 1: it achieves by reaching its arm up through the victims
Speaker 1: anus to snatch the desired organ. So in order to
Speaker 1: steal the liver, uh, they believed that the kappa had
Speaker 1: to uncork the butt, had to uncork the human anus,
Speaker 1: removing this organ known as the shii kodama, which is
Speaker 1: quote a ball once thought to be at the mouth
Speaker 1: of the anus. This is this is fascinating because you
Speaker 1: have not only you have an imaginary creature here in
Speaker 1: the Kappa, but it is interacting with imaginary parts of
Speaker 1: the human body. Yeah, imagine ary organs. Now, of course,
Speaker 1: one read on this myth is that is that this
Speaker 1: all has to do with the observation of the corpses
Speaker 1: of drowning victims, right, that when people were pulled from
Speaker 1: the water, they would be found to have a gaping anus,
Speaker 1: and so it looked like something had been removed that
Speaker 1: had been corking it up before. But in fact this
Speaker 1: is just caused by you know, relaxation of the muscles
Speaker 1: upon death. Right. But it also I think comes back
Speaker 1: to this idea that maybe we don't really we don't
Speaker 1: really think about the anus much, so you could smuggle
Speaker 1: in an imaginary body part and maybe people would be
Speaker 1: sort of a blind to it, are okay with They're like, okay, yeah,
Speaker 1: I guess there's a cork down there. Yeah, I guess
Speaker 1: if you were going to invent an imaginary organ for
Speaker 1: any you know, semi external part of the body, that'd
Speaker 1: be the place to do it, right, But that would
Speaker 1: be the place where people might buy it. Now, there's
Speaker 1: another Japanese of folkloreic creature. This is a a member
Speaker 1: of the Okai, you know, the sort of fabulous pantheon
Speaker 1: of spirits that encounter in Japanese folklore, and it's known
Speaker 1: as the shira May. Now. I can't find a lot
Speaker 1: about the chira May from academic writings, but it's at
Speaker 1: least enough of a thing that it pops up a
Speaker 1: lot in Japanese art and in Japanese pop culture. In fact,
Speaker 1: it apparently even shows up in the studio ghibli film
Speaker 1: pom Poco, which is a wonderful film. It's a it's
Speaker 1: an animated adventure that involves these shape shifting tonukis with
Speaker 1: magical testicles, which is a whole subject unto itself. But uh,
Speaker 1: this this Japanese your CoA shows up. It is a
Speaker 1: humanoid creature with an eyeball in its anus, and that's
Speaker 1: how it kind of looks around at the world. You'd think,
Speaker 1: given the nature of the human posterior and glutes and
Speaker 1: all that, that that might not be a great place
Speaker 1: to put an eyeball, because it would be kind of
Speaker 1: hard to see out of a lot of the time. Well,
Speaker 1: but you have the fantastic body of a of a
Speaker 1: spirit creature. I guess if everything is possible. Now. I've
Speaker 1: looked around for some their myths related to the anus,
Speaker 1: and I couldn't find a lot. So certainly, listeners out there,
Speaker 1: if you have run across some wonderful folk tales or
Speaker 1: myths are certainly mythological or folkloric monsters, uh with some
Speaker 1: sort of cool anal curio about them, be sure to
Speaker 1: let us know. But I did find one cool example
Speaker 1: in a text by John beer Horse titled Mythology of
Speaker 1: the Lenape Guide and Texts. He points out that there's
Speaker 1: an ice giant cannibal in the traditions of the Lenape
Speaker 1: people known as the Mooe, and it's similar to other
Speaker 1: cannibal ogre traditions that you encounter in Native North American
Speaker 1: people's such as most famously the Windigo. But the movie
Speaker 1: is this this cannibalistic monster. It's basically impervious to harm,
Speaker 1: but it's also rather stupid, and you can kill it
Speaker 1: by driving a steak into its anus. Wow, that that
Speaker 1: is a great variation on vampire lore, because the vampire
Speaker 1: doesn't really need a heart, does it? I mean, come on,
Speaker 1: it's dead. Why does it really does it really need
Speaker 1: to oxygenate all its tissues? But then again, it's we
Speaker 1: know it's drinking blood. So if it's drinking blood, it's
Speaker 1: got to be pooping, right. It's a creature defined by
Speaker 1: its hunger, so why is it not equally defined by
Speaker 1: its defecation? At least we see that with this creature.
Speaker 1: This creature is defined by its ravenous hunger. And then
Speaker 1: it's it's a Kelly's heel is essentially it's a Kelly's anus.
Speaker 1: I have an interesting question, or you can judge whether
Speaker 1: it's interesting. Why are giants in so many folklore traditions
Speaker 1: believed to be dim witted? M hmm, well, you know,
Speaker 1: giant monsters, they're usually not the smartest. I don't know,
Speaker 1: but you don't you see that a lot? I guess
Speaker 1: maybe part of it has to do with with something
Speaker 1: we've touched on already, ancient humans having to compete with
Speaker 1: apex predators creatures that are that have far superior physical strengths.
Speaker 1: But then how are humans able to overcome them and
Speaker 1: even eradicate them? In many cases they use their intellect,
Speaker 1: they use their cunning, and so so many of these
Speaker 1: cases are a giant monster is threatening the smaller human
Speaker 1: and how do they defeat them? They outsmart them. So
Speaker 1: maybe the giants are modeled on sabretooth cats and bears
Speaker 1: and stuff. Maybe. So that's just my you know, off
Speaker 1: the hip. Read on that. I'm sure there are papers
Speaker 1: out there to dive a lot deeper into it. We'll
Speaker 1: have to look into it. The stupidity of giants coming
Speaker 1: soon to stuff to plow your mind. Well, now that
Speaker 1: also makes me wonder if anybody ever hunted bear or
Speaker 1: sabretooth tigers by attacking the anus? Mm hmmm, we we
Speaker 1: can we can move on, Okay, so we should talk
Speaker 1: about the evolution of the anus. Where does this organ
Speaker 1: come from? So for this portion the podcast, we turned
Speaker 1: to a couple of key sources, including Getting to the
Speaker 1: Bottom of Anal Evolution by Andreas Heynal and jose M
Speaker 1: Martin Duran, both from the University of Burke and Our Way,
Speaker 1: and Hey, nol seems to be the key figure in
Speaker 1: some of these studies because he's also the primary author
Speaker 1: on another piece, The Mouth The Anus in the Blast,
Speaker 1: a poor colon open questions about questionable openings. And that's
Speaker 1: when he wrote with Mark Q. Martindale, I love how
Speaker 1: both titles here remind us that you probably have to
Speaker 1: have a sense of humor if you're an anus researcher.
Speaker 1: I wonder if anus puns in in the titles makes
Speaker 1: it harder or easier to get published in serious academic journals.
Speaker 1: I don't know. I feel like that the anus is
Speaker 1: a special case. It kind of comes back to the
Speaker 1: sexual reproduction thing was mentioning earlier, Like we most most
Speaker 1: of us have an ability to switch back and forth
Speaker 1: between the serious and the comedic, but not so with
Speaker 1: the anus. And it seems to even spill over into
Speaker 1: into the academic world. Yeah, okay, Well, these start with
Speaker 1: an observation, which is a pretty simple one, right, the
Speaker 1: anus is not actually universal in animals. Obviously, lots of
Speaker 1: organisms don't have an anus. A plant doesn't need an anus,
Speaker 1: it doesn't eat mushrooms don't need anuses. But even not
Speaker 1: all animals have anus, is right, That's right. Some lineages
Speaker 1: of animals such as uh Poropera, the sponges, Placazoa, the
Speaker 1: which are simple multicellular animals, UM Cestoda. Those are flat worms,
Speaker 1: including the tape worm and a can'to Cephala. This is
Speaker 1: another group of parasitic worms. They don't have a digestive
Speaker 1: track seas no digestive track, no, no digestive track. Now
Speaker 1: UH sea sponges and tape worms are good examples specifically
Speaker 1: for these. Others have a gut with a single opening
Speaker 1: that both the takes in food and excretes waste, such
Speaker 1: as UH the to no offera, comb jellies, UH the Nigeria,
Speaker 1: which is a large invertebrate phylum that includes the hydra, jellyfish,
Speaker 1: sea an enemy, and coral. And then you also have
Speaker 1: acyl A morpha and these simple soft bodied plankton animals
Speaker 1: that live in the water uh. And then you also
Speaker 1: have various flatworms and jaw worms as well. And the
Speaker 1: the Acyla morpha are going to come up several times
Speaker 1: because they are a really interesting reference organism when we're
Speaker 1: trying to understand our evolutionary history and go back to
Speaker 1: the beginning of what it was like when bilateral animals
Speaker 1: first appeared. But a great many animals do have what
Speaker 1: is called a through gut, a linear track. Food goes
Speaker 1: in one specialized in for food uptake, and travels through
Speaker 1: specialized regions for nutrient absorption, and then it all leaves
Speaker 1: through a specialized excretion valve. And this of course is
Speaker 1: the anus. Now, the anus actually becomes very evolutionarily relevant
Speaker 1: here because you can't have a one way digestive tract
Speaker 1: without an anus. Right has to go some Well, we
Speaker 1: have some special cases lat on, but for the most part,
Speaker 1: what goes in has to come out. That's right. I
Speaker 1: guess there are a few exceptions, but generally, yeah, this
Speaker 1: is how it works. If you don't have anus, then
Speaker 1: you've just got another one of these digestion buckets. Basically,
Speaker 1: you have a bucket in your body where food comes
Speaker 1: in and digestion happens and waste comes out. Yet again,
Speaker 1: this is one of those things that I maybe you
Speaker 1: would like it if you were like that, but given
Speaker 1: that you're not like that, you're probably glad you're not
Speaker 1: like that. Well, hey, no has brought this up, he says,
Speaker 1: Can you imagine if we had a digestive system like this,
Speaker 1: what do you eat? And then you have to wait
Speaker 1: eight hours or more until you can eat again, Like
Speaker 1: there's no snacking. If you're hungry, it doesn't matter. Maybe
Speaker 1: you wouldn't be hungry in this case, but you have
Speaker 1: to wait until you can defecate out your mouth and
Speaker 1: then eat again. How would that change your perception of
Speaker 1: of everything in life? Yeah, and it's not just what's
Speaker 1: appealing to you. I mean, Heynal points out in multiple
Speaker 1: places that there are several reasons that having a through gut,
Speaker 1: a one way digestive tract with an anus, is very
Speaker 1: evolutionarily appealing. There's a lot of advantage to it. So
Speaker 1: one of the things that's a real advantage here is
Speaker 1: what you just mentioned, the simultaneity of digestive stages. Yeah,
Speaker 1: you can eat more food while you're while you're you're
Speaker 1: still digesting your last meal. Yeah, you can eat one
Speaker 1: big mac and while it's digesting, you can eat another
Speaker 1: big mac. Maybe in bed it doesn't matter. You can
Speaker 1: do whatever you want instead of just sitting around waiting
Speaker 1: to poop, So you can eat the second one. It's
Speaker 1: getting cold, but the second one, the second one is
Speaker 1: really interesting. I think a one way through gut allows
Speaker 1: more efficient metabolism of food because different parts of the
Speaker 1: digestive system can specialize in different things, and you can
Speaker 1: perform those special functions in the best possible order so
Speaker 1: that one gets done definitely before the other one. If
Speaker 1: you're doing all of your gut stuff in just one bucket,
Speaker 1: it's going to be pretty much impossible to sequence these
Speaker 1: specializations like this. But what would these specializations be. How
Speaker 1: about you've got a tongue and a sensitive mouth and
Speaker 1: that it's useful because it can detect the nutritional value
Speaker 1: of foods or reject potentially dangerous substances. Then you've got
Speaker 1: teeth at the top of the track to begin the
Speaker 1: processing chop stuff up. You've got a stomach full of
Speaker 1: hydrochloric acid and other chemicals to break down foods and
Speaker 1: trigger digestive enzymes. Uh, You've got a liver to secrete
Speaker 1: bile and help with fatty foods. And then you've got
Speaker 1: a long curled up in testine to absorb nutrients, and
Speaker 1: then a colon to shuffle waist out the door. And
Speaker 1: it's important that all this stuff happens in the order
Speaker 1: that it happens. Yeah, I can't help but think of
Speaker 1: an assembly line. You know. It's the difference between a
Speaker 1: clockmaker's shop where material raw materials go in and a
Speaker 1: single shop maker goes through every stage of production, testing
Speaker 1: and then the clock comes right back out the front
Speaker 1: door when it's ready. And if you compare like the
Speaker 1: time involved there with a an assembly line where you
Speaker 1: have multiple individuals, specialized individuals working on different parts of
Speaker 1: the clock's production and testing and and raw materials coming
Speaker 1: in one section, and at the end of the line
Speaker 1: you have finished clocks just rolling off the conveyor belt. Yeah.
Speaker 1: I think that's a great analogy, or one analogy to
Speaker 1: the sack like gut might be that maybe you've got
Speaker 1: all these maybe you've even got all these specialized workers,
Speaker 1: but they're not in a line. They're just all standing
Speaker 1: in a huge room and waiting for their turn or
Speaker 1: kind of you know, reaching over each other's shoulders to
Speaker 1: work on the clock. Yeah. Um. Yeah. And you can
Speaker 1: imagine if you try to imagine your body working this way,
Speaker 1: where you don't have well ordered organs to specialize in
Speaker 1: all of the stages of your metabolism as it goes on. Uh,
Speaker 1: not too good, is it? Chief right? Yeah. One more
Speaker 1: thing I'd say is that you can also have different
Speaker 1: species within the through gut organisms which specialize their body
Speaker 1: parts to adapt to their diet. So, for example, once
Speaker 1: you've got a one way digestive tract, you can say, well,
Speaker 1: I want to have this certain type of teeth to
Speaker 1: take advantage of this hard, chewy stuff that most people
Speaker 1: around me can't eat, and that will be my biological niche.
Speaker 1: So it gives you more ways to evolve. It also
Speaker 1: means that you can grow to greater size because ultimately
Speaker 1: you have improved digestion. You can you can you can
Speaker 1: harvest more nutrients, and you're also not limited by I believe. Hey. No,
Speaker 1: it makes this point as well. If you have a
Speaker 1: particularly long organism, if it had to swallow its food
Speaker 1: and then digest it and then send it right back
Speaker 1: up to the head, that would be ridiculous. Imagine a
Speaker 1: giraffe having to do that. A giraffe does not have
Speaker 1: to do that because everything can come right out the giraffe.
Speaker 1: As He also points out that there are two sets
Speaker 1: of genes in particular that are tied up here, known
Speaker 1: as the barrack. Your a gene and the para hawks
Speaker 1: gene UH, which is also referred to as just c
Speaker 1: d X for caudal c d x UH. And these
Speaker 1: are present and nearly all animals, and they play a
Speaker 1: key role in the formation of the anal orifice. Yes,
Speaker 1: so he's saying that if you see these genes being
Speaker 1: expressed and tissue is the brachi re gene or the
Speaker 1: Caudal c d x often just c d X, you
Speaker 1: know that that tissue is forming an anal orifice almost
Speaker 1: every time. And if the animal loses its anus, and yes,
Speaker 1: we will mention to some animals that have lost their
Speaker 1: anus entirely, it often loses these genes as well. It
Speaker 1: can't be true. How could you lose an anus? Well,
Speaker 1: you know it's it's not just a matter of misplacing it.
Speaker 1: It's just uh, it no longer becomes necessary to the
Speaker 1: functions of the organism. Alright, So hen Al and his
Speaker 1: colleagues they they set out to explore the evolution of
Speaker 1: the anus, right because they said it while it had
Speaker 1: been studied some, it hadn't gotten as much attention, especially
Speaker 1: through genetic research, as some other types of evolutionary innovations had.
Speaker 1: That's right, we see that's the same for the same
Speaker 1: reasons that various ancient cultures have have either focused more
Speaker 1: on the heart or more Today we just focus on
Speaker 1: the brain. It seems like the anus has just received
Speaker 1: less attention. No fewer people have asked the question, where
Speaker 1: did the anus come from? What is the evolutionary heritage
Speaker 1: of the anus? But studying the anus is actually pretty
Speaker 1: interesting for learning about where at what points in evolutionary
Speaker 1: history organisms divided off from one another. Yeah. They point
Speaker 1: out that studying the anus and animals is difficult in
Speaker 1: part because it appears and disappears again within many animal
Speaker 1: groups convergent evolution. Yeah. For instance, that most flat worms
Speaker 1: are anus lists, but others have independently independently evolved one.
Speaker 1: And then there's the polyclad flatworm actually has multiple anuses
Speaker 1: all over their backs. How many anuses multiple? It's like,
Speaker 1: I think it's less than fifty. I'd say it's more
Speaker 1: like six to a dozen. Based on the image that
Speaker 1: I saw in the paper. What if you had fifty
Speaker 1: anuses on your back and they all just pooped a little?
Speaker 1: I don't know if that would be helpful. I mean,
Speaker 1: it does not seem adaptive for our ecological niche up.
Speaker 1: Thankfully that is not a design that really was picked
Speaker 1: up by natural selection. But most of this is interesting.
Speaker 1: Most members of the super phylum due to Rostomes, which
Speaker 1: includes everything from c cucumbers to all vertebrates, they have anuses.
Speaker 1: But see stars have dropped the anus from its anatomical
Speaker 1: lineup completely. Okay, so they were in this group, but
Speaker 1: then they lost the anus, right, These are the losers
Speaker 1: of the anus. And then some animals develop anuses as
Speaker 1: they grow. This is I feel like I've touched on
Speaker 1: this in the past, but lacewings, you know, a small insect,
Speaker 1: they don't poop during their larval stages. They have what's
Speaker 1: called a blind gut, in which everything just pushes to
Speaker 1: the back of the gut as they eat. And then
Speaker 1: after they go through metamorphosis they gain an anus, and
Speaker 1: then immediately upon emerging they poop out everything they ever
Speaker 1: ate prior to their metamorphosis. That's beautiful. And then the
Speaker 1: adults probably say, oh to be young and anus list again.
Speaker 1: And then there of course animals that lose their anus
Speaker 1: during the course of their lifetime. A big example here,
Speaker 1: and this is one we've touched on before in our
Speaker 1: our our two part are on tails, is that of
Speaker 1: a certain scorpions that shed their tails an act of autotommy.
Speaker 1: This is like when lizards are attacked and they drop
Speaker 1: a tail, that sort of thing. Well take that, I'll
Speaker 1: run away. Yeah, I'd rather you just eat my tail
Speaker 1: than eat my entire body. But the thing is with
Speaker 1: the scorpions, they have their anus on one of their
Speaker 1: tail segments, and if they lose it, uh, they lose
Speaker 1: their anus and then they simply never poop again. They
Speaker 1: simply fill up with poop for the rest of their lives,
Speaker 1: swelling with their their own excrement, unable to release it.
Speaker 1: That's no good. And this is a super fun too.
Speaker 1: Anuses can be multi purpose. Oh yeah, so this is
Speaker 1: where we're going to talk about c cucumbers right. Oh yes,
Speaker 1: So the c cucumber does have an anus that it
Speaker 1: defecates through it's anial opening, but it also breathes through
Speaker 1: its anus. That is an interesting trick. Yeah. I have
Speaker 1: not figured out how to do that yet, I would say,
Speaker 1: I dare say most of you out there haven't either,
Speaker 1: but yeah, amazing. So the c cucumber lives under the
Speaker 1: water and it can contract and expand its anal cavity
Speaker 1: to draw in breaths of water in much the same
Speaker 1: way that we expand and contract our lungs to draw
Speaker 1: in air. Right, So we've got like a diaphragm. We
Speaker 1: can open up the lungs, suck in the air, and
Speaker 1: get the oxygen we need out of it. They expand
Speaker 1: the anal cavity, suck in the water, and then they
Speaker 1: extract dissolved oxygen from the water where the water it's
Speaker 1: fed into this large branching set of tissues known as
Speaker 1: a respiratory tree, kind of like the you know the
Speaker 1: pathways you see in the lungs when they expand, and
Speaker 1: then when you've extracted the oxygen, the water is pushed
Speaker 1: back out of the anus. Another fact about the c
Speaker 1: cucumber's anus that I found interesting it is often inhabited
Speaker 1: by a crafty little stowaway. One of the best parasite
Speaker 1: riders out there, Ed Young has a great blog post
Speaker 1: from sixteen where he tells a story about this, and
Speaker 1: I have to relate it. So in this story he
Speaker 1: tells in ninety a biologist named Victor ben o'myer Rachao
Speaker 1: was diving in the water off an island in Indonesia
Speaker 1: when he collected a leopard sea cucumber. So it was
Speaker 1: about forty centimeters long and fourteen centimeters wide. And he
Speaker 1: gets the sea cucumber home and he stores it in
Speaker 1: a bucket of water under refrigeration. Quote. Sometime later, a
Speaker 1: slender eel like fish swam out of the sea cucumber's anus.
Speaker 1: It was a star pearl fish, and it wasn't alone.
Speaker 1: Another wriggled out, and another. After ten hours, fourteen pearl
Speaker 1: fish had evacuated from the animal's bomb, each between eight
Speaker 1: and sixteen centimeters long. Another one stayed inside, so fifteen
Speaker 1: pearl fish in its anus. Now there is more than
Speaker 1: one species of pearl fish, and they occupied the bodies
Speaker 1: of lots of different marine animals, even oysters. It writes
Speaker 1: that the pearl fish get their name from a case
Speaker 1: when a dead specimen was found not only inside an oyster,
Speaker 1: but buried inside a pearl uh and some species of
Speaker 1: pearl fish merely hide inside the sea cucumber, leaving the
Speaker 1: anus to forage for prey and then returning, but others
Speaker 1: have been thought to parasitize the host, like eating its
Speaker 1: gonads in the walls of the respiratory tree. So does
Speaker 1: the does the cea cucumber get anything out of this
Speaker 1: or is it not that I found Uh, if they
Speaker 1: do get anything back, I've not discovered it yet. So
Speaker 1: that is a good question. If the sea cucumber doesn't
Speaker 1: get anything out of it, why doesn't it just close
Speaker 1: off its anus and restrict access to the pearl fish. Well,
Speaker 1: wait a minute, it has to breathe, remember, breathes through
Speaker 1: its anus. So for the full body horror equivalent, try
Speaker 1: to imagine a parasite that wanted to get in your
Speaker 1: lungs and you could try to plug up your nose
Speaker 1: in your mouth to deny it access, but you'd have
Speaker 1: to breathe sometime. Interesting, so we we we've probably are
Speaker 1: seeing the trade off to an adaptation here. Like it's
Speaker 1: on one level, yes, you can breathe through your anus,
Speaker 1: but then the tradeoff is this opens your anus to
Speaker 1: even more parasitic activity. Yes, exactly. Now, to go back
Speaker 1: to autotomy. When we talked about the scorpion that drops
Speaker 1: its own tail as a defense mechanism, see, cucumbers have
Speaker 1: an even more amazing version of anal defensive autotomy. It's
Speaker 1: known as quote evisceration. This is a defensive ejection of
Speaker 1: one's own internal organs, Like, is it nearly turning itself
Speaker 1: inside out? Is it uh an inversion of its body cavity,
Speaker 1: or is it just straight spraying sprays its own guts
Speaker 1: out and lets them go. So if you go handle
Speaker 1: a c cucumber, which we are not recommending, do not
Speaker 1: be surprised if it poops all of its guts out
Speaker 1: at you. When the c cucumber opts for defensive advisceration,
Speaker 1: it contracts its muscles to push much of its respiratory
Speaker 1: tree out through its anus at the perceived attacker, and
Speaker 1: once ejected, the respiratory tree kind of turns into this
Speaker 1: sticky net which can confuse and entrap a predator. And
Speaker 1: it also contains toxins called saponins. So after doing this,
Speaker 1: the sea cucumber can regenerate it's lost tissues. Not sure
Speaker 1: why it doesn't do this to protect to protect against
Speaker 1: the pearl fish. I think we don't know the answer
Speaker 1: there yet. I wonder it just basically breaks down to
Speaker 1: like the cost of spraying out its gusts and then
Speaker 1: regenerating them versus the cost of having the parasites there,
Speaker 1: and maybe it's just not quite worth the effort, Like
Speaker 1: it's it's ultimately cheaper to allow the parasites to do
Speaker 1: their thing. It could be the case. But one more thing.
Speaker 1: When it comes to anal breathing, it is not just
Speaker 1: the sea cucumber. I don't know if you've read about this, Robert,
Speaker 1: but some turtles breathe through their butts. Oh no, this
Speaker 1: is all new to me. Yeah. So some water dwelling turtles,
Speaker 1: such as, for example, the Fitzroy River turtle, use a
Speaker 1: anal respiration or I guess I should be saying more
Speaker 1: accurately cloacal respiration. Yeah, honoring the distinction there, but uh,
Speaker 1: anal chloacle, whichever way you call it. They breathe out
Speaker 1: of the backside opening of their their digestive tract. Uh.
Speaker 1: It's sort of like having gills in your rectum. They
Speaker 1: suck water into the cloaca, absorb oxygen, and then expel
Speaker 1: the water that they've taken the oxygen out of. Huh.
Speaker 1: I wonder if the if the kappa would be capable
Speaker 1: of a similar feat. I don't know, I'm not considered it.
Speaker 1: All right, we're gonna take one more break and when
Speaker 1: we come back, we will touch on the topic of
Speaker 1: transient anuses. All right, we're back, Okay, Roberts. So we've
Speaker 1: discussed the evolutionary benefits of anuses, what creatures can do
Speaker 1: with their multi purpose annuses. But what's this idea that
Speaker 1: transient anuses some organisms can gain and lose their anus. Yeah.
Speaker 1: According to hay Now quote, there are several cases in
Speaker 1: which additional openings, connections between openings of different organ systems,
Speaker 1: and reductions of a through gut to a sack like
Speaker 1: gut can be identified. So there's a jaw worm called
Speaker 1: Haplognatia and it has an anal poor. And then there's
Speaker 1: a microscopic uh platozoan animal known as Limnognathia, And this
Speaker 1: is actually a fairly recently discovered organism, and it has
Speaker 1: a temporary opening that likely serves as an anus. But
Speaker 1: it's never been caught or at least as a as
Speaker 1: of the publication of this paper, it has never been
Speaker 1: caught in the act of defecating. Wow, So it can
Speaker 1: get an opening that appears and people suspect it's ananus,
Speaker 1: but they've never seen it poop. Right, And in both cases,
Speaker 1: these are on the creature's dorsal side, and H. Haynal.
Speaker 1: Points out that the secondary evolution of the anal openings
Speaker 1: this seems to be connected with the evolution of the
Speaker 1: of the extension of body length or overall size of
Speaker 1: the body. Okay, Well, this would go with the general
Speaker 1: idea that as organisms become larger and longer, they have
Speaker 1: more of an incentive to develop a through gut instead
Speaker 1: of just a sack gut. Yes, and thus the invention
Speaker 1: of the anus or the evolution of the anus. Okay,
Speaker 1: But I want to ask a kind of different question. Now,
Speaker 1: how did the anus come to be? We've established that
Speaker 1: the anus has evolved multiple times in different animal lineages,
Speaker 1: so it's sort of a convergent evolution. Different clades figured
Speaker 1: out over time that they want to that they want
Speaker 1: to have a back opening of the digestive system. And
Speaker 1: also that the anus evolved in animals as they grew larger.
Speaker 1: As your body grows larger, it makes less and less
Speaker 1: sense to have a sack shaped or bucket shaped digestive system. Um. So,
Speaker 1: so you've got all these advantages. That's how evolution pays
Speaker 1: for the through gut and the anus. But how did
Speaker 1: it happen? How did animals go from one gut opening
Speaker 1: to two? Well? To answer that question, I think we
Speaker 1: first want to go back to a paper that Hainal
Speaker 1: was one of the authors of in two thousand eight.
Speaker 1: So this was by Hanal and another researcher named Mark Q.
Speaker 1: Martin Day. I think we already mentioned him also, But yeah,
Speaker 1: the two of these published paper in Nature in two
Speaker 1: eight called a seal development indicates the independent evolution of
Speaker 1: the Bilaterian mouth and anus. All right, now that that
Speaker 1: paper title is lacking in a humor department, I would admit, yeah,
Speaker 1: they didn't. They had didn't have their pun game going yet.
Speaker 1: So what did they find? How do you get from
Speaker 1: one opening to two? Well, in previous thinking, and this
Speaker 1: was expressed in a Nature News article on the paper
Speaker 1: by a researcher named debt Leva Rent who's at the
Speaker 1: European Molecular Biology Laboratory in Heidelberg, it doesn't make sense
Speaker 1: for a new hole on the opposite end of the
Speaker 1: body from the mouth to just appear, so instead a
Speaker 1: Rent and others believed that over time what happened is
Speaker 1: the mouth elongated and eventually separated into two mouths more
Speaker 1: side by side connecting to the same digestive sack, So
Speaker 1: you wouldn't have a one way through gut, yet you'd
Speaker 1: have sort of a U shaped digestive sack with two mouths. Okay,
Speaker 1: so the ideas imagine an alien species eats through its mouth,
Speaker 1: digest and then poops at its mouth, and then it
Speaker 1: evolves to where it just has two mouths, the pooping
Speaker 1: mouth and the eating mouth. Yeah, exactly. So you've got
Speaker 1: to all purpose mouths that go both ways, and this
Speaker 1: evolves over time to a through gut that goes one way.
Speaker 1: And you know, once you have these two mouth openings,
Speaker 1: one of them could sort of migrate back over time
Speaker 1: and go down to the bottom of the organism, developed
Speaker 1: different specialization and eventually become an anus. Of course, we
Speaker 1: do have some organisms where they still have that essential
Speaker 1: you shape, uh say, say snails and slugs. Slugs even
Speaker 1: though they have no shell, evolved from shelled snails and
Speaker 1: therefore they still have the front loaded defecation model. Oh
Speaker 1: but deem know if in their case, is it just
Speaker 1: two mouths and it goes either way or is it
Speaker 1: a one way system? I believe it is a one
Speaker 1: way system. Yes, okay, I'm thinking back to pass slug
Speaker 1: and snail research. All right. Uh, so here's where Hanal
Speaker 1: and Martindale disagreed. So they so that that was the
Speaker 1: old view, right, that you'd have two mouths and eventually
Speaker 1: the two mouths became a mouth and an anus differently specialized,
Speaker 1: but Hanal and Martindale disagreed. They studied an organism called
Speaker 1: convolo taloba longefic euro, which is a flat worm with
Speaker 1: this kind of U shaped two gut or two mouth gut,
Speaker 1: and they compared it to worms with a one way
Speaker 1: gut containing a mouth and an anus. Now, earlier we
Speaker 1: mentioned that there are genes associated with the presence of
Speaker 1: an anus, right, Uh, there were the two genes we
Speaker 1: mentioned earlier. Now, when those get expressed, the body is
Speaker 1: usually building anal tissue. Well, in this earlier case from
Speaker 1: two thousand eight, Hanal and Martindale discovered that longer Ficura
Speaker 1: expressed mouth building genes, not anal or hind gut building
Speaker 1: genes when building its two mouths. So both of those
Speaker 1: genes were genetically reading as mouths or both of those mouths. Sorry,
Speaker 1: we're genetically reading his mouths. But but the longer ficure
Speaker 1: did express hindgut or anal building genes found in other
Speaker 1: species at the rear end of its body. And this
Speaker 1: suggests that a mouth did not turn into an anus,
Speaker 1: but the anus developed from some other structure being expressed
Speaker 1: at the rear end of the animal. So if it
Speaker 1: wasn't a mouth that turned into an anus, what is
Speaker 1: this structure or tissue at the rear end of the
Speaker 1: animal that could give rise to the development of an anus.
Speaker 1: And they thought, what about sexual tissue exactly? So this
Speaker 1: brings us back to the two fifteen paper by Hano
Speaker 1: and Martin Duran, and all of this relates to something
Speaker 1: known as the gonopour. This is an opening that releases sperm.
Speaker 1: In the Aceila class of simple or at least evolutionarily
Speaker 1: simple invertebrates, they have no through gut, no circulatory system,
Speaker 1: no respiratory system, and no anus. And the researchers think
Speaker 1: that the origin of the gnipur may be linked to
Speaker 1: the origin of the anus. Yeah, going back to that
Speaker 1: point about the genes, they say the gene expression of
Speaker 1: the seal orthologues of Brachii and the caudal c d
Speaker 1: X gene c d X in the posterior male gonopore,
Speaker 1: meaning the male sex organ at the back of these
Speaker 1: little organisms. It suggests that instead there is quote an
Speaker 1: evolutionary relationship between the bilaterryan hindgut and the acal gonopre.
Speaker 1: So they're looking at the way genes are expressed and
Speaker 1: saying like, there there appears to be a genetic to
Speaker 1: tissue link between this sex organ in this very simple
Speaker 1: multicellular organism and what eventually turns into the anus in
Speaker 1: more complex creatures that have an anus. But they admit
Speaker 1: in their paper that this is not a lock. It's
Speaker 1: not like we know exactly where the anus came from
Speaker 1: or that it's linked to the secial gonopre. They say
Speaker 1: it's still vague, quote how the acal gonop or should
Speaker 1: be related to the bilaterryan hindgut. A possible scenario, they write,
Speaker 1: could be the connection of the male reproductive organ system
Speaker 1: to the bilatery in digestive tract forming back to the cloaca.
Speaker 1: So so you'd get a cloaca because remember, as we
Speaker 1: said earlier, the cloaca combines a hole that deals with reproduction,
Speaker 1: It deals with excretion of liquid waste, and excretion of
Speaker 1: solid waste. It puts it all in one hole. So
Speaker 1: they're saying, what if what happened is you got this, uh,
Speaker 1: you know, this ancient double duty hole that became a cloaca,
Speaker 1: And then they say, quote, this would thus provide an
Speaker 1: alternative hypothesis which would connect first the male reproductive system
Speaker 1: with the gut and later with the female reproductive system. Alright,
Speaker 1: So if I'm understanding this argument correctly, something like the
Speaker 1: ganabar is an arcade serves as an archaic body opening. Yes,
Speaker 1: this primitive sex organ that we think something like it
Speaker 1: was present in our way way distant, and sters with
Speaker 1: that had bilateral symmetry, and as such it's something of
Speaker 1: not only a primitive sex organ, it's sort of a protoanus. Yes,
Speaker 1: it becomes the proto anus, which eventually joins together the
Speaker 1: reproductive and the digestive tract, and then over time, in
Speaker 1: much later organisms, those things can separate again. In two
Speaker 1: thousand fifteen, when this paper came out of the BBC
Speaker 1: talked to Hainal and he had this wonderful quote that
Speaker 1: he shared. Our own hypothesis is that the anal opening
Speaker 1: has some evolutionary connection to the male ghanipour. This of
Speaker 1: course makes the whole subject even more delicate, But this
Speaker 1: is how nature is. Nature does not care about taboos
Speaker 1: in human society. Look at him flout in those taboos. Yeah. Yeah,
Speaker 1: and it's you know, it's just another example of how
Speaker 1: if we ignore the anus, we do ourselves a disservice,
Speaker 1: in this case, in the realm of evolutionary biology. Yeah,
Speaker 1: don't don't let social morays keep you from studying ancient anus.
Speaker 1: Is exactly so. I I hope at the end of
Speaker 1: this episode everyone does have a new respect for the anus,
Speaker 1: and new respect for the development of the anus and
Speaker 1: how we we got to the point that we have them.
Speaker 1: Because unless you had some sort of magical idea in
Speaker 1: your head that you know, a fallen Titan brought the
Speaker 1: Promethean anus to the people of Earth and and and
Speaker 1: thus relieve them of their uh, their dire constipation, you
Speaker 1: know it had to come from somewhere. And I think
Speaker 1: part of that whole like taboo aspect of the anis
Speaker 1: don't think about the anus. It makes us often not
Speaker 1: question where it came from and how it developed over time. Well. Also,
Speaker 1: one thing you will hear from doctors and proctologists is uh,
Speaker 1: you know, you you might want to pay attention to
Speaker 1: your anus. You might want to think about it. Like
Speaker 1: some anal cancers can be caught early if you pay
Speaker 1: attention to it. Also, one thing I randomly came across
Speaker 1: while we were preparing for this episode. Apparently you shouldn't
Speaker 1: sit on the toilet for a really long time. Doctors said, don't.
Speaker 1: Don't just sit there on your phone for an hour.
Speaker 1: I know people do that now sometimes phone the sun
Speaker 1: games are better than ever before, so it's understand bole.
Speaker 1: But apparently that's not good for your anus. Okay, So
Speaker 1: if you are listening to this podcast right now on
Speaker 1: the toilet, and you have listened to the entire episode
Speaker 1: on the toilet, it's probably time to move. Can I
Speaker 1: add one more thing about the research process here? While
Speaker 1: we were reading, uh, you know, I was looking for
Speaker 1: good scientific articles about the anus, uh, And one thing
Speaker 1: I came across was this article full of obvious lies
Speaker 1: about how brown recluse spiders make nests in the human anus.
Speaker 1: It's not true, but I laughed a very hard. I'm
Speaker 1: not sure what prompted the writing of such a thing.
Speaker 1: I ran across a few things that made me giggle.
Speaker 1: One in particular, though, I saw one of these questions sites.
Speaker 1: I forget which one it was, but it's the one
Speaker 1: where you click on the answer and like it slides,
Speaker 1: you click on the question and it slides over and
Speaker 1: gives you an answer. It's also users submitted. Oh boy, Yeah,
Speaker 1: some good answers of it. Yeah. The question was do
Speaker 1: butterflies have anuses? And the answer was yes, they have
Speaker 1: the second largest on Earth. I do not the leave
Speaker 1: that is is accurate, but it it made me laugh.
Speaker 1: Oh man, they have the second largest on Earth and
Speaker 1: it's often colonized by brown recluse nests, probably according to
Speaker 1: you know, user generated scientific knowledge. So yeah, hopefully you're
Speaker 1: leaving this episode more knowledgeable of the anus uh than
Speaker 1: you were when you came in. Yeah, the anus. It's
Speaker 1: scientifically interesting, it's useful. You should appreciate it. All right,
Speaker 1: As we uh reach the posterior end of the podcast,
Speaker 1: we should drive home that. Hey, if you want to
Speaker 1: check out more episodes of Stuff to Blow Your Mind,
Speaker 1: if you want to explore some blog posts and find
Speaker 1: links to our very social media accounts, head on over
Speaker 1: to stuff to Blow your Mind dot com. Big thanks
Speaker 1: as always to our audio producers Alex Williams and Tarry Harrison.
Speaker 1: And if you want to get in touch with us
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Speaker 1: any other, or to let us know a topic you'd
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