Speaker 1: Welcome to Stuff to Blow Your Mind production of My
Speaker 1: Heart Radio. Hey you welcome to Stuff to Blow your Mind.
Speaker 1: My name is Robert Lamb and I'm Joe McCormick. And
Speaker 1: for the next few episodes we're going to be doing
Speaker 1: a series on a symmetry. And to introduce this series,
Speaker 1: I wanted to talk a little bit about a favorite
Speaker 1: animal of ours, the nar wall. Yes, the what is it,
Speaker 1: the corpse whale um of of the ocean, the unicorn
Speaker 1: of the sea. Right, yeah, so corpse whale. That's literally
Speaker 1: what its name means, whale of course wall, but nar
Speaker 1: meaning corpse. So yeah, it's like a dead body whale,
Speaker 1: having to do with its gray and modeled appearance as
Speaker 1: it sort of floats around near the top of the water.
Speaker 1: But the more famous feature of this whale, apart from
Speaker 1: looking like a corpse, is its horn or tusk or
Speaker 1: we can dispute what's the best word to use for
Speaker 1: it here, but yeah, as you say, it is the
Speaker 1: unicorn of the polar seas. So the nor wall is
Speaker 1: a medium sized Arctic marine mammal in the suborder of
Speaker 1: toothed whales or Odonto ceti. And it is immediately recognizable
Speaker 1: because most males of the nar walls, and occasionally some
Speaker 1: females as well, possess a giant spike or tusk growing
Speaker 1: straight out of their faces. And this tusk can grow
Speaker 1: absurdly long, up to about three meters or ten feet,
Speaker 1: and the orientation of this tusk looks very unusual compared
Speaker 1: to most other mammals. So you think about other mammals
Speaker 1: with horns or tusks. Uh, you might think about bo
Speaker 1: vines in which the horns rise up off the top
Speaker 1: of the head, or you might think about the rhinoceros
Speaker 1: where it points up from the end of the snouts
Speaker 1: kind of you know, up from the ground. Or you
Speaker 1: might think about the tusks of a bore an elephant
Speaker 1: kind of coming out of the mouth at an angle.
Speaker 1: But but no, in the In the narwhall, you have
Speaker 1: a whales body, which again is a sort of modeled
Speaker 1: gray tube that can grow about four to five meters
Speaker 1: long in adulthood, and then the tusk just juts straight
Speaker 1: out of the face, adding another three ms or so
Speaker 1: or up to another three ms or so in length.
Speaker 1: So when the tusk is present, the animal is sort
Speaker 1: of shaped like a dart. Or like a spear. Now,
Speaker 1: when we've talked about in Our Walls before, I think,
Speaker 1: especially in our episodes on the unicorn legend, uh, we
Speaker 1: we talked a lot about the theories behind the origin
Speaker 1: and the purpose of the tusk. We're not going to
Speaker 1: completely rehash that discussion here, though, I did want to
Speaker 1: note a development which was in a more recent paper
Speaker 1: I came across addressing the biological function of the tusk.
Speaker 1: So a long running question for marine biologists who study
Speaker 1: the nar wall is why this giant tusk it's it
Speaker 1: looks very unwieldy. What is it for? What is the
Speaker 1: evolutionary justification? And this can be difficult to study because
Speaker 1: it is not a trivial task to go out and
Speaker 1: just observed in our walls. In the wild, not only
Speaker 1: do they live underwater, but they live under the Arctic ice.
Speaker 1: So they remain veiled in a great deal of mystery.
Speaker 1: But we're not without some clues. And I guess the
Speaker 1: place to start is that the tusk looks so threatening
Speaker 1: to the naive human brain that we immediately want to
Speaker 1: say it is a weapon, right, you know, it is
Speaker 1: a spear, It is a dark that That's what I
Speaker 1: without even thinking about it compared the animal too, right, right,
Speaker 1: you think of it being some sort of a javelin
Speaker 1: or spear um harpoon on the front of this, uh,
Speaker 1: this whale that it's using to to skewer things, or
Speaker 1: that it's using this to sort of fence with other whales. Yeah,
Speaker 1: so you think it must be for you know, stabbing
Speaker 1: sharks or skewering fish prey or something. Though it's funny
Speaker 1: that people think, oh, yeah, it's for for skewering fish
Speaker 1: that they're going to eat. But if that were true,
Speaker 1: wouldn't that be a little awkward? Like how would it
Speaker 1: get the fish to its mouth after that? Like you
Speaker 1: would normally you don't need a stab and then eat.
Speaker 1: If you're a whale, you just eat, You just bite
Speaker 1: and then swallow. Anyway, there have been some accounts of
Speaker 1: what appeared to be various offensive uses of the tusk,
Speaker 1: but these might be coincidental or secondary behaviors. And then
Speaker 1: there are all other odd proposals, including things like stabbing
Speaker 1: through surface ice to create holes for breathing. Of course,
Speaker 1: remember the nar walls and air breathing mammal, but the
Speaker 1: fact that the tusk is hollow and filled with sensitive
Speaker 1: nerve endings, has led some researchers to believe it is
Speaker 1: a sensory organ and there there is some evidence that
Speaker 1: it can be used for gathering and even potentially for
Speaker 1: sharing information about the characteristics of seawater, maybe things like temperature, salinity,
Speaker 1: and so forth. However, one of the most important clues
Speaker 1: about the primary evolutionary justification of the tusk is the
Speaker 1: fact of sexual dimorphism. So the tusks are almost always
Speaker 1: found in males, and one obvious conclud lusion from this
Speaker 1: is that the tusk can't be necessary for survival, or
Speaker 1: else females would have them as well. Right, so it
Speaker 1: can't provide a major individual survival advantage, or else you'd
Speaker 1: expect all individuals to have them, or we would at
Speaker 1: least observe, uh, you know, the the whales that have
Speaker 1: them out competing the other one the ones that don't
Speaker 1: have them in survival, which is not the case. So
Speaker 1: one of the leading theories then is that it's a
Speaker 1: sexually selected trade. It's a body feature without a major
Speaker 1: role in survival, which grows very prominent in males because
Speaker 1: it increases reproductive success, maybe by being more appealing to
Speaker 1: female in our walls, or maybe by causing rival males
Speaker 1: to stay away and so forth and anyway. As so,
Speaker 1: the recent paper I found was one by Graham at
Speaker 1: All published in Biology Letters called the longer the Better
Speaker 1: evidence that narwhal tusks are sexually selected. This was from
Speaker 1: and of course this paper acknowledges that it's really difficult
Speaker 1: to study nar walls in the wild to figure out
Speaker 1: what the tusk is for, so instead it asks if
Speaker 1: we can infer anything about tusk function from examining the
Speaker 1: natural variation in narwhal tusk measurements that have been taken
Speaker 1: over the course of the last thirty five years. And
Speaker 1: so their sample comprised two D forty five individual adult males,
Speaker 1: and based on these measurements, the authors conclude that the
Speaker 1: evidence does suggest the primary driver of tusk evolution is
Speaker 1: sexual selection. Quote. By combining our results on tusk scaling
Speaker 1: with known material properties of the tusk, we suggest that
Speaker 1: the narwhal tusk is a sexually selected signal that is
Speaker 1: used during male male contests. So how would you conclude this? Well,
Speaker 1: the tusk demonstrates a growth pattern known as hyper alimentary,
Speaker 1: which means a body feature that grows faster than the
Speaker 1: body as a whole. So, for example, most body features
Speaker 1: are roughly alometric. They're linearly allometrics. They grow in size
Speaker 1: proportional to the rest of the body. If your body
Speaker 1: is bigger overall, you probably also have longer shin bones
Speaker 1: and larger hands and so forth. Some features might be
Speaker 1: hypo allometric or you know, sublimetric, they grow less than
Speaker 1: the body as a whole. But narwhal tusks are hyper alometric.
Speaker 1: In the largest individuals, the tusks grow longer than simple
Speaker 1: linear scaling would predict. So they're not just big in
Speaker 1: proportion to the rest of the body, they're way bigger
Speaker 1: than that. There they just they get ridiculously huge. And
Speaker 1: so this is not proof, but it is characteristic of
Speaker 1: traits that are sexually selected. And the authors write in
Speaker 1: their conclusion quote, sexually selected signals used in mail mail
Speaker 1: competition are more likely to exhibit hyper elimetry when compared
Speaker 1: to other sexually selected traits. Because the information being signaled
Speaker 1: is simple, I am bigger than you. To convey this message,
Speaker 1: males exaggerate the size of their signals, which facilitate the
Speaker 1: detection of size discrepancies. Between individuals, reducing the likelihood of
Speaker 1: engaging in potentially dangerous fights, and they note that this
Speaker 1: could explain the so called tusking behavior that's been observed,
Speaker 1: where male narwhales sometimes appear to be crossing tusks are
Speaker 1: almost like dueling with their tusks um, which could actually
Speaker 1: be not a form of fighting, but a way for
Speaker 1: the animals to compare the size of their tusks in
Speaker 1: order to avoid a fight. So, in an interesting twist,
Speaker 1: it could be the case that our naive intuition that
Speaker 1: this tusk is a weapon is true in a sense,
Speaker 1: but it's a weapon designed specifically to look scary because
Speaker 1: it will discourage actual fighting between males and sexual competition
Speaker 1: most of the time. So it's you know, two rival
Speaker 1: males are are competing for a chance to mate, and
Speaker 1: one of them goes, wow, that that other one's tusk
Speaker 1: is absurdly long. No need to fight this out, my mistakes,
Speaker 1: see you later. Now. They say that the existing evidence
Speaker 1: sort of points us in this direction, but it's not conclusive.
Speaker 1: Their alternate explanations. Maybe the large tusk plays a role
Speaker 1: in mate choice itself. Maybe females prefer males with larger tusks,
Speaker 1: but they're in general, there's still just a lot we
Speaker 1: don't know about these animals, so so the book is
Speaker 1: not completely closed on this question. And it's also possible
Speaker 1: that the tusk has multiple secondary functions, for example, as
Speaker 1: a sensory organ like we talked about earlier. Though again,
Speaker 1: as I mentioned earlier, that those secondary functions can't be
Speaker 1: all that crucial for survival or we would see that,
Speaker 1: you know, we would see that playing out in nar
Speaker 1: whale populations, the ones with the tusks would be more
Speaker 1: likely to survive, and that's not what we find now.
Speaker 1: To bring it back to the reason I wanted to
Speaker 1: talk about narwhals in today's episode, you may remember one
Speaker 1: strange fact about the narwhal's tusk from our previous episodes
Speaker 1: where these animals came up, and it's that the normals
Speaker 1: tusk is not an external caratinous horn like that of
Speaker 1: the rhinoceros. Instead, it is a tooth. And I don't
Speaker 1: just mean it is made out of the same stuff
Speaker 1: as a tooth. It is literally a tooth. It is
Speaker 1: a tooth from the upper jaw that has been repurposed
Speaker 1: by evolution to grow into a tusk. By changing the
Speaker 1: orientation of growth so that it grows straight out forward forward,
Speaker 1: out of the jaw and then erupts from the flesh
Speaker 1: of the face. It literally grows through the flesh of
Speaker 1: the upper lip and then continues growing rapidly, and as
Speaker 1: we've seen, even hyper elemetrically. But here's what I've been
Speaker 1: getting hung up on. The nor Wals tusk is not
Speaker 1: only a tooth. In almost all cases, it is the
Speaker 1: left canine, the left maxillary canine tooth having erupted from
Speaker 1: the upper lip. And this is this is certainly something
Speaker 1: when you learn for the first time it does it
Speaker 1: does feel a little bit wrong. I mean, a number
Speaker 1: of these these factoids about the norwell perhaps feel a
Speaker 1: little wrong, you know, because ultimately it's just a far
Speaker 1: weirder and perhaps sillier animal than than most of us assumed.
Speaker 1: It is not silly, is deadly serious, but it does
Speaker 1: have one tooth just poking out of its lip for
Speaker 1: I don't know, ten feet. But you're not allowed to laugh,
Speaker 1: um so, But yeah, anyway, So, to quote from a
Speaker 1: paper from in the Anatomical Record by Nuilla at all quote,
Speaker 1: males usually exhibit an erupted tusk on the left side
Speaker 1: and an unerupted embedded tusk on the right. So it's
Speaker 1: got two of these teeth. It's got, you know, that's symmetrical.
Speaker 1: There's one on each side, except usually one just kind
Speaker 1: of grows a little bit and then stays inside the
Speaker 1: upper jaw and doesn't do anything, while the other one
Speaker 1: breaks through the skin and grows up to ten feet long.
Speaker 1: So that's what you usually see. But then the quote continues,
Speaker 1: whereas females usually have two embedded tusks, neither erupting. Other
Speaker 1: less common expressions of narwhal dentition include males with two tusks,
Speaker 1: males with two embedded tusks so neither one comes out,
Speaker 1: females with one erupted and one embedded tusk, and females
Speaker 1: with two erupted tusks. And I checked. I think there's
Speaker 1: only been one documented case of the ladder of the
Speaker 1: females with two tusks coming out. But the authors of
Speaker 1: this paper do extensive analysis to confirm that these are
Speaker 1: not horns, they are teeth, and they figure out exactly
Speaker 1: what teeth they are. They are the upper canines, and
Speaker 1: in almost all cases, the left upper canine. Now I
Speaker 1: don't know if I'm alone in this, but I am
Speaker 1: just as struck by the fact that the tusk is
Speaker 1: actually the left canine as I am about the fact
Speaker 1: that it's a tooth to begin with. Why the left canine,
Speaker 1: As the paper mentions, narwhal's occasionally have two erupted tusks,
Speaker 1: two tusks of about the same length coming out to
Speaker 1: other It's rare, but you find some like that, And
Speaker 1: if you see pictures of the narwhals with two tusks,
Speaker 1: they look much more appropriate to the preferences of nature.
Speaker 1: You can look up images of this online. In fact,
Speaker 1: even though they're much more rare in the wild. Uh.
Speaker 1: A lot of the images of narwhal skulls have two tusks.
Speaker 1: I guess because the rare ones get photographed more often. Well,
Speaker 1: I mean, I guess. On one hand, the left handed
Speaker 1: side is the sinister side the sinstral side. So if
Speaker 1: you're going to have a crazy, super long tooth emerged
Speaker 1: from your face and maybe the sinister side makes sense, well,
Speaker 1: that's just your twisted mind working. It's it's fancy. I mean, no,
Speaker 1: come on, like the two tusks, they look more like
Speaker 1: something that you would just buy intuition expect to find
Speaker 1: in the ocean, much more so than the common one
Speaker 1: tusk skull, which when I see it, I mean, it
Speaker 1: is beautiful, but it also it looks unbalanced and wrong. Though.
Speaker 1: I will say that the two tusks or wall, if
Speaker 1: you look up images of specimens of this creature like
Speaker 1: this one is perplexing as well because it kind of
Speaker 1: it doesn't form um. They're not perfectly parallel to each other.
Speaker 1: It creates kind of a V shape that is a
Speaker 1: little confusing and certainly makes you lean more into possibilities. Yeah,
Speaker 1: that this is not about stabbing or using these uh
Speaker 1: these tusks for some sort of a a physical practical use,
Speaker 1: but something else like that they look more like communications
Speaker 1: array when you see two of them as opposed to
Speaker 1: just one. Well, yeah, I think having two of them
Speaker 1: even further highlights that these are obviously not practically useful
Speaker 1: for something like like catching prey or eating you know,
Speaker 1: you just you look at that and it's like, how
Speaker 1: how's that going to work? And it's obviously they're not
Speaker 1: using it for that, at least not most of the time.
Speaker 1: I know. There are these little anecdotes of somebody saying
Speaker 1: that you know, they saw a nar wall like tap
Speaker 1: a fish with a tusk or something, so maybe, but
Speaker 1: that that clearly does not appear to be a prime
Speaker 1: very use of them. But I wanted to come back
Speaker 1: to the idea that it looks it looks wrong at
Speaker 1: least even though of course you know this is what
Speaker 1: evolution selected. It is, uh, it is right for something,
Speaker 1: it has a use, but it looks wrong to our brains,
Speaker 1: and so it causes you to ask the question, well,
Speaker 1: first of all, why is it that evolution drove the
Speaker 1: narwhall to be unbalanced in this way? And and second,
Speaker 1: why is it that my intuition tells me incorrectly that
Speaker 1: a long, single tusk should not emerge from the socket
Speaker 1: of the left maxillary canine, like if an animal has
Speaker 1: one tusk, it should come out of a hole right
Speaker 1: in the middle. And so this is going to be
Speaker 1: the beginning of a series of episodes. We're gonna do
Speaker 1: at least two maybe more. What we'll see, uh, but
Speaker 1: there will be on a symmetry in the animal world
Speaker 1: when an animal's left and right do not match. So
Speaker 1: in future episodes we will we will explore some theoretical
Speaker 1: questions about about embryonic developed meant and how animal asymmetry
Speaker 1: comes about. Uh, probably look at some crabs and other crustaceans.
Speaker 1: But today I think we're gonna we're gonna look especially
Speaker 1: at like whales and uh and other swimming creatures of
Speaker 1: the sea, UH, and just generally highlights some interesting examples
Speaker 1: of asymmetry in the natural world. Now, I think it's
Speaker 1: important to acknowledge at the beginning that the kind of
Speaker 1: symmetry or asymmetry we're talking about, the kind of symmetry
Speaker 1: we expect to see in animals is only one specific
Speaker 1: type of symmetry, called bilateral symmetry, and not all animals
Speaker 1: actually possess it, even in an approximate sense. So bilateral
Speaker 1: symmetry is actually a fairly restricted type of symmetry. There
Speaker 1: are three dimensions of space, and if you plot a
Speaker 1: human body on those three dimensions, you'll notice we are
Speaker 1: actually only symmetrical along one of those three axes. So
Speaker 1: on height, our head in our feet, of course, are
Speaker 1: not mirror images of each other. On depth, we're also
Speaker 1: not symmetrical. Our backs do not mirror our fronts. We
Speaker 1: don't have faces or butts on both sides. It's only
Speaker 1: across our width that you find approximate symmetry our left side.
Speaker 1: Roughly mirrors are right side. And in three dimensional space,
Speaker 1: the most perfectly symmetrical form is actually a sphere, since
Speaker 1: if you divide a sphere in half along any plane
Speaker 1: you want, no matter it's orientation, the two sides will match. Uh.
Speaker 1: And I hesitate because I'm about to make a generalization
Speaker 1: about geometry. I'm always afraid I'm gonna say something wrong there.
Speaker 1: But I tried to look this up and confirm it.
Speaker 1: I believe this is unique to the sphere, that all
Speaker 1: other three D shapes can be bisected in ways where
Speaker 1: the two halves may have equal volume but will not
Speaker 1: match an outline. But if you cut a sphere in half,
Speaker 1: it's always two perfect hemispheres, no matter what direction you
Speaker 1: cut from. And this actually connects to a passage in
Speaker 1: a book I came across by the mathematician Herman Vile
Speaker 1: called Symmetry from Princeton University Press in nineteen fifty two,
Speaker 1: and Vile is writing about about the history of association
Speaker 1: between symmetry in the geometric sense and the concept of beauty. Uh.
Speaker 1: You know, moral virtue, and perfection, and he writes quote
Speaker 1: because of their complete rotational symmetry, the circle in the
Speaker 1: plane and the sphere in space were considered by the
Speaker 1: Pythagoreans the most perfect geometric figures, and Aristotle ascribed spherical
Speaker 1: shape to the celestial bodies because any other would detract
Speaker 1: from their heavenly perfection. Now it's interesting, knowing what we
Speaker 1: know now about the cause of spherical objects in space,
Speaker 1: namely gravity, right that as as the mass of an
Speaker 1: object increases, it tends to become more and more perfectly spherical,
Speaker 1: with the I guess the end point of that being
Speaker 1: that a black hole theoretically is pretty much perfectly spherical,
Speaker 1: whereas smaller objects in space, because gravity is not as
Speaker 1: strong a force on the on the smoothing of their
Speaker 1: outer edges, they can have more irregular shapes. This is
Speaker 1: why you get irregular potato shaped comets and asteroids. But
Speaker 1: you know, you start getting up into planet size and
Speaker 1: you move closer and closer to spherical perfection. But anyway,
Speaker 1: Vile goes on to quote a poet named Anna Wickham,
Speaker 1: which was actually the pseudonym of a modernist poet named
Speaker 1: Edith Alice Mary Harper uh in connecting the idea of
Speaker 1: symmetry to God or the divine being, so Wickham rights quote, God,
Speaker 1: thou great symmetry, who put a biting lust in me?
Speaker 1: From whence my sorrow spring for all my frittered days
Speaker 1: that I have spent in shapeless ways, Give me one
Speaker 1: perfect thing, and then vile rights. Symmetry, as wide or
Speaker 1: as narrow as you may define its meaning, is one
Speaker 1: idea by which man, through the ages has tried to
Speaker 1: comprehend and create order. Beauty and perfection. And equating symmetry
Speaker 1: with beauty, goodness and perfection and even divinity can be
Speaker 1: found all throughout literature. I think of Blake's The Tiger.
Speaker 1: You know what immortal hander eye could frame thy fearful symmetry.
Speaker 1: I guess it makes you want to say symmetry there,
Speaker 1: But this clearly is has not just a geometric meaning,
Speaker 1: where you will the two halves of the tiger do
Speaker 1: match one another roughly because it is an animal with
Speaker 1: bilateral symmetry, but that it means something more than that.
Speaker 1: Symmetry here is in some sense synonymous with greatness or divinity. Yeah,
Speaker 1: it's so that the tiger is is a perfect organism
Speaker 1: and Blake's I here, um yeah, And you know, I
Speaker 1: can be said about our obsession with with symmetry to
Speaker 1: the point where it's like a flawed obsession with it.
Speaker 1: Like we think that we want, say, perfectly symmetrical faces,
Speaker 1: when most faces are certainly not a symmetrical And if
Speaker 1: you take even famous and you know, often held up
Speaker 1: his beautiful faces and you do the trick of creating
Speaker 1: a symmetrical symmetrical face out of it, it's going to
Speaker 1: look wrong to your eyes. It may it may look
Speaker 1: very well look unnatural. Well. The the whole quest for
Speaker 1: symmetry in in aesthetic beauty um is one of those
Speaker 1: where it's like there's almost a kind of inverse uncanny valley.
Speaker 1: It seems like people's natural preferences or something that tends
Speaker 1: very close to symmetry. But then if you get right
Speaker 1: up to it and go to actual symmetry, it's like,
Speaker 1: oh no, no, no, that that looks all wrong. So
Speaker 1: you want to be like right in the zone where
Speaker 1: you're approaching symmetry, but not there. Yeah, though there, Certainly
Speaker 1: when you get into design it gets it gets weird
Speaker 1: because take airplanes, for example, airplanes tend to look best
Speaker 1: to our I when they are perfectly symmetrical, and then
Speaker 1: there are various reasons for that. And if you see
Speaker 1: an asymmetrical airplane, and there there have been certainly done
Speaker 1: some some very asymmetrical looking airplane designs uh uh here
Speaker 1: and there throughout aviation history, they do look incredibly wrong
Speaker 1: to the eye. Um, and that shouldn't fly. Yeah, Like
Speaker 1: how how how is that a good idea? But I
Speaker 1: mean it can work, it's just you you generally don't
Speaker 1: see it. Well, there's a different logic at work here.
Speaker 1: But that just sort of reminds me, incidentally of how
Speaker 1: I'm always surprised at the idea that a plane can
Speaker 1: continue to fly with one engine, you know, as like
Speaker 1: two jet engines, Like one engine fails, but it can
Speaker 1: keep flying with the other one, which makes that that
Speaker 1: doesn't seem right. It seems like, well, if only one
Speaker 1: engine is going, then shouldn't it just sort of like
Speaker 1: spin out of control? But no, I mean, as long
Speaker 1: as it's generating forward thrust, it can keep going usually Yeah.
Speaker 1: But anyway, so there's always a strong argument, you know,
Speaker 1: that much of what we find beautiful and good is
Speaker 1: biologically contingent, that it has at least in part to
Speaker 1: do with the kind of animals we are and how
Speaker 1: we relate to our environment. And of course we are
Speaker 1: part of that clade of animal all is known as biolateria.
Speaker 1: These these are the animals featuring bilateral symmetry during embryonic development. Now,
Speaker 1: of course this is always approximate, right, because while you're
Speaker 1: left and you're right in one sense do match. There
Speaker 1: are mirror images of each other, as you were just
Speaker 1: talking about, they're not perfect mirror images of each other,
Speaker 1: and especially on the inside, because we have say, asymmetric
Speaker 1: distribution of our internal organs, like the hearts more to
Speaker 1: one side, the livers more to the other, and so forth.
Speaker 1: But for it, for approximate terms, at least externally are
Speaker 1: left in our right sides match. But not all animals
Speaker 1: exhibit bilateral symmetry. Some have radial symmetry, meaning they grow
Speaker 1: in like repeated structures in a more spiral pattern. And
Speaker 1: there are some like sponges for example, those are animals,
Speaker 1: but they have no symmetry at all. But most animals,
Speaker 1: like humans, are bilaterally symmetrical. As as our bodies grow
Speaker 1: during embryonic development, they grow into basically mirrored halves on
Speaker 1: the left and right. But as we've already seen with
Speaker 1: the narwhale, some animals with bodies that mostly adhere to
Speaker 1: bilateral symmetry present with isolated but radical deviations, such as
Speaker 1: the nar walls left maxillary canine turning into a tusk
Speaker 1: almost as long as the animal itself. And this is
Speaker 1: not even the only example of fascinating a symmetry in
Speaker 1: the bodies of whales. Yeah, yeah, I want to get
Speaker 1: into something that we may have touched on this a
Speaker 1: little bit in the past, But despite the number of
Speaker 1: times the whales come up, I don't think we've really
Speaker 1: gotten into everything here. And it concerns the nature of
Speaker 1: the blowhole of of whales. Um Again, it just drives
Speaker 1: home just how mysterious and weird whales really are. Um
Speaker 1: So I want to start sort of back up before
Speaker 1: we get to where we're going with this discussion of blowholes,
Speaker 1: and start with the baileeen whale. You know, these are
Speaker 1: filter feeders, which, as Ryan Tucker Jones points out in
Speaker 1: red Leviathan uh the book about Soviet whaling, and interviewed
Speaker 1: uh Ryan last week on the show. It's really fun episode.
Speaker 1: If anyone wants to go back and listen to that.
Speaker 1: But there's he touches on just sort of how intertwined
Speaker 1: folk tale and legend and mythology is with our understanding
Speaker 1: of whales and misunderstanding of whales. I want to read
Speaker 1: this one passage quote. Ancient Greeks knew far less about
Speaker 1: whales than did the whaling Scandinavians. And as these word
Speaker 1: origins suggests, whales remain mysterious for Russians. For one thing,
Speaker 1: baleen whales methods of feeding perplexed them. Lacking teeth, the
Speaker 1: giants seemed to have no way of capturing prey. One
Speaker 1: tenth century Russian poem wondered whether wales quote the mother
Speaker 1: of all fish unquote fed themselves on quote heavenly fragrances.
Speaker 1: Direct experience was not necessarily more helpful. A medieval Western
Speaker 1: whaler who cut into a stranded whale stomach and found
Speaker 1: a gray mass of food included that it had fed
Speaker 1: on quote internal fog. That's great. So yes, whales are mysterious,
Speaker 1: and yeah, you can you can imagine if you really
Speaker 1: didn't know what was going on with the baleen whale,
Speaker 1: you might have trouble figuring out what's going on with
Speaker 1: their with with their mouths. What do they truly feed on? What?
Speaker 1: What is there enough of on the ocean for them
Speaker 1: to consume if they're not eating our ships and so forth.
Speaker 1: So anyway, if you look at a baleen whale and
Speaker 1: you look away from its mouth, you'll notice, yes, it
Speaker 1: has it has the blowholes. The blowhole falls well in
Speaker 1: line with bilateral anatomy. There are two of them, in
Speaker 1: kind of a V shape. And uh, and guess what
Speaker 1: if you weren't aware of this, here's your your fun Uh.
Speaker 1: Initial fact, they are repositioned nostrils. Imagining the evolutionary journey
Speaker 1: of those nose holes. Yes, because that's it is a journey,
Speaker 1: the nose holes traveling from the front of the snout
Speaker 1: all the way to the top of the head. I mean,
Speaker 1: we can imagine it. It's hard to imagine with our
Speaker 1: own face, but imagine it with a much bigger and
Speaker 1: more prolonged heading. So, as Raston and Roth point out
Speaker 1: in a paper published in the Journal of Anatomy, uh,
Speaker 1: the nasal passage in in these whales has rotated dorsally
Speaker 1: over the course of evolution and early in development cessation
Speaker 1: embryos have head morphologies that resemble other mammals, so you
Speaker 1: can actually look up embryo images and observe the nasal
Speaker 1: openings shift from the tip of the snout to the
Speaker 1: back of the head. If you want to see some
Speaker 1: some some easily accessed examples of this panda's thumb. A
Speaker 1: science blog has some great images of this in their
Speaker 1: post whale evolution The Blowhole, and I included these for
Speaker 1: you to look at here, Joe Um. If you if
Speaker 1: you look up this blog post, you'll see a trio
Speaker 1: of images with the embryo and there's a little white
Speaker 1: ero pointing out where the nostrils are and then where
Speaker 1: they travel to. It's just as you say, yeah, so
Speaker 1: earlier in development there there towards the front like they
Speaker 1: would be on the snout, and more like they would
Speaker 1: have been on the whales, on the whales land walking ancestors.
Speaker 1: But yeah, then as development moves on, they move up
Speaker 1: the head up to where I don't know, I don't
Speaker 1: know if this is the right terminology, but you might
Speaker 1: call like the forehead and then further and further. Yeah. Yeah,
Speaker 1: now it's it's obviously natural selection went this way. Um
Speaker 1: and it's easy to just sort of assume, okay, natural
Speaker 1: um evolution and natural selection and knows what it's doing.
Speaker 1: Who are we to question it? So it's easy to
Speaker 1: sort of overlook the basic question and all of this,
Speaker 1: why why does the nostril why did the nose open on?
Speaker 1: The nasal openings on these creatures wander over the course
Speaker 1: of their evolutionary development until they're on the top of
Speaker 1: the head. The basic answer is that while these creatures, yes,
Speaker 1: technically could still ether through their nostrils when they were
Speaker 1: positioned at the end of their snouts, they would have
Speaker 1: to lift their snouts out of the water to do so,
Speaker 1: and that requires more energy. If it's if you have
Speaker 1: the nose and the nasal openings positioned higher up on
Speaker 1: the snout, well, that's less lift required to do so,
Speaker 1: less energy, And so this is why we have that
Speaker 1: gradual movement of the nasal openings. And we have fossil
Speaker 1: evidence to back this up, and there are examples of
Speaker 1: this in that panda's thumb post as well. We for instance,
Speaker 1: we have fossil evidence of of Rhodo satus. This is
Speaker 1: a whale from roughly forty six million years ago, and
Speaker 1: this one offers a midpoint where we see the nasal opening,
Speaker 1: not at the end of the snout like we see
Speaker 1: in uh in really ancient UH whale ancestors, and also
Speaker 1: not at the top of the head like we see
Speaker 1: with modern whales, but that midpoint in between. No, I'm
Speaker 1: not speaking from an expert perspective here, but it seems
Speaker 1: very sgnificant that the that the blowhole eventually moves back
Speaker 1: to above where the eyes are right because you can
Speaker 1: imagine if a whale has to lift its eyes above
Speaker 1: the surface of the water every time it wants to breathe,
Speaker 1: or at least to point its eyes up away from
Speaker 1: where it's scanning. That's really it's not just taking energy.
Speaker 1: I mean, of course, the energetic investment is significant. Imagine
Speaker 1: if you had to like lift your head up every
Speaker 1: time you wanted to breathe, that would that would get
Speaker 1: tiring after a while. But also if you basically like
Speaker 1: couldn't see what was going on around you every time
Speaker 1: you had to take a breath, because you know, you
Speaker 1: need if you're living under the water, you want to
Speaker 1: keep your eyes fixed below the water, that's where the
Speaker 1: relevant stuff is going on. If you have to lift
Speaker 1: your eyes above the surface of the water. Uh you
Speaker 1: are you are losing sight of your surroundings exactly. Yeah,
Speaker 1: this is the world that the whale has adapted to
Speaker 1: the marine environment, and so over time it just gets
Speaker 1: to the point where as little of the animal as
Speaker 1: possible has to breach the surface of the water. Thank
Speaker 1: So that's basically the symmetrical whale blow hole. But here's
Speaker 1: the here's where it gets fun. This is where it
Speaker 1: gets asymmetrical because not all whales have two blow holes.
Speaker 1: Not all have those two nasal openings repurpose nasal openings
Speaker 1: on the top of their head. Toothed whales like the
Speaker 1: sperm whale, have just one. In fact, on the sperm whale,
Speaker 1: this single blowhole is at an angle on the left
Speaker 1: side of the head, and this causes it to blow
Speaker 1: forward and slightly to the left. So this can actually
Speaker 1: make sperm whale spouts harder to spot for humans, but
Speaker 1: also makes them easier to identify if you do spot them,
Speaker 1: because it's not just blasting straight up again, it's blasting
Speaker 1: forward and slightly to the left. But this, oh, this
Speaker 1: is this is putting me back in our wall tusk territory.
Speaker 1: So it has one nostril. So this is not just
Speaker 1: the nostrils have moved back along the center line of
Speaker 1: the skull of cross evolutionary time. The nostrils have actually
Speaker 1: split and one of them has moved back here and
Speaker 1: the other one, I don't know what it's doing something else, Yeah,
Speaker 1: the other one. The crazy thing is essentially the one
Speaker 1: is still open and active. The other one has sealed
Speaker 1: over the other. So the other nasal passage is there.
Speaker 1: It just does not connect to the surface anymore. Uh.
Speaker 1: That doesn't mean it's not doing anything. It has another purpose.
Speaker 1: So instead of connecting to the exterior of the animal,
Speaker 1: this other nasal passage supplies air to the phonic lips.
Speaker 1: The phonic lips produce clicks that travel the length of
Speaker 1: the nose and through the spermssete oregon of the head
Speaker 1: UH to aid in echolocation, or at least this is
Speaker 1: the most well accepted theory of what's going on here
Speaker 1: with the structure of the sperm whale's head. So echolocation
Speaker 1: is using sound waves in order to be able to
Speaker 1: UH image underwater to see where things are not with vision,
Speaker 1: but by producing clicks that like hit things in the
Speaker 1: water and then come back to the sensory organs on
Speaker 1: the whale so they can navigate their environment. And as specifically,
Speaker 1: I think nowhere prey is in the dark waters. Yeah,
Speaker 1: so if you dive in down to eat yourself some
Speaker 1: some squids, some giant squid maybe, uh, this is what
Speaker 1: you would you would use. Now. The evolutionary divergence likely
Speaker 1: occurred during the oligo scene. This would have been thirty
Speaker 1: three to twenty three million years ago, as toothed whales
Speaker 1: diverged from the ancestors of filter feeding whales, and this
Speaker 1: would totally make sense of predatory Toothed whales develop asymmetry
Speaker 1: related to their ability to echo locate because they need
Speaker 1: to use echolocation to hunt. Filter feeding whales do not
Speaker 1: have the same hunting needs, so their skulls remain balanced
Speaker 1: on the left and right. Um and uh rob I
Speaker 1: I thought this was a really interesting end and so
Speaker 1: I was looking at to support this. I found a
Speaker 1: paper on the cranial asymmetry of whales and this was
Speaker 1: by Ellen J. Coombs at all published in BMC Biology
Speaker 1: in and for this paper, making use of museum collections,
Speaker 1: the researchers compared whale skulls across time, reaching back to
Speaker 1: whale ancestors that lived fifty million years ago, and the
Speaker 1: author's write quote early ancestors of living whales had little
Speaker 1: cranial asymmetry and likely we're not able to echo locate
Speaker 1: our cho seats display high levels of asymmetry in the rostrum,
Speaker 1: potentially related to directional hearing, which is lost in early
Speaker 1: neo seats. The tax on, including the most recent common
Speaker 1: ancestor of living cetaceans naso facial asymmetry. So again, asymmetrical
Speaker 1: placement of the nostrils in the face becomes a significant
Speaker 1: feature of odonto cetti or toothed whales in the early
Speaker 1: oligo scene, just like you said, um reaching its highest
Speaker 1: levels in extant taxa. Separate evolutionary regimes are reconstructed for
Speaker 1: odonta seats living in acoustically complex environments, suggesting that these
Speaker 1: niches impose strong selective pressure on echolocation ability and thus
Speaker 1: increased cranial asymmetry. So, to summarize the skulls of toothed whales, specifically,
Speaker 1: the toothed ones just keep getting weirder and more asymmetrical
Speaker 1: over evolutionary time. Uh So, as the millions of years
Speaker 1: march on, the heads are getting less and less symmetrical,
Speaker 1: and this is especially true apparently in places where echolocation
Speaker 1: is more difficult due to environmental conditions. And what could
Speaker 1: be an example of this, Well, I was looking in
Speaker 1: the paper and this could be a coincidence, but they
Speaker 1: note that the nar wall has an unusually asymmetrical skull
Speaker 1: apart from the tusk that juts out on one side.
Speaker 1: So to read a quote from this paper with a
Speaker 1: bit of paraphrasing, uh, and remember the genus of the
Speaker 1: narwhall is Monodon one tooth, meaning Monodon monodon remains the
Speaker 1: most asymmetric skull in the sample, even when the rostrum
Speaker 1: is removed, which rules out the possibility that an asymmetric
Speaker 1: tusk and residual teeth may be skewing the overall result.
Speaker 1: Their unique sound repertoire narrow band structured in BS is
Speaker 1: ideal for projecting and receiving signals in icy shallow waters
Speaker 1: where the animals can detect targets in high levels of
Speaker 1: ambient noise and back scatter. So that's interesting. This could
Speaker 1: be a total coincidence. I would not want to suggest
Speaker 1: a causal connection, but I don't know. It's stuck out
Speaker 1: to me that nar walls have both strongly asymmetrical skulls,
Speaker 1: probably to aid in echolocation in a difficult environment, and
Speaker 1: also extreme asymmetrical teeth, producing these tusks, probably as a
Speaker 1: sexually selected trade. Yeah. I mean again, it just goes
Speaker 1: to show you just how weird whales are. Like, they're
Speaker 1: just so delightfully strange. Um and and again it's easy
Speaker 1: to it's easy to take it for granted if you don't,
Speaker 1: you don't lean in closely enough, you know. But as
Speaker 1: wonderful as as whale bodies are, they are not the
Speaker 1: only creatures in the sea with striking and fascinating imbalances
Speaker 1: between their left and right sides. Yeah, they're There are
Speaker 1: a number of fascinating examples we could turn to, and
Speaker 1: I don't know, we may we may come back to
Speaker 1: some more in future episodes. But one that really caught
Speaker 1: my attention is histeo tooth, the cock eyed squid. So
Speaker 1: this is another example of essentially divided attention and divided
Speaker 1: bodies in the deep ocean. Uh So, histeotoothis resides and
Speaker 1: the mesopelagic zone or the twilight zone of the ocean.
Speaker 1: And you can certainly think of this as a realm
Speaker 1: situated between different kingdoms of illumination because above the zone
Speaker 1: above the creatures of this realm, well, there there's the
Speaker 1: that there's the distant kingdom of light. Okay. Uh, there's
Speaker 1: a dim illumination coming down from the sun from the
Speaker 1: more sunlit portions of the ocean, and so silhouettes can
Speaker 1: be viewed of creatures above you against that that faint
Speaker 1: light below you. Well, there's the great darkness of the
Speaker 1: of the depths. But in that great dark darkness you'll
Speaker 1: glimpse or if you're a squid to mule, glimpse uh,
Speaker 1: sparkles and pulsations of bioluminescence here and there. Uh. And
Speaker 1: of course both of these sightings are important because they
Speaker 1: both have to do with organisms that may be a
Speaker 1: threat that maybe food, et cetera. Oh, well, this is
Speaker 1: so interesting because we know of lots of examples on
Speaker 1: the surface world, say like lots of herbivores on the
Speaker 1: this world that have one eye on each side of
Speaker 1: their head to try to provide a sort of you know,
Speaker 1: as wide field of you as possible, so you can
Speaker 1: see things approaching you. But this is a scenario where
Speaker 1: you might have a head structured like that, but you
Speaker 1: have totally different seeing needs on either side exactly. And
Speaker 1: so that's that's what we see with his teo toothis
Speaker 1: as as described by Thomas, Robinson and Johnson in their
Speaker 1: paper in the Philosophical Transactions of the Royal Society B
Speaker 1: it is a creature with quote two eyes for two purposes.
Speaker 1: So the squids two eyes here are dimorphic in size,
Speaker 1: shape and sometimes lens pigmentation. I included an image for
Speaker 1: you to look at here, Joe, and you can folks listening,
Speaker 1: and you can look up images this as well. Um,
Speaker 1: not all images of the squid are going to really
Speaker 1: capture this, but you'll find some that do. And it's
Speaker 1: it's very weird when you can see both eyes at
Speaker 1: once because one, uh, the image I was looking at.
Speaker 1: One eye is this great, big, kind of swollen looking
Speaker 1: eye that has kind of a yellowish or greenish tint
Speaker 1: to it. Um it may appear to be glowing the
Speaker 1: way that the light is catching it, and the other
Speaker 1: eye appears a smaller, flatter um. You know, almost looks
Speaker 1: like if you didn't know what you're looking at, you
Speaker 1: might think, oh, this poor squid, one of its eyes
Speaker 1: is inflamed and swollen, or one of its eyes has
Speaker 1: been severely wounded and doesn't look like it's it's operating anymore.
Speaker 1: But no, both eyes are operating. They're just pointed in
Speaker 1: different directions, and they have evolved to see differently depending
Speaker 1: on uh the environments that they're gazing into. It's beautiful,
Speaker 1: one looks like a setting gangrenous sun, and the other
Speaker 1: looks like a blueberry that's a little bit rotten. Right,
Speaker 1: So it's thought that the larger of the two eyes
Speaker 1: is honed to spot objects silhouetted against that dim light above,
Speaker 1: while the smaller eye specializes in spot the sources of
Speaker 1: bioluminescence in the darkness below, and the squid will actually
Speaker 1: position itself in a tail up position in order to
Speaker 1: maximize the split vision. Furthermore, the authors share that that
Speaker 1: the there that we do seem to have yellow pigments
Speaker 1: in the larger eye that may serve to break the
Speaker 1: counter illumination camouflage of their prey above. Counter illumination is
Speaker 1: an active camouflage method by by which lights are produced
Speaker 1: on the body to match background lights. So this would
Speaker 1: be used by a creature to blend in with the
Speaker 1: light above it, so the creatures below them don't so
Speaker 1: cleanly make out their dark bodies against the dim lights above. Oh,
Speaker 1: that's a good survival strategy. Yeah, you have lights on
Speaker 1: your underside to mimic the sunlight. Yeah. And so that
Speaker 1: the yellow pigments in this larger eye apparently helps to
Speaker 1: sort of break through some of that. So the theory
Speaker 1: is that we see dimorphic specializations in each eye as
Speaker 1: an adaptation to the split visual world. And this actually
Speaker 1: reminded me of of a bit from a Doctor Seuss book.
Speaker 1: I had trouble in getting to Solo Salu, where you
Speaker 1: have this character who's dealing with a bunch of threats
Speaker 1: and it goes So I said to myself, now, I'll
Speaker 1: just have to start to be twice as careful and
Speaker 1: be twice as smart. I'll watch out for trouble in
Speaker 1: front and back sections by aiming my eyeballs in different directions.
Speaker 1: And you have this character that's kind of like a
Speaker 1: little bear creature in his eyes are gazing off in
Speaker 1: different directions. But essentially like that's that's kind of what
Speaker 1: is going on with the with the cock eyed squid here.
Speaker 1: That's great. It is, so I was trying to imagine
Speaker 1: what scenario could give rise to something like this on
Speaker 1: a on a land dwelling herbivore. You know, so you
Speaker 1: have like a bo vine that's grazing what it needs
Speaker 1: have totally different types of eyes or vision on one
Speaker 1: side of the head. And I imagine what about some
Speaker 1: kind of bovine that lives on a tidally locked world,
Speaker 1: and it it lives at the terminator line. So it's
Speaker 1: I one eye needs to be like shielded because it's
Speaker 1: always facing towards the hot side of the planet, and
Speaker 1: the other eye needs to be very sensitive because it's
Speaker 1: always facing towards the dark side. I don't know, Oh
Speaker 1: that's interesting. Uh yeah, I mean I guess that would
Speaker 1: be the region that you a life form might be
Speaker 1: likely to to live in because you would have less
Speaker 1: of an extreme of heat or cold. But of course
Speaker 1: it would also be a like a chaotic region as well.
Speaker 1: You would have probably have a lot of climactic weather
Speaker 1: going on there. It's highly locked planet. It's probably not
Speaker 1: great for goats. But I was just trying to imagine,
Speaker 1: you know, that that's conceivably that's the kind of environment
Speaker 1: that might require some sort of drastic change in the
Speaker 1: positioning of the eyes and the specialization of the eyes. Um,
Speaker 1: I mean it I feel like we I mean, we're
Speaker 1: so hardwired for our surface world environment. It is difficult
Speaker 1: for us. It's it's a little challenging to put ourselves
Speaker 1: in the mindset and ultimately the the ocular world of
Speaker 1: something like a goat or something like a you know,
Speaker 1: a purely predatory cat or something much less, to put
Speaker 1: ourselves in the mind said, in the ocular world of
Speaker 1: the squid or or you know, to get into the
Speaker 1: sense worlds of whales and so forth. It's, uh, you know,
Speaker 1: it's it's it's a different environment altogether. And these environments,
Speaker 1: as we see from these examples, we've looked like they
Speaker 1: almost literally can pull us in in half. You know,
Speaker 1: they can they can change it. They can break whatever
Speaker 1: uh seeming symmetry was there in the body originally as
Speaker 1: it adapts, as it evolves to fit this environment over time.
Speaker 1: This raises a question that comes to my mind actually
Speaker 1: quite often, uh, when you think about, like if there
Speaker 1: were other clades of animals that that became very intelligent
Speaker 1: and had something like art what would what would they
Speaker 1: find beautiful and how would it be different from what
Speaker 1: we find beautiful based on on our brains and our biology. Yeah,
Speaker 1: but I maybe we're gonna have to call the first
Speaker 1: episode there. We will certainly be back with with more
Speaker 1: marvels of asymmetry, and in subsequent episodes we're gonna talk
Speaker 1: about uh, crabs and crustaceans, and I think we'll talk
Speaker 1: about snakes some probably come back to some fish and
Speaker 1: maybe some larger developmental theoretical concerns about where asymmetry comes from.
Speaker 1: In in the Kingdoms of Life. That's right. Uh. In
Speaker 1: the meantime, you can check out other episodes of Stuff
Speaker 1: to Blow Your Mind and the Stuff to Blow Your
Speaker 1: Mind podcast feed, which you can find wherever you get
Speaker 1: your podcast. Tuesdays and Thursdays are our core episodes. Uh.
Speaker 1: We have a short form artifact or monster fact on Wednesday,
Speaker 1: Little listener mail on Monday, and and then on Friday
Speaker 1: we do Weird How Cinema. That's our time to set
Speaker 1: aside most serious concerns and just talk about a strange film.
Speaker 1: Huge thanks as always to our excellent audio producer Seth
Speaker 1: Nicholas Johnson. If you would like to get in touch
Speaker 1: with us with feedback on this episode or any other,
Speaker 1: to suggest a topic for the future, or just to
Speaker 1: say hello, you can email us at contact. That's Stuff
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