You're Dead to Me - Hannah Fry and Dara Ó Briain introduce Curious Cases
Episode Date: October 8, 2025Hello, You’re Dead to me listener. Hannah Fry and Dara Ó Briain here, we thought you might like to know we have a brand-new series of Curious Cases. To start things off we look into the world of cr...abs and look into the possibility of us all eventually turning into crab like beings.So, we thought we’d claw our way into your feed, with our very first episode of the new series. Enjoy!
 Transcript
 Discussion  (0)
    
                                        This BBC podcast is supported by ads outside the UK.
                                         
                                        What makes a bank more than a bank?
                                         
                                        It's more than products, apps, ATMs.
                                         
                                        It's being there when you need them, with real people and real conversations.
                                         
                                        Let's face it, life gets real.
                                         
                                        RBC is the bank that we Canadians turn to for advice,
                                         
                                        because at the end of the day, that's what you deserve.
                                         
                                        A track record, not some trend.
                                         
    
                                        Your idea of banking that's personal happens here.
                                         
                                        RBC, ideas happen here.
                                         
                                        Are you after more fascinating conversations about the past?
                                         
                                        Well, History Extra might be just the podcast for you.
                                         
                                        Made by the team behind BBC History Magazine,
                                         
                                        the History Extra podcast brings you gripping historical stories,
                                         
                                        compelling interviews with the world's leading historians,
                                         
                                        and the real history behind your favorite films and TV shows.
                                         
    
                                        Coming up, we've got deep dives into Tudor lines,
                                         
                                        the Nazis on trial, the real story of the gunpowder plot, and plenty more.
                                         
                                        So to join us on our journey into the past, just search for the History Extra podcast wherever
                                         
                                        you listen to podcasts.
                                         
                                        Hello, Your Dead to Me fans. It is Hannah and Dahr here from Curious Cases.
                                         
                                        You might remember me from a past episode of You're Dead to Me, where I joined Greg Chenna.
                                         
                                        Have you been cheating on me on different podcasts?
                                         
                                        Yeah, I do other stuff.
                                         
    
                                        I mean, but the implication this is,
                                         
                                        that these people only ever listen to your dead to me
                                         
                                        and no other media in the last 20 years.
                                         
                                        And then we'll go, oh, who's that guy?
                                         
                                        Oh, he was once on an episode of You're Dead to me.
                                         
                                        And that is the only reason
                                         
                                        why I recognise this extremely distinctive Irish voice?
                                         
                                        It was a really good episode about Leonardo da Vinci.
                                         
    
                                        I was out strongly in McGrath.
                                         
                                        It was one of the live ones with a crowd, and it was very funny.
                                         
                                        What can you remember?
                                         
                                        That I trashed Leonardo da Vinci
                                         
                                        and then Greg Jenner went,
                                         
                                        he's one of my favourite people in history.
                                         
                                        He never built a weapon.
                                         
                                        He painted seven paintings.
                                         
    
                                        And he just basically bluffed his way around
                                         
                                        around the Renaissance.
                                         
                                        The man invented
                                         
                                        helicopters.
                                         
                                        He invented a
                                         
                                        fom-pom-bom-bomba machine
                                         
                                        like I mean
                                         
                                        no one's built
                                         
    
                                        and made it work.
                                         
                                        Right.
                                         
                                        Okay, so if you're still angry
                                         
                                        with Dara O'Brien
                                         
                                        from his appearance on
                                         
                                        you're dead to me
                                         
                                        the podcast
                                         
                                        where he trashed one of your heroes
                                         
    
                                        Greg Jenner's heroes
                                         
                                        Leonardo da Vinci
                                         
                                        then please forget about that
                                         
                                        please forgive him.
                                         
                                        Okay, fine.
                                         
                                        Okay, look, I've reformed
                                         
                                        the show doing this show
                                         
                                        yeah, I don't trash anything
                                         
    
                                        thing. And we wanted to share a little bit of what's coming up on
                                         
                                        Curious Cases. In fact, a little bit more than that. We're actually
                                         
                                        going to drop the entire first episode here for a while so you can
                                         
                                        have a listen to it. Oh, are we? Yeah, we are. That's what we're doing. On their
                                         
                                        feed. Yeah, I know. I'm sorry about that.
                                         
                                        You just finished the thing going, oh, I'm ready. I've walked a dog now. That's
                                         
                                        done. If you thought you hated Donor O'Brien before.
                                         
                                        I went to you get a full half hour about crabs.
                                         
    
                                        So I'm disrespectful to Leonardo da Vinci. I am no more
                                         
                                        positive about crabs.
                                         
                                        You know how you sort of keep track of your fans?
                                         
                                        Do you also keep track of your anti-fans?
                                         
                                        Oh, they're more, even more vocal.
                                         
                                        My fans are such, like I just people who go,
                                         
                                        oh, I think I saw you once, yeah, it's all right.
                                         
                                        Whereas, disliking me is for life.
                                         
    
                                        Like it's a proper passion that people have.
                                         
                                        Well, anyway, to both Dara's fans and non-fans
                                         
                                        and people who are ambivalent about either of us,
                                         
                                        enjoy the episode on crabs.
                                         
                                        And don't forget to search for Curious Case on BBC Sounds
                                         
                                        to stay up to date with the latest episodes
                                         
                                        and check out on our extensive back catalogue.
                                         
                                        You're about to listen to a brand new episode of Curious Cases.
                                         
    
                                        Shows are going to be released weekly,
                                         
                                        wherever you get your podcast.
                                         
                                        But if you're in the UK,
                                         
                                        you can listen to the latest episodes first on BBC Sounds.
                                         
                                        I'm Hannah Frye.
                                         
                                        And I'm Dara O'Brien.
                                         
                                        And this is Curious Cases.
                                         
                                        The show will we take your quirkiest questions
                                         
    
                                        your crunchiest conundrums.
                                         
                                        we solve them?
                                         
                                        With the power of science.
                                         
                                        I mean, do we always solve them?
                                         
                                        I mean, the hit rate's pretty low.
                                         
                                        But it is with science.
                                         
                                        It is with science.
                                         
                                        Here's an interesting thing I did recently.
                                         
    
                                        I did something with the Natural History Museum,
                                         
                                        just in a kind of standing in the room
                                         
                                        while they're doing proper work, like whatever.
                                         
                                        For a new exhibit that's running at the moment.
                                         
                                        But space, right?
                                         
                                        Is there life in outer space?
                                         
                                        But as part of it, I was nudging them,
                                         
                                        and they went for this,
                                         
    
                                        that they'd have a speculative bit at the end.
                                         
                                        they were thinking of doing this, where they would
                                         
                                        basically say, well, what might life be like
                                         
                                        under different gravitational conditions
                                         
                                        and different stars? Exactly, in different plans, what it might look like?
                                         
                                        So they kind of went, okay, what could be
                                         
                                        fairly safe to make a guess that an alien life might look like,
                                         
                                        because it's not going to be Chewbacca, right?
                                         
    
                                        You can't say that for sure.
                                         
                                        I'm fairly sure I can say.
                                         
                                        It's not all going to be what looks like a person in a suit.
                                         
                                        And so they have this kind of like, you know,
                                         
                                        nicely presented to kind of a vague sense of what these things might look like.
                                         
                                        And a lot of them look like paramecium.
                                         
                                        A lot of them look like, you know, very, very evolutionary, very kind of simple cell of life.
                                         
                                        Like, you're kind of going, okay, grand, that makes sense.
                                         
    
                                        But the only really recognisable thing was a crap.
                                         
                                        A crab?
                                         
                                        A crab.
                                         
                                        Yeah, yeah, that'd be a crap.
                                         
                                        No, there'll definitely be a crap.
                                         
                                        The most evolutionary, stable possible.
                                         
                                        It seems to be like a very evolutionary friendly thing, a crab.
                                         
                                        You're low.
                                         
    
                                        You're low.
                                         
                                        You're hard.
                                         
                                        You can walk sideways.
                                         
                                        Oh, look, no one's expecting that.
                                         
                                        That's the weird thing about it.
                                         
                                        No one is expecting, oh, where do you go?
                                         
                                        No idea.
                                         
                                        I'm looking at you. I'm looking at you.
                                         
    
                                        I'm looking at my crab eyes.
                                         
                                        I'm looking to stay on your right.
                                         
                                        No, I'm now going left.
                                         
                                        Yeah.
                                         
                                        Also, the crab eyes can move around.
                                         
                                        I mean, independent of the crab legs.
                                         
                                        I mean, we don't acclaim them enough.
                                         
                                        They're amazing.
                                         
    
                                        I think you're absolutely right.
                                         
                                        Which is why there's an excellent question about crab.
                                         
                                        Certainly is.
                                         
                                        Hello, we are Carston and Emily from Cornwall.
                                         
                                        And we're interested in the weird and wacky nature of evolution.
                                         
                                        We read about carcinisation, which is when non-crab organisms evolved to have crab-like bodies.
                                         
                                        Why have so many different species evolved into crabs?
                                         
                                        Does this mean that crabs are the ideal life form?
                                         
    
                                        And if so, could humans eventually become crabs?
                                         
                                        Okay, how cool do they sound?
                                         
                                        And also, I really like the fact that there is implicit in this
                                         
                                        a sense of these two young women going,
                                         
                                        will this happen in our own life time?
                                         
                                        What year are we talking?
                                         
                                        We're young and we're staring at our old future ahead of us,
                                         
                                        but it's part of it going to be a click-click-click-click.
                                         
    
                                        Are you going to get castanetting with our claws?
                                         
                                        2060.
                                         
                                        Yeah.
                                         
                                        Everything's crabs.
                                         
                                        There's a meme about this.
                                         
                                        I don't know if you've seen this.
                                         
                                        No, I haven't.
                                         
                                        All the people on the internet have been making jokes about how eventually everything's going to involve into crabs.
                                         
    
                                        There was Monterey Bay Aquarium, for example, you know, one of the most prestigious and respected marine institutions on the planet.
                                         
                                        They just posted a picture of some humans dancing and a crab in a corner with a party hat looking on at them saying, I was like them once.
                                         
                                        This is, you know, one of the most respected institutions in the world.
                                         
                                        the entire world, just posting a crab content meme with zero context.
                                         
                                        So we're basically saying this is a thing.
                                         
                                        I mean, look, we've got questions of plenty that we need to answer.
                                         
                                        And that is why we have got three brilliant guests who are going to help us get to the bottom of things.
                                         
                                        We have Matthew Wills, who is a professor of evolutionary paleobiology at Barth University.
                                         
    
                                        Joanna Wolfe, who is an evolutionary biologist affiliated with Harvard and UC Santa Barbara,
                                         
                                        and Ned Sissat Williams, who is the director of the Crabb Museum in Margate.
                                         
                                        Ned, everything evolving into crabs.
                                         
                                        Is this something people are aware of, do you think?
                                         
                                        Do they ask you about it in the museum?
                                         
                                        Yes.
                                         
                                        Yeah, people ask us about it probably every day.
                                         
                                        I've never quite been able to give a fully satisfactory answer to either myself or them.
                                         
    
                                        I think the thing is carcinisation, which is the thing that we're talking about,
                                         
                                        which is about when animals evolve into a crab-like form.
                                         
                                        that was memed quite heavily.
                                         
                                        It's not necessarily more of a thing
                                         
                                        of other convergent evolutions.
                                         
                                        It's just sort of won the PR game.
                                         
                                        It's a pretty good one, to be fair.
                                         
                                        Crabbs rule.
                                         
    
                                        Why wouldn't you want to evolve
                                         
                                        into a crab-like form?
                                         
                                        I mean, yes, there are various forms
                                         
                                        of convergent evolution,
                                         
                                        which is basically where
                                         
                                        evolutioning forces on different species
                                         
                                        will come with the same results.
                                         
                                        So they can claim it's part of a shared heritage,
                                         
    
                                        but just the environment has created.
                                         
                                        Our eyes and octopus eyes, for example,
                                         
                                        are a very good example of that, like whatever.
                                         
                                        But the idea that you get eyes,
                                         
                                        even though you don't have shared ancestors.
                                         
                                        Exactly, yeah, yeah.
                                         
                                        I mean, dolphins and sharks, one is a mammal,
                                         
                                        one of the fish, and yet they have shared fins and flippers
                                         
    
                                        and a similar kind of skin, like whatever.
                                         
                                        So it happens a lot.
                                         
                                        But as you say, there aren't memes about that.
                                         
                                        Let's be real, and I'm going to go on record
                                         
                                        and just say that crabs are weird and funny looking.
                                         
                                        And that is...
                                         
                                        Hot take from the crabby.
                                         
                                        I know, no.
                                         
    
                                        I mean, it's the fact.
                                         
                                        We've got it on one of our boards, in fact.
                                         
                                        But crabs are weird and funny looking, and yet they are part of the world in which we inhabit,
                                         
                                        and they are intriguing because of their weirdness, their spikiness, and their funny-lookingness.
                                         
                                        So why wouldn't you hinge a whole discourse about evolution on a crab?
                                         
                                        Joe, this is something you study extensively.
                                         
                                        You've a brilliantly title paper, How to Become a Crab, for example.
                                         
                                        Did you ever think your study would become, we'd get this much attention?
                                         
    
                                        I didn't.
                                         
                                        And I probably wouldn't have written it the way that I did.
                                         
                                        Had I known.
                                         
                                        I don't know if I would have called it
                                         
                                        how to become a crab
                                         
                                        because people can't become a crab.
                                         
                                        What is it that's so special
                                         
                                        about the evolution of crabs
                                         
    
                                        that has spawned all this?
                                         
                                        Well, I think like Ned said,
                                         
                                        it's actually just one example
                                         
                                        of many, many examples
                                         
                                        of convergent evolution
                                         
                                        across the tree of life.
                                         
                                        We should probably define
                                         
                                        what crabs are, right?
                                         
    
                                        Oh yeah, okay, Grant.
                                         
                                        I mean, I have a strong visual image,
                                         
                                        but I put it in a proper context.
                                         
                                        There's two groups
                                         
                                        that are each other's closest relatives.
                                         
                                        They're the true crabs and the false crabs.
                                         
                                        That's not a valued judgment.
                                         
                                        It's just basically...
                                         
    
                                        Sounds a bit judging.
                                         
                                        I'll be honest.
                                         
                                        It doesn't sound a bit.
                                         
                                        It's based on the taxonomy, which was named first.
                                         
                                        So true crabs are also called brachyura,
                                         
                                        and they represent about 8,000 living species.
                                         
                                        And those include groups like fiddler,
                                         
                                        Crabs, spider crabs, shore crabs, most of the things that you think look like a crab are within
                                         
    
                                        the true crabs. Then there's the false crabs, which the Latin name of that is Anamura.
                                         
                                        The false crabs are the closest relative of the true crabs. So they're not like human-level
                                         
                                        distant, but the common ancestor of those two is still almost 300 million years ago, which is
                                         
                                        older than the dinosaurs, right? So it is a long time ago that these two groups split. And yet,
                                         
                                        within the false crabs, these groups include things,
                                         
                                        and I'm sorry that the English names are so misleading.
                                         
                                        They include things like squat lobsters, which aren't a lobster.
                                         
                                        They have hermit crabs, which aren't really a crab.
                                         
    
                                        They have porcelain crabs, king crabs.
                                         
                                        None of this is a true crab.
                                         
                                        Hermic crabs are like my favorite crab, and they're not a crab.
                                         
                                        I know, right?
                                         
                                        A false crab.
                                         
                                        They're false crab.
                                         
                                        But still a crab, no.
                                         
                                        Exactly.
                                         
    
                                        Is it a subject to debate?
                                         
                                        What is a crab?
                                         
                                        Yes.
                                         
                                        Really?
                                         
                                        Hugely.
                                         
                                        I don't think we can neatly
                                         
                                        put things in boxes necessarily.
                                         
                                        I mean, I do agree with you
                                         
    
                                        that there are definitely
                                         
                                        two very distinct families,
                                         
                                        but I feel that there is some overlap.
                                         
                                        I'm just taking it personally
                                         
                                        that this is hermer crabs
                                         
                                        who are very much the collectible crabs
                                         
                                        on beautiful beaches
                                         
                                        that you go, look kids,
                                         
    
                                        look at this crab.
                                         
                                        And to know that I have lied all those times
                                         
                                        I said, look at this.
                                         
                                        I mean, if they're not crabs,
                                         
                                        what are they?
                                         
                                        Sorry, they're still crustaceans,
                                         
                                        but they're not.
                                         
                                        Well, they're like a false crab, if you will.
                                         
    
                                        So they're definitely stult crustaceans.
                                         
                                        They're decapod crustaceans.
                                         
                                        So that also includes a little further away lobsters and shrimps.
                                         
                                        The things that are officially lobsters and shrimp.
                                         
                                        Again, this is taxonomy.
                                         
                                        So this isn't necessarily describing what their morphology looks like, what they look like, as Ned said, can vary quite a lot.
                                         
                                        And that, I think, is kind of the crux of what is interesting in carcinization.
                                         
                                        because oftentimes there are things that you think look like a crab,
                                         
    
                                        but they're not closely related to other things.
                                         
                                        They don't have a shared ancestor with other things that also look like a crab.
                                         
                                        So the hermocrabs, though, I at least think of them as not looking like a crab
                                         
                                        because what we think a crab morphotype is is basically this sort of rounded, flattened carapace
                                         
                                        and also having the abdomen folded under the body.
                                         
                                        Now, in a hermit crab, usually you don't see the abdomen because it's in the shell, right?
                                         
                                        But they have a soft abdomen and it curls inside of the shell.
                                         
                                        If you took one out, it wouldn't just, like, be held completely under the body.
                                         
    
                                        I guess the equivalent of what it would be like is if you were permanently doing a stomach
                                         
                                        crunch forever, that's basically like what a crab's.
                                         
                                        Oh, okay.
                                         
                                        That's what I'm just like.
                                         
                                        Okay.
                                         
                                        That's certainly vivid.
                                         
                                        because I just think claws, claws and shell.
                                         
                                        Yeah, but a lobster has claws and shell.
                                         
    
                                        Well, actually, Matt, you've got a plastic lobster here in the studio with you.
                                         
                                        Here's a lobster.
                                         
                                        It's also got a claws and a shell,
                                         
                                        but it's got its abdomen stuck out behind the body.
                                         
                                        And this is great because animals with this kind of body plan
                                         
                                        can move around in three different ways.
                                         
                                        They can walk around on their walking legs.
                                         
                                        They can swim.
                                         
    
                                        They've got little all-like limbs on the abdomen,
                                         
                                        and they can sort of beat these in a rhythm
                                         
                                        and they glide along quite elegantly.
                                         
                                        But the killer thing they have
                                         
                                        is the ability to contract all of the muscles in the abdomen
                                         
                                        and the back end of a lobster and the back end of a shrimp
                                         
                                        is spayed out into this lovely tail fan.
                                         
                                        And when they do this, they shoot off backwards at high speed.
                                         
    
                                        Now, if you become a crab,
                                         
                                        if you bend the abdomen back down underneath this front part of the body,
                                         
                                        the cephalothorax, as it's called,
                                         
                                        then it makes you more compact and you can armour yourself
                                         
                                        but what you sacrifice is this
                                         
                                        it's called the caridoid escape reaction if you want to
                                         
                                        it's this ability to snap yourself
                                         
                                        and to shoot off backwards at a vast rate of...
                                         
    
                                        So you lose the...
                                         
                                        I can know anything ago, the yummy lobster tail.
                                         
                                        It is yummy, it's fabulous, yes.
                                         
                                        But you lose that.
                                         
                                        That is what is being folded underneath?
                                         
                                        Yes, yeah, that's right.
                                         
                                        Okay, fine.
                                         
                                        So Matt, what does it mean to say,
                                         
    
                                        when we say that,
                                         
                                        Crabbs have evolved five times.
                                         
                                        Biologists talk about what they call clades or monophyletic groups.
                                         
                                        And all that means is if you had a model of the tree of life in front of you,
                                         
                                        kind of made out of plastic.
                                         
                                        A monophyletic group is one that you can remove just by making one cut.
                                         
                                        So you get the ancestor and you get all of the descendants within that group.
                                         
                                        Now there are other groups that turn out to be what's called polyphyletic.
                                         
    
                                        And that's to say if you want to cut them out of the tree,
                                         
                                        you have to make several snips in several places
                                         
                                        but what that of course means is
                                         
                                        they've evolved independently
                                         
                                        more than once
                                         
                                        two three however many times
                                         
                                        and what if you see one on the desk in front of you
                                         
                                        you're going to call well that looks like a crab
                                         
    
                                        if you plot that across the tree
                                         
                                        you've got several instances of those
                                         
                                        evolving from things which are actually pretty crab like
                                         
                                        so you have to have all the sort of building blocks
                                         
                                        you have to already have the in order to make that
                                         
                                        so that the story has sort of become
                                         
                                        everything's evolving
                                         
                                        into crabs. And that doesn't mean that humans are evolving into crabs or trees are evolving
                                         
    
                                        into crabs. You have to have, you have to be in an environment where that's an advantage to you.
                                         
                                        And you also have to have, you know, you're also living around clefts in rocks and so forth
                                         
                                        such that be conquering down, becoming crab-like is an advantage. So it would be, the meme would
                                         
                                        be less popular, but more active was like many crab-like things are evolving into things that resemble
                                         
                                        crafts. It doesn't have the same ring. No, it doesn't.
                                         
                                        So we're not going to have one massive clamping arm like a fiddler crab.
                                         
                                        Yeah, not done.
                                         
                                        Give it 560 million more years and let's see.
                                         
    
                                        I mean, crabs have maintained their shape as well in general.
                                         
                                        So we've got a castanus, minus, a shore crab at the museum that we show kids
                                         
                                        and they wave around and drop all the time.
                                         
                                        And that's like a modern day crab.
                                         
                                        And it looks like a crab.
                                         
                                        But then we've also got a 90 million-year-old fossil of a crab, which looks still like a crab.
                                         
                                        So that's 90 million years
                                         
                                        That's not a particularly long time
                                         
    
                                        But then within 50 million years
                                         
                                        You've got like dog animals
                                         
                                        Going and becoming whales
                                         
                                        So evolution can happen really really quickly
                                         
                                        But despite all that
                                         
                                        There are some animals that have been like
                                         
                                        I am a crab and I'm going to stay as a crab
                                         
                                        Because what I've got going on is clearly working
                                         
    
                                        That kind of gets to the point though
                                         
                                        Actually that these independent evolutions
                                         
                                        Of this body plant
                                         
                                        Didn't all happen at the same time
                                         
                                        So in the true crabs
                                         
                                        They were, well, actually, probably the second oldest porcelain crabs,
                                         
                                        their fossil record suggests that they are older,
                                         
                                        even though they're not in the true crabs.
                                         
    
                                        So potentially those were actually the first.
                                         
                                        I know it's so ridiculous.
                                         
                                        I'm sorry, so now we've got pre-crabbs along the true crabs and the false crabs.
                                         
                                        And post-crabbs, and post-crabbs.
                                         
                                        Like on the table here in front of me, I've got a specimen of Renina-Ranina.
                                         
                                        And this was more crab-like.
                                         
                                        So we were talking about when we were looking at the lobster,
                                         
                                        about the abdomen being spayed out the back.
                                         
    
                                        Now, at one point in the fossil record,
                                         
                                        Renina, Renina, the frog crab,
                                         
                                        had its abdomen tucked more under,
                                         
                                        and now it's evolving its abdomen
                                         
                                        to being tucked out.
                                         
                                        So this is a kind of example of decarcinization.
                                         
                                        Although I would definitely add
                                         
                                        that it wasn't within that species, right?
                                         
    
                                        This happened over millions of years,
                                         
                                        so it was absolutely.
                                         
                                        To describe this, to describe this for the listeners,
                                         
                                        I mean, it's sort of like lobster
                                         
                                        had a child with an armadillo, you know?
                                         
                                        And, you know what I mean?
                                         
                                        Oh, no, that side's very, very scorpion.
                                         
                                        Yeah, that's his bumhole right there at the bottom.
                                         
    
                                        Delightful.
                                         
                                        I mean, it's quite beautiful in a weird way,
                                         
                                        but it's sort of halfway between a crab and a lobster.
                                         
                                        Yeah, yeah, yeah, yeah.
                                         
                                        There's less eating that one.
                                         
                                        There is a lot less eating.
                                         
                                        Actually, I think people eat that species.
                                         
                                        Yeah, very much so, very much so.
                                         
    
                                        Oh, people will eat a lot of things.
                                         
                                        People are really amazing.
                                         
                                        Don't make judgments based on that.
                                         
                                        Yeah, so it's a messier situation,
                                         
                                        but the fact remains,
                                         
                                        they're just,
                                         
                                        something about this shape,
                                         
                                        the structure is very good for this environment,
                                         
    
                                        that the environment is.
                                         
                                        Well, you know,
                                         
                                        crabs live in a lot of different environments, though.
                                         
                                        They live in every ocean, pretty much.
                                         
                                        They also live at every depth.
                                         
                                        So some species that are crab-like
                                         
                                        are down in hydrothermal vents,
                                         
                                        you know,
                                         
    
                                        thousands of meters below the surface, crab-like and non-crab-like live at the shore.
                                         
                                        And even on land, some of them even go up trees.
                                         
                                        So what is this environment, right?
                                         
                                        What environment is it that they're adapted to?
                                         
                                        And I honestly do not know the answer.
                                         
                                        Here's the question though, Matt.
                                         
                                        So if things evolve into crabs and then stay as crabs and lots of environments favor the crab shape,
                                         
                                        in the limit, will everything become crabs?
                                         
    
                                        I want some truth to this meme somewhere.
                                         
                                        If you gave infinite time
                                         
                                        No
                                         
                                        All right, damn I agree
                                         
                                        Was there a point
                                         
                                        Where we didn't really understand
                                         
                                        Convergent evolution
                                         
                                        And thought that this type of crab
                                         
    
                                        Was actually directly descended from this type of crab
                                         
                                        Did we get it wrong initially?
                                         
                                        So before people had molecules
                                         
                                        They could sequence and look at
                                         
                                        and Joe's push the bounds of this.
                                         
                                        What you had to do is you had to do basically comparative anatomy.
                                         
                                        You had to look at your animals under a microscope.
                                         
                                        You had to code their characteristics,
                                         
    
                                        and you had to try to produce a phylogenetic tree using that sort of information.
                                         
                                        I think the phylogeny of anamurans and brachyrians was,
                                         
                                        at least in terms of the two major groups.
                                         
                                        I think that was fairly solid from morphology.
                                         
                                        But there are other examples where that's not
                                         
                                        in the case, and perhaps the best known one, is the tree of mammals.
                                         
                                        So it used to be thought, go back about 20 years, 25 years ago, we kind of thought
                                         
                                        when you knew how the major groups of mammals were related.
                                         
    
                                        And then a bombshell dropped because people started doing phylogenomic analyses
                                         
                                        based on lots and lots of genes, and they found that the whole tree of mammals completely
                                         
                                        changed.
                                         
                                        So it turns out, for example, that we had a group called ungulates, so things that had hooves,
                                         
                                        cows and horses and so on.
                                         
                                        It turns out that horses
                                         
                                        are more closely related to bats.
                                         
                                        It turns that...
                                         
    
                                        I'm sorry, why?
                                         
                                        It's absolutely true.
                                         
                                        Elephants and sirenians and...
                                         
                                        I'm sorry, cyrenians and we're having it.
                                         
                                        These are manatees and so on.
                                         
                                        Great. Does that say my...
                                         
                                        These are animals that are so different in their ecology,
                                         
                                        in how they look, their morphology, their anatomy,
                                         
    
                                        their size, everything about them.
                                         
                                        There's absolutely no way
                                         
                                        that you would unite them into a group
                                         
                                        unless you knew about their genomics.
                                         
                                        The minute we started to do DNA testing,
                                         
                                        we just found that there were a lot more cousins in the world,
                                         
                                        a lot more related animals than we'd previously thought.
                                         
                                        Well, at least the natural groups, the clades,
                                         
    
                                        turn out to be things which the comparative anatomists just couldn't see.
                                         
                                        And this wasn't because they were being slapdash,
                                         
                                        that this is really painstaking comparative work going on for decades and decades.
                                         
                                        It's very similar to what happened with the human genetics, really, isn't it?
                                         
                                        There's a lot more cousins all over the place than...
                                         
                                        Yeah, absolutely.
                                         
                                        Oh, we all found family links you weren't expecting.
                                         
                                        Bats and horses is quite a stretch, though, isn't it, really?
                                         
    
                                        Yeah, yeah.
                                         
                                        I mean, if you've been raised by a bat and you find that you're actually a horse,
                                         
                                        that would be a difficult conversation for any family.
                                         
                                        But this is where the extent of convergence becomes really apparent
                                         
                                        is when you start looking at these molecular trees,
                                         
                                        those throw up so many examples that we kind of didn't see before.
                                         
                                        So moles, for example.
                                         
                                        So there are five groups of moles that look remarkably similar.
                                         
    
                                        And there's a group that's evolved out of the shrews.
                                         
                                        There's a group that's actually more closely related to the elephants.
                                         
                                        There's a marsupial group of moles.
                                         
                                        Again, like a crab, if I put one on the desk in front of your age,
                                         
                                        well, it's a mole.
                                         
                                        It behaves in the same way.
                                         
                                        It does the same sort of thing ecologically.
                                         
                                        But it's arrived at that end point convergently.
                                         
    
                                        So tell us about, Ned, tell us about crabs then.
                                         
                                        So, I mean, in terms of people misunderstanding that the path they took through evolution to get here, was their confusion in the past?
                                         
                                        Look, to be honest, I am here on this radio show as a little bit of a shrimp poster, right?
                                         
                                        I suffer eternal shrimposter syndrome, right?
                                         
                                        I'm not, like, we're not a scientist at the Grab Museum.
                                         
                                        We are just a couple of likely lads who love crabs, right?
                                         
                                        And we've come to it from the outsides.
                                         
                                        But for me, what makes a crab is if it's giving crabs.
                                         
    
                                        we have the mole on a table
                                         
                                        it looks like a mole
                                         
                                        it's a mole
                                         
                                        like a crab is a made up word
                                         
                                        like we have horseshoe crabs
                                         
                                        they are not crabs
                                         
                                        neither are they horses or shoes
                                         
                                        but we still recognise them for the wonderful
                                         
    
                                        beings that they are
                                         
                                        Ned let me put the question in a slightly different way
                                         
                                        why are crabs cool
                                         
                                        right
                                         
                                        well have you seen them
                                         
                                        they're much smarter than we assume they are
                                         
                                        for example they wear hats
                                         
                                        some crabs will live inside the bums of sea urchins
                                         
    
                                        other crabs will wear jellyfish on their heads upside down
                                         
                                        as kind of hats
                                         
                                        crabs are underestimated
                                         
                                        they're everywhere
                                         
                                        they are a hugely important part of the world around us
                                         
                                        like take for example we mentioned mangroves
                                         
                                        and sort of tropical environments earlier
                                         
                                        the way mangroves are
                                         
    
                                        is that they are
                                         
                                        it's like a sludgy anoxic environment
                                         
                                        there's no oxygen in the mud of a mangrove
                                         
                                        and you need to have the
                                         
                                        crabs to dig their burrows, to aerate the roots. Without crabs, mangroves choke and mangroves
                                         
                                        die. So crabs are ecosystem engineers. They're also just all around us and they have been
                                         
                                        for all of our history. We've been talking about crabs from as long as we can like scribble down
                                         
                                        things. They're part of our lives and I think that we have forgotten how close they are to us
                                         
    
                                        and ended up pigeonholing them into a kind of leisure activity for bored kids.
                                         
                                        Okay, Joe, by the way, when Ned started talking about how cool they were, you, and I could see this on the screen, started doing the crab claw thing as an indication of what, I mean, you were quite eager to go in on that, like, whatever.
                                         
                                        I just tend to do that on crab zooms because I think it's funny.
                                         
                                        But it's still pretty, I mean, it's a fairly useful tool to have to be able to grip things.
                                         
                                        Yeah. We think it's related to what they eat. And also, in some cases, think about fiddler crabs, right?
                                         
                                        in the males, they have one very enlarged claw,
                                         
                                        and they use those for sexual displays
                                         
                                        and sometimes even to battle one another.
                                         
    
                                        So there are a lot of different functions
                                         
                                        that they may have.
                                         
                                        So those shapes are related often to the function.
                                         
                                        I'm a big fan of fiddler crabs as well.
                                         
                                        They're my second favourite.
                                         
                                        Are they?
                                         
                                        Do they know what I'm noticing, though?
                                         
                                        Yeah, they're cool crafts.
                                         
    
                                        All of these crabs, they're all very similar sizes.
                                         
                                        I mean, do you get, could you have a crab
                                         
                                        the size of a Labrador, for example?
                                         
                                        You can. So there's two ends of the largest crabs. So the largest in terms of like leg span is the Japanese giant giant giant. And the name being giant, that's a pretty good indicator. And it can be like bigger than my arm span. I mean, I'm not that tall. But it's the length of a 1997 Nissan micro. There you go.
                                         
                                        Okay. New SR unit. Yeah. Yeah. So that's one way. And then the other way, the heaviest. And actually the heavyest. And actually the heavy.
                                         
                                        atheist arthropod ever known is alive with us now. And it's the coconut crab, which is not
                                         
                                        truly a crap. It's a hermit crab. It's funny with coconut crabs because people have talked about
                                         
                                        them as always being scary because they're on land with us and they're big. Last year, I was
                                         
    
                                        in Okinawa. I had the opportunity to meet and basically play with a coconut crab. And I found out
                                         
                                        they're really slow. They can crush a coconut. But you
                                         
                                        can move away from them so
                                         
                                        easily. So there's nothing
                                         
                                        to be afraid of. They're actually pretty cool.
                                         
                                        Dara, can I show you a picture of this coconut crab?
                                         
                                        These do. Obviously, that looks like something
                                         
                                        out of a film. And not a happy film.
                                         
    
                                        Not a happy film. Not a happy film. It's a something
                                         
                                        nightmare. But yeah, that's pretty
                                         
                                        substantial, isn't it? That's a pretty substantial.
                                         
                                        They're your friend. They're not your friend.
                                         
                                        You can't establish. It was crawling
                                         
                                        in my lap like a cat. I don't know what to tell you.
                                         
                                        Matt, top crab
                                         
                                        characteristics that you envy?
                                         
    
                                        Lots of different appendages.
                                         
                                        doing different jobs. And that's the secret to the success of many groups of arthropods.
                                         
                                        They've managed to subdivide and sub-functionalise their limbs. Even the pincers, they have a
                                         
                                        slightly different function for either side of the body. So they tend to have a crushing claw
                                         
                                        and a cutting claw. And if you look at many species of crabs, it's about 50-50 right to left.
                                         
                                        And it depends how they start to use the claw. And it's self-reinforcing. If they use one,
                                         
                                        claw a bit more, that becomes the
                                         
                                        crusher, and the one that they
                                         
    
                                        use less becomes the slicer.
                                         
                                        They're programmed to become
                                         
                                        asymmetrical. So you've got left and
                                         
                                        right-handed crows. Yeah. I think one of the
                                         
                                        characters, which I think you've all adopted, which is
                                         
                                        that, while asking
                                         
                                        you about the crabs, you've not been defensive
                                         
                                        and I've been hard-shelled about them in any way,
                                         
    
                                        but you have evaded a lot of the
                                         
                                        question you've asked. So your sideways movement
                                         
                                        has been next.
                                         
                                        Through this entire discussion, we've asked you
                                         
                                        one question, and you quickly shifted to
                                         
                                        left or right and answer to the different...
                                         
                                        That's very, very impressive.
                                         
                                        I would have been...
                                         
    
                                        That looks awkward and looks unusual,
                                         
                                        sideways movement.
                                         
                                        Is there, what's the...
                                         
                                        What's going on there?
                                         
                                        Maybe it's surprising.
                                         
                                        Maybe it's the element of surprise.
                                         
                                        Not that, I mean, you'd have thought
                                         
                                        that maybe sort of predatory fish
                                         
    
                                        might have worked out by now.
                                         
                                        Well, they've had 90 million years.
                                         
                                        Yeah, yeah, yeah, but slow learners of fish.
                                         
                                        What I can say that's good about sideways walking,
                                         
                                        regardless of what your body shape may be,
                                         
                                        you can go equally fast
                                         
                                        in either left or right direction.
                                         
                                        can't go equally fast
                                         
    
                                        if you're walking backwards now, can you?
                                         
                                        Wow.
                                         
                                        There we go.
                                         
                                        Although I will say
                                         
                                        if I came across a crab
                                         
                                        that suddenly walked towards me
                                         
                                        that would be the next leaf
                                         
                                        because I'd find that surprising.
                                         
    
                                        If you see a spider crab,
                                         
                                        a spider crab can walk towards you.
                                         
                                        Soldier crabs as well.
                                         
                                        Soldier crabs kind of go in huge baggles.
                                         
                                        Again, there's no statement
                                         
                                        we can make about these things.
                                         
                                        Thousands of them coming towards you,
                                         
                                        the little balls.
                                         
    
                                        and they walk straight towards you.
                                         
                                        No, thank you.
                                         
                                        Yeah.
                                         
                                        It's probably nightmare stuff, to be honest.
                                         
                                        I was with you, Ned, when you were saying
                                         
                                        every interaction you have with a crab,
                                         
                                        you're lucky that you've had that interaction with them.
                                         
                                        That one, no, no, thank you.
                                         
    
                                        Yeah.
                                         
                                        Oh, yeah, I mean, but I mean, wouldn't it be cool, though?
                                         
                                        I think this programme has been absolutely excellent PR for crabs.
                                         
                                        I'll tell you that.
                                         
                                        Really?
                                         
                                        Yeah, I mean, there's a crowd.
                                         
                                        Very good.
                                         
                                        Some sort of just clicking their little things together.
                                         
    
                                        The crab gods are going to be very happy.
                                         
                                        Oh, very, very good to say.
                                         
                                        Castanetting away.
                                         
                                        Clickety, like, clack, clack.
                                         
                                        Very good.
                                         
                                        You've been a joy, by the way, all of you.
                                         
                                        Yeah, that's been wonderful.
                                         
                                        Really, really interesting.
                                         
    
                                        It didn't go where we thought it would go.
                                         
                                        It really didn't.
                                         
                                        I mean, I think we've solved the issue of convertive evolution,
                                         
                                        but you have fan-boyed and fan-girls
                                         
                                        quite consistently, and in a way which is really, really enjoyable.
                                         
                                        Yeah, absolutely.
                                         
                                        Thank you very much.
                                         
                                        Thank you so much.
                                         
    
                                        Joe Wolf, Matthew Wells, and Ned Sissette Williams
                                         
                                        for helping us get to the bottom of this.
                                         
                                        Thank you very much.
                                         
                                        Thank you.
                                         
                                        I've got a new found appreciation for crabs
                                         
                                        I was always like faintly pro crap
                                         
                                        I think I'm anti-crabbing before now
                                         
                                        but now it's turned you around
                                         
    
                                        but whereas I do know
                                         
                                        the next time I'm on a beach
                                         
                                        in a beautiful tropical island
                                         
                                        which is like semi-regular
                                         
                                        and we're finding hammer crabs
                                         
                                        I'll be shouting
                                         
                                        you're not a crab
                                         
                                        you're a crab of lies
                                         
    
                                        you false crab
                                         
                                        I abjured the false crab
                                         
                                        let me take away your shell
                                         
                                        and see you with her.
                                         
                                        What's your abdomen doing, your weakling?
                                         
                                        Yeah, stick it underneath you, like a proper crab.
                                         
                                        So anyone who is on their honeymoon
                                         
                                        in the next three to five years?
                                         
    
                                        Shout as a, shout as it.
                                         
                                        Yeah, just you'll see Dara bring it on your beach.
                                         
                                        It's in the back of your shot.
                                         
                                        Well, it's been a wonderful magic agent.
                                         
                                        No, you're a liar, crab.
                                         
                                        If you want to be notified
                                         
                                        as soon as a new episode,
                                         
                                        is released, make sure you're subscribed to curious cases on BBC sounds and have push notifications turned on.
                                         
    
                                        Nature Bang.
                                         
                                        Hello.
                                         
                                        Hello.
                                         
                                        And welcome to Nature Bang.
                                         
                                        I'm Becky Ripley.
                                         
                                        I'm Emily Knight.
                                         
                                        And in this series from BBC Radio 4, we look to the natural world to answer some of life's big questions.
                                         
                                        Like, how can a brainless slime mould help us solve complex mapping problems?
                                         
    
                                        And what can an octopus teach us about the relationship between mind and body?
                                         
                                        It really stretches your understanding of consciousness.
                                         
                                        With the help of evolutionary biologists,
                                         
                                        I'm actually always very comfortable comparing us to other species.
                                         
                                        Philosophers.
                                         
                                        You never really know what it could be like to be another creature.
                                         
                                        And spongeologists.
                                         
                                        Is that your job title? Are you a spongologist?
                                         
    
                                        Well, I am in certain spheres.
                                         
                                        It's science meets storytelling, with a philosophical twist.
                                         
                                        It really gets at a heart of free will and what it means to be you.
                                         
                                        So if you want to find out more about,
                                         
                                        yourself via cockatoos that dance, frogs that freeze, and single-salamoebas that design
                                         
                                        border policies, subscribe to NatureBang. From BBC Radio 4, available on BBC Sounds.
                                         
                                        Bang!
                                         
                                        Are you after more fascinating conversations about the past? Well, History Extra might be just
                                         
    
                                        the podcast for you. Made by the team behind BBC History Magazine, the History Extra
                                         
                                        Podcast brings you gripping historical stories, compelling interviews with the world's leading
                                         
                                        historians, and the real history behind your favorite films and TV shows.
                                         
                                        Coming up, we've got deep dives into Tudor Life, the Nazis on trial, the real story of the
                                         
                                        gunpowder plot, and plenty more. So to join us on our journey into the past, just search
                                         
                                        for the History Extra podcast wherever you listen to podcasts.
                                         
