How Did Dinosaurs Have Sex?
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Hello my lovely Betwixters, it's me Kate Lister, your listing tool Betwixt the Sheets, and because we are a naughty podcast discussing naughtiness throughout history, I have to give you the fair dues warning, because well then, fair dues, you were warned, and here it is. This is an adult podcast spoken by adults to other adults about adulty things in an adulty way, covering a range of adult subjects, and you should be an adult too. So this is your chance to get out now while you still can, and for the rest of you, let's crack on.

Tread very carefully, Betwixtons, and keep your voice down. We are deep in what will one day be Midwest America some 80 million years ago. I'm doing my best David Attenborough impression, because somewhere around here, I'm trying to find out how the T-Rex had sex. Don't you giggle. This is serious scientific work, I swear.

We could be close. I'm dying to find out if their tiny arms helped or hindered their sex lives. Certainly, it was going to be no use in putting on a dino condom. Are you curious to hear more about how the dinosaur did it? Well, stick around with me and we'll find out.

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Something you never saw in the Jurassic Park films as far as I remember is dinosaurs actually having sex. There was that whole asexual reproduction. There were some eggs and there was something about tree sap and a mosquito. But nobody was actually getting down and dirty unless I missed an extra on the DVD. But obviously dinosaurs were doing it for like millions upon millions of years. So what might that have looked like?

How did they overcome their huge physiques and thick armour? How do you have sex when your neck is as long as a diplodocus? Or you're as spiny as a stegosaurus? I'm not good with dinosaur names. But somebody who is, is the fantastic Dr David Hone of Queen Mary's University London. And he is going to tell us how the dinosaurs did it.

And if this crossover of science and sex history tickles your fancy, why not have a scroll back and listen to an episode from the start of last year on the ancient origins of sex. Fossil brushes at the ready, Betwixters. Let's do this.

Hello, and welcome to Betwixt the Sheets. It's only Dave Hone. How are you doing? All right, thank you. Teaching is finished for the year, so that always puts me in a slightly better mood. Yeah, finished on Friday. Well, thank you very much for taking any of your precious time out to come and talk to us about dinosaur sex.

I'm always happy to talk about dinosaurs. Sometimes sex comes up, so it's not a natural combination. Obviously they were having sex, but this is not something I've ever spent much time thinking about. So I'm thrilled to be talking to you about this. I have so many questions and they're probably going to be really stupid ones too. I mean, to be clear, I haven't spent that much time thinking about it either. But, but,

Probably more than you, but I don't want to give the impression that this is a regular afternoon for me. So tell me first, what is your area of expertise and what period of history are we thinking of here? Because dinosaur encompasses so much.

Right. So, I mean, the first thing to do, we need to get clear for people who don't realise, is to get rid of birds, because birds are literally dinosaurs. So we mean all the classic dinosaurs that people would think of, Tyrannosaurus, Stegosaurus, Triceratops, Diplodocus, etc., but we're not.

somewhat artificially excluding birds as their direct descendants. So I work on non-avian dinosaurs and some other groups as well. I also do quite a lot on pterosaurs, the flying reptiles that are also not dinosaurs that lived alongside them. Why are they not dinosaurs? In the same way that we are not elephants. Oh, right. Sorry, that sounds... That's an annoyingly pretentious answer, but...

We're relatively closely related to each other. We're both mammals, but one group is primates and the other group isn't. I'm with you. So they are not dinosaurs because they're a different evolutionary ancestry, even though they're close relatives. Right. Okay. I'm with you. Okay. Yeah. Yes. Dinosaurs, the oldest dinosaurs are somewhere around 230-ish million years old. And then they go extinct 65.5 million years ago, brackets, except birds. So we're talking about a span of 180-ish million years. Wow.

Wow. I mean, I speak to historians whose specialist is like one month in France in the 18th century. That's a hundred million years. No, 180 million years. You can nearly double that. Yes. And worldwide distribution as well. Oh, my God.

I have recently discovered that maybe all of the dinosaurs weren't around at the same time as each other. Is that true? Absolutely not in any way, shape or form. In the same way that we don't have Amazon saber-toothed tigers now. Yeah, I knew that. But you know, you have faunal turnovers. We think most species, there's a kind of general average and it's a very loose average with huge extremes either side. But a regular species might last two or three million years. Wow.

which means every few million years, there are not many things around now that were around, you know, 5 million years ago. So yeah, when you've got a span of 180 million, you know, dozens of completely different faunas.

So was T. rex around at the same time as the Diplodocus? No. So this is the classic one that you actually see as a meme. So Diplodocus around about the same time as Stegosaurus. So there is less time between us and T. rex than T. rex and Diplodocus and Stegosaurus by about 20 million years as well. It's not even close. I'd have to double check the exact numbers.

dinosaurs were around for a really long time and people just don't get it yeah if you're not used to it it boggles me my dad always used to ask like how do you deal with these kinds of numbers and the truth is you don't really you just kind of use them because that that's what they are but in terms of like can i mentally handle what three million years might actually look like no um i've been doing this for decades and i still can't wrap my head around it it's

Just such an absurdly unhuman timescale to even begin to think about.

And just for context, how long have humans been around for? It depends how you define humans. So early members of the hominid lineage are at least 5 million years old. I think the genus Homo is something like 1.5 when you're getting into Homo sapiens, our species, something like about 300,000. And then modern humans, so Homo sapiens sapiens, our subspecies, what we'd call anatomically modern humans.

something like you know 20 or 30,000 maybe 40 or 50,000 we're very very very very new indeed whichever way you cut it it's not 180 million years is it no the first thing is some I

I don't. I'm very impressed with dinosaurs. But there is a kind of narrative around them that they were a failed species. But you can't be a failure as a species if you've been... I mean, yeah, that's a classic Victorian argument because obviously humans needed to be superior in some way, shape or form because obviously we're best because we can think and do other things. And Douglas Adams said you can't make digital watches.

But yeah, dinosaurs were famously unsuccessful because they were only around for 180 million years. And then again, in birds, you can add the last 65 million years on top of that. And then there's only 11,000 species of birds alive now, which is getting on for twice as many mammals. So obviously dinosaurs are spectacularly unsuccessful. Well, they are very, very successful. And one of the ways that they are able to be successful is they must have been having sex.

What kind of sex with dinosaurs?

That's a huge question. That's far too big. The truth is, I mean, in terms of like straight up active copulation, we really can't say very much at all beyond the fact that almost certainly all of them were doing it. There's at least the possibility we had asexual species. There are a handful. So there's various lizards and snakes which are capable of asexual reproduction. There's two, if not three birds we've observed doing it. So it's very, very rare in birds, but it does turn up.

And even those, I think they're all facultative. So in other words, this is something they can do, but it is not what they habitually do. And asexual reproduction is where you can produce an offspring where you haven't had sex at all. Basically, yes. And that's really common in lots of invertebrates and lots of amoeba. And there's quite a few fish and things like this that do it and bacteria. But once you're into the inverted commas, kind of higher vertebrates, once you're into lizards, reptiles, mammals, birds, it's...

fairly rare. But yeah, as I say, there's a couple of birds that can do it. It would be weird if dinosaurs couldn't do it. And this is one of those big things going back to that like age issue. When we say kind of like, did dinosaurs do X? The answer is almost always yes, because if you've got a lineage that was around for 180 million years and probably produced hundreds of thousands of species in that time,

Almost certainly one of them somewhere could do it. The question is, do you know which ones and do you have any evidence for it? And that's when things start falling down very rapidly. So yeah, dinosaurs must have had sex. Otherwise there wouldn't have been little dinosaurs, certainly not for a very long period of time.

And that means they must physically have had sex. Once you get past amphibians, reptiles, birds and mammals, so a group we call the amniotes, they all have internal fertilization. So you do not have the frog egg thing of females laying eggs and males just sticking sperm onto them. Something has to basically go into something else or at least physically contact it to do an internal sperm transfer.

So dinosaurs were doing that. And then the real question starts to become, well, how? Because while there's lots of them that probably wouldn't have any obvious problems at all, they're no less oddly built than many birds or reptiles or crocodilians, for example, you get things like the really big sauropods, so the long neck, long tail, diplodocus-like things. The really big ones of them are weighing 50 plus, 5-0 plus tonnes, right?

Getting them together is going to be interesting. You have something like Tyrannosaurus, where the upper estimates are nine tons, but it's a biped, a kind of horizontally standing biped. There's not a very obvious way of getting the two necessary bits together. No. A third, then, you have the Ankylosaurus, the armored dinosaurs with the club tails.

Their whole body is like a sheet of solid bony armor. And they have weirdly actually very wide pelvises. So as in it's a squat animal that's standing on all fours, but the back end of it is really, really wide whilst not being very high. And then a stiff tail with bony armor all the way down it and a body that's got bony armor all the way down it. They're not like the most agile, able,

running around jumpy flexible animals that probably the big ones probably weigh you know five six seven tons and

How are you getting, you know, to take the IKEA approach, how are you getting tab A into slot B? Carefully, with a lot of lube, I think. Well, it's more the physically, how do you get into position? And of course, the really obvious answer to this is a very long tab A. And this does turn up in various things. So I will very quickly name drop, I was on Joe Marler's podcast when this came up, explosively inflating duck penises. Yes.

or anything okay you've covered them but you can have a phallus that is as long if not longer than the actual animal that holds it so this is the kind of thing we don't know this yeah but they all say that right we do get soft tissue you know we do get skin we do get bits of muscle claws um there's stains of eyeballs there's an alleged fossil brain and fossil heart and various other bits and bob so soft tissue does preserve it's just very very very very rare

But something like this...

is probably not ever going to preserve, but the odds of us ever finding one are very, very, very, very, very remote. So if they exist, and then if we find one, it would still only tell you about one species. But wait, wait, wait, just a sec, just a sec. The missing link here, the theory is that some of them at least must have had a huge penis, but we don't know that because it didn't survive.

Well, yeah, it won't preserve. Yeah, it will be very soft, squidgy tissue because there's going to be a lot of blood or lymph or something else that's inflating it. So even if it happened to be at maximum size at the time the animal died, it's all going to dry out and shrink. You get lots of that. You get this mummification where the skin shrinks as the whole animal dies up.

You know, you occasionally see photos on the internet of like, you know, we found a cat stuck in the floorboards or something like this. You know, they're all dried up and shrunk. That's what you'll find. We get those for dinosaurs where they had mummified and dried out before they were fossilized.

So yeah, will we ever find one? And even if we did, if miraculously tomorrow, we do have these sites of exceptional preservation in China, Canada, Germany, and a couple of others. If you suddenly found a perfect dinosaur with a penis or equivalent preserved, unless it happens to be out and obvious, would you even know what it was? Because that's not usually how these sit. They sit internally in these animals. Yeah.

And then unless it was something like one of the giant sauropods or one of the armadanchylosaurs, they probably didn't need a large one, in which case you're not actually going to see it. One of the things we rely on a lot with paleontology, or at least vertebrate paleontology, is what we call osteological correlates. So that is something in the bone, the osteology, which correlates with a soft tissue structure. I mean, a pretty obvious one is eyeballs. You have a hole in the bone and that's where your eyeballs sit. Yes.

And some penises do have bones in them. So the mammalian baculum, yes, which turns up in lots of things, including primates, but weirdly not us, which has all kinds of interesting biological implications in its own right. But that's very much a mammalian thing. And even then it's...

I'm trying to remember the acronym. So primates, rodents, what were insectivores, so hedgehogs and some other relatives, bats, carnivorans, and I believe there's one rabbit. Well, technically a pike, a legomorph. So those are the groups that have them. But there's all kinds of others that don't. There's an acronym for animals that have got bones in their penises. Yes. The acronym used to be, so this is the problem with taxonomy. So there used to be a mammalian group called insectivorae.

We've now recognised that that's not a true evolutionary group. That was several other groups artificially welded together. So the acronym was Primata, primates, Rodentia, rodents, Insectivora, Chiroptora, which is the bats, and Carnivora, P-R-I-C-C. The mammals with a baculum were pricks. LAUGHTER

That's how you remembered. Unfortunately, insectivora doesn't exist and now there's a legomorph, so it doesn't work very well. Damn it. All right, but that's... That's an amazing fact to know. But dinosaurs, no. They were unlikely to have had bones in their penises because they're not mammals. As I say, it's only in certain mammal groups. There's no bird, no crocodilian, no reptile that I know of that has ones. And don't forget, we have...

hundreds of very very good exceptionally preserved complete and articulated dinosaur skeletons if this was present we'd have found one by now in fact we'd have found lots so it's just not going to be there but going back to what i was saying what we can find though is are there correlates so for example if you you know there are certain um rough patches on bones that correspond to certain muscle groups or certain ligaments so if for example you had something like that in

all the ducks and all the other animals that had a particularly large one that then had to articulate or in some way connect to the bones, maybe you could get that signal, but that doesn't appear to be the case. So we really are left with the case of this would just be a soft tissue fin.

And so if the preservation was good enough to preserve that, it's also going to preserve viscia and lungs and liver and kidneys and all the other bits and all the goo of the body, in which case you probably wouldn't be able to tell anyway. So this is one of those things where we're left with inferences. And so people say, oh, you're just guessing. And it's like, well, we're not, but we can look at ankylosaurs.

And they, you know, they weigh twice as much as an elephant whilst being half as high and three times as wide and covered in bony armor. If you can think of another way you can get them together without this, I'm intrigued to know what it is because no one's thought of one in certainly a good 20 or 30 years of serious thought about this. So when you're working with these kinds of sources, and I suppose it is, it's mostly fossilized remains that you're working with.

How are you able to extract information about the kind of sex? Because it's not just they must have had an enormous retractable penis. There's also things like this was penetrative, that wasn't. What kind of position would they have had? Even if you've got a penis that can reach somebody from the other side of the room, there's still a question of positions and things.

How do you go about determining something like that? It's a lot of inference and a lot of, you know, what is definitely possible and what is definitely impossible. So, for example, they could have had external fertilization. You know, there's things like newts and salamanders where the male will basically drop a packet of sperm on the ground and then the female will bend over or crouch down and basically suck it up.

maybe they did that, but it would be very, very odd. You know, this is something that this evolutionary group left miles behind. It's never reappeared. You know, we can't rule it out, but it seems so incredibly unlikely. I think you can effectively dismiss it, but, you know, there is a possibility, for example. I mean, the first thing you can do is just do the sort of

that we do do anyway. When you see something like Jurassic Park films, we're doing stuff like that in as much as we can scan the 3D preserved skeletons, we can digitally re-articulate them, we can use those osteological correlates and compare them to modern birds to work out where the muscles go and how big those muscles would be

and rebuild the body. We can look at the flexibility of joints and how strong the ligaments are because there's osteological correlates for ligamentous attachments and things like this and go, right, this leg could probably flex this much in this orientation and that much in that orientation. And this leg can, you know, the thigh bone can take this much strain and we think the animal weighed this much.

And then you can try and work out, well, can I physically get a T-Rex leg over the leg or back of another one? Well, actually not really. Or yes, you can. Let's talk T-Rex because looking at their...

quite famous shape and quite famous frame, these tiny little hands, like how they must be like those Weeble things that we had as kids where they just like, there's nothing. If they slip over, that's that. So how are they having, they can't even grab onto each other's hair with that. Like, what are they doing? There was an idea in, I think the early nineties where someone basically said, oh, this is, this is,

this is a mating thing. The reason T-Rex didn't get rid of their arms entirely is it's important for the male to hold onto the feeder, which is absolute nonsense, frankly. A T-Rex's arm is about the same size and proportion as mine. I've got a, not on me, but I've got a cast of a T-Rex arm. And if I put it alongside mine, it's surprisingly similar size and shape. A big T-Rex weighed seven plus tons, up to nine tons. I am not going to be able to hold the weight of nine tons if I slip. Yeah.

Not even half a ton. So let's just rule that out. But again, you look at what is potentially mechanically, physically possible. Because of course they don't have to stand up and get into some kind of Kama Sutra position. The female could lie down on the floor and lift her tail up as far as possible. The male could stand half sideways and crouch down or something like this. You can get the two back ends together and

probably quite closely for even animals that size. And as I say, in a bunch of birds, you know, do effectively do not have penetrative sex. So I should say birds and reptiles and amphibians and fish. Again, mammals are weird. We always think of mammals as being the norm. And for, of course, for a lot of things we're not. So they have a single exit.

where everything comes out or potentially goes in called the cloaca. And then in birds, they have what's called a cloacal kiss. So literally the male cloaca and the female cloaca basically meet and the sperm is just pushed across that gap. But you don't actually need to push anything physically internal.

So for a lot of dinosaurs, I'm sure that was pretty much it. You know, there's lots of smaller species or lots of ones that were relatively agile or relatively flexible. And therefore, that's going to be the limit of it. You just need to get close enough for the two bits to connect.

But once you start getting into, yeah, the armoured stuff, the very heavy stuff or the really heavy bipeds, well, that's probably going to be... Again, you know, there's no obvious solutions to this. There have been a handful, and it is a handful, like two or three scientific papers where people have tried to work out literally sex positions with...

really well-made articulated toys, because there are some really good ones out there, or very well-articulated models, and just trying to work out, well, just how far can we push those flexibilities? Now we're doing that with digital models, but it's functionally the same thing. You know, what bits can you get where and how close can you get them together? And then coupled with, well, what behaviours do we see in living species? What do birds have to do? What do crocodiles have to do? MUSIC

I'll be back with David after this short break.

Feel your body getting lighter and lighter and enjoy a full night of peaceful sleep with the A20's long-lasting battery. Then wake up feeling fresh with a personal built-in alarm. Get the sleep you deserve with Soundcore Sleep A20 earbuds. Discover more on Soundcore.com. S-O-U-N-D-C-O-R-E. Soundcore. Use code SLEEP at checkout to get $30 off. S-L-E-E-P in all caps. So, they had sex, right?

How is a matter of ongoing debate? It looks like there was a kind of a docking procedure that they kind of got. I mean, as there is for basically every person. For everyone, right? Yeah. What about something like mating rituals? Because like you can't see that in bones and fossils, but presumably they must have had like a

So you can, and then this is where we can actually do much more. This is one of the things that I work on. So there's one example, but it's a multiple sites in central and southern US, which is described specifically as being a mating ritual. And I didn't write the paper, but I was one of the academic...

referees for it. And it's a classic case of you read like the headline title of evidence of a mating ritual. And I'm really quite conservative on this stuff. And I was like, there's no way you're going to convince me that you can actually...

demonstrate this or even have vague evidence. It's going to be something very vague and then you're going to insanely over-interpret it and I'm going to be really frustrated. And I got to the end of reading this paper. What is it? What's the dinosaur Netflix and chill? The really short version of this is what they have is it's footprint. So it's a whole bunch of track sites

where what you have is two sets of pairs. So you basically have a pair of lines that are quite long and quite deep, so a pair of furrows basically side to side, and then they face another pair of furrows. So it's like you've got two equal signs on the keyboard kind of next to each other with a couple of spaces in between, something like that. It's a time and place where we have large carnivorous dinosaurs. There are lots of large carnivorous dinosaur footprints around,

in the area in general and in this bed. So this is where a lot of large carnivorous dinosaurs are wandering around. And then you have these furrows, which are clearly very artificial. You know, nothing in nature is going to produce four lines that are all matched up and then lots and lots of sets of these. There's not just one set, there's lots of sets and in multiple different places as well.

And their argument was, well, this is two animals face to face and they're bipeds. So they kind of do a scrapey dig with the left foot and then a scrapey dig with the right foot. And over time, as they do a little dance and there's probably bobbing and yelling and other things going on, they'll dig a pair of furrows. And each animal's doing that face to face and you'll end up with two pairs of furrows. And that's what you say is a nice just so story. It's perfectly reasonable. It sounds right. It makes sense. It would explain the pattern and what you see.

But the really nice thing is they went, and you know what? There's a bunch of seabirds that do this. And there are. There are a bunch of birds. Off the top of my head, I cannot think of an example, but I think it may have been boobies or something like this. Of course it would be, yes. Where one of the things they do is they line up face to face and the males and females do a little nod and a little dance and then they scrape with the left foot and then the right foot and they dig a little furrow. Wow.

So we've got literally modern dinosaurs doing the exact same thing and several different species which are not particularly closely related. So it's not like it's, oh, well, that's the pheasant thing or that's what pheasants do or that's what starlings do or that's what crows do. These are relatively distantly related groups.

all have settled on this same ritualistic behaviour. And then it's like, well, now that's really quite a convincing case because, again, what else is going to generate this sort of thing except that? And then you have a modern analogue. No, I can't think of anything else that would do that. A kind of stumpy, stumpy thing. Right, because, for example, animals that fight often have ritualistic pre-fighting behaviour. Getting into a fight with someone who...

you might beat, but you might not is really dangerous. And finding out if it's worth it is for both sides really important. And that's why you have, you'll see it with things like deer where they'll walk side by side and kind of stereotype walk and look at each other. And there'll be a little bit of antler clash and a little bit before they decide. Cause if one of you realizes, hang on, I'm probably going to get flattened here.

Yeah. Pull out now. And if you're certain you're going to win, amp it up and make sure the other guy backs down. But if this is serious, it then accelerates. So maybe it would be something like that, but those animals rarely just stand face to face and then digging wouldn't be showing your size or your prowess or anything like that. What about...

What about the dinosaurs' bodies themselves? I mean, you've convinced me. That's got my random seal of approval. That's what that sounds like to me. But what about their bodies? I'm so sorry, I don't know the names. The ones with the frilly necks, where they've got that rough thing that comes up, or the stegosaurus, like all the spikes and stuff. Is that anything to do with a mating ritual, or just accessorising? So I think you're thinking of Triceratops and its kids. Thank you, yes. And then, yes, Triceratops is...

everyone's familiar with spikes on the nose and then a big frill it's actually the back of the head it sticks out over the neck but we often call it a neck frill because it kind of covers the neck which is basically largely solid bone actually triceratops is weird it's solid the others have holes in them but this is a group of dinosaurs called the ceratopsians and i specifically have worked on an animal called proto ceratops from mongolia and china and it's

It's like sheep-sized, a big proto-ceratops, but in particular, it has this really big frill, which all the ceratopsians, or nearly all the ceratopsians have.

And this has been the subject of arguments for years, basically exactly what was it for? And some form of sexual communication or sexual dominance and social, you know, I'm big and I'm sexy, basically signal was always kind of the favoured idea. But then how do you test that? And I realised that actually there were ways of getting to that. If you looked at modern species as your analogue.

And the example I always give is, I know not everyone's necessarily familiar with this level of agriculture, but you will probably know if I tell you. If you imagine if you've seen cows in a field or sheep, they can be quite big, not yet adult size, but quite big. And they have really stumpy little horns. And then a few months later, they'll be full size and suddenly, whoop, their horns are massive.

And this is basically a super normal pattern in biology and for very clear biological reasons. When you are young, the biggest threat to you is basically being eaten.

It's really easy to be eaten and killed when you are small. And so what you need to do is grow as quickly as possible. If you want to mate and have offspring, and there's obviously a very strong evolutionary imperative to do so, so you grow, grow, grow, grow, grow, grow, grow until you are sexually mature, until you're big enough to compete as a male or big enough as a female to lay large enough eggs or have a large enough baby that it's likely to survive and you've got the resources to do that. At that point, naturally,

Now, growing is far less important than having sex. So suddenly, sex kicks in as a driver. And that's when, if you're a fighting animal, you grow your big horns. Or if you're a signaling animal, like a peacock with its train, you suddenly grow all your pretty bright feathers. And you can see this in dinosaurs, because with Protoceratops, we have got lots and lots of specimens, everything from tiny hatchlings through to big adults.

So you can measure how big they are and then measure how big their frill is and compare the two. And lo and behold, the growth curve of the frill is it doesn't grow very much for ages. And then about the age we think they hit sexual maturity, it suddenly grows much faster. Is anybody working on dinosaur vaginas?

Just out of interest. Like there's a lot of work being done on penises, but what are vaginas doing? There is, well, so again, they do not have a vagina. They have a cloaca and even the males would have a cloaca. It's just the penis would extend from that.

So they just have this single urinary genital opening. There is one known. So it's an animal called... Genital opening. Yes. A urinal genital opening. A combined exit for all systems, as I say. There's effectively a one-stop shop. Why isn't this classed as a vagina? I mean, I get the idea that it's like a one-stop shop. It's like everything in one. But why don't they call it a vagina? There's two possible answers. It

Could be both. So one possible answer is some anatomists and taxonomists get very het up about what you should or shouldn't call certain structures depending on their evolutionary history. So the vagina is a mammalian structure that only mammals have.

therefore you shouldn't call that in anything else. Now, that obviously doesn't work very well because as a friend of mine pointed out, well, we call eyes eyes, but actually the eyes, for example, that you see in clams and the eyes that you get in octopus and vertebrae eyes are completely independent evolutionary structures. They do not have a shared ancestry, but no one doesn't say octopus has eyes. They just go, it's got eyes.

So that one, but I think the second one more importantly in this case is it is fundamentally different because a vagina in mammals is effectively just to have sex through and then give birth through. Whereas, as I said, both a male and female dinosaur would have a cloaca. So they're really not comparable and it's then very odd to say it, give it one name in a female and a different name in a male when they're effectively identical structures. MUSIC

I'll be back with David after this short break.

In the animal world, true monogamy is actually incredibly rare. Like the idea that you see somebody, you fall in love with them, and then that's it. That's you forever and ever and ever. I think that there's a handful of species it's been observed in, and even some of them have been found to be cheating. It's like it's hardly any. Yeah, they usually do. I think there's some albatross, which are extremely reliable. Yeah, like there are some birds that do it. But that made me think, what do you think? Were dinosaurs monogamous? Yeah.

So almost certainly not, because as you say, even supposedly monogamous things often cheat. And there's lots of cheating going on in lots of things that we have studied. I think what's really interesting is when you start getting into the sexual selection stuff that I've worked on with the frills, one of the common patterns that we see, not just in things like the ceratopsians, but lots of other dinosaur groups too, is males and females are often very similarly ornamented.

And this is quite unusual. It does turn up in various groups. Actually, seabirds is another one. Penguins are the same. It's actually true of a whole bunch of parrots. And there's actually a whole bunch of fish, seahorses and pipefish and that group as well. It's what we call mutual sexual selection, where rather than going down like the classic lion route or the peacock route or the deer route or elephant seals, where males are much, much bigger or...

have their horns or have their displays or fight or whatever it is they actually do, the males and females are very similar to each other. And that usually kicks in in species, or I think almost universally kicks in in species, where males and females are both investing in their offspring. Because the short version is from a purely reproductive success out

If you're a female, you're putting a lot of effort into your eggs. That's a lot of energy versus like a small packet of sperm. So you are putting your energy into that next generation. You want them to have the best possible chance of surviving and doing well and spreading your genes. So you want the biggest, bestest male, whatever that is.

And in general, that's the biggest one or the fightiest one or the one with the best colours and display because he's demonstrated, well, I'm fit and healthy. I wouldn't have all these feathers if I couldn't escape predators, if I didn't have time to groom them, if I couldn't find the nicest food and I was free of parasites. It was what we'd call an honest signal. And therefore, all the females want to mate with them. And that's why you'll get deer with a harem or lions with their pride or peacocks mating absolutely everything if they're the top, top one.

And from the male perspective, their effort is going into that signal or that combat or being big and then just a little bit of sperm everywhere. And hopefully they'll get quite a few kids out of that. But what happens if the male isn't doing that? You look at something like the emperor penguins where the male sat on the ice for six months with an egg on his feet.

If the male doesn't do that, that egg is never surviving. So the male is putting just as much effort in as the female. The female may have laid the egg, and that's more expensive than the sperm, but standing on the ice for six months trying not to die in an Antarctic winter, that's...

That's an enormous energy effort from a male. So he's now in the same boat because he doesn't want to end up with a duff female. He's got one shot at mating and he's going to put his entire reproductive effort into the year into one egg.

So now you've got a system where the female wants to advertise for the best male, but the male wants to advertise for the best female. And what happens is they both end up with signaling structures to signal to each other. And that's where this kicks in. So when you look at something like Triceratops, we've got dozens of specimens with Triceratops. Every single one has horns and a frill. You don't have anything like deer where stags have antlers and females don't.

That doesn't rule out cheating because, boy, you know, blue tits are the classic example of this. So blue tits were like the original study animal for this. It was like, oh, there's this lovely monogamy and the male and female work together to raise the blue tits and then they find that both males and females cheat rampantly. So yeah, so that doesn't mean it's not happening. But,

is your base system. I think there's a lot of mutual parental care going on in a lot of dinosaurs. So as a final question, then just as a complete random question, do you think dinosaurs had orgasms? Um,

I'm not aware that birds or reptiles do. Is that just a mammal thing? Is it more than a primate thing? This is where you need to speak to a mammologist or a primatologist. We do, don't we? Not me. In mammals, obviously, the orgasm... Well, actually, there's a lot of debate about why women in primates orgasm. But the general thought is that it's because it feels nice and it helps you want to...

I'm just wondering what the payoff is for dinosaurs if they had sexual pleasure. I think we're getting into the realms of if, which is well beyond normal speculation, I'm afraid. Should we just say that we hope that they did? Make them happier, yeah.

Dave, you've been so much fun to talk to. If people want to know more about you and your work, where can they find you? The obvious thing is davehoden.co.uk is my central website. So that has links to absolutely everything. I have a podcast called Terrible Lizards. You can guess what the subject of that is. I have several books out, both pop-sci and more technical and a bunch of kids' books. I write for The Guardian occasionally. I'm on a lot of the classic social media sites. That should lead you to everything else.

Thank you so much for coming to talk to us today. You've been wonderful. Thanks for having me. Thank you for listening and thank you so much to David for joining us. And if you like what you heard, please don't forget to like, review and follow along wherever it is that you get your podcasts. If you'd like us to explore a subject or maybe you just fancied saying hi, then you can email us at betwixtoutofhistoryhit.com.

We've got episodes on everything from Lilith, the original biblical sinner, and, speaking of sinners, Genghis Khan, all coming your way. This podcast was edited and produced by Stuart Beckwith. The senior producer was Charlotte Long. Join me again betwixt the sheets, the history of sex, scandal, and society, a podcast by History Hit. This podcast contains music and epidemic sound. ACAST powers the world's best podcasts.

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