What was Darwin's strangest idea? Sexual selection by mate choice is the idea that Darwin had alongside natural selection and which he maintained was a very different process. Almost nobody agreed with him in his lifetime. It was a failure in the sense that... You know, he couldn't persuade people that this was an important thing. And when people did agree with him, they thought, well, yeah, but it's just a small niche thing in the corner of biology.
And I don't think that's right. I think he was onto something, that actually when mates are selective, which they are in many species, It drives a huge amount of evolution in the other sex, and it's a very different process from natural selection. I call it the fun version of evolution because it produces loud songs and things like that. It's less utilitarian. Yeah. What was the reaction when Darwin first proposed sexual selection?
Well, he mentioned the idea in The Origin of Species very briefly. And he said, I think that he had a friend called Sir John Seabright who'd been breeding rather beautiful bantam, new varieties of bantam. And he said, if a man can produce a beautiful bantam in a short time, then why can't a female produce a beautiful male in over a thousand generations?
And he was ridiculed for it. And by the time of the fourth edition of The Origin of Species, he felt it necessary to put in a sentence saying, yeah, look, they are beautiful, these male birds, to us. But that doesn't mean they were put on earth to please us. They could have been put on earth to please females. And this made things worse because everyone else said, I'm sorry, are you suggesting that female birds are capable of aesthetic discrimination?
Give me a break. And Wallace, in particular, deserted him on this topic. So did Thomas Henry Huxley. Herbert Spencer, all his normal defenders, were not prepared to defend this idea. Partly, these crusty old Victorians were a bit uncomfortable with the idea of women having sexual agency at all, of course, let alone love.
So, you know, one has to take into account that. But I'm very fond of a person who features in my book called Edmund Salus, who was a... an amateur naturalist who watched the same species as me, the black grouse, as well as a number of other species. And he said, you know, Darwin was right.
The evidence speaks trumpet-tongued in his favor, which is such a nice phrase, I think, because it's clear when you watch some of these birds that the females are being very selective and are in charge of whether or not mating happens. Yeah, I can imagine that Victorian England wasn't superbly keen on the idea of flipping the...
gender hierarchy upside down and saying, well, maybe the males were shaped by female preferences. And that also sort of has in it a sense of... almost sort of promiscuity in a way, a degree of female sexual agency, which again, Victorian England, probably not superbly popular. Yeah, and we don't need to be all that smug about Victorian because we too tend to say, well, hang on, isn't female beauty to males more important than male beauty to females in our species?
And it might well be the case. I mean, that's true in some bird species. But actually, in our species, both sexes are highly selective when they choose long-term partners. And so there's going to be... you know different criteria but similarly choosy similar choosiness in both sexes but yeah no people people find it instinctively odd that females should be choosing males on the basis of appearance. What is the fundamental mystery when it comes to sexual selection?
The fundamental mystery is why so many species? indulge in growing and displaying features that hinder their own survival, take a lot of energy. and can be amazingly flamboyant. You know, if you look at some of the birds of paradise that do a sort of shape-shifting display where they disappear into a sort of black hole and projector. iridescent smiley face on it you know it it's what on earth is going on it's it's such an eccentric outcome to come from evolutionary biology that that it
it still doesn't... Where's the rhyme or reason, is another way of putting it. And actually, I see evolutionary biologists' arguments over the last 150 years as being... a series of last-ditch attempts to put rhyme or reason back into this process. And there might not be rhyme or reason. It might be just...
be extravagant for your own sake because females are going to go for the most extravagant thing you can do. And I'll explain why I think that works as a technique. Yeah, I can imagine, I can see especially in a... A civilization which still has the sort of conceptual inertia of intelligent design, of beauty being sort of divinely bestowed from above.
that you observe these birds doing crazy dances and making themselves into smiley faces and hopping around and pecking and doing all of this stuff and thinking, well, how lovely that God... has made these birds do this dance for our benefit this is beauty incarnate i get to observe and enjoy you go maybe it wasn't for you Right. And the bird that Wallace and Darwin ended up arguing about most in 1868 when they're...
dispute over this came to a head, was a bird called the Argus pheasant, which is a sort of peacock-sized bird in the jungles of Southeast Asia, newly discovered at the time, which has enormous wings, very, very long wing feathers. And these wing feathers have a series of... objects depicted on them that are clearly intended to be three-dimensional optical illusions. In other words, they look like little spheres because they've got highlights at the top and shading at the bottom.
So somebody's gone to great trouble to make these things look as if they're actually three-dimensional. You know, they're sticking out of the feather like a sort of pebble or a jewel. Genuinely, Darwin's critics, including a guy called Wood, who was doing the pictures, actually, for his book, said, look, I'm sorry. For this to be created by females...
female birds, you've then got to posit that females have an aesthetic sense. But the idea that a bird with a brain the size of a walnut is capable of appreciating and enjoying three-dimensional optical illusions is for the birds. I mean, he didn't use that phrase, but that was the implication of what he said. So there's real... you know, you know, people like Sir Joshua Reynolds have been writing books about aesthetics at this stage.
and saying, you need to have been to Oxford to really understand aesthetics. But sorry, can I go back to one thing you said, which intrigues me, and that's the... the idea of intelligent design. Because in some way, Darwin is flirting with something that looks a bit more like intelligent design here. And it's been pointed out by Eveline Richards and others, who's a historian of this period, that his
His interest in natural selection almost seems to dry up after The Origin of Species. He doesn't spend a lot of time talking about it. His next books are about things like the domestication of animals. Well, that's not natural selection. That's artificial selection. And then sexual selection, which again is females driving the selective process. And Wallace, his friend and rival, reacts against this.
in exactly the way that you might, where he sort of says, look, I'm now more Catholic than the Pope. I really believe in this bottom-up natural selection, survival of the fittest thing. And I think... Bird beauty is just, for some reason, something that helps the species survive or the individual survive. And it's a part of natural selection. And I don't like the way Darwin is flirting with. Conscious beings, which female birds are,
choosing what males should look like. Now, Darwin isn't going that far. He's not literally saying that females are sitting down and planning what they want peacocks to look like. But there's a little bit of, you know, he's prepared to accept. that evolution can be directed in a way that looks a little dangerous to people like Wallace.
Isn't it interesting that Darwin, someone whose proposals were recently heretical to the previous dominant ideology, inside of his own new ideology becomes a heretic. You know what I mean? That's a lovely way of putting it. Thank you. Yes, absolutely. And there's a plaintive quotation from him at one of his last meetings at the Linnaean Society before he died, where he says, I still think I'm right. I know all you guys tell me I'm wrong.
by this point he's he's sort of pleading with them yes exactly as he's being i mean again look i i um maybe he doesn't have the spear in the side and the crown of thorns on the head but it does feel a little bit like a guy who's being like prostrated a little bit sort of begging for a bit of like guys please like it's ultimately this is going to hurt you more than it's going to hurt me on judgment day you know like he does have this like messiah thing going on although as far as i've read um
Robert Wright's book was the first one, Moral Animals, what got me into evolutionary psychology. Again, for- Wonderful book. I mean, that book is 30 years old now. More than 30 years old. It's like 92 or something it came out. And for anyone that wants a good kind of...
half-biographical look at Darwin's life with framing of evolutionary psychology. There's some stuff in there that... a little outdated obviously it's three decades of a relatively new field so some stuff's moved on but it's so great but in that um darwin seemed to be pretty sort of racked by self-doubt, uncertainty. He had like a little bit of a disposition toward low mood sometimes. And I imagine...
He doesn't get mad, he gets sad. And he doesn't have the big sort of fuck you energy that a renegade, rebellious, anarchist thinker would have. So I think he's actually kind of an unlikely... individual to go so hard against the dominant sort of mainstream hegemon that was whatever came before him. And I do wonder what would have happened, how much further his work could have got if...
he didn't have to get over not only himself, but then the additional pressure of everybody else saying he was wrong, and then his own self-doubt being reinforced by what people were saying from outside of him. It must have been really tough for him to navigate.
Because he didn't have, I think I'm right in saying this, by the time that he died, he still didn't have a fully perfect explanation of the peacock's tail. It was this sort of, it's kind of there, and I think I've got this inclination, but I don't have something that... concrete. And then if all of your peers are saying, yeah, mate, I mean, you hit the lottery once with that thing, but you don't get to run it. You can't wheel it up and run it back another time. It's just isn't going to work.
Yeah, that's all true. I mean... He is a cautious, conservative establishment figure. you know, he's wealthy and mixes in upper middle class circles and... And, you know, he's not a boat rocker in the sense – I mean, Wallace is a socialist and a feminist and all sorts of – a man of humble background and things like that. So in that sense, Darwin is an unlikely revolutionary. But in another sense, I don't think you're right to say that the self-doubt held him back.
Once he'd committed to writing The Origin of Species, which took a big leap, took 20 years of angst, as you say, before he did. Once he did, he very rarely... gave an inch well no that's not true he compromised actually the later editions of the origin of species are much less convincing than the early ones because he is trying to compromise with his critics And he's obviously feeling the pain of some of the criticisms.
But he then plows on finding all these stories about... animals and plants and details that can buttress his ideas and you know he there's no sense in which he um he sort of wants a quiet life Well, he does. He doesn't want to get involved in the controversies himself, but he wants to keep pushing the ideas out there. So he's a magnificent person. Robert Wright was the one who pointed out, and I'd never thought this before until I read Robert's point on it, that the...
Way in which Wallace's letter from Papua New Guinea, or from New Guinea, was handled. was quite cunning on Darwin. And they're quite selfish, actually. We tend to think of him as being magnificently generous and saying, look, this chap has scooped me, but why don't we both present our ideas at the Linnaean Society together? Yeah, but when it came to it, Wallace was off in New Guinea, didn't know this was going on, they didn't have time to tell him. Lyle says, look, look.
You poor chap, Darwin, don't get too head up about it. We'll have a meeting and we'll present your paper first and then Wallace's and you'll get the credit. And so in a sense, Wallace does get shafted by this process. And Darwin, for all his politeness, He's got a ruthless streak in him. He's got a ruthless streak and he wants his priority on this topic. But back to sexual selection, Wallace wins the argument in their lifetime.
And continues to, really, in many ways up until today, actually. The versions of Wallace's theory are still pretty popular. We can come back to the details of that, if you like. And some of the things Darwin says in his dispute with Wallace are quite stupid, actually. For example, Wallace said, look...
female birds are mottled brown because they want protection on the nest. They don't use the word camouflage because it hasn't been coined yet, but that's what they mean. And the reason I know that is because... female birds that breed in holes are often quite brightly colored, things like parrots or kingfishers or woodpeckers. And Darwin says, no, no, no, no, I don't believe that females are camouflaged. And you think, why not? And it's because he's
He's desperate not to give an inch on the idea that sexual selection is driving bird colour. Why are birds so useful to use for this study? What is it about birds? Why is it not... dogs? Why is it not cows? Why are we not using sheep for this study? Birds are a bit more like us than many mammals. They like song, they like color, they like visual things. We've got pretty good color vision for mammals. Most mammals have only got two color channels. We've got three, as have other primates.
So we see a much more colorful world, rather like the world the birds see, not nearly as colorful as they see. They've got at least four channels. They've got ultraviolet vision, all sorts of things. So to some extent, we can sort of empathize with birds. But in terms of the study of sexual selection, Birds really do stand out because there has been an explosion of dramatic... shapes, crests, plumes, colours, displays, dances and songs.
in the birds that dwarfs other species. So if you just take song, for example, I was out this morning when the sun came up and the bird song was fantastic at springtime. There was no mammal noise at all. Maybe I heard a sheep at some point. Maybe a dog barked in the distance, but that was it. You know, if we didn't have birds, think how silent it would be. And song is quite a useful thing to study, actually, if you want to understand what's going on here. And so without birds, well, also...
human beings into natural history and then into biological sciences. Me, I was a bird watcher before I ever thought of being a scientist. And that's true of a lot of people. Jim Watson, who discovered the... co-discovered the structure of DNA. He was a birdwatcher as a teenager, and that's what got him interested in biology, etc. So I think...
Now, you could say butterflies, dragonflies, lots of sexual ornamented colors fish lots of bright colors but they're not as easy to study they're either too smaller or they're harder to observe or they're underwater or something birds are the obvious ones to go for mammals with very few exceptions. I mean, there's a black one and a gray one, and a few monkeys have colorful faces. But apart from that, they're really grim to look at. And the noises they make are terrible, really.
And also, they do a lot more sexual coercion than birds. There's another way in which we're similar to birds, and that is forming pair bones. to bring up offspring birds do a lot of that most birds Black grouse are an exception. Beacocks are an exception. But most birds, the male and female, collaborate to rear the young. And again, we empathize with that.
In an awful lot of mammals, all the work is done by the mother, both gestating and lactating, obviously, and nurturing the offspring. So there's a sense in which we are honorary birds. This episode is brought to you by Gymshark. Gymshark makes the best gym wear on the planet. Their hybrid shorts in onyx gray and navy are a complete game changer. They're the best men's training shorts.
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slash modernwisdom and using the code modernwisdom10 at checkout. That's jim.sh slash modernwisdom and modernwisdom10 at checkout. Getting into the meat of it, why do females choose certain males based on beauty and performance rather than obvious survival traits? Right. So why not just choose a strong male who will give you strong children? And the answer is that there's a seduction going on. It's a charm. It's a persuasion. It's not a coercion. That's the first point.
The second point is, yes, but why let yourself be charmed by a flamboyant tale or bright colors or whatever? And the argument that Wallace... raised and that has reverberated since through the topic is that it's a proxy for fitness of some kind. It's telling you if you can grow that peacock's tail and keep it in good nick. and display it frequently, then you must be quite healthy. You must have good disease resistance genes or something like that.
And that's the kind of version of sexual selection we always hear from natural history programs and that is generally pursued by most biologists. And it's probably not wrong. But there's another thing going on that is, I think, usually more important, particularly when you get these exaggerated flamboyant plumages. And that is the idea that...
Ronald Fisher first thought of in 1930 and was later mathematically proved by Russell Landy and Mark Kirkpatrick in 1980. And that is that that the fitness the females are after may not be just whether their offspring survive, but whether their offspring seduce. The thing that really matters to them may be having offspring that can persuade members of the opposite sex to mate, particularly male offspring, and that it's no use.
choosing an ugly male partner that is particularly strong and disease resistant so that you can have strong and disease resistant sons. If those sons can't persuade other females to mate with them because they haven't got flamboyant tails. Otherwise known as the sexy sun hypothesis. The sexy sun hypothesis. And that's a sort of runaway effect.
Seduction of the Hottest versus Survival of the Fittest is another way I put it. I didn't think of that until after I'd finished the book. What a shame. That was good. That's good. Okay, so we have this sort of Fisherian runaway selection thing going on. Traits that are sexually attractive are selected. Over time, that causes sons to become sexier, but eventually you end up with a risk and a trade-off for the males. Even before we get on to risks and trade-offs.
Why is it that there is such a thing as sexiness that isn't just utility of survivalness? Why is it not that maximized survivalness is sexiness? Why is there this? other pathway, this other attribute. Right. Well, the answer to that, I think, the clue to it
And I can't prove this. And this is the problem with this version of sexual selection. There is very hard to devise experiments that prove it. I will mention one in a minute. But the answer, I think, is that... in a random direction, will get exaggerated. And it doesn't really matter which direction it's in, it will run away. You can't stop it. And so the clue is the fact that you get such extraordinary diversity of sexually selected ornaments in birds and other animals.
There is no pattern, you know, there's no... general practice that they tend to have eyes. It's not always the biggest tails. It's not always the brightest front. It's not always the tails. It's not always the wings. It's not always the crest.
It's not always the breast. It's not always the back. It's not always red. It's not always yellow. Do you see what I mean? And once you start looking at the extraordinary diversity of... ways in which sexual selection has gone mad in the birds of paradise in the pheasants in the mannequins in in species like that
You know, why do puffins have red and blue stripes on their beak? You know, that's a sort of completely different way of doing things. There's a bird called the tragopan, which pops out from behind a log when he's... trying to seduce a female and lowers from his throat an electric blue apron with red patterns on it. I've seen that. Of skin. Why? So it's the very arbitrary.
nature of the features that i think argues for uh this process now you can still say yeah but why you know why would it matter and of course Probably what's going on is that to start with, being a bit brighter than another male does mean your immune system's in better order or you haven't been infected with malaria or something like that. So they're probably...
At the end of the book, I say, hang on, we're constantly trying to choose between these two theories, fitness and hotness, if you like, and we shouldn't have to. They're obviously both going to end up. assisting each other. Well, if you assume that the reason that you have fitness is to survive in order to be able to reproduce. and hotness allows you to reproduce more quickly. They end up netting out at the same outcome, even if they sort of get there in different paths.
Yes, but it might be worth mentioning that... What I think is the best experiment I describe in my book, it doesn't feature birds, unfortunately. It features a small insect. And it was done by Andrew Bownford and one of his students on a sort of Brazilian fly. And what he did was he allowed them to make... and in in the laboratory this is and the she actually it was she who did the work and i can't try to remember her name but but andrew's student and um He bred from the...
And he took the unsuccessful males and put them on one side and the successful males, and he bred a lineage from one and he bred a lineage from the other. So he's now got the failures and the successes fathering the next generation. And he does that for several generations. And then he says, what's the difference between these flies at the end of several generations? Are they less able to survive because they've been bred from the failures? And the answer is no.
Are they less able to persuade other flies to mate with them? Yes. So that's quite a nice, that's the best experiment for teasing out these two hypotheses that I've come across. That's really cool to understand that there is one dial for fitness and one dial for hotness and they're maybe interrelated.
upstream before them, there is something that causes them both to happen. And maybe they do on average tend to happen sort of synchronously that fitter tend to be hotter. I would also imagine that that's the case. but that they are distinct and they are interpreted in different ways. So that's cool. So just to kind of round out the Fisherian runaway thing. Any minor advantage in terms of sexual selection trait display that a male has.
51.49 over time that will be selected for sufficiently that it continues to get more and it continues to get brighter and it continues to get more elaborate. And that's where you end up with after a few million years of evolution, you just end up with these sort of very, very extravagant displays. Yes, although if the runaway process is as accelerating as Fisher thought,
then it might not be a million years. It might be one of these things that happens really very quickly in a few thousand years. you know, the peacock might have gone from having a short tail to having a huge tail in the sort of blink of an evolutionary arc. And one of the ideas I tie with in the book is, can we catch a speech? In the moment when it suddenly starts having a runaway selection. And come back in a thousand years and see what's happened.
I don't know. I feel like you need to sow the seeds with... girly daytime magazines you know that have got the new trend what to look for in this this summer's new boyfriend or whatever and uh that's how you sort of inject it socially and from there the the runaway begins Well, this is why I went and sat for two nights running on top of a mountain in Norway.
not allowed out of my little canvas blind from 8pm to 8am, watching a bird that displays at midnight, through the middle of the night, called the Great Snipe. Of course, it's not dark in Norway at that time of the year. The great snipe looks like any other snipe. There are 17 species of snipe on the planet, and they are all sort of really well camouflaged in marsh vegetation, including this one. It doesn't look much different.
But this one does this lecking. Males gather together and competitively display. And at the height of its display, it flushes the white feathers in its tail. And it's like turning on a light. It's a very bright little flash, very bright. But the tail feathers are not very exaggerated, and they're not much whiter in the male than the female, a little bit. And if you tipex some of the males' tails, so they're...
Young people don't know what Tippex is, but, you know, if you put white paint on some of the males' tails, you can improve their mating success, according to us. scandinavian biologists who are very ingenious oh it's like a it's like a snipe esthetician giving them some beauty beautification augmenting so it's a boob job it's a boob job for snipe exactly exactly And so, but my point is,
Male snipe and female snipe look almost identical. In fact, you can't really tell the difference, and the tail is a bit different, but you can't see it very well most of the time. So maybe this is a species that's only just started. having highly skewed sexual mating success so that one male gets to mate with 10 females, which is roughly what happens.
It hasn't had time for the tale to get huge and white and dramatic, and that might be about to happen. The conventional explanation for The Great Snipe is that it... because it's often displaying in very poor light, there's no point in being brightly colored. And a lot of the display involves making clicking noises, and maybe it's an auditory lek rather than a visual lek.
But other birds make noises on the lek too. So I kind of like my idea best that this is a species that's only just begun to lek. And there's another bird called the buff-breasted sandpiper, which sort of lecks, but sort of doesn't. And I'd like to watch that species for a thousand years and see what happens. What's the leck paradox?
The leg paradox is that the black grouse, which leg, live next door to the red grouse, which don't. They pair up. So one male, one female, and they both bring up the kids. Therefore, because the one male gets to mate with 10 to 20 females in the black grouse, But the other 19 or 9 or 19 males on his leg don't get to mate at all that year. the bird will have less genetic diversity in its population than the red crab.
it will be more genetically monotonous. It will be more inbred. Not to the stage where it's a... sort of health problem because the males usually only get one year at the top and the females disperse and so you know the the species is fine in that sense But it must be the case that there is less genetic diversity in a lecking species like the black grouse than a monogamous species like the red grouse.
in which case there's less point in being choosy because the genes are going to be more similar. I mean, when you go on to elect, you're bound to be looking at some half-brothers. because they tend to recruit to elect near where they were born. And if they were born in the same year, then the chances are they had the same father, even though they might have had different mothers. Um, so if they're half brothers and they look the same, and by the way, they do look very similar to us.
then what's the point of being so choosy? The species that are most choosy about making sure you get the very, very best male and not settling for second best. which the Red Crows do all the time. They say, look, I just want a bloke who's going to look after the kids. I don't care what he looks like. I'm anthropomorphizing, but you get the point. The species that are most choosy have least reason to be choosy. That is the Leck paradox.
And I think the Fisher theory shows you a way out of it. It doesn't matter how little variation there is, you've still got to follow the fashion. But not really. I mean, I'm struggling with it too. So it is a paradox and it's an intriguing one. This episode is brought to you by Whoop. I've won Whoop for over...
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I'll just give you your money back. You can get the brand new Whoop 4.0 and that 30-day free trial by going to the link in the description below or heading to join.whoop.com slash modern wisdom. That's join.whoop.com. slash modern wisdom. Right, so... Birds that have these speed dating, which is bird speed dating is what sort of the lecking is in a way.
Yeah, but speed dating where they all end up mating with the same male, remember? Yeah, yeah. Okay, good. That doesn't happen to you and me. Non-monogamous speed dating for birds.
In those situations, you have a lot of the reproductive rewards accruing to a few at the top. You also have to assume that that would mean the more... sexually selective uh that the women are being the more that they're skewing toward that single male or small number of males at the top there's going to be less of a chance of survival for that next generation that comes along just due to some of the inevitable reduced
genetic diversity. So you think, okay, these two things kind of do come into conflict a little bit with each other. The hotness and the fitness can actually start to, it feels like they can fight against each other. Yes, well, the conspicuous plumage for a start is a threat to survival. the dancing and fighting that you do for months on end is a threat to your survival. So yeah, males are putting themselves at risk to present themselves. But one way of looking at it is that...
The black grouse and the red grouse, the males are putting in an awful lot of effort in both species. The red grouse the effort is going into... escorting the female, defending the territory, escorting the chicks, helping the chicks, sheltering the chicks, being vigilant over the family, things like that. Whereas the black grouse, the effort is going into endless displays, fights, competitive.
dances and so on so you end up um uh deciding which way to to push your effort and when you push all your male effort into display You are wasting it as far as the lineage is concerned, as far as the chicks are concerned.
in the sense that, you know, so if I go out in June, find a pair of red grouse in which the male is standing up looking around and the female is down in the heather with the chicks and and he's got his eyes out and if he sees a hawk coming he gives an alarm call and they all hide um he's very valuable in that If I find a blackrouse with chicks, there's no sign of the male. He's miles away. He's had his two seconds of fun two months ago or whatever.
The female is entirely on her own, and having one parent looking after the offspring as opposed to two is bound to be a disadvantage. And sure enough, blackgrass seem to have lower chick survival through that period of when chicks are small. And indeed, they have smaller broods, actually. So the species as a whole is not going to do as well. And that's a rather intriguing thought, I think, that sometimes these sexual selection arms races end up making a species more likely to go extinct.
That's fascinating. So sexual selection could actually be a maladaptive force sort of that pushes species toward an unsustainable extreme. This idea has been around for a long time, and there was a sort of rather cartoonish version of it that was in vogue for a while.
Do you remember the ancient Irish elk, this species that went extinct at the end of the Ice Age, which was an enormous... deer bigger than a moose and with huge antlers much bigger than a moose's atlas but similar in shape to a moose's atlas and um uh How on earth these poor deer managed to carry these vast antlers around is a sort of bit of a mystery.
And what were they for? Were they for fighting or were they for displaying? And actually, there's some quite good evidence that they might have been more about display than fighting based on how good they would have been. as weapons, if you like. But the question of why that species went extinct... used to be dominated by the theory that the antlers got too big. And the deer couldn't fit between the trees when your and my ancestor was running after them with a spear. And so they caught.
Now, nobody thinks that's why it went extinct. It was a large animal. Our ancestors were very good at wiping out large animals, which were slow breeding and easy to find. They wiped out mammoths and woolly rhinoceroses. step bison and things as well um so at the end of the ice age it was doomed because it got predated by human beings not because or because climate changed or something, not because...
their antlers were too big. And besides, if you look in some of the best bogs in Ireland that have lots of these animals in them where they got stuck in the mud... there was higher mortality among young than old deer, as you'd expect in any species. So that, you know, the... You can take these arguments about sexual selection being a handicap.
a little too far if you're trying to use them to explain the extinction of a species, but maybe it does play some role. How extreme can these traits become then? Well, there's a little bird called the club-winged mannequin. which has a display in which it makes a sort of... resonant twanging noise with its wings, which carries a long way through the Ecuadorian cloud forest where it lives.
In order to make this noise, the bird has had to redesign not just the feathers of its wings, which are contorted in a sort of strange way. but the wing bones themselves. Wing bones are generally the same in all birds. I mean, obviously, there's a scale difference, big birds and small birds, but the shape of a wing bone is generally...
pretty well defined as being, you know, the best strength to weight ratio and things like that. Not in this species. It's got a sort of weird, heavy, club-shaped wing bone in its body. I mean, in its wing. which is there purely to enable it to make a twanging noise in the springtime or the breeding season. They don't have spring on the equator. And Richard Prum has written about this in his book, The Evolution of Beauty. And it's quite a...
It's quite a good example of just the length. I mean, this must make it harder to fly. for a start the lengths to which actual selection can go a peacock's tail a uh uh the the the There are...
There's a bird called the bulwars pheasant, which lives in Borneo, where the male, when he displays, disappears into an enormous sort of white... disc, which actually comes from his tail, and his head is then hidden by fleshy that stretch before and after the head um so he looks like a sort of plate with a blue knife on it that's not a very good description but do you see what i mean and and and you know you get to think
Poor creature. You know, what have the females done to this species to make it, to submit it to these ordeals? But that gets to another point. sexual selection can be possibly a more creative force than natural selection. Because instead of just saying in a utilitarian way, I just want to enable you to survive, it says, let's try something really wacky.
and see what we end up with. And Richard Prum has this theory. He's the guy who worked out what color the feathers were on dinosaurs, by the way. And he has this theory that feathers were invented for display before they were ever used for flight. and that we wouldn't have had flight if we hadn't had sexual display. Wow.
That is cool. Yeah. I suppose if you're just rolling the dice in so many ways, it's like, hey, they might be attracted to this. Try it on. You know, here's a new outfit. Here's a new fashion. Have a crack. Yeah. And I haven't mentioned the bowerbirds, but I've got to get them in at some point. Australia and New Guinea, where bowerbirds live, these are birds that have basically invented art.
They build complicated structures, not to nest in, but to seduce females in. It's the males that build them. And they decorate them with colourful objects arranged. in ways to enhance perspective and ways to look decorative and sorted by color and all sorts of things. And I watched a great bowerbird at his bower trying to seduce a female with a red chili pepper.
which he was displaying to her on the edge of a cemetery in Queensland in Australia. But his main art installation was a... a huge patch of... grey and white objects. snails shells and bones and things like that but also bits of plastic and bottle tops and bits of broken glass etc because we were in the edge of a town And this art installation included not only a plastic hand grenade, but a tiara. a toy tiara i think it was a toy maybe it was a real diamond tiara
What about seemingly tiny traits? Very sort of minuscule things that for us to look at, we wouldn't realize that it was actually a different, but that is something that's sexually selected for as well. Yes. I mean... Some of the song things are very, very obscure. A lot of seabirds, things like puffins, You really can't tell the difference between them. They can, but we can't. And they're both brightly coloured. So there's a bird called the Crested Auclid, which is a...
cousin of the puffin, which lives in the Pacific Ocean. And there was a very neat experiment done on that in... the 1990s, where they said they grow just a tiny little black sort of forward-pointing crest on the top of the head, and their beak gets much redder in the breeding season. So they took some birds, caught some birds, and they lengthened the top knot on the head or shortened it.
and then measured how long it took for that bird to acquire a mate. And by lengthening the top knot, you shorten the time that the bird takes to acquire a mate. The bird is more attractive, and that was true for both sections. So that's rather intriguing. That proved what we had suspected for a long time, that you can get mutual sexual selection. You can get choosiness in both sexes in some species for the same criteria.
And then there's a bird in New Zealand called the Paradise Shell Duck, where the male and female are both smart, but they look very different. The male has a black head and a... gray patterned body and white wings the female has an orange body and a white head they're both striking birds um but they look quite different now Clearly, the females are saying, I want the male with the blackest head, and the males are saying, I want the female with the whitest head.
Well, does that ring a bell? Do human beings have mutual sexual selection? Yes, we're both very choosy when we pick long-term partners. But we don't have the same criteria, do we? You know, male beauty and female beauty are different things. on the outside of the body and possibly on the inside of the brain. in other news you've probably heard me talk about element before and that's because frankly i'm dependent on it for the last
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modern wisdom okay so could sexual selection have shaped the human mind we've talked a lot about birds so far let's bring it a little bit closer to home for what it could have done to us Yeah, my book isn't about one ugly African ape, but inevitably, you know, one... feels obliged to put a chapter in at the end about this and i'm absolutely sure that sexual selection is going on in our species i'm also pretty sure it's mutual and not
not like the black grass in which, you know, it's female selectivity that's driving male appearance. I think both sexes are very selective. We're a monogamous. species at least socially monogamous. That doesn't mean we're necessarily faithful and we can be much less choosy when it comes to short-term sexual encounters, but for long-term people... Both sexes are pretty damn choosy about who they settle down with. That, after all, is the plot of every romantic comedy ever made.
So what's going on in human beings? What are we selecting for? Well, clearly there are... sexually selected features of bodies like breasts or beards or something that may be involved in beauty. But I think it's more interesting to look at the inside of the head. Because the human brain did something very odd. It exploded in size over a relatively short period of about a million, two million years. maybe three, I don't know, but not a very long period. It accelerated.
The increase in brain size was very steady until around Homo erectus it suddenly takes off. And actually, it's got slightly smaller again in the last 50,000 years. We think it reached its maximum size about 50,000 years ago on average. And that might be something to do with... you know, agriculture enabling us to live on more meager diets or something like that. But it was very costly. I mean, the human brain is a huge...
user of energy. It takes a lot of energy to build. It takes a lot of energy to run it. Why? What's the purpose of growing such a big brain? No other species needed it to survive on the savannah. And if you say, right, well, it helped us get through the ice age on the savannah when the climate was very variable. Plenty of other species managed to survive on the savannah, you know, buffaloes and gazelles and baboons.
chimpanzees in similar habitats and so on um they didn't need uh 1200 cc brains um uh so maybe it wasn't all about survival maybe it was about something else Now, there's two other possibilities. One is that it was a social thing, that we needed big brains to understand the groups of people we were living in. We lived in big groups. We were plotting and scheming.
deceiving each other. So we needed big brains to figure out what other people were up to and that kind of thing. And that's a very popular thing called the social brain hypothesis. And that's obviously, to some extent, true as well. But there's a third possibility which almost never gets discussed.
but which was laid out in a very good book by Jeffrey Miller 25 years ago called The Mating Mind, in which he says, actually, this looks awfully like a sexually selected feature. It's a mental peacock's tail. The sudden takeoff, the fact that it didn't happen to other species, and the fact that the things we use it for... are not just solving practical problems or understanding how to get on with each other in society.
We also use it very conspicuously for things like wit and humor, music and song, verbal dexterity. poetry, all these kinds of things, tool making as well, you know, I mean, practical things as well, some of which looks awfully like showing off. to members of the opposite set. So maybe, and it's not at all difficult to see that people with... Great minds are attractive to members of the opposite sex in human beings.
verbal dexterity of George Clooney or the singing ability of Mick Jagger. You know, these guys don't do badly in the attractiveness state. I've chosen male examples, but I genuinely want to keep stressing that I think in our species it's going both ways. Humor is a very good example. If you ask people, Helen Fisher did this, how important is humor to you in choosing a sexual partner? It scores very highly. And, you know, the personal columns,
Where people advertise for, well, I guess they don't do it anymore, they do it online. But, you know, good sense of humor, GSOH, is a very important part of it. And what's the point of humor otherwise? Watch what people do with humor. They show off with it. They're not doing it. to find out information from other people, they're doing it to impress other people. And that looks awfully like sexual display.
Miller says, and I think he's right, that this isn't a slam dunk this isn't a proven idea But to spend the whole of the 20th century thinking about Freud and Marx and Piaget and all the other sort of theories of mind, behaviorism and all these things without taking into account. that the organ we're doing all this behavior with was probably subject to sexual selection and was probably being used to seduce as well as to survive.
To do all that without taking that into account is a mistake. And we might have left an enormous hole within a lot of our... social science within psychology and sociology and economics and all these other disciplines, the whole being sex. And we need to put it back in there. It's mating all the way down. It was always mating.
It's turtles all the way down. It is. So, you know, one of the things that you've mentioned there is this, I guess, bi-directional sexual selection that traits happen both not just male to female, but female to male as well. What determines whether it is unidirectional or bidirectional? Yeah, what does that sort of say about the environment and the child rearing and the expectations of that particular species? How does that all fit together?
Yes, and the person who solved that problem was a brilliant evolutionary psychologist called Robert Trivers. who said something that's blindingly obvious, but none of us had thought of it before. And he said it in the early 70s. He said, the species where the... The sex that invests most in rearing the offspring will be competed for by the sex that invests least.
So it's called parental investment. So, you know, but it's a vicious circle because… As I say, the red grass, they both invest a lot in looking after the kids. the black grass they don't the female does it all so the black grass you get huge amount of male-male competition to try to mate with females and a lot of sexual selection, less in the red grouse. But which came first, the chicken or the egg? Did the parental investment come first or the sexual selection come first?
And the sort of exception that proves the rule here is those species of birds where it's reversed, where the brightly colored... forward and aggressive females compete for dull-coloured males because the males sit on the egg. And I studied one of these species. It's called the gray phalarope. It lives in the Arctic. Phalaropes, Chicanas, Dutterals, there's a number of species that do this. It's not very common, but it's not all that rare either.
And the female is much more conspicuous, much more boldly colored, spends much more time displaying and much more inclined to... fight with other females. So that kind of proves Trevor's parental investment theory right. Now, in human beings, You can say that women do more of the work, and of course they do. They do gestation and lactation, which men can't contribute to at all. But compared with gorillas or chimpanzees...
Males do contribute an awful lot more parenting than most other great apes. And we are... We have less sexual dimorphism than most other great apes. I mean, a male gorilla weighs twice as much, if not more, three times as much as a female gorilla. And he has a harem of six or seven. In chimpanzees, they have a multi-male system where each female mates with lots of males, partly to frustrate the tendency of males to commit infanticide. which they do in a lot of mammals, to bring.
females back into fertility, probably in human beings too. Look at the number of stepchildren that get killed compared with... biological children, the murder rate is much higher. The Cinderella effect, as it's known. The Cinderella effect, exactly. You know, it's unfortunate that there's only four great apes, orangutans, chimpanzees, gorillas, and us, plus the gibbons are similar species, because if there were 30 or 40 species of apes...
then we could really do some good comparative analysis and see how we ended up with the mating system that we did. But I would argue that the... the need for fathers to be involved in provisioning and protecting. offspring as well as mothers has been a feature of hunter-gatherer life for a very long time and it has made us into a species in which females are going to be pretty choosy about. as well as males being pretty choosy about femur.
Are there any parallels between bird mating behaviors or whatever and human romantic displays or social structures? Well, it's hard not to watch some of these bird displays. and not draw parallels with nightclubs and other things. You know, there's a strutting that both species do, I suppose. I think that's mostly anthropomorphism. We human beings...
Well, I think song is actually the most intriguing one, because there's no other mammal that is as interested in singing as we are, with the possible exception of Gibb. Maybe Howler Monkeys, but... You know, we... Song and language... are very unique and remarkable human features, and they feature heavily in seduction and display. That's true of many birds as well. And the complexity of song in birds is truly extraordinary. The number of...
different phrases and different motifs. Oh, sorry, I've left out whales, haven't I? Whales really sing as much as we do, so they're another example. I think we... When you try and teach a chimpanzee to speak, it's really tough. And you can get up to a few hundred words. You can't get grammar. You can't get syntax, really, to speak of. When you try and teach a parrot to speak, and this has been done, there was a famous African parrot called Alex who had an enormous vocabulary.
and really seemed to understand grammar in a way that... Most other animals can't. The word order or whatever matters in terms of what it means. In that sense, there are similarities between us and birth. Okay. Another similarity question, I guess. Do birds and humans have an innate appreciation for beauty? Is the drive for aesthetic pleasure some evolutionary force?
There's a rather good quote from Darwin on this, which I'm rather fond of, which is, birds appear to be the most aesthetic of all animals, excepting, of course, man. and they have nearly the same taste for the beautiful as we have. And he's really flirting with a dangerous... uh idea there um that you know there's something uncannily similar about us and birds here because there's no reason why you know it's convergent evolution if if we and birds
have this similar taste for the beautiful. And one of the things that I've been thinking about is It's unlikely to have been inherited from a common ancestor, this taste for the beautiful. because our common ancestor with birds we now know lived about 400 million years ago That's an awfully long time ago. And we know what that common ancestor looked like, roughly. It was a lumbering reptile that lived in a swamp.
It gave rise to both the dinosaurs, which gave rise to the birds, and to the so-called mammal-like reptiles, which gave rise to the mammals. So, were not close cousins descended from a creature that had a sense of the beautiful? Probably. Maybe we are, but it doesn't seem likely. It seems more likely that... We have ended up with an appreciation of color and tune and song and melody and fashion and all these kind of things, and so have quite a lot of bird species.
And it just so happens that those have ended up with similar outcomes. Now why might that be? Well, notice that... on the whole sectional selection goes for pure colors not browns and grays so it goes for limited number of wavelengths you know limited number of frequencies um pure hue If you've got every hue you can think of, then you end up looking brown.
And it's the same with song. If you just want to make a noise... a click or a roar or something it's got every sort of frequency in it but if you go for just specific frequencies you get a whistle or a tone or a or a tune And that's, of course, much harder to do. I mean, you can make a boring noise by dropping a rock or you can... paint something brown just by mixing lots of materials together, but to actually create something that has a pure color or a pure sound is much more improbable.
much more unlikely, much more conspicuous, much rarer. And that's why we find it. That's why we use it in our sexual displays, and that's why birds use it in their sexual displays. And so there's a sort of almost a thermodynamic idea at the root of this. But as you can see, I'm beginning to wave my hands a bit, and I haven't thought this one through properly. I like it. Definitely the... refined nature of it not being everything.
suggests that you're purposefully doing this one thing. If you're brown, you didn't mean to be brown. You just are brown. But if you're such a pure color, if you're such a pure note or tone or sound or whatever... that suggests that there's been some thought put into it, some pressure selected for it. Yes, there's a sort of watchmaker aspect to it. So what do you think? So, you know, taking a broader picture here.
Lots of past failures in evolutionary theory, trying to work out why things were the way that they were. What do you think we should learn about biases in interpreting our nature, what we should consider, where things come from, given the replete history of us putting both of our feet in our mouths and getting stuff wrong all the time? Well, for me, the history of science always teaches the importance of humility. Overconfident rejection of maverick ideas is the constant theme of all science.
That doesn't mean that every maverick who comes along waving a new theory is Galileo. quite a lot of the time he's not or she's not and how for me that's that's the the big puzzle of my life is how do i know when to listen to a Maverick, and when to tell them to get lost. Because there are many, many scientific debates where you just want to say, oh, for God's sake, get real. That idea can't be right. And 95% of the time, you're right to have that.
But 5% of the time you're being like Catholics and being dogmatic and telling a perfectly sensible chap to get lost when you shouldn't. And this was true of Darwin generally, isn't it? He was a maverick and a heretic, and he had to work really hard to get taken seriously. And evolution was rejected and still is by many people. And it's true of his sexual selection idea, where he was rejected as a nutcase in his lifetime, and for quite a long time afterwards. And wrongly so.
Lots of people have put forward fresh ideas about why birds are colorful. For example, to go back to this, there was a theory in the 1980s that it was all about warning predators. that you were in good health, and therefore there was no point in chasing you. Well, I don't really see why a kingfisher needs to do that more than a sparrow. But, you know, maybe there's an idea there. And in general... I'm more frustrated by science being too dogmatic.
than being too open to new ideas. Yes, if you're too open to new ideas, if you open your mind too much, your brain falls out, as someone wants to put it. I would like generally to teach the lesson that we need to be more tolerant of disagreement, of heresy, of mavericks, and give them at least the... privilege of testing their ideas. That said, You often get told by people, I've got this new theory and the...
The line I always come back with was, how are you going to test it? And that often shuts people up. So it's lazy to come up with an idea. It takes work to test it. Awesome. Matt Ridley, ladies and gentlemen. Matt, I'm a massive fan of your work. I think this is really, really interesting. I didn't realize I was going to become such a garage ornithologist for the afternoon. Where should people go? They want to keep up to date with your work and what you've got coming out.
Well, I have a website, which I mostly keep up to date. It's called mattridley.co.uk. I am just about to get on Substack, I think, so I can churn my stuff out there. But, and I'm on. Well, I'm on Twitter. I'm not very active on Facebook and LinkedIn, but I try and be. And I write. books and journalism as well. And the book is called, I should say, Bird, Sex and Beauty. Oh, what's the subtitle? The Implications of Charles Darwin's Strangest Idea. Heck yeah. Matt, I appreciate you. Thank you.
Thank you so much for having me on and allowing me to rabid on at such land. I get asked all the time And that's why I made a list of 100 of the most interesting and impactful books that I've ever read. These are the most life changing reads that I've ever found. And there's descriptions about why I like them and links to go and buy them. And it's completely free and you can get it. right now by going to chriswillx.com slash books. That's chriswillx.com slash books.