When a female animal is checking out her prospects, natural selection would dictate that she pay attention to how healthy, or strong, or fit he is. But when it comes to finding a mate, some animals seem to be engaged in a very different game. What if a female were looking for something else - something that has nothing to do with fitness? Something...beautiful? Today we explore a different way of looking at evolution and what it may mean for the course of science.

This episode was reported by Robert Krulwich and Bethel Habte and was produced by Bethel Habte.

Support Radiolab today at Radiolab.org/donate

United States


00:00:00Joel and Gatineau quebec-- Radiolab is supported by transferwise the cheaper way to send money internationally The Economist says transferwise takes a machete to the Hefty fees Banks charge but don't take their word for it more than four million people are already saving sign up at transferwise.com podcast or download the app
00:00:26hi this is Beth Parker from Grand Rapids Michigan Radio Lab is supported by quick with a quip electric toothbrush sticking the good habits is simple one of the first electric toothbrushes accepted by the American Dental Association quip has a built-in support system for better brushing go to get quip.com Radiolab to get your first refill pack for free
00:00:51equate you listening to Radiolab
00:01:09pad is this enough mine oh my gosh but for your hand reading your handwriting is not awful it's actually a very elegant legible not so much but can hear is Radio Lab so not too long ago Robert and our producer Bethel habte has a nice lean-to it full moon to the studio to walk me through this story that they've been working on together for quite some. Everybody here is everybody yes yes or should I could rather tell you a riddle Once Upon a Time Birds evolved from dinosaurs so they was originally scary things in the scales turn to feathers in the feathery things began to fly we call those things Birds but I guess I'm going to just ask this to you out of the blue because it's a basic appendage how many birds have penises
00:02:09there are like ten to twenty thousand different kinds of birds but you by modern times so again how many of those species have penises how what percentage of currently existing birds bird species has one in the mail saying word penis looks so meant to do you know how many times I have absolutely no frame of reference
00:03:0010 lower AR15 lower
00:03:06133 3% 97th percent of birds don't have penises how a scientist named Patty Brennan the thing that's so weird about birds is precisely the fact that they they lost a penis or you just say you're just using interesting. So that you say the birds lost the penis or so does that mean that earlier editions of birds that have them that's right I guess of penises are widespread traits of all vertebrates right except for you know some amphibians and fish ever recorded you go back two hundred million years or so birds were like all those other creatures 100% of them had penises vast majority of birds a penis was then lost
00:03:57now the deep well that's the question how do you lose a penis like if it seems like a pretty handy thing to have when you went to put your sperm close to female eggs to the 97% of birds that don't have a penis now what do they have David kind of hold the mail and the females have these holes in the shirt to open up anime line them up a calendar meeting and that's it that's it and it works just fine but if you're thinking about the engineering what appendages going to work best for you to make a baby's penis is the one because it gets your female eggs so far all of these penises to just vanish like she says that evolutionarily that just doesn't make any sense why would you lose a thing that's so useful for there to be selection for the penis to get to go away there's going to be a very important reasons what's the reason there's a few possibilities
00:04:53number one people have speculated for example that you might have been sexually transmitted diseases
00:05:00you're putting this Pinos way deep into the female and then you're pulling your penis back into your click I like they could be potentially a very easy exchange of of sexually transmitted diseases cuz you're like digging deeper I got exactly yeah yeah yeah so even though the penis has its advantages obviously maybe it's slowly went away because the birds that had the penises just kept getting these infections that's the beat but so far nobody's found a link between penises and STDs so then the other possibility that's really intriguing actually
00:05:32is the babies because penises are heavy
00:05:36number to study flying and getting rid of the penos would have been an easy thing for lowering your body weight maybe they'll also so they could fly I don't believe that I mean I think that's unlikely to have being a strong enough selection because ducks for example are among the most long-distance migrants and they still happiness it there in a 3% and sometimes they have penises that are bigger than their own bodies so so my God
00:06:10pretty much yes I think the record is a male that had a 43 cm long penis and this is a male that was only about 40 centimeters long himself a pretty large penis and fly just fine but oddly enough the Ducks are also sort of the key to a third theory for The Disappearance of the penis I was going to say some this idea that I actually had to do with female Choice against males that controlled reproduction to explain Patty actually thinks that the original bird penis is like when they might have been a lot like the modern-day duck penis which is essentially
00:06:55a weapon
00:06:58I'm so one of the things that we learned when we were studying to Ducks is that the males have about this erection mechanism that he's crazy they have an explosive erection mechanism what that means he's not the mail actually efforts his penis and ejaculates in a third of a second a a pistol with what does though is that it allows these mails to forcefully inseminate a female even when females don't want to be inseminated right to voicemail is anywhere near a female he's just going to go and push right through you know that's not something desirable for females often times with females will be struggling right there trying to get away from these emails that are trying to forcibly copulate so probably thinks or what might have happened here is that female Birds trying to get away from males with large penises and
00:07:58he's really violent ways of approaching reproduction again systematically choosing gendler and smaller meals with smaller penises so if females to start selecting males that are less violent less sexually violent did that might lead to The Disappearance of the penis do I think you just said Is overtime because the ladies were ladies were discomforted the gentleman changed and lost their penises
00:08:28yep you got it she's saying that the two females essentially castrated males well this is a slower process suppose that what makes what makes you what evidence is there for such a thing I mean we're talking about penises which are soft tissue and they don't fossilized so even if we went back into the fossil record it would be really hard to fight find evidence of what was happening so that's the part that is difficult you know it's kind of like a a wonderful story that that I think makes a lot of sense given what we know about the way these penises work now but we can only speculate I like this idea good but is this just a one-off I mean
00:09:20what about Gorillas in Moose who fighting Clash their horns I mean there's so many species where it just seems like the females have zero choice so I know that there are a lot of cases like that bed bugs are specially horrifying Google it I don't you talk about bed bugs but there are actually a lot of cases where when the females do get to choose they choose in ways that completely change what we see in nature are we found a group of scientist who now argue that if you look around nature you will see females driving evolution in ways that I certainly didn't expect and when they get into the details of how this actually works I think is going to flip your ideas about evolution in a way that you are totally unprepared for do they have evidence for this idea cuz I got to say to you haven't yet convinced me the first thing they said dad that females have evolved the penis is away like I still have a guest
00:10:20I think will spell it speaks for itself in his regards and they are really cool beautiful beautiful iridescent blue with a violet blue eyes this is Gail Gail patricelli and I'm a professor of evolution attic and ecology at UC Davis do I say that again without stuttering on and no no it's anyway so the bowerbird what makes them most amazing is that they build Bowers so about our these things a bird spilled is basically a structure made out of sticks which can be up to 3 ft tall and it repeats whole but it's really a kind of Seduction theater with one seat and that end and that's for her this is Richard prum of Yale University's are biologists there and he says that on and around this
00:11:20the mail will a real a whole bunch of found objects objects beautiful things. Feathers and berries and flowers and leaves stuff that the bird gathers from the forest Asobi structures can be very ornamented an elaborate species has its own style of all be blue everything blue feathers blue flowers and of course blue trash like drinking straws and bottle caps
00:11:52the male Barber. Basically dedicates his whole life learning how to build these structures like take the satin bowerbird they take 7 years before they reach sexual maturity and during that. Of time they look just like females an elephant fly around the valley and get courted by adult males so they play the role of the female and learn how courtship works from other males in the valley and then when they get a little older as teenager will start building practice Bowers Mill Court each other and eventually want to borrow bird figures out how to make a really good structure
00:12:28female has arrived females often check out the bower itself isn't symmetrical is it will build and if she likes what she sees slender the bower this is where things get interesting because the bower has a very particular and purposeful architecture won the classic Bauer designs is called an Avenue Bauer so it's it's two parallel walls of sticks that that are close to one another and the female sits between them there different variations on the basic design but in all cases the female is in a protected position there's always some kind of barrier or wall between her and the mail so the male wants to try to force himself on her for whatever reason he has to run around the back and she can just fly away out the front
00:13:25even as he's trying to win her attention completely he's built a building that keeps her at a distance absolutely the bower is like insurance against date rape for the female it allows the female to observe him at an intimate close distance for as long as she likes while still maintaining our freedom of choice for the female if she likes the Bauer
00:13:49so settle into this protected space where she can back out whenever she likes
00:13:56and then time to begin the show
00:13:59Doyle start out with his own his own displays many of them very loud and electronical sound do they do they do imitations of kookaburra you know
00:14:17sometimes they imitate
00:14:22then along with singing
00:14:24the dance they puff up when they run vigorously back and forth right in front of the female and she's standing between the walls of the Bauer watches all of this from her safe spot for as long as she likes and she can decide she would like to meet with this guy or girl
00:14:52that was particularly interesting here is a gale has done studies that show when the males play very close attention to the female body position the way that she's like pastured that can actually signal whether she's interested or not the males that respond the most of the signals are the most successful in mating you know the words you can mail makes his move too early and too aggressively she's gone and that mail doesn't have any babies but it also seems like the females are of toying with the males like seeing what they're willing to do for them like if you if you want you can see in 1 hour bird she comes in he like a list of his wing with a cape and then just like sort of rotates his wing like this like it's so funny like a matador and then right after that she picks up a bluebird
00:15:52from the ground and then she drops the blueberry and then he does the Matador thing with the blueberry in his mouth
00:16:12seems to be all about her
00:16:18play I see what you mean in this case yeah I did females are definitely driving driving the bus here and when you start to really think about the implications of all about her that can lead you to a fairly deep rethink of the very basic rules of how Evolution works really well normally the classical argument reason this male bird is so colorful so rare. Whatever the reason the peacock has these gigantic and beautiful feathers on its tail is sort of a signal that the mail is sending to the female of Fitness look at me I am healthy to have a tail like this I don't have parasites I'm strong I be a great mate like survival of the fittest ask you if you just heard about bird story you have these females with these crazy taste like this one likes blue only blue and this one likes iridescent shells so
00:17:18sell sell sell sell sell than this one likes green leaves but they have to be right side up and never write that you're upside down Fitness signals or is this more like art
00:17:31maybe she just likes blue or she just likes shells but you're saying that
00:17:39these birds evolve based on on whims and tastes well Rick and there's other planets like him save absolutely yes it's about beauty I'm really focusing in on aesthetic choices choices that are based on what it is the animal likes
00:17:59where is it the whole darwinian thought was will yeah okay there might be Beauty there but on some level the logic behind those beautiful things is survival survival of the fittest it does not sound very darwinian of well as you drop the name I propose at my view is the legitimately authentically Darwin interview. He had an idea about beauty he actually can I bring you some okay pastry 97 Descent of Man stripes and marks and ornamental appendages have all been indirectly games through the influence of Love jealousy through the appreciation of the beautiful and through the exertion of a choice
00:18:44how interesting they saying that his love jealousy and beauty and choice and choice and that is definitely not what I learned what I learned about driving so it's over a hundred and thirty years later and I'm still pissed he thinks there was some kind of plot to reduce Darwin's idea into something smaller and eventually eliminated entirely I would like to go historical let's go out with Darwin said okay let's go with Wallace said and then let's go to the 20th century and where we got so screwed okay
00:19:20Charles Darwin spent 20 years working on his theory of natural selection he was not particularly noisy about it because you knew it would very much Disturbed his wife was quite religious and other people in his church so during the twenty years while Darwin was working away at his book this other guy comes on the scene his name is Alfred Russel Wallace kind of skinny and Scrappy and self-taught 14 years younger than Charles Darwin but Wallace also went around the world collecting specimens and he also came up with a theory of natural selection
00:19:54independently what was the relationship to each other I mean to date where they friends where they collaborators where they won't you don't they close collaborator said first they kind of both got credit for the idea but a little later Darwin rocket it out his book into its breath when he published his On the Origin of Species very popular book Darwin got the Lion's Share of the credit as I think rightly so because he's been working on the idea for literally for decades then 20 years later Darwin dies meanwhile Wallace lived until the dawn of War II document after Darwin die Wallace kept saying over and over and over again that would have came to female Choice animals didn't have the sensory and cognitive capacity to make aesthetic judgments and nature so these elaborate decorations and be artistic behaviors could only evolve if it communicates
00:20:54information about Vigor quality and general fitness to survive and wasn't around to argue back the the battle over credit for the discovery of adaptation by natural selection what do you want the war over what evolutionary biology would become the 20 Century we have inherited both the science and the culture of flattened dumb down and ideologically purified version of Darwin's actual richness fighting words about you see Rick is pretty fired up about this and he's written a book of evolution of beauty where he argues that ever since Alfred Russel Wallace scientists have been trying to squeeze everything they see in these maille patterns male dancers male songs male plumage has do a single explanation a dogmatic category called Fitness and that female choice they claim is always always about
00:21:54Fitness Fitness Fitness has no no that is that's a stretch there's no way to boil down all this variety into fitness I'm not saying that the emperor wears no clothes I'm saying that the emperor is wearing a loincloth what I mean by that is that humble garment covers about the same percentage of the human body as the idea of a adaptive covers all the ornaments of a sexual ornaments in the world is that most or most of what you see in the world you think is his desire of the desire between creatures expressed in in beautiful phone absolutely not a fitness not that oh that she's just looking at him thinking he's strong Keys genetically trustworthy none of those just I love him
00:22:48yes what he said most most of the time when you see the ornaments that's not Fitness at all that's if you have those what he said most yeah he's big-time on most
00:23:01know that I mean it as a human how would you ever even know the inner workings of another creature's mind to know enough to say what it isn't this driving them or not I got this very quiet I know I asked that very question $200 just came by SWIC right isn't it impossible for you as a human being that any idea what a lady animal wants to see in a guy if that lady animal is a peahen what you aren't or a trollop I'm ready to answer this I hope I'm in here it is I don't know what she wants now but I know historically she's wanted exactly what you see in those males the peahen has wanted that big ol tail she's wanted the show that she's one of the blue chest she has at some time or another in the last I don't know how many thousands of years she has wanted everything you see on him from the Fancy Feathers to the white skin around his eye to the iridescent blue the shaking that's what she has wanted in the past
00:24:01because it's there seriously yeah so you just happened to have this like fine nanostructured iridescent colors in your feather because like 42 interacting jeans across five different chromosomes came together to give you ear doesn't blue know the way you get to iridescent blue says Kim is you start small you give your female a bunch of choices which are the males and her block so imagine a female bird surrounded by a bunch of males who are all just boring or gray or black or whatever then totally randomly email shows up who just happens to have a little bit of blue on them and she noticed when the sun glints off of his black plumage there's just a little hint of blue in that black of kind of a glossy shiny blue black and she's like I like that I like that.
00:25:01is a little different than everybody else and I like it and who knows why it could be totally random too but for whatever reason she decides to make with the blue guy I like that and because he's passing on his jeans her sons are likely going to be a little bit blue to her offspring are going to have those beautiful jeans and we already know that the females chose him because he was attractive and so she's going to have attractive sons and her daughters are going to also find those traits attractive and the so what you get our generations and generations of females you say and then you're creating your your evolving the males to please the female and it all starts with our like that but I like that does it feel to meet opposite of Fitness like I like that could be
00:25:51a desire that is driven by Instinct and couldn't like the walls person walk in and be like yeah she likes that because she was designed to like that he's not thinking about the the the why there she's just having a desire but behind that desire is maybe a drive to get her to the mail that is the best like it could be the same with us to with people like that what we find sexy might have logic to it I told you about an animal who has a fierce desire for beauty
00:26:31and this particular desire for beauty is so strong that Fitness is out of the picture as another bird is another bird because they're beautiful Jazz you'll take a break and take a break and afterward we'll we'll come back with a third bird hi this is Sarah calling from Scarsdale New York Radiolab is supported in part by the Alfred P Sloan Foundation enhancing public understanding of Science and Technology in the modern world formation about Sloan and www.slha.org
00:27:09dad Robert battle Radiolab we're back mid battle between Beauty and fitness bird Battle Star third Bird Okay so there's a bird out there called the club winged Manakin and this mannequin lives in the jungles of Africa where she was somewhere in the jungle. America Colombia the mannequin that has a very small range in Columbiana quador is a little tiny bird the males and females are mostly red body and black and white wings with little flecks of yellow underneath them so these are small bird lots of color and female can raise the babies on her own so she doesn't need guys except for the Fizz the sexual act right he doesn't have to provide for her he just has to attract her
00:28:13SO2 that ends this is what our little read Romeo will do
00:28:19he'll sit on a branch in the Indian jungle and he'll wait a while until a female shows up
00:28:26and then when she does he has courtship display and he bounces back and forth on The Purge
00:28:33and while he's bouncing around every so often stops lowers his head sticks his butt up in the air as his wings all position and he throws them up
00:28:43behind his back and then he's vibrates or just Shivers he Shivers his wings together
00:28:52so that the only things that touch are those feathers across the back the tips of those funny feathers are going knock knock knock knock knock knock knock knock knock 39 times in a row and it takes about a third of a second for those 39 Knox their wings vibrate so fast but they make this sound can you make a can you make the sound
00:29:16it's impossible for humans to make with their voice
00:29:21is that seriously yeah yeah
00:29:25it's like a truck backing up exactly so he's not using his voice
00:29:33yeah it's like it's called speculation so this is a cricket winged Manakin would be perfectly good name for this part
00:29:42in any case something about that sound that specific sound excites the female
00:29:49that we don't know why but when it started but somewhere in The Byrds past a female decided she liked that sound and so the males just started to make it but here's the thing
00:30:01in order to make that sound yeah they really have paid they had they have paid because to vibrate your wings that fast
00:30:11107 times per second you need a rigid wing bone that you can really control
00:30:22and so the club winged Manakin has done something unheard of
00:30:29their wingbonz went solid just like a rock inside there this is a big deal because all flying birds have hollow bones actually can fly the even Velociraptor and T-rex half hollow that predates the origin of birds and the origin of flight but this guy has given this up in order to make these extraordinary Wing socks what does not hurt your ability to fly be able to LEAP buildings in a single bound cost of doing business for a display right
00:31:12think about that you're in a crowded Forest lots of competitors lots of predators trying to eat you and you have made yourself slower more vulnerable and it gets worse because Americans have to start this process of building these hard bones really early like when they're very very tiny in the embryo before the embryo has become either male or female so you got an embryo that can go either way and they're already making the big bones and some of them are going to be mailed but some of them are going to be female female also has daughters with distorted and inferior Wing Bones that they will never use
00:31:56both the females and the males get these thick bones so she is choosing to hear that sound and has designed him to produce that sound but in the bargain he comes out with heavier bones I could fly that swell and weirdly enough she comes out with heavier bones I could fly less well so both of them are hurting their chances to survive for the chance to hear the beautiful tone that she wants to hear that he wants to give her so she has her but she doesn't know bro Rick Scott immediately like I was like all this we are the females got the bumps on her bones till he's like
00:32:43talking about to let the females have it but they don't use it she's bearing the cost of her own choices decadence and this is like 20 years ago we both have such strange moments lyrics to see what did he mean so everybody in the population becomes worse off because females are so choosy and choose Beauty point of view you got a contest going on here to Primal drives and on the one hand there's the desire to survive survival of fittest right and according to that logic the mannequin should go for the things that make him Swift and powerful and agile
00:33:29but on the other hand there's a second drive to see or in this case to hear something they like something beautiful
00:33:39and in this case that second Drive is so strong that it's winning
00:33:45it's it's pushing the birds away from Fitness and others have as well and there is nothing in theory nothing to prevent this kind of process from leading to Extinction
00:34:04oh my God like you just got away with you just turned what I totally think of throwing Evolution on its head like we've always been taught that what these animals are doing is they're adapting as best as they can to new and changing conditions and they're getting better. But here you say that they are so hung up on desire and beauty that they even are going to get worse right well you know that's why this example is Checkmate but there are biologists
00:34:36eminent biologist hello baby sucking a lollipop or whatever you're doing is Jerry like Cherry Queen of the University of Chicago is it is it a lollipop or scarf dropped Jerry redrix book and is not not convinced by his argument well I think it's a good book but it's not a great but it's good because it has really great stories about mating behavior which are accurate stories as far as I know and they're quite absorbing promised a good writer this is great but instead it's tendentious that is his written to promote a cause which is of course that males with beautiful ornaments are shaped by female sense of beauty not Fitness exit the word Fitness is a huge problem and I don't use it anymore that you can't just say that and have it accepted by scientists unless you can test it okay and that is the problem when it comes to the store
00:35:36just heard like the bowerbird or the mannequin he thinks that more is going on here than what Richard says in his book you know take the female bowerbridge preference for Bowers at keep her apart from me I mean Richards explanation that it allows the female more time to choose it doesn't freak her out because she feels protected that might be the right right explanation but we don't know how many could be that females have an innate preference for being sheltered because it gives them a sense of security she like cats cats like to be a boxes right because they feel sheltered and they feel safe and could be the female bowerbirds of the same way and that will lead to exactly the same situation but with a completely different explanation and it's not just a random aesthetic phenomenon maybe some female bowerbirds like blue so much because blueberries are really good for them and their innately drawn to blue because of that
00:36:36set simply Delights the females but suppose that the females prefer males to have a certain frequency of when beating because they were attuned to that frequency perhaps because it indicates something in their environment that's useful to unlike the presence of a predator sound of a mannequin friendly animal or the protective animal or maybe the call of their own babies baby chicks and so they just have their nervous system innately tune to that frequency that's called sensory bias and that's another theory of sexual selection so they doesn't dispute the fact of female birds like Bowers to do for the day like a beautiful tone he just think that there might be a reason behind their liking and not reason could include that distract you are you are you hoping I guess is that the right word hoping that there might be a parasite signals involved here like you don't know you just want to know I don't know I mean that's my whole point and that's why I don't think I don't propose my own
00:37:36I'm not sure which one is that account for these mannequins with the heavy bones sweets just don't know oh my God don't know the difference between me and Doctor promise I have been I don't know
00:37:55the suggestion here is it Rick is clinging to a faith in one explanation for Wallace it was Fitness for Rick its beauty but still at dogmatic insistence I just think that adaptation by natural selection is is pretty boring
00:38:14you know we've been going to 150 years and we whip whip whip whip that pony quite a bit and we made a whole bunch of progress but you know what there was this huge world of opportunity in the static Evolution that that has been missed in fact we could set the whole point of a sense of beauty is it can be many many different things
00:38:36it is a beauteous fundamentally subjective
00:38:43so the aesthetic model requires that we put the subjective experience designer itself at the center of our of our scientific explanation
00:38:54what can you even have a science it's based on subjective experience or I think that that is science of subjective experience is not only a good idea it's necessary to understand the natural world
00:39:13yeah there is idiosyncrasy again ornithologist Kim Bostwick you can't take the individuals out of it is that science or is that just really comes down to Sheila carplex what that mail carp has she the worm lights with the worm has she the bird like what the bird has a half a trillion explanation of each one different and depending upon the lady didn't see you don't don't don't worry you that so-called Beauty and desire a category of an explanation as to not tell you very much at all I you all of us we are individuals we have unique histories
00:39:57and life on this planet has a unique History Science has a hard time dealing with unique instances but biology is it just in your face with it there are individual females making choices if that individual female had not made that choice history might have been different in the species might look different and that is true that's just true
00:40:30get in physics and chemistry there's a sort of conceit that but a scientist is supposed to do is take all this variety that you see in front of you and say look I can boil this down to rule which is always true of science usually is just to find some kind of Oneness inside the Menace but now we've got nature and living things and they have this crazy spectacular variety and now you've got a group of people who say you don't maybe we shouldn't even try to explain all this with one rule or one Paradigm but you know I wonder
00:41:15if some
00:41:17if that's still science or or is it more like history what if every species or every animal comes with its own stories interesting so which once upon a time and then once upon a time and once upon a time and then once upon a time once upon a time and only once upon a time once upon a time once upon a time once upon a time
00:42:18is this was reported by you have a crow witch and mental health day and Bethel produced the story thank you Bethel and special thanks to Jessica ski for her working peacocks and Mikayla Gunther for her work on hyenas we did mention that but we are very grateful to both of you say goodbye goodbye I'm not done with you. Okay thanks for listening and start New York
00:42:55where do rappers created by God album Rod and is produced by Soren wheeler Dylan Keith is our director of sound design movie luckenburg is our executive producer Dan Adler Becca Bressler Rachel acoustic David devil devil have the Tracy hunt Matt kielty Robert krulwich Julia Longoria and lettuce Nassar Melissa O'Donnell Kelly Prime sarakari Ariana wax Pat Walters and Molly Webster with help from FEMA and kneeled Denisa R fact Checker is Michelle Harris and I can verify that Michelle Harris is also cool thank you bye and this message

Transcribed by algorithms. Report Errata
Disclaimer: The podcast and artwork embedded on this page are from WNYC Studios, which is the property of its owner and not affiliated with or endorsed by Listen Notes, Inc.


Thank you for helping to keep the podcast database up to date.