Science Friday - Undiscovered Presents: Like Jerry Springer For Bluebirds

Episode Date: November 20, 2019

“Do men need to cheat on their women?” a Playboy headline asked in the summer of 1978. Their not-so-surprising conclusion: Yes! Science says so! The idea that men are promiscuous by nature, while women are chaste and monogamous, is an old and tenacious one. As far back as Darwin, scientists were churning out theory and evidence that backed this up. In this episode, Annie and Elah go back to the 1970s and 1980s, when feminism and science come face to face, and it becomes clear that a lot of animals—humans and bluebirds included—are not playing by the rules.   GUESTS Angela Saini, author of Inferior: How Science Got Women Wrong Patricia Adair Gowaty, professor emeritus at UCLA, editor of Feminism and Evolutionary Biology.   FOOTNOTES Sarah B. Hrdy is an anthropologist, feminist, and a major figure in this chapter of science history. In this book chapter she addresses the myth of the “coy female” and reviews the relevant scientific happenings of the 1970s and 80s, especially in the primatology sphere. Angus John Bateman’s 1948 paper about fruit fly mating and reproductive success, popularized by this paper from Robert Trivers in 1972. Bateman finds that males have more reproductive success the more females they mate with, and that females don’t benefit as much from mating with multiple males. Patty Adair Gowaty found holes in Bateman’s study. Bateman didn’t know exactly how many sexual partners his fruit flies had because he didn’t watch them. Instead, he counted up how many offspring they made. Unfortunately, a lot of them had harmful mutations and died—skewing his numbers. Not only do they not meet Mendelian expectations, but in Bateman’s data, he consistently counts more fathers than mothers—which can’t be right, since every baby fly has one mother and one father. Patty found that eastern bluebird females successfully raise offspring without help from their male partners. Patty and Alvan Karlin found that eastern bluebird babies aren’t always related to the parents raising them. True “genetic monogamy,” where bird couples only have sex with each other, appears to be the exception, not the rule in passerines. Polyandry—where females have sex with multiple males—has been found most of the species studied! In the late ‘70s and early ‘80s, a psychology study at Florida State University found that most men, and no women would accept a sex invitation from a stranger. In this more recent Germany study, 97% of the women expressed interest in sex with at least one strange man, but only when researchers promised to arrange a (relatively) safe encounter.  Btw, Patty tells us bluebirds don’t actually have sex in the nest, so having sex “outside the nest” is the norm. We were using the expression figuratively, but worth noting. The nest is really for storing the babies.   CREDITS This episode was reported and produced by Elah Feder and Annie Minoff. Our senior editor is Christopher Intagliata. Fact checking by Robin Palmer. I Am Robot and Proud wrote our theme. All other music by Daniel Peterschmidt. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Hey, Ira here, letting you know that our beloved podcast, Undiscovered, is back for a couple of final episodes. I'll let Annie and Ella take it away. Hey, everyone. Hey. So it's been a little while, and you might not have expected to hear from us again. Some of you declared us dead prematurely. But after two seasons, Undiscovered is unfortunately saying goodbye. It has been an honor to play in your ears, to get your emails and reviews, and

tweets and see you sticking your undiscovered stickers on things. That was really cool. Yeah, it's meant so much to us and we're going to really miss sharing these stories with you. But the good news is, before we go, we do have a few final episodes for you. So Undiscovered, it's always been about how science happens. And, you know, it's not a steady march toward truth and wisdom. And it wouldn't be nearly as interesting if it was. And some of our very favorite stories that we have discovered in the process of making this show are about things that us humans, scientists included, got wrong and how we changed our minds. And how we'll probably change them again.

Inevitably. So this is undiscovered. We were wrong edition. First up, we have a story about sex. I want you to imagine, it's 1978, Florida State University. There's a young woman. She's standing in one of the quads on campus. It's a weekday. I know that it was not raining. That is all I know about that day.

And this woman, she's scanning the area for men that she finds attractive. This is what we female college students do. So he has to be not only attractive, but attractive enough that she would consider sleeping with him. According to whose rule. I'm going to get to that. You'll find out who's pulling the strings here. Okay. It already feels like kind of perverse. Just stare with me. So she's scanning for attractive men. and when she finds one, she consults a notebook that she's carrying.

The notebook tells her what she's supposed to do next. So the notebook always contains one of three instructions. It tells her to ask this man on a date or to ask him to come back to her place tonight. What? Or to ask him to have sex. So this time, let's say it's option three. Just like, hey, you? Well, it is.

This is how it goes. She walks up to the man. She tells him she's noticed him on campus. She finds him very attractive. And then she asks him, the actual wording is, would you go to bed with me tonight? And when he gives her his answer, she thanks him for his participation in a psychology study. Yep. That's the worst.

Yeah. Awkward study. But there was a reason for it. It all started when a professor was having an argument with some students about who wants more casual sex, men or women. It was the late 70s. By now, the sexual revolution had come women's liberation. Our views about women were changing. Women were now judges and astronauts and Billy Jean King had beaten a man at tennis. And some people thought, hey, without all our old cultural baggage, men and women are more similar than different. And this professor was saying,

not so fast. When it comes to sex, we are still different. Men, he thinks, are always down for sex. A man, he says, will sleep with any woman who asks, but women, whole other story. His message is not well received. One woman threw a pencil at him during this, but this professor figures, okay, we can actually settle this. We don't have to debate it. We can do an experiment. And that's how this study happens. He sends out young college students, some men, some women, to ask strangers of the opposite sex, one of three questions. Do you want to go on a date? Do you want to go to my apartment? Do you want to go to bed? I really want to know what happened. I mean, I think I know what happened. Do you though?

I'm Annie. And I'm Ella. And in the next few episodes of Undiscovered, we're talking about the science we used to believe and how we changed our minds. Today's episode, we're talking about the idea that men want sex with as many people as possible. While women are monogamous, they're looking for love and commitment from just one person, that this is in our biology, and the idea that might not sound so unfamiliar even today. I feel like we've heard all probably a version of this idea. Today we're going to find out what could possibly be wrong with it. Do you know, I think for a long time I always bought into this idea too.

That's Angela Saney, science journalist. I just assumed that this was how it was, that biologically, this is really how men and women are. So, sure, it sounds like a tired old stereotype. But on the other hand, it is an old idea, and there's some science that seems to support it. Even Darwin wrote about this. He took it for granted, really. He took it as a given that women are naturally more chaste and modest. And in Victorian society, certainly, they must have seemed that way to him. Darwin wrote that the males of almost all animals have, quote, stronger passions than the females. But Darwin didn't really have a good explanation for why.

And then in 1948, a geneticist named Angus John Bateman comes up with a simple experiment. He puts male and female fruit flies in bottles, leaves them out for a few days to have sex and make baby flies. And he finds that for a male fruit fly, the more sexual partners he has, the more babies he makes. For a female, one partner? Often plenty. More partners didn't necessarily mean more babies. And if evolution is about reproducing and spreading your genes, this would explain what Darwin noticed. You'll see biologists talking about eager males and choosy females. Eager males that have a lot of mates make more babies, get more of their genes into the next generation.

Cheosy females, on the other hand, they'll mate with only the very best male available to them, because, you know, why bother with extra males if you get diminishing returns on the baby front? So I actually studied evolutionary biology, and I incredibly never questioned this idea, you know, setting aside that me and a lot of people I know are actually gay and don't see ourselves in these rules of sexuality. From a theoretical perspective, it just made so much sense. And there was evidence backing it up. Lots of species that fit this pattern, Bateman's cool fruit fly experiment. And by the 70s, there's human evidence, too. Oh, no. We're coming back to the study.

Yeah. Okay, so here's what that study found. Remember, we're going back to Florida in the late 70s. When it came to dates, men and women were about equally likely to agree to go on a date with a stranger. Actually, higher than I thought, about half agreed to go on a date with a stranger. I mean, it's very nice to hear that someone has been noticing you. Well, it depends on what they're proposing. When it came to going back to a stranger's apartment, men agreed.

69% of the time. Wow. And when it came to being invited back for sex, even higher. 75% of men said yes. Wait, if it was just like because you're getting rid of the ambiguity of the apartment. Yeah, this is clearly a sex invitation. Women, on the other hand, none of them said yes to sex with a stranger. And they made it known just how offended they were to even be asked.

So the people who wrote this study assume that this confirms this stereotype that men are promiscuous. They must be in order to be so willing to have casual sex with a stranger, whereas women were clearly not interested in sex because otherwise at least a few of them would have taken up this offer. Okay, but here that the man number being that high is surprising to me. Wow. But I feel like actually the low number for women, it's like a safety issue.

That is one of the criticisms of this study. and someone does eventually put that to the test, but we're going to get there. For now, this professor seems to have won the argument. He actually does the study a second time in 1982, nearly identical results. And the newspapers eat this up. He tells them that men want recreational sex, women are looking for love and commitment. He actually adds that the results are offensive to most of his female grad students. And he's just like, well, sorry, dudes, like my data has spoken.

I mean, basically, it seemed like science was backing up our stereotypes. You know, feminists might not like it, but look at the theory, look at other animals, look at these college students at Florida State. Evolution made us this way, or so it seemed. After the break, a young biologist notices some animals are not playing by the rules. Keep your best leg forward, sweetie. This one March day in 19th, 1970, a group of women headed out to Wall Street to sexually harass men.

Oh, they're so beautiful, all of them. Oh, those men, those sex objects. This is some of the least credible sexual harassment I've ever heard. Hey, how do you like that hat over there? Oh, why the shat foam? How about glasses? I like them with glasses. ABC trailed them around for this documentary.

Some men look amused, others are just ignoring them. A few actually crowd around to sneer and heckle. but these women have the microphone. You like people to understand what it feels like to have someone go all the time. And they tell us that we're supposed to think that it's a compliment. In the early 70s, women's liberation took center stage all of the major networks ran reports about it, and feminists were challenging ideas about how women should be treated,

who we were, what we were capable of, and a young biologist named Patricia Adair Gowdy. She was here for it. I simultaneously became biologist. and a feminist. These happened at the same time. I called up Patty a few months ago, and obviously for her feminism and science, they are not inherently in conflict. She says a lot of feminism's ideas, you can actually turn them into testable hypotheses, and science can be used to test if they're true. In the 1970s, Patty's studying Eastern Bluebirds for her Ph.D.

They're like little songbirds, like the kind that dance around Disney princesses. male and female bluebirds raise their babies together in pairs. And the reason that was given in the old literature was that females needed all the help they could get to raise all those kids. And I thought, hmm. And so I did an experiment. She took their males away. And she found females do quite well, thank you. They can do a whole lot of work without the additional help from males.

Next, Patty decides to test another bit of conventional wisdom about songbirds, technically passerines, which is that they were almost all monogamous and that females never or rarely had sex outside the nest, shall we say. And Patty again thinks, hmm, let's find out if that's really true. Why don't we run bird maternity tests? This is like Jerry Springer for bluebirds. Yes, somebody is going to be throwing chairs by the end of this because it does not end well. She takes blood samples from dozens of bluebird nests, including 16 complete bird families.

These weren't fancy DNA tests back then. She's looking at just two proteins. And what she finds is that in at least four of the nests, something is up. There's a baby whose proteins don't match either the mothers or they don't match the fathers. And some of that could be basically bird adoption. Eastern bluebirds sometimes lay eggs in other bluebirds. birds nests. But Patty thinks another part of it, females are having sex with males other than their main partner. Patty will not call it cheating because they're birds. And to be fair, we do not know the terms of their couplehood. But whatever you call it, in the mid-80s, she's talking about this at a conference. And a very famous ornithologist said, oh, Patty,

those females are being raped. And those were his words. and I just rolled my eyes. Oh, this took a dark turn. I mean, there is a lot of rape in the, well, this seems like an inappropriate word to use, but. Forced copulation. Yes, that's the word I'm looking for. There is a lot of that in the bird world. Yeah, in the duck and goose world especially, but in bluebirds, Patty says no way,

not if you know anything about bluebirds and their physiology. She says females are mating with other males. But this guy dismisses it out of hand. And actually, at this point, it's not super clear. what's going on? There's no smoking gun of infidelity, just a surprising number of baby birds that don't match their parents. But Patty wasn't the only one noticing that female animals seem to be breaking the rules. A bunch of studies were coming out in the 70s that found female animals are not all as choosy and monogamous as people had previously thought. Like red-wing blackbirds. So they live

in harems, groups where multiple females apparently mate with just one male. Emphasis on apparently. Because in this one study, they gave that male of vasectomy and yet the female's eggs were still getting fertilized. Other researchers caught female lions sneaking off to places where their current male partners couldn't see them or waiting until their partners fell asleep to go have sex with other males. And in songbirds, remember how when Patty started, conventional wisdom said that songbirds were almost all monogamous. Yeah. Well, after a bunch more paternity and maternity tests, it turns out that even though

they do generally pair off, males and females still sometimes have sex with other birds. In the songbird species we've studied, strict monogamy is the exception. The list of not-so-coi females goes on and on. You know, pipefish, baboons, our closest relatives, the chimps. But, you know, these examples, they don't necessarily prove that the idea of eager males-chusy females is wrong. Like these could just be kind of exceptions to a very well-established rule. Exactly. There are always exceptions. We still have lots of examples that do work with this rule. And we had that really cool study in fruit flies. So do you remember the main takeaway from that study?

Yes. I'll remind you. Yes, please do. For a male fruit fly, more sexual partners meant more babies, not so much for females. But remember, this was nice. So if Bateman throws a bunch of fruit flies in a bottle, how does he know who had how much sex with who, aside from watching them day and day out? So it's actually very, very clever for its time. Bateman gives every fly its own visible mutation, things like having a tiny head or hairy wings. So when you look at the babies, if you see one with, say, Bob's tiny head, Bob's a fly. Yeah, I got it. Okay, if you see one with Bob's tiny head and Cheryl's hairy wings, you can see, aha, that means that Bob and Cheryl did it.

Got it. And so that's how he calculated who had sex with who. So it's a great idea. Except just over a decade ago, Patty decides to take a more careful look at that paper. And she notices a few things that don't add up. For one, babies are missing because Bateman hadn't fully taken into account just how powerful and harmful these mutations were. They died like flies. So Bateman wasn't totally clueless. He knew that if a baby fly got two copies of, say, the curly wings mutation, it was dead. But what Patty figures out

is that if you get two different mutations, that kills flies too, which threw his calculations way off. And there were a few more problems with this study, but the upshot... His estimates were biased and they were biased in such a way that, oh my goodness, made his point. And yet somehow for decades, people miss this. And despite Patty's work, they still miss it. I looked at Patty's paper on Google Scholar, 69 citations since it was published in 2012, which is respectable. Bateman's paper, though, in the same time, over 1,400. Bateman's paper, you know, there's only one way to really understand the fact that people continue to cite Bateman's paper.

They believe it. They believe it without data. But I think most people don't understand it, because if they understood it, they would see the empirical difficulties. So to recap, our famous foundational study has massive cracks in it. And we've got a lot of species where females do go after sex with more than one sexual partner, sometimes very enthusiastically. And if that's true, you have to ask why. Based on what we said earlier, females should not be doing this. They shouldn't get anything out of it. Well, Patty thinks it's time to scrap that whole theory.

She's come up with something called the switchpoint theorem, which doesn't have any a priori assumptions about males versus females. But a lot of other people will tell you it's not that the theory is wrong. It's just not the whole picture. Because it turns out there are a lot of reasons for females to have sex. besides making more babies. It's fun? On top of fun.

Okay. Like hedging your bets. More fathers means more genetic diversity in your kids, which ups the odds that at least one of your kids is really successful in the evolutionary sense. Another one. In crickets, and I'm going to put a gross warning on this. Okay. So the male will present a female with what's called a spermatophore. Are you familiar with these?

No, not at all. It's like, it's a bundle of sperm and food. Basically, she's getting sperm, but she's also snacking. Is she eating it? Yeah, so it's a meal. Oh. And also somehow a sperm delivery vehicle. And so for these female crickets, you know, more sex, more snacks. And on the flip side, for males, we were saying more sex, more babies.

Well, that's not the only thing they need to consider either. For example, STIs. Yeah. Not just a thing that affects humans. If you're a male and you have sex and you contract a virus that kills you or weakens you and makes you vulnerable to predation, you know, maybe that's not going to result in more babies long term. Yeah. And so I think where we're at is a lot of people still believe that the general trend across species is that males are more eager and females are more choosy. Because all else equal, males should get more babies out of mating a lot.

But as one of my old profs told me, not all else is equal. There are actually a lot of factors at play, which is why you see so much variation across species. Angela Saney, the science journalist we met earlier, she credits people like Patty for the progress we've made. You know, people who see female bluebirds cheating when other people don't. When we all bring our particular assumptions and biases to the table, and we all do have them, men, women, everybody, then we get a kind of check on the mistakes. then it's more difficult for people to propagate bad ideas because there are people there to ask,

actually, well, have you taken this perspective? Have you thought again? And the other big lesson for Angela is actually, you know, if we're going to go back to our original question, are human men and women fundamentally biologically different? We got to watch how much we're reading into animal studies. Angela says, look, like scientists will run these great experiments in mice or in flies. And then the natural tendency of the scientist is to say, not just publish a paper saying we see this in mice or we see this in fruit flies, isn't that interesting for mice and fruit flies?

But to say, well, what implications does this have for us? And this is where you get a hell of a lot of speculation. We are not fruit flies. We are not mice. So what about us, humans, if we're going to ask that question? I really, really hope we're going back to Florida. We are going back to Florida. upset me so much and I would like you to tell me now why it is wrong.

Okay. So a few years ago, some researchers in Germany were wondering, you know, they instinctively did not buy this study. Or at least they looked around at the men and women that they knew and they knew plenty of women who were interested in casual sex. So they decided to do the study again, this time it was in 2013. And basically what they found, you're not going to like this. It held up the original finding. But. But as a woman in the 70s on a college campus, some strange man comes up to you.

The things going through your head are not just, do I feel like sex right now, but also will this guy kill me? You know, what is going on here? There are so many other social factors. Not least, let's be honest, the idea of judgment, you know. It's not okay even now for a woman. to go around saying to people, yeah, I'm up for casual sex in the same way that it's okay for men.

There is still a social taboo around that. Yeah, social taboo and safety. Like this dude is already kind of acting outside of norms by being like, I just saw you for the first time and have been watching you from a distance. And then you're like, come to my place where it's just going to be us and we're going to have sex. No. So this is actually what the German scientists were thinking. You know, why don't we do another experiment that's a little safer?

So they presented men and women with pictures of people who were interested in having sex with them. They were told. And they said, would you have sex with any of these people? And actually it wasn't just a hypothetical as far as the subjects knew. They're like, we will, if you choose some people for sex, we will set that up. In a controlled environment. And what they found instead was that very many women were interested then in having casual sex with one of these people. In fact, 97% of women chose at least one man for possible sex.

So that ran completely counter to the original study. And if you're wondering, 100% of men chose at least one woman for sex, but statistically, no difference. So this experiment, it's not perfect either. I mean, yes, they take out the danger component. But it's totally artificial. So think about it. You're looking at pictures in a lab, you know, telling researchers, yes, please kindly arrange this sex meeting for me. And actually, not only do they say we'll set up sex in a controlled environment, they say,

we're going to film the first 30 minutes of the encounter before we leave you alone to do as you please. Like, who is signing up for that? Did they really buy that this was going to happen? The researchers actually did ask people afterwards, hey, did you buy the experimental setup? And people said, yes, they did for the most part. So I don't know. Maybe I don't understand people or maybe they were being very polite to the researchers. Either way, I doubt this is the final word on human sexual appetites.

But I hope this is the last of this particularly awkward kind of study. Because these people have feelings, damn it. Right? Like don't tell them that somebody's into them and then yank the rug out when they say they're interested back. Undiscovered is reported and produced by me, Ella Fedder. And me, Annie Minoff. Our senior editor is Christopher and Taliatta, and our composer is Daniel Petershmit.

You can read more about Patty in this story in Angela Saney's book, Inferior, How Science Got Women Wrong. And as always, get links, get footnotes, get all that good stuff at undiscoveredpodcast.org. Ira here again. Next week, Annie and Ella are back with another episode. This one's about the killer ape theory.

Intriguing. Look for that on Wednesday.