Science Vs - True Love

Episode Date: May 11, 2017

What is love? With half of first time American marriages ending in divorce by the 20th anniversary, and infidelity being widespread, Science Vs asks: have we been lied to by our love songs? On today��s episode we explore: What happens to the brain when we fall in love? Is the compulsion to stay together biological? And, is monogamy really unnatural? We talk to Dr. Helen Fisher, Professor Larry Young, and Dr. Dieter Lukas about their labors of love. Our Sponsors:Everyday Bravery - Listen to Everyday Bravery, a podcast from Prudential, by going to everydaybravery.comVirgin Atlantic - Listen to their podcast, The Venture, wherever you get your podcastsZiprecruiter - try Ziprecruiter for free by going to ziprecruiter.com/sciencevs Credits: This episode has been produced by Wendy Zukerman, Heather Rogers, Ben Kuebrich, Shruti Ravindran and Rose Reid. Kaitlyn Sawrey is our senior producer. We’re edited by Annie Rose Strasser. Extra editorial help from Alex Blumberg. Production assistance from Stevie Lane. Fact checking by Ben Kuebrich. Music production and original music written by Bobby Lord. Special thanks to Joseph Lavelle Wilson, Austin Mitchell and to Professor Karen L Kramer, Professor Garth Fletcher, Dr. Alexander G. Ophir, Professor David Barash, Richard Bethleham . Check out Gail and Rose Reid's podcast Details Please.  Selected References:CDC - Data on First Marriages in the United StatesHelen Fisher fMRI Paper on Early-Stage LoveLarry Young Review Paper on the Neurobiology of Pair BondingDieter Lukas’s Paper on the Evolution of Monogamy in MammalsThe monogamy camp - review paper arguing “we evolved to be monogamous” Learn more about your ad choices. Visit podcastchoices.com/adchoices

Hi, I'm Wendy Zuckerman and you're listening to Science Versus from Gimlet Media. On today's show, we're pitting facts against fairy tales and we're exploring the science of love. And by that, we mean true love. That one true love. That person you're supposed to find and spend the rest of your life with. So at this moment right now on a scale of 1 to 10, how much do you guys love each other? I love you a 10.

Oh yeah? Yeah. You better never say 10. I was going to say 9.5 but I think it's a 10. This is Gail and Matt Reid and they've been together for 44 years. 44, it'll be 44 this fall. Yeah.

Gail and Matt met at college and still remember those first moments when they got together. I remember that we were walking in the rain in the field where the chapels were, and he went up to the, there was like a podium outside. And so I stood up at the lectern and I began to recite something from the beginning of one of the Doors albums.

But the wonderful thing was she didn't know I was quoting an album. So she thought I was being original, which is really fabulous. Tell it brother. When I was back in album, so she thought I was being original, which is really fabulous. Tell it, brother. When I was back in seminary school, a fellow put forth the proposition that you can petition the Lord with prayer. Petition the Lord with prayer.

You cannot petition the Lord with prayer So I must have been flirting Probably so Gail and Matt believe that true love is possible One person for life, happily ever after You know, what happens in the love songs For this is love. But not everyone believes in this idea of true love.

There are also one true love skeptics. Monogamy is ridiculous and people aren't any good at it. We're not wired for it. We didn't evolve to be. It's unnatural. I don't think as an animal, as a male animal, I don't think we are meant to be monogamous. In the past, in my monogamous partnerships,

sometimes I would have desires, like, and I would feel shame. A study published last year of more than 8,000 unmarried Americans found that one in five of them said that in their lifetime they had engaged in some sort of consensual, non-monogamous arrangement. And about half of first marriages in the US end in divorce before their 20th anniversary. So clearly, lots of people are reconsidering this idea about one person for life. So who's right? The true love believers or the sceptics? Today on our show, we'll try to answer this question and we'll do it a little bit differently to our regular show. We're going

to consult with advice columnists and relationship bloggers. Just kidding. We're obviously not going to do that. We're going to look at the science, like we always do. OK, so for the true love believers, we're going to investigate, one, that bolt of lightning, what happens in the brain when we fall in love, and two, happily ever after. Is the compulsion to stay together biological? And for the sceptics, we're going to investigate a counter-theory. Is monogamy unnatural and is cheating written into our very DNA?

When it comes to true love, there are lots of cheesy storylines. So this is the miracle. But then, there's science. Science vs True Love is coming up. After decades of shaky hands caused by debilitating tremors,

Sunnybrook was the only hospital in Canada who could provide Andy with something special. Three neurosurgeons, two scientists, one movement disorders coordinator, 58 answered questions, two focused ultrasound procedures, one specially developed helmet, thousands of high-intensity focused ultrasound waves, zero incisions, and that very same day, two steady hands. From innovation to action, Sunnybrook is special. Learn more at sunnybrook.ca slash special. What does the AI revolution mean for jobs, for getting things done? Who are the people creating this technology and what do they think? I'm Rana El-Khelyoubi,

an AI scientist, entrepreneur, investor, and now host of the new podcast, Pioneers of AI. Think of it as your guide for all things AI, with the most human issues at the center. Join me every Wednesday for Pioneers of AI. And don't forget to subscribe wherever you tune in. It's season three of The Joy of Why,

and I still have a lot of questions. Like, what is this thing we call time? Why does altruism exist? And where is Jan Eleven? I'm here, astrophysicist and co-host, ready for anything. That's right, I'm bringing in the A-team. So brace yourselves. Get ready to learn. I'm Jan Eleven. I'm bringing in the A-team. So brace yourselves.

Get ready to learn. I'm Jana Levin. I'm Steve Strogatz. And this is Quantum Magazine's podcast, The Joy of Why. New episodes drop every other Thursday, starting February 1st. Welcome back. So to figure out the science of true love, let's start with that feeling you get when you're newly in love. Matt Reid remembers when that bolt of lightning hit him. This is the story he told us. Gail had really needed this book that she left at her place. And it was like a winter night and there was actually like snow on the ground.

It might have even still been like snowing slightly. And I went over to your room and got the book and jogged down there with it. You did? And gave you the book. And I remember consciously thinking, I'm going to make her fall in love with me. Really? And now you've forgotten. I completely forgot.

So, Gail, do you remember when you fell in love with Matt? I just remember knowing, like feeling in the spring that I loved him. And then in the summer when they both went back to their homes for the holidays? The first summer that we were apart, I would sit in my room and I would play Midnight Train to Georgia, the song by Gladys Knight and the Pips, over and over and over again and just, you know, cry, you know, from the sadness of being apart. But what is that obsession, that craving, scientifically speaking? What is being in love doing to your brain? Recession, that craving. Scientifically speaking. What is being in love doing to your brain?

To answer this question, we met Dr Helen Fisher, an anthropologist at Rutgers University at her apartment in Manhattan. The doorman buzzed us in. Everyone comes here for Dr Fisher. Helen has spent her career studying romantic love. She pioneered some of the early research in scanning the brains of people who are intensely in love. Hello. Hi, Helen.

Hi, I'm Wendy. She wanted to see what was happening inside their brain when they had this crazy feeling. Before I ever put them into the scanner, I had to make positive that they were madly in love. So I would talk to them for hours, just hours. And of course, when you're madly in love, you can talk for hours. And I must be so patient.

I mean, teenagers are like in the early 20s talking about love. Oh, my God. It's fascinating. And the times that they talk about are charming. I mean, I remember one young girl saying, well, we walked home from the 7-Eleven at 3am and we had a lemon and he kept tossing it back and forth with me. And we were laughing, you know, and somebody else will say, well, you know, we were under the Brooklyn Bridge and we looked up and he said it looked like a cathedral.

Okay, okay, okay. So once Helen has established that these people are disgustingly in love, she then asks each participant to bring two photos to her, one of their sweetheart and the other someone neutral. Somebody at the laundromat, your distant cousin who you see once a year and just don't know at all. Then she pops them in the scanner. So I will flash on the computer and they will see a huge picture of their sweetheart, three inches from them, so close you could kiss them.

Helen alternates between showing them the photo of their sweetheart and then the neutral face, while the brain scanner is snapping images of what's happening in their brain. And then she'll compare the differences to see which parts of the brain lit up when looking at their honeys. They all showed in common activity in a tiny little factory near the base of the brain called the ventral tegmental area and it lies right next to the brain regions that orchestrate hunger and thirst. That tiny factory in the brain that Helen is talking about pumps out a particular chemical called dopamine.

And dopamine plays a big role in the reward system, which is what drives us to seek out food and water. It's part of what motivates us to stay alive. It's this chemical that ramps up when we have sex and take drugs like cocaine. In fact, researchers say that when they look at the brain on cocaine, it's, quote, remarkably similar, end quote, to someone in love. And to Helen, this means that we start seeing our beloved

in a totally new light. Everything about them becomes special. You know, the house they live in, the car they drive is different from every other car in the parking lot, the movies they see, the books they read, everything about them becomes special. Bottom line is that basic feeling of romantic love is generated in brain regions linked with wanting, with craving, with obsession, with focus and motivation. You're a huge romantic.

I guess I am, yeah, sure. Because with the study, because you interviewed a lot of people to make sure who was madly in love. Absolutely. And I was wondering whether maybe that was selecting for a particular type of person that falls in love in a very particular way. I wouldn't be surprised. There's always going to be human variation.

I've never met two people who were alike in my whole life, and I'm an identical twin. That's as far as science has gotten. No question about it that I was selecting for a person who was powerfully in love. I needed to have the full-blown experience. So, it's possible that not everyone falls in love this hard. Plus, interpreting how brain scans relate to feelings

is notoriously difficult. And Helen's first study, it only had 17 people in it. But her findings have since been replicated in other groups, including in a small study with gay men and women which showed that their dopamine factories also lit up when they were looking at pictures of their beloved. Conclusion. Under a scanner, the brain in love looks different

to the regular old brain. And it seems that chemicals in our brain, like dopamine, are at least partly responsible for that love-drunk feeling we get when we're in love. But can those chemicals keep us together for life? What does science tell us about our question number two, happily ever after? Is the compulsion to stay together biological? To figure out what's driving people to stay together in a monogamous relationship, we need to look closely at monogamous couples

to see what's happening in their brains. But the monogamous couples we need to look at are furry. Oh, here they are! These guys are actually quite vicious towards humans. Inside a little plastic container is a cute couple nesting. And these couples are chubby little rodents. They're called prairie voles. They're about the size of mice and basically look like cute rats.

And the scientist who studies them is Larry Young. He's a professor of neuroscience at Emory University in Atlanta. And Larry tells us that these little puffballs are in it for the long haul. They're monogamous. Yeah, these guys have been together for a while. Larry says that in the wild, the male vole wouldn't

hold back from trying to get a female's attention. He'd be a real flirt and if she decides she likes him, then... He mates with her and they find a nest together. After just 24 hours of living together with a mate, prairie voles will then hang out with their partners, in some cases for life. And if one of the voles dies, they will rarely pick another. One paper described the enduring nature

of this fluffball bond as extraordinary. You could just see how in love they were in their eyes. No, you couldn't see that. They're just rodents. They just have beady little eyes. But they were cute. Anyway, Larry led us out of the lab. Bye little guys. And back to his office to tell us about a similar but very different little animal. There's another species of vole, which is what really got me excited, that looks exactly the same, but they prefer to be alone. There's another kind of vole called a meadow vole.

But this little vole likes to hook up with whoever and it doesn't have a vole buddy for life. You see, it's all about free love for these guys. And they don't bond at all. For them, they mate, they have sex, but nothing happens. No bond is formed. Larry showed me a photo of the prairie and the meadow voles side by side. And, yeah, they looked exactly the same. Cuddly, fat rodents.

And as soon as Larry knew about these two species, he knew he wanted to study them to know what was going on in their brains. I thought as a scientist, you know, this is a cool system to be able to look in the brains and the genes to try to figure out what's different biologically between those guys that form these bonds and the ones that don't. To start his investigation, Larry cut up their brains to look for differences. And he found one big difference between these two species of voles. But to understand what he found, we first need to know how a receptor works in the brain.

So for a chemical to have an effect in the brain, it needs to have a receptor. This is a little protein that fits the chemical perfectly. No receptor and the chemical can't latch on and won't work. Larry was looking for receptors in the voles that would latch onto a chemical called oxytocin. Oxytocin is another chemical, like dopamine, that's associated with feelings of love. And Larry found that in the monogamous voles, there were a whole bunch of oxytocin receptors in a particular area of their brain.

It has a kind of weird name. It's called the nucleus accumbens. And you can see the prairie voles have lots of oxytocin receptors there. But the free love voles didn't have those oxytocin receptors in that area. You can imagine that when this animal mates and there's lots of oxytocin release, you're completely having a different effect on the brain. So we said, wow, could this be what's responsible for the prairie vole for being monogamous? The next step to test his idea that concentrations of oxytocin receptors were responsible for getting the monogamous voles to couple up was to block the receptors, meaning that the oxytocin was not going to work in that particular spot in their brain.

Larry thought maybe if he could mess with that part of their brains, the nucleus accumbens, then maybe they would become like the free love voles. So we stuck the tiny needle down into this area and infused just one microlitre of this oxytocin receptor blocker. And then we just let them mate. Then he got another group of monogamous voles and got that tiny needle down into that area. But this time, he infused it with a placebo. So the oxytocin receptors were working just like normal. We could see very clearly that the animals that made it, that got the placebo, they all wanted to be over with their partner.

What were they doing? They kind of cuddle. We call it huddling, kind of sit next to each other, very motionless, and maybe groom each other. What is groom? What are they doing when they groom? So they groom, it's just sort of licking, and you're like with their fingers sort of grooming through the hair. Larry's currently doing like a little, I guess it would be my impersonation of a rat, but I guess that's your impersonation of a vole.

Yes. So the voles injected with the placebo. They were still being all cutesy and hanging out with their partner and fixing their hair and stuff. But the animals that, where we blocked their receptors and we tested them the next day, they could care less. That is, they didn't give their partner extra attention. No special huddling, no special grooming.

It didn't matter to them that they had mated with this other animal the night before, two nights before. They treated them like a stranger. They treated them like a stranger. You unmonogamised voles. Exactly. So how is all this working? Well, Larry thinks that when the voles mate,

oxytocin gets released, which floods the area of the brain that he was shoving those needles into. He then thinks that information about the vole's sweetheart, like their smell, gets encoded into that area of the brain. And this, he reckons, helps the voles remember which particular vole gave them the time of their life. So they couple up with them and then they act all cutesy.

Right, so the oxytocin is helping to make new neural connections. And we think that this is making the nucleus accumbens now say, hey, this is a special situation. But no oxytocin receptors in that particular area, like the free love voles who don't couple up, then you don't know that your partner is special. Knowing this led me to ask Larry one obvious question. Do you think it's amazing that vol and love have the same letters in them? Yeah, that's pretty cool. Just two nerds

hanging out. Okay, no, there was another obvious question for Larry. Does oxytocin-fueled huddling in voles bear any resemblance to human true love? If you had to rank the evidence that what's happening in voles is happening in humans, say an A plus is we have so much evidence that what is happening in voles is definitely happening in humans. This is a driving force in humans humans a f is that happens in voles and we're all mammals so maybe where would you rank the the research well the evidence that that is happening in people is pretty strong b plus b plus well i mean i think it's an A that something is happening, right? To the extent to which it is happening, we're not quite sure. Larry points to studies showing that oxytocin in humans

can affect how we interact with our partners. And as for those oxytocin receptors, well, just this year they were found in that special spot in the brains of humans as well. But still. I want to make one thing very clear. Vol bonding is not the same as human love. When we love someone, you know, we can use our elaborate cerebral cortex to think about how wonderful our partner is, what we can do in the future, all kinds of, it's much more complicated. But underneath that, there's something, there's this gut feeling that we want to be with that person. And I think that's what voles experience.

They don't experience all the cognitive complexities that we do, but they just have this gut urge to be with their partner. And I think that oxytocin is sort of creating that gut urge. Conclusion. Oxytocin receptors have an important role to play in driving the voles to stay together for life. We humans also have that same special pattern of receptors in our brain, but humans have a big, complicated brain,

so it's not clear how far these receptors and these chemicals are motivating us to couple up. Because as anyone who's ever been in a relationship can tell you, our big human brains definitely complicate things. It's not all about gut urges for us. Sometimes other things just get in the way of true love. Here's Gail and Matt again. He started giving me s**t all of a sudden about lowering the toilet seat

and I thought I was just going to kill him over it. It's the stupidest thing. Do you remember that? Not the seat, the lid. The lid. The lid. She was telling me to lower the seat and I said, you know, what really makes sense is to lower the lid. Why is there... Okay, do you see what kind of minutiae bull**** this is? So my point was that if there's a lid, the only reason to have the lid is to close it. I couldn't believe we were even discussing it. I didn't bring it up. You said lower the seat. No, no, no. No, you brought it up. You told me it was very important to you

that from now on, I lower the lid. And you were mad at me. And I just thought, go f*** yourself, Matt, with the f***ing lid. Don't I do enough? I clean the f***ing toilet. I do this. I do that. What kind of simpleton obsesses over the f***ing toilet lid? Or really? Come on, Matt. It's stupid.

Okay. I need to answer what kind of simpleton I am? Yes, you do. It's a simpleton thing. No, I don't have to answer that. You see what I've lived with all these years. You know, you've asked me to fold T-shirts a certain way. I do.

You want them folded the way they came from, f***ing at Hanes, without the cardboard, without the plastic. But they've got to be folded a certain way. Unlike most people who just throw their s*** in their drawer and it looks like crap. But I'm just saying, if I can fold a T-shirt in a way that makes you and your mother happy, you can close the toilet seat. I do.

I do do it. I do it. And it's not that big a deal. No. And just because you fold t-shirts like a simpleton doesn't make me love you less. I put flowers in the bathroom. I like flowers in the house. I buy flowers.

I really like having flowers in the house. Daddy likes having flowers. He does. And I buy flowers mostly for him. I buy flowers. I really like having flowers in the house. Daddy likes having flowers. He does. And I buy flowers mostly for him. She keeps them around for me. I do. So how does it get to a point in a relationship where it can be so annoying when someone asks you to put the lid down?

It's hard to know, Wendy. It's really hard to know. So it can be pretty tricky to stay with one person for life, especially when they leave the toilet seat up. Or was it the lid? Coming up after the break, we examine the true love skeptics case. That is, we're not built to be with one person for life. What science and our evolutionary past has to say about that. Plus, we'll tell you the story of Matt's relationship with another woman called Gail. Yes. Not his wife.

Gail number two. You stupid piece of s**t. Welcome back. So we've talked about the chemicals in our brains potentially driving us to couple up. Now it's time to look at true love from the skeptic's position. That is, that we are not built to spend our entire lives with one true love. So let's start with this question. Did we evolve to be monogamous for life? Now to find that out, we really have to know how our ancestors were bonking hundreds of thousands or even millions of years ago. Well, it's pretty hard to look back that far. But one way of doing it is by thinking through the theory of evolution.

So, according to old Darwin, the whole idea of evolution is about survival over generations and generations. So, the most successful individuals would have traits that drive them to have the most kids, because more kids means more chances that one of those kids lives to have kids of their own. Now, by this logic, you would think that monogamy would not be a successful trait, because surely having sex wherever you can get it rather than trying to tie yourself down to one mate would be the way to go, right?

And this is why when it comes to monogamy, a lot of scientists are asking... Why the heck are they doing that? Scientists like Dieter. Hi, yes, my name is Dieter Lukas. I'm a researcher at the University of Cambridge in England. Dieter is an evolutionary biologist, and he's looking at the family tree of mammals to figure out why monogamy evolved. And here's the first thing you should know. According to Dieter,

only 9% of mammals are monogamous. So in the group that we belong to, the mammals, it's actually quite rare. The majority of mammals have sex and then separate, leaving females to take care of the kids on their own and males to keep on breeding. But there are lots of other ways that mammals do it. There's polyandry. That's where you have one female and many male partners. Sorry, ladies, but it's actually very rare in the animal kingdom. But we do see it in some primates, like tamarins. There's also polygyny, and that's where you have one male with many females,

like in gorillas. Then there's our closest relatives, chimps and bonobos, who seem to practise free love, with males and females both sleeping around. And then, yeah, there is monogamy. One female to one male, which you see in Gibbons. So, Dita tells us that it's believed that our earliest ancestors were polygynous.

That is, there was one male to several women. And you see, when we spot polygyny in other animals, the males tend to be much larger than the females. That is, there's one male who's big who can fight off the other males to keep his harem of females. And when we look at our ancestor who lived three million years ago, Australopithecus afarensis, some estimate that the female was about two-thirds the height of the male, which suggests that at one point we were polygynous. Here's Dieter. The early ancestors, after we split from our common ancestor with the chimpanzee,

that there was still quite a bit of difference in body size between men and women, that men were quite a bit larger than women, and that it actually declined then over the millions of years. From about 1.9 million years ago, those body size differences shrunk and shrunk, which brings us to today. Based on CDC data, American men are on average about 8% taller and 15% heavier than women. So still bigger, but not by much. So, have modern humans evolved to be polygynous or monogamous or even something else? Because academics actually don't agree. And there's a big debate.

So do we have any idea as to when humans began being monogamous? So don't quite know at what stage monogamy really first started in humans. There's huge debates. For those who think that humans are still polygynous, they point to the fact that men are still larger than women on average. But the other camp of researchers say that we shouldn't be putting so much stock into this bone size difference theory. They argue that if animals are around the same size,

like humans are today, then you actually can't tell much about whether a species is polygynous or monogamous based on the size. But there's other evidence on both sides. So, for example, the monogamy camp point to the fact that there are those love chemicals like dopamine and oxytocin and they say that suggests we evolved to bond with one other person, while Team Polygyny look at rates of male violence or even beards and other male displays

to suggest that men are still competing for a harem of women. All in all though, Dieter? Hi, yes. He warns us that it can be really hard to know what to make of some of this evidence, partly because it's informed by our current notions about how men and women are supposed to behave. So, I mean, we always think that science is so objective and science can tell us the truth, but of course the questions we ask are already informed by what we want to know. And if we wanted to know whether males use aggression

to fight over females, we can find evidence for that. And if we never asked whether females use aggression to fight with each other, we just didn't see it so there is i think this bias in what has been studied that is now changing where people are realizing no the situation is much more balanced among the sexes that really is helping us to get a better picture of the behavior and dita ultimately says that when it comes to this question of whether humans evolved to be monogamous. I currently can't think of any way how we could ever know without a time machine. Great Scott! So until we get our

time machine, Dieter kind of throws his hands in the air. I don't even know how to classify humans within this whole system. They don't fit with this pattern of it's easy to say okay they're monogamous or not. Conclusion. It's really hard to know how our ancestors lived and loved, and if we really did evolve to be monogamous or not. Some scientists say yes, some say no, but there's no slam-dunk evidence on either side. But here's the thing. Even the most romantic of evolutionary biologists, those who do say that we are monogamous, don't necessarily think that we evolved to be with a one true love for life. In fact, when scientists say the word monogamy, that often means that animals are just staying with a partner for a breeding season or

two or three before heading off into the sunset with a new love, a mating system called serial monogamy. Here's Larry, our vole whisperer. When we say monogamous as biologists, we're differentiating them from the most of the other species that don't form any kind of bond with their partners, right? So most mammal species, they mate and then there's nothing. So there's a sexual attraction, but nothing else. So we're differentiating humans and prairie voles and a few

other species in the sense that when there's, after the mating, they actually like each other and they want to be with each other. So if we humans evolved to be monogamous, even if just for a breeding season or two, Does that mean we're not going to cheat? Remember those voles? The ones who stay together for life? Well, there's something else that they do. And that's sleep around. Yep, even the monogamous voles have an occasional side piece.

Here's Larry. Even though they bond for life, that doesn't mean they'reamous voles have an occasional side piece. Here's Larry. Even though they bond for life, that doesn't mean they're never going to have an affair. Mm-hmm. A group of scientists ran genetic tests on the babies of paired-up, so-called loved-up voles and found that 20% of the litters were sired by someone other than their supposed dad. Which means the mum was having a bit of fun on the side. If you look in nature and you take a nest, and she'll have a number of babies, say four to five babies,

most of the times those babies are all, they belong to the male who is her partner. But oftentimes they do not. And we see cheating all over the so-called monogamous animal kingdom. It's been estimated that around 90% of bird species are monogamous, but the eggs they're hatching together sometimes come from another birdie daddy. And what about us, humans? Humans. Well, even for our true lovers, Gail and Matt, even they've struggled with a little bit of eye-wandering. Who is the Gail?

Her name was Gail also. The marathoner? Yes. Enter the story of Gail number two, another Gail. Matt had met her while he was training for a marathon. And that was like the most important thing that he was doing. And I remember one Sunday in particular when the kids had the chicken pox, he was training for his marathon and then he went and had bagels and coffee

and I was just livid. When I went out for bagels and coffee, it was just livid. When I went out for bagels and coffee, it was me. Whoa, whoa, whoa, wait, wait, wait. So while the kids have chicken pox, you're getting bagels with Gail number two. Yes. It all escalated to the point where Gail was convinced that Matt was having an affair.

And then to top it all off, there was this dinner arranged for the marathon runners. Matt said to me, spouses weren't invited. So I called, and they said, oh, of course spouses can come, you stupid piece of s***. So why did you say that spouses couldn't come? I know, I don't make s*** up. Somebody must have told me. Because I never have ever done anything that excluded Gail in my life.

Because this woman was really hot for him. And he was probably enjoying it. And I don't blame him. Because, you know, it's not easy to have small children and, you know, your wife is bitchy. Did you have a crush on Gail too? No. Yeah, you did. Did you enjoy flirting with Gail too?

I'm sure I did. I liked to flirt. Did you enjoy flirting with Gail too? Yes, he did. I'm sure I did. I like to flirt, but I like to keep my distance. You know, I don't get scared if somebody actually, like, responded to being flirted with. I believe that is true. So have either of you ever cheated? No. I've never cheated.

I've never cheated. No. No, I've never cheated. I never. She's told me she hasn't, and I have to believe cheated. No. No, I've never cheated. I don't, I never, she's told me she hasn't and I have to believe her. Okay, so Gail and Matt say they haven't cheated, but many have. A 2015 review paper wrote that, quote, infidelity is relatively widespread, end quote. Widespread. Anyway, 20-25% of married men and 10-15% of married women in the US

admit that they have had extramarital sex. And while it's possible that married women are more faithful than men, it's also possible that women just don't like to admit to their infidelity. Conclusion. Infidelity is found throughout the animal kingdom. There's just no escaping it. But when we do look at the animal kingdom in search of what is natural,

there's one final point to consider, and that is this. There are always individuals who break the mould. So remember that genetic study of the monogamous voles with the mums who had cheated on their partners? Well, in that study, two females didn't bond with their male partners. Instead, they coupled up with each other to raise the kids. And get this, not all monogamous voles even couple up at all.

They're not cheaters. They're just their own vole person, or what Larry calls wanderers. In nature, 60% of male voles will form this bond with a female and will nest with that female. The remainder of 40% are wanderers. So you can't say voles have this one kind of behavior. Wait, so 40% of the male monogamous voles are non-monogamous? Right, exactly. What about the females?

Females are the same way. Point is, this is science and it's complicated. And even the voles, our pin-up animals for monogamy, are complicated in their own way. So when it comes to science versus true love, does it stack up? First up, what happens in the brain when we fall in love? Under a scanner, the brain in love looks different to that regular old brain of ours. Chemicals that play a powerful role in our drive to have sex

and eat and take drugs also get pumped out when we're in love. Two, what drives our compulsion to stay together? Well, we know that voles and humans have chemical receptors in their brain that play an important role in making us couple up. But when it comes to our evolutionary history, it's not clear whether for most of our ancestry we were polygynous or monogamous. Finally, is cheating written in our DNA? Well, throughout the animal kingdom, and that includes us, infidelity happens. So perhaps the propensity for cheating is somewhere in our DNA. But the thing is, when you're looking for guidance on how to live your life, evolutionary theory can only take you so far. The fact that

millions of years ago, some pre-humans might have been living in a harem or even that all kinds of animals cheat, even the voles, that doesn't mean that you should or shouldn't be monogamous in your own life or even that your true love fairy tale ending can't happen for you. Bottom line is, don't let Darwin tell you how to live your life. He's dead. Here's Helen. Now, I mean, we're not puppets on a string of DNA. All kinds of people say, oh, God, that girl is cute. You know, if I weren't married, I'd go for her in an instant. And they choose not to. Because, I mean, you know, we make decisions in our lives. We've got a big cortex to do that. But it's remarkable how many people do fall into, at some point in their life, an adulterous relationship

and then one way or another they solve it. Still, this is clearly no fairy tale story. Science Versus senior producer Caitlin Sori asked Helen about it. This is a different kind of happy ever after story than the one we were sold, that, you know, you find the one and that's it. It's like, no, choose your own adventure and, you know, you can do what you like.

Yeah, we were lied to by our love songs. So this is life. Given that it's all messy and choose your own adventure-like, I asked our true believers, Gail and Matt, any advice? Well, no. I just, I don't really understand, you know, how one does this. Because, you know, we were just so lucky to find each other and then more or less figured out that we had found each other. And I think there's a lot of luck to that.

I really do. I love you, honey. Oh, I love you. And I always have, and I always will. I will always love you, too. That science best is true. The trifecta is when I shop, I cook, and I clean. And I say, oh, I got the trifecta.

And she looks at me, and instead of saying, thank you, honey, instead that she gets that little fire in her eye. Because I do it all the time, but I never shove it down your throat. You don't do it as often as I do. That's science versus true love. This episode has been produced by me, Heather Rogers, Ben Kebrick, Shruti Ravindran and Rose Reid. Caitlin Sori is our senior producer. We're edited by Annie Rose Strasser.

Extra editorial help from Alex Bloomberg. Production assistance by Stevie Lane. Fact-checking by Ben Kebrick. Music production and original music by Bobby Lord. Special thanks to Joseph Lavelle-Wilson, Austin Mitchell and to Professor Karen L. Kramer, Professor Garp Fletcher, Dr Alexander G. Ophir, Professor David Barash and Richard Bethlehem.

Also, if you liked hearing from Gail Reid, she actually has her own podcast with her daughter, Rose Reid, who helped make this episode. It's called Details Please. It's just been launched and it is hilarious. The first episode has an interview with Mel Brooks. It's called Details Please. Also, stick around after the break to hear perhaps the cutest old couple you've ever heard. It's Gayle's parents and they're still married and they're still in love.

After 60-something years, it's ridiculous. I'm Wendy Zuckerman. Back to you next time. So we had dinner and then we were in the living room and my mother had out a bowl of fruit. So we had dinner, and then we were in the living room, and my mother had out a bowl of fruit, and in the bowl was the ring box. And Norman said,

Why don't you have a piece of fruit? And I said, I don't feel like having fruit. He says, Have a piece of fruit. So I said, All right. So I took a piece of fruit and there was this ring box. I said, what's this? And he said, just open it and you'll see. So I opened it and there was the engagement ring with a nice size diamond. And said hmm this is pretty good so I accepted 64 years and we're still happy and we're still in love that's a big deal They say that for me, love is wonderful, marvelous.