Sex disrupts society – evolutionary psychologist 

SS: All right, so what a topic to talk about. One of your books is called ‘The Evolution of Desire’. Human mind has evolved in the course of human history and continues to evolve, as well as our values. But what you call ‘desire’ basically describes our most ancient and core feature, the drive to procreate, which as I understand hasn't really changed much since the dawn of human society. So there isn't much evolution to our desire after all, is there? 

DB: Well, the short answer is yes, there's a huge amount of evolution in the sense that our current minds, our current mating minds, are the product of a long history of evolution. So basically, evolution deals with differential reproductive success, which boils down to essentially differential mating success. And that is, we are all successful descendants of a long chain of ancestors, all of whom have succeeded in finding a mate, attracting a mate, engaging in sex with a mate, and investing in the children for a long enough period for those children to survive to reproductive age. And so as the successful descendants of this chain of ancestors, these successful ancestors, we have inherited from them the desires that lead to successfully attracting a good mate, a fertile mate, a mate who will invest in them. So, our minds, everything in sexually reproducing species of which humans are one, everything has to go through mating. And so, if at any point in our evolutionary history, one of our ancestors failed to succeed in mating, they would not be one of our ancestors, they would basically hit an evolutionary dead end. And as a consequence, we have a very complicated mind, a very complicated mating psychology that has evolved over many, many, many thousands of years.

SS: Right, so our desire to procreate could be seen as, on one hand, purely selfish, egoistic drive to pass on our genes, to leave a trace in history to achieve some sort of immortality, etc. On the other hand, it could be seen as a very altruistic, selfless thing to make more humans to help the species, to help civilisation, enrich everyone. Which way do you think is closer to the truth, if any, really? 

DB: Well, the way that I think about it, we don't have a desire to procreate. What we have is just like when we're attracted to food, and we find food delicious. We just find the food delicious because we have inherited from our ancestors food preferences for things like sugar, fat, salt, and protein. But we don't think, ‘Oh, I'm eating in order to survive.’ Our mating minds are just we're attracted to mates of high mate value, of high fertility, of high status, of high investment potential. And so in the here and now we're just trying to mate, have sex, enjoy a relationship, have a satisfying romantic relationship. We haven't necessarily inherited a desire to reproduce per se.  

SS: So when we experience falling in love, there are so many hormones having a party in our brain, right? Can we be considered slightly mad when that happens?  

DB: Yes. 

SS: And what kind of evolutionary purpose does that serve? If any, once again. 

DB: Yes, well, it does. And love is an evolved emotion. And it evolved in the context of long-term committed mating, pair-bonded mating. And that temporary insanity that you described that when people fall in love that can't last very long. I mean, it lasts six weeks, maybe three months or so before people have to do things like work and eat and engage in other tasks. But I think that what that does is that causes the intensity of pair-bonding, and when coupled with sexual involvement, it releases, as you said, a suite of hormones, including oxytocin, that causes people to bond with this partner for the long term. 

SS: So it's basically evolution’s fault that men are more likely to go around mating with as many females as they can, while females will prefer a male to stick around and ensure her and her offspring survival. And if these behaviors are so deeply ingrained in us by our biology, then why do our cultural norms about relationships try to contradict biology so hard? 

DB: Well, I don't see them as necessarily contradictory. And the way I would describe it is this. We have inherited a menu of mating strategies, we have short-term mating, as you imply, we have long-term pair-bonded mating, and everything in between: intermediate-term relationships, extra-pair sex or infidelity or cheating. And so men, as well as women, have this long-term mating motivation. And men also, and women have a short-term mating motivation in certain contexts. So are there sex differences in desire for sexual variety in seeking or being receptive to a number of sex partners? Yeah, absolutely. [I’ll] mention one study that supports this sex difference, and it is an evolved sex difference, and that is a study where people of the opposite sex simply approach strangers, and ask them, ‘Hi, I've been noticing you around town lately,’ and asked him one of three questions: ‘Would you go on a date with me?’, ‘Would you come back to my apartment with me?’, ‘Would you have sex with me?’ Women approached by the man, 50% agreed to the date, 6% agreed to go back to his apartment, 0% agreed to have sex. Women need a little bit more information about a total stranger and are unwilling to do that. But of the men approached by the women, about 50% agreed to go out on a date with her, 69% agreed to go back to her apartment, and 75% agreed to have sex.  

SS: There you go.  

DB: With a total stranger! And so that illustrates that men and women do have very different mating minds, or in this case, different sexual psychology in the short term. But, and this may disturb some men, women also have a short-term mating psychology. It's not so much sleeping with strangers, but it involves mate switching. So women who, for example, are unhappy with their relationships, sometimes look out and sometimes have affairs as a way of exiting a bad relationship in order to transition to a better relationship or trading up in the mating market. 

SS: Alright, but still, overall, when I look around me, at least, I don't know about you, but I do see men are more prone to change life partners in numbers. I'm not even talking about wanting to have sex with as many women as possible, including total strangers, but also committing themselves to mating partners. I know men who changed their wives because they just strived to be with younger women. And then for women, it's not like that, in general. In general. 

DB: And for men, it's not like that, in general either. You're absolutely right about your observation. But it's men who are in a position to do so, do what I call ‘mate switching’, they engage in a serial mating strategy. And it's men who have power, men who have status, men who have resources that are attractive to women. And so they have a sufficient mate value that they're able to switch partners, as you say. But there are a lot of men who don't have status, power or resources, and they are unable to engage in that serial mating strategy. 

SS: Okay, but if we come down to this, if all women and men had those resources, mating resources, would you say that women and men would change partners equally? 

DB: Well, not in terms of external resources. So this is one way in which evolution has dealt an unfortunate hand that disadvantages women. And that is that women have a much more compact period of reproductive capability, so that is when women hit 40-50, their fertility and reproductive capability is very, very low whereas men can still reproduce at 50, 60 and sometimes 70 or 80. And so there's a sex difference in the sort of reproductive span of males and females. And so that's, that's partly what accounts for this sex difference in engaging in a serial strategy. But I can guarantee you that women who are high in mate value, do switch partners when they're able. 

SS: Alright, so like other animals, men and women are made to procreate and it's the most natural thing to be engaged in this very pleasant process. But for the past couple thousand years at least, our culture - be it Christian, Muslim, Hindu, Confucian, doesn’t matter, you name it - has tabooed the topic so deep, forbade public discussion of it, frowned upon deriving pleasure out of it, tried to control who does it with who, and when, and why. Why has sex itself been treated - and still is, really - as if it was something that is, like, almost dangerous to humans?  

DB: Well, because humans have evolved to interfere with other people's sex lives, in a nutshell. And the reason is that the evolution occurs by differential reproductive success. And that means that one person success is another person's failure. So if you're a woman or a man, and you're trying to attract a high mate value individual, one person's success in attracting that person is another person's failure. And so we have evolved to try to control other people's sex lives, including our partners. So we in long-term pair bonding, we engage in mate guarding, which is driven by the evolved emotion of jealousy. And we also try to instill social norms that control other people's sex lives. That is, we don't want a bunch of promiscuous people in our social environment because they're going to be poaching on our long-term mates, and they're going to be causing a disruption. Sex is a very disruptive force in social life. It's also a glorious and wonderful force, can be. But it is dangerous, and we shouldn't underestimate the danger of it.  

SS: Is jealousy also a biological thing. And I mean, is female or male jealousy connected to procreation? 

DB: Yes, I don't use the term ‘biological thing’. Biology is defined as the study of life and life processes. And so there's a sense in which everything we talk about is biological, including culture. Okay, but yes, jealousy is an evolved emotion. And that is, it evolved with long-term pair-bonded mating. Once you have long-term pair-bonded mating, which is very, very rare, in the mammalian world, you have to have adaptations to ensure the pair-bond. And one of them is jealousy. You want your partner... It motivates you to guard your partner, to keep that partner faithful, and to keep that partner from leaving you. And so without it, it's kind of like, if you have a very expensive house, you don't want to have a house with no locks on it. You want locks and security systems to guard that valuable house. And the same thing in mating. We have jealousy which motivates mate guarding and mate retention, both on the positive and negative side. So jealousy can lead to violence, an intimate partner violence, but can also lead to wanting to keep a partner by bestowing a lot of resources on the partner, showing love, giving gifts and so forth. So jealousy evolved right along with sex and long-term mating in our species. 

SS: Homophobia - is that widespread, very old tradition connected to evolutionary psychology in some way or no? Is there an evolutionary perspective on why gay people encounter hostility towards them for most of our history? 

DB: That's a great question. And the short answer is, it's a puzzle. I don't understand that myself because you would think that there would be just the opposite of homophobia, that is, from a male perspective, for example, you would think heterosexual men would be delighted if other men were gay because that would mean a greater access to a pool of women for themselves. So I find homophobia a very puzzling phenomenon, and I don't have an explanation for it. 

SS: Okay. Oh, this is also a growing polyamorous movement around the world and with people who establish some kind of rules to let them love or mate with more than one person while staying in a relationship with another or having two relationships at once, just sharing your relationship with two or more people. From scientific point of view, is this possible? Or is it an approach doomed by the way evolution shaped is? 

DB: I think it's possible for some people. So one of the things that is involved in polyamory is... First, there's a sex difference. So men are more likely to want to have a polyamorous situation where they have sexual access to more than one woman. Some women do as well. Some women have a high desire for sexual variety. But jealousy is a very powerful emotion in polyamorous relationships. And so what polyamorous couples try to do, or polyamorous triples or quads, they try to instill rules to keep jealousy at bay, to keep jealousy at a minimum so that it doesn't disrupt that polyamorous relationship. So what you have is you have competing mechanisms here, you have a desire for sexual variety, on the one hand, which polyamorous relationship can satisfy, but you also have sexual jealousy and the desire to keep a partner for yourself and faithful. So I know one polyamorous couple that I’ll just mention, they have a primary relationship, he's heterosexual, she's bisexual. And so she sometimes sleeps with other women, sometimes with other men. He gets very upset if she sleeps with other men. He's okay with her sleeping with other women. And from her perspective, she doesn't mind him having sex with other women, but she minds if he gets emotionally involved with another woman, and so that emotional involvement is very critical to women's sexual jealousy. 

SS: What about polygamy? I mean, we have societies with polygamy and they seem to be doing perfectly fine. I mean, ancient polygamous societies also never complained. Why is monogamy in today's world, our default stance? Is it rooted in our evolution in a way, or why? 

DB: Yeah, that's a great question. And... Couple of things. First of all, most cultures historically have been polygamous in the sense of it legally permitting men to marry more than one woman. About 83% of the cultures around the world historically have been polygamous. But most people don't engage in it. So even in polygamous, polygynous cultures, it is only a minority of people who engage in it. So it's men who have high status and high resources, who can afford to attract two or three or sometimes more women. But it's not a happy situation necessarily because there's conflict among co-wives. The women in these polygamous relationships sometimes get along fine. But there's conflict and competition over the man's attention, investment and resources. Now, monogamy, what we have is we don't really have monogamy precisely for the reason that we talked about earlier when you asked this question about mate switching, and people engaged in trading partners. So we have this, what I call, presumptive monogamy where this is held up to be some ideal, but in reality, we don't. We engage in serial mating before marriage, we have infidelity after marriage sometimes, we have divorce and remarriage. And so we don't really effectively have a monogamous culture. We pretend that we do. And legally, in many cultures, we do. But in actual behaviour, it's not truly monogamous for most people. When you have a polygamous culture, it creates a large pool of bachelors. So in other words, a large pool of single men for whom there are no potential mates. And that's a recipe for trouble. Because when there's a large pool of young, I would say, horny young males, sometimes they engage in violence or other forms of social disruption because they are mateless. I mean, we evolved to mate. And when you have a pool of males who can’t find a mate, it's a recipe for trouble. I mean, similar things are happening. I mean, not just in those cultures, but, for example, in China, where they had a one-child policy for many years and a male-biased culture, so that women, girls were selectively aborted or sometimes killed. And so you have the surplus of something like 40 or 50 million single men in China. And so when you get the sex ratio imbalances, this causes a lot of trouble. 

SS: I don't know, David, I think right now we're experiencing quite the opposite. I think women numbers are twice as much as men numbers. 

DB: This is especially true among educated people, so women are exceeding men in college degrees, they get better grades, higher degrees as well, doctors lawyers, there's been this general trend where the greater equality has created a sex difference such that there's a surplus of women. And it's especially true among educated women. And given that women are very, very choosy about who they mate with, and women who are successful and educated, want partners who are at least as educated and successful as they are, there aren't enough educated successful men for this large pool of educated women. And so I call it in my book ‘the mating crisis among educated women’, and I hope that there's a solution to that because women are not exactly happy with that situation. 

SS: Yeah, that's true. What about the widely available birth control change? Does it change our mating habits? I mean, I know it hasn't been around for too long to make a lasting impact yet, but theoretically speaking, a pill and a condom enable sex for purely pleasure purposes with no childbearing consequences. So evolution drives us to have sex for procreation. Pleasure is just it’s tool to make us like having babies, right? But if you make pleasure the ultimate goal, how is that going to change the love equation or the equation in general? 

DB: I would say pleasure is only one of the goals. So one of the things I discuss in my book is the many reasons that people have sex and pleasure is just one of them. So people also have sex to make their partner happy, to solidify the pair bond, they have sex in order to get resources, people have sex for a variety of reasons, not just pleasure, although, of course, pleasure is very high up there. And you're absolutely right that evolution has instilled in us an adaptation to make sex very, very pleasurable. I mean, it motivates us to do things that historically have led to successful mating and successful reproduction. Now, the pill, which was introduced in the early 1960s, does sever that link between sex and reproduction. And so what it means is that people have more control over their timing of when and under what circumstances they have children. And so I think this has led to, in essence, a greater freedom because of that severing of the link between sex and reproduction. But we still have the same evolved psychology now as we did when the pill was first introduced, our fundamental mating psychology has not changed. And so that's still what we have. And that's what drives our behavior. 

SS: The results of your experiments sell the idea that males and females are creatures from totally different planets, if you will. The way we'll look at sex, mating are not just slightly different, but very contrasting, right? And this makes me think, if both sexes serve the same idea to procreate, why has evolution made us so conflicting in our nature? 

DB: Okay, so that's a great question. So first of all, men and women are not from different planets.  

SS: Yeah, that was a figure of speech, obviously, we're not. 

DB: We're similar in many respects. But we're also different in many respects. The differences come out because men and women have faced different adaptive challenges over human evolutionary history. For women, one adaptive challenge has been securing a man who's going to invest resources in her over the long term because these resources have made the difference between survival and death for her and her children. And so we may not think about that so much in the modern environment because we have a lot of food abundance, but over evolutionary time, there were droughts, there was starvation, there were harsh winters when there was very little food available, and a man who could invest and provide those resources was an extraordinarily valuable mate from a woman's perspective. From a man's perspective, one adaptive problem that he faces is identifying fertile females. And then, here's one other critical sex difference is that fertilisation occurs internally within women, not within a man. And what this means is that women are always 100% sure that they are the mothers of their children. No woman has ever given birth and wondered, ‘Gee, is this kid really my own?’ No, they're 100% certain. Men – not so much. So some cultures use the phrase ‘Momma's baby – papa’s maybe’ to capture this sex difference. And that stems from a fundamental fact of our reproductive biology that fertilisation occurs internally within women. And so men can never be sure. And so men have evolved high-intensity sexual jealousy, for example, in post-mate selection, so they want to keep their partner sexually faithful. And so we do have done studies, for example, where we asked people what would upset you more – if your partner had passionate sexual intercourse with someone else or if your partner become deeply emotionally involved with someone else? And most women say, ‘Oh, it's a no-brainer, the deep emotional involvement would upset me more.’ And men are more likely to say, ‘No, the passionate sexual intercourse is what causes men to go crazy.’ And so the sex differences really boiled down to the domains in which men and women have faced different adaptive challenges over human evolutionary history. 

SS: Right, Dave, I could go for hours and hours talking to you. And I hope we get to do this again. Thank you very much for this wonderful insight. And good luck with everything with the future books and experiments and I really, really hope that we get to do this again.  

DB: Okay, I do too. It's been wonderful chatting with you. 

SS: Thank you so much.  

DB: Okay. 

SS: Bye-bye. 

DB: Bye-bye.