The Uncomfortable Science Of Sex Differences - Steve Stewart-Williams

Do you think that you could have published this book 6 years ago? >> I think that I could have, but it would have been a less wise move. >> [laughter] >> I think it would have gone down a lot worse 6 years ago. Things have kind of cooled off a little bit, I think. >> Why is talking about sex differences so controversial? >> Well, it's a good question, and I think that it's a few things. I mean, sometimes it surprises me cuz sometimes I think a lot of the differences that we're talking about, they're really quite modest differences. Um they are often differences in preferences rather than cognitive abilities. So, they're kind of neutral as far as I'm concerned. Um and if anything, I think probably they put men in a worse light than women. Um so, sometimes it surprises me, but I think really the main reason is a long history of sexism against women. And I think that we've got quite a long science as well has a bit of a sorted history in terms of how we've spoken about women, especially in the 1800s. I've got a quote, one of my favorite quotes, one of my favorite examples of this is from um scientist by the name of Gustave Le Bon, and he he wrote that uh sure, there are some women who are as intellectually accomplished as your typical man, but they're about as rare as a as a two-headed gorilla. And so, therefore, we don't really need to think about think about [clears throat] them. Um so, with stuff like that in our background, it's I guess not surprising that people are a little bit a little bit nervous about talking about evolved sex differences, a little bit worried that if we start doing that, it's going to open the door to that kind of that kind of sexism. Um I think they're wrong to worry about that. I think that really the science of sex differences has disproved those kind of ideas. Um and I think I think as well that we can treat men and women respectfully and uh and as you mainly and treat them well uh even if men and women are not identical on average on every single trait. >> Yeah, I suppose the history of science is to sex differences what the Nazi Party is to behavioral genetics. >> Right. Right. Exactly. Yeah. Yeah. And I do think that science is the solution to the early sexism rather than a continuation of it. >> Yeah, that's a great way to put it. All right. Why is it important to study sex differences then? Why why should anybody care? >> Uh I think lots of reasons. The main reason for me is I think it's just deeply deeply fascinating. I just think it's >> It's the [laughter] best. Yeah. It's the It's the best, dude. Me and you fell in love with the same book, The Moral Animal by Robert Wright. He He changed my life. >> Yeah, likewise. It changed my life. It um shaped the rest of my career. Um just I think it's deeply fascinating. And um Yeah, I remember when I read that book uh that's when I fell in love with uh fell fell in love with evolutionary psychology. And in particular, fell in love with the evolutionary psychology of sex differences. And I got the same feeling that I did when I was a a kid and I first understood how the phases of the moon work. And everything just clicked into place. Suddenly, the whole thing made sense. >> Oh, that is why it looks that way. That is why people are different in that way. >> Exactly. Exactly. It all made sense. It was clear that it was true. And uh yeah, just uh sort of instant insight. And uh yeah. >> Interesting. Even as you're saying it, I can hear this sort of critic preparedness inside of my mind going "Why would you when you read a book Why would both of us when we read a book be so enamored by sex differences dot dot dot That must be because you are secretly a sexist who is looking to try and keep people in their place and not ever have any progress and da da da da da You know what I mean?" Like the conversation around this has become so tarnished. Um that >> Accusatory. >> Yes. Yes. Yeah. That you can't have an interest in something which is fundamental and fascinating and really important, right? So that you don't try and people aren't trying to fight against something so that we don't fully account for and understand why behavior unfolds in particular ways that can allow us to have a better society, a society that's got outcomes that's more close to what we want. Fascinating. >> Yeah, it is. Um yeah, so I do I agree with that and I think uh yeah. Sorry, I just uh I just went blank. What was What was I going to say about that? >> No, no, no. Uh just why is it important to study sex? >> Oh, yeah, why is it important? Yeah, so that is that points to another reason. So, one big reason why it's important is just the fact that it's fun uh fascinating. Um but I think also that like you say, it is important in terms of steering society in an positive directions. And uh underst- understanding ourselves, uh understanding interactions between men and women. Um in terms of yeah, trying to keep people in their place and the like. That's certainly not the philosophy that I come away with um from having studied all this over the years. Um I instead of it, my basic philosophy, I think I can summarize in just four words. And those words would be, let people be themselves. Uh so, if they if they fit with traditional uh gender roles and expectations, that's great. Uh but if they don't, that's great as well. It doesn't matter. The fact that something has evolutionary origin doesn't necessarily mean that it's good. Uh it doesn't necessarily mean that it's bad, either. I think that it's it's morally neutral and that it's up to us to decide whether it's good or bad or somewhere in between. >> I think that's a big fear that people have that by looking at the evolutionary explanation for why certain traits show up the way that they do, why certain differences occur the way that they do, it sounds like you're excusing away that behavior. >> Indeed. Like a lot of people do worry that that's the case and that people will assume that it's the case. >> It's a naturalistic fallacy in your way through all of the bad behavior of men or all of the worst behavior of women or all of the most repressive ideas that we have for how people should behave. >> Yeah, yeah. And I don't think that it does justify any particular behavior. Um but I do think it's right to worry that people might assume that it does, falsely assume that it does. So, I do think when we discuss these issues, uh that we should take into account the concerns that people have about this whole topic of sex differences. And we should discuss them carefully. And we should always emphasize that most of the gaps are not huge. Most of the psychological sex differences are not huge. Um that there's a huge amount of variation within both sexes, tons of overlap between the sexes. And also that there's no um normative implications or disimplications. So, no um sense of because something is evolved, because something is natural, that that therefore means that it's good or even permissible. Again, it's up up to us to decide that. >> Right to say that the the differences are modest at best, but when you start to stack them on top of each other, you end up with huge You basically end up with two completely separate Venn diagrams, right? It's not just preference for violence and risk-taking and parental investment and da da da da. It's when you put all of them together, you do have two very different groups of people. >> Yeah, those are called multivariate sex differences when you sort of cluster the differences together. Um I think that while that's statistically true, I think we have need to be a little bit wary about the concept of multivariate statistic multivariate um sex differences just because often we are thinking about single traits. So, often we're thinking about sex differences in parenting, sex differences in sexual interests and aggression, risk-taking, uh and and so on. Um but also if you were to divide up take take a group of people, divide them into two based on a flip of a coin. Um they're not going to be identical on every trait. There's going to be small differences between them. But then if you add up all those traits, you could just as well stack up the differences between these two randomly chosen groups of people, stack up the differences, and you'd find that they equally uh massively discrepant from each other based on the multivariate statistical approach. So, um so, I think we you to be wary about exaggerating the magnitude of human sex differences based on that statistical approach. Cuz you could just as well exaggerate the sex differences between New Zealanders and New Zealanders and Australians or and the British and the French or or like I say two randomly >> British and the French do that enough already. All right, there's been a last few years there's been a huge debate about what sex actually is. >> Yeah. >> What's the definition that you land on? >> Uh well, there are a few definitions. The one that I land on is the traditional scientific definition uh via which sex is defined in terms of gamete size. So, in the vast majority of sexually reproducing species, uh you have two different gamete sizes and the small gametes are called sperm, the larger gametes are called eggs. >> Is that across the board? >> That is across the board. >> No way. Like so, every every almost every sexually reproducing male >> Yes, produces sperm and sexually reproducing female produces eggs. >> Right. >> And and >> might this might be like the most facepalm thing in my life. Wow, I didn't know that that was those are the only two currencies at play. >> [snorts] >> Um I mean, it seems like so so in biology, it's not like math, right? So, in biology, there are very rarely uh generalizations that apply to every single species. >> Mhm. >> Um this is one of them, but the reason is that it's a definitional it's a definitional truth. So, we define males as the ones that produce the smaller gametes. Um the empirical truth that in principle could have gone another way is the fact that in the vast majority of species, you have where the gametes are not identical, you only have two different types. And one is bigger and one is smaller. And that's true right across uh you know, all species except the minority where you uh you have So, that's called anisogamy where you have two different sizes and you have a few isogamous sexually reproducing species, but the vast majority anisogamous. >> Can you what is what's an isogamous sexually reproducing species What are some examples of them? >> Uh there are some very uh I think no animals and no plants, but I think maybe some simple bacteria and things like that. And I think that would that would have been the starting position. So, we all evolved from species that originally were isogamous. >> Mhm. >> They They first of all sexual reproduction would have evolved, then isoga- and they would have been isogamous. They would have produced the same gametes and mixed them. But then that's evolutionarily unstable and that tends to fall apart into uh smaller and larger gametes. >> Why Why is it unstable? >> Uh because when you when you have same-size gametes, uh the selection for any trait that will increase the chances of being one of the gamete I I producing gametes that are going to uh produce offspring that survive. So, that creates a selection pressure for maybe loading up your gametes with some extra uh supplies to help them survive. >> Mhm. >> Um so so some gametes uh get a little bit bigger because of that. But as soon as they get big enough, the larger gametes, you have a selection for smaller gametes that seek out the larger gametes and kind of ride on their coattails. >> Mhm. >> And uh so and you get this it pushes them apart. And >> uh from a sexual survival or a gamete survival perspective, >> Yeah. >> it's the gray area in the middle of the barbell is where you go to die and the black and the white on either end are actually the ones that are most effective. >> Exactly right. Cuz the ones in the middle, they're not big enough, they don't survive as well as the bigger ones, they pack a picnic for their offspring. >> Mhm. >> Um but they're also >> in their motility mobility by the the smaller ones. >> Exactly. And and just numbers, you know, so like if you are producing small gametes, you can produce many more. So, individuals that produce the medium-size gametes, they don't survive as well, plus they don't produce as many. >> remember what the stat is. There's some stat around. Jerry, can you look at ChatGPT, um how many sperm are produced per day, human sperm versus human eggs? It's a It's such a hilariously big difference. Yeah. Um Okay, so broadly across the animal kingdom, in almost every single sexually reproducing species, there's a binary. >> Yeah, there's a sex binary. >> There's a sex binary, yeah. There's also a ton of variation in terms of the phenotypic characteristics within each of those sexes. But yeah, there is there is a sex binary. You know, you and you do get intersex individuals. >> Yeah, what about the challenges to this? We we have hermaphrodites, within-sex variation, intersex conditions. Does that disprove this? >> Uh it doesn't. Um so the I guess the easiest one is the within-sex variation. There is tons of it. So there's variation in terms of levels of masculinity, levels of femininity, um just uh size dimorphism versus size monomorphism, where they're they're about the same size. Um but nonetheless, they are all either producing sperm or eggs. >> Yep. >> The vast majority within each within each group. >> You've seen that uh image, right, of the bell curve graph, and you say, "On average, something something." And then somebody says, "Well, I know a person who is actually more that than the other group. I know a a woman who's 6 ft 7." And and and she's actually taller than most men. Most men on average are taller than women. Well, my friend's 6 ft 2. You go, "Right, okay, but that doesn't necessarily disprove the way that >> yeah. >> Exactly. The gen- The fact that the generalization's there. And even more so, the fact that the gamete size is definitional, as you say. Oh, here we go. I don't even know what that number is. Is that sperm Is that a billion sperm? >> 100 to 300 million sperm per day produced by healthy adult male. >> no, no, no, no. I want this globally. Total global sperm production, 200 quadrillion. Eggs released, 70 million. Step it up, ladies. >> So. >> So, I think [ __ ] lagging behind. We need to up the egg production, so I say. So much of the so debate falls around nature versus nurture. >> Yeah. >> So much of it. How do you even begin to start to separate this out, right? No almost no women have grown up in a society that hasn't had other women with the expectations of women and almost no men have grown up in society that doesn't have the expectations of men. How do we know that all of the sex differences aren't just socialization? >> It's a good question and um I think the first thing I want to say about that is that evolutionary psychologists don't deny that socialization has a very important uh impact on the nature of sex differences in any given culture. We know that it does have a big impact cuz we know that sex differences, their size, and the exact details of them, many of them, vary across cultures and vary across times. Um but in terms of how we know that it's not just socialization, there are various lines of evidence that point in that direction. None of them are perfect, none of them by themselves seal the deal. But the reason I'm persuaded is that they all point in uh when you get a sex difference and they all point in the same direction, um that just makes a very strong case, I think, that that is not just due to socialization. And in the book I I lay out six different lines of evidence uh for an innate contribution to any given uh difference. Um see if I can remember the name. So, the first one is um that a lot of sex differences they appear very very early in the lifespan. Uh so early in fact that even though it's conceivable that it could be a result of socialization, it just seems less plausible than that there's actually also an innate push. So, uh the aggression sex difference and the risk-taking sex difference, both of those appear basically as soon as kids are mature enough that they can move around the place and are capable of risk-taking, capable of aggressing. Uh you get that sex difference um like immediately. And and [clears throat] good example of that is that uh right from the get-go, right from early childhood, more boys than girls end up in the ER from doing more risk-taking. >> Mhm. >> Uh and and also if it appears at puberty as well, um, like a lot of sex differences innate sex differences with an innate basis, they >> What do you mean when you say innate? >> Uh, unlearned. >> Right. >> Unlearned, yeah. >> Right. Right. >> So there's an innate contribution, an unlearned contribution, and where that's the case, often you find that the sex difference, um, you may you may get it to some degree early in the lifespan, but then post puberty, it just skyrockets and and expands. >> Right. Okay. Which would suggest that there is a biological basis, or else >> Yeah. >> why would this big change occur when puberty happens? >> Exactly. And and do so right across cultures. >> Yeah. Is it a Would the suggestion from social roles, socialization theorists be that well, during puberty, culture ramps up its pressure on people? There's greater expectation on young men and women to change their behavior? >> That would be the way that you would have to you'd have to try to explain it, uh, something like that, yeah. >> Uh, [clears throat] I think they're more malleable. They're more they're more uh >> Yeah, more plastic at that age, perhaps. Yeah. You could you could do that as well. Um, and that's sort of implying an innate, uh, contribution to the plasticity, I guess. But yeah, not to the specific sex difference. Uh, the reason I don't buy that, though, is that most cultures actually try to suppress male aggression, for instance. Uh, in every culture, male aggression, uh, post puberty, young male aggression, violence, risk-taking, homicide, uh, is a big problem that the society has to, uh, deal with. And so, uh, usually they they try to try to clamp down on it, rather than trying to, uh, encourage it. And nonetheless, you get, uh, this uh, increase in aggression. That's true. And actually, this is the second line of evidence. Is that often these sex differences appear despite culture, rather than just because of culture. >> Mhm. >> Culture's trying to push down aggression like right from early on. Uh, parents, teachers early on, they they actually tell off boys for aggression more than they tell off girls for aggression. Not cuz they disap- disapprove of girls' aggression, but just simply because boys are more aggressive. >> Right. >> So, they have more cause more cause to do it. >> Mhm. I think fMRIs of developing fetuses in the womb can detect sex differences at 3 months. >> They can I think I think even younger in some cases as well. >> Yeah. What are they are these boys and girls, these tiny un- minus 6-month-year-olds, are they learning that their brains are supposed to develop differently? >> Yeah, they've been socialized to develop different brains inside of the womb. Yeah. >> Okay, so early development. >> Early development um appearing despite culture rather than because of culture. >> Yep. >> Uh another one is that um they persist often for a long time. So, for instance, uh sex differences in mate preferences were really consistent right throughout the entirety of the uh 20th century and the in the US. >> Mhm. >> Uh sex differences in career preferences as well or or career-related interests. >> Mhm. >> Uh they were evident from like the early 1900s when people first started measuring them. And then they just stayed the same. So, so the average difference, the fact that men for instance on average more interested in things and things-related jobs, whereas women on average are more interested in people and people-related jobs. That was that was the case right throughout the 20th century uh despite the fact that there was quite a strong uh social there was a lot of social pressure to try to get more women into uh traditionally male roles and it persisted nonetheless. >> Mhm. Okay. I've learned from over a thousand podcast episodes that the easier you make your health routine, the more consistent you'll be. Take golf, right? You want to keep it simple and not mix a bunch of pills. You want the eye of the tiger, not the DUI of the tiger. That's why I'm such a huge fan of AG1. One scoop contains 75 vitamins, minerals, probiotics, and whole-food sourced ingredients in a single daily drink. And now they've taken it a step further with AG1 next gen backed by four clinical trials. 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So, I guess we know because of cross-cultural differences and male-typical behavior, female-typical behavior, and the size of the differences, there's something that's making the difference. But, it is actually quite tricky to to figure out what what it is that's making the difference. Um cuz we know, for instance, that I guess like a popular explanation is that it's how parents treat their kids. And that seems incredibly plausible that it's going to have an effect. There are a few reasons to think maybe that it has less effect than we might think. So, one is that a lot of research in the West finds that men finds that parents don't particularly treat their sons and daughters differently in some important ways. But, they're equally likely to encourage them to be successful, equally likely to encourage them to be independent. Uh and another line of evidence against parents having a big role is what's called the second law of behavioral genetics. Uh and that's the finding that um when two people, I guess like I say, take identical twins. Two identical twins that grow up in the same home, you'd expect them to be more similar to each other than two identical twins who are separated at birth and reared apart. And in childhood, they often are quite a bit more similar than you would expect by chance. Um by adulthood though, they're often not much more similar at all, and in some cases not no more similar than they would be um if they had grown up apart, which is a surprising finding, but a very consistent finding. And it suggests maybe that um parental treatment affects individuals less than we might think that they would. This kind of pulls out the rug a little bit from the idea that parents are having a huge impact on sex differences specifically. >> What about the gender equality paradox? >> Uh well, that uh undermines another kind of uh social cultural explanation, which is the idea that um the sex differences that we see are products of the social roles of a culture. And shaped by >> Is that social roles theory? >> Yeah, social roles theory, exactly. Um and patriarchy theory, the idea that it's due to patriarchy, um uh that as well is undermined by the gender equality paradox. Um cuz both of those theories would predict that in like like more patriarchal societies societies that are more patriarchal, uh societies that have stricter gender roles >> Yeah. >> you'd expect that it predict that the sex differences would be bigger in those societies uh than they are in less patriarchal societies, and ones that have less strict social roles. >> What would be some examples of how that would play out if that was true? >> Uh basically any sex difference you care to name, uh aggression sex difference, sex differences in masculinity versus femininity, all of those should be bigger. Sex differences in career-related preferences, they should be bigger as well. And the gender equality paradox is the deeply counterintuitive finding, an incredibly fascinating finding, that often it goes the other way. Seems to go the other way, that actually in more gender equal societies, societies that are less strict in terms of the gender roles, uh and societies that are less patriarchal, you actually find larger sex differences often rather than smaller ones. Uh which is >> in the direction that you would predict as well. >> Uh, yeah. So, so opposite to the direction you predict if social role theory was correct. >> But, in the direction you would predict if you were taking an evolutionary perspective, I would imagine. >> Um, well, actually, you know, taking an evolutionary perspective, I I didn't originally predict that. I I thought that in more patriarchal societies, e- even given that there's an innate push towards certain sex differences, I still thought that patriarchy and stricter sex roles would pry the sexes apart even more. >> Right. >> So, I was actually very surprised that it doesn't and that it does the reverse is the real surprise. >> What are the rebuttals to socio- that socio-cultural explainers have for the gender equality paradox? >> Uh, there are a few. One is that, um, people in more patriarchal societies, they tend to the the men and women have little to do with each other. >> Right. >> And so, that they have a more sort of exaggerated picture of, uh, the other sex. And so, when they fill out personality inventories, for instance, they they're comparing themselves with with other men if they're men or other women if they're women. And they therefore see themselves as being more similar to the average for their comparison group. But, their comparison group is just their sex. >> they're just in they're so siloed off in these patriarchal societies that they don't know what the [ __ ] the other side's doing. >> Exactly. It is. [laughter] It is. >> You're just in a bunker so much that you don't know what's going on. >> Exactly. >> It makes sense. It does. >> It does, but, um, there's also a plausible rebuttal to that rebuttal, >> [laughter] >> uh, which is that, um, >> It's [ __ ] love it. So good. This is my [ __ ] This is my [ __ ] [laughter] >> Uh, so, it doesn't just apply to self-report things like personality. You also find it for, uh, some cognitive abilities. I think spatial ability, for instance, you find it. >> Yeah. >> Um, you find it as well for physical traits like height. >> Are you saying that in more gender equal societies boys get even better better at throwing. >> Um I don't know if that is actually the case, but that that would be an example if there's research on that. I'm not sure there is actually cross-cultural research on that. >> Throwing's my favorite one, dude. >> It's huge huge difference. >> my It's one of my absolute favorite. Did you ever look at that study where um so the the the difference in throwing uh velocity, accuracy is a pretty big sex difference. But one of the um appropriate pushbacks was, well, uh men's shoulders articulate differently, uh the length of the forearm means that you've got more leverage, etc. etc. I think the the sex difference at 8 [clears throat] years old in throwing velocity and accuracy is basically the same as adult men and women being able to detect adult women and men just by their face. >> Right. >> It's a 90% It's a huge huge huge difference. So, there was this My favorite study on this was uh in order to negate the articulation argument, the issues of sort of biomechanics, uh they got a tennis ball serving machine and fired tennis balls at students. >> Yep. >> And got the boys and the girls to see if they could get out of the way. And I don't think any of the males were hit. And I think that I This is before you wouldn't have been able to get this past an ethics board. Um but yeah, just the sort of spatial uh awareness, that spatial rotationy stuff is um the sex difference is is is pretty large. And apparently Maybe maybe in a more gender-equal society, even more would be women would be hit by the tennis balls. >> Well, that's possible, yeah. Um so, the gender equality paradox, it doesn't apply to every trait. So, it might not necessarily be that. But um yeah. But but you are right. I think that was probably a 70 I think it was a 70s study. I'm not sure you could do that. Yeah, in fact, you couldn't do that. You couldn't aim projectiles at uh participants in studies anymore, sadly. >> What's the largest sex difference between men and women? >> Um well, the largest ones are physical differences. Physical sex differences. So, um the very largest uh sex differences in reproductive anatomy, where basically all males have penises, all females have vaginas, and so on. Um but other physical sex differences um are also very very large. So, the sex difference in upper body strength is is huge, and there's very little overlap, close to no overlap uh for that one. Um the sex difference in voice pitch is another very very large one as well. That's huge, uh which is quite interesting because uh the voice pitch sex difference other apes isn't isn't as big. It's nowhere near as big. And that's even the case for um for other species that are much more dimorphic than us in terms of the size, like gorillas and and orangutans. So, that's a bit of a puzzle, not quite sure why that is, why that's the case. Uh when it comes to psychological sex differences, the vast majority of them are much more modest, um but there's one that stands out as being as being almost as big as some of these physical ones. I always ask people if they can guess what it is. I think last time I was on your show I asked you if you could guess, and and you didn't, but then no one does. >> I've read the book now. >> You've read the book now, so >> Yeah. Yeah. Yeah. >> So, you've got a head start on that. >> what it would be, Jared? The the single biggest psych psychological sex difference between men and women? >> Hm. Is it aggression? Um >> It's not aggression. I'll give you a clue, and that's that it is it's related to reproduction pretty closely. What was that? >> Diversion. >> It's Well, actually, that is a big sex difference, but >> Not as Not as big as this one. You speak to yourself. >> Speak for yourself, dude. >> [laughter] >> It's the sex difference in which sex each sex is primarily attracted to. So, men most the vast majority of men are primarily attracted to women, the vast majority of women primarily attracted to men. And when I say it, it's obvious right it's so obvious that it's a big sex difference, and um but but it's curious, people don't think of it. Even um scientists often don't think about it. I've read a bunch of papers that summarize evolved sex differences, and they don't tend to mention that one. They often neglect to mention that that very very large one, but also that one that has quite a clear evolutionary rationale. That's very interesting. >> because if that wasn't the case, we wouldn't be here. >> Exactly. >> Literally. >> We literally wouldn't be here. Yeah. >> Uh okay, so what are the biggest sex differences? Let's get down to some brass [ __ ] tacks. What are the biggest sex differences when it comes to sex? >> When it comes to sex, >> Yes. >> one of the largest ones is the sex difference in interest in casual sex and sexual variety. And so basically so sociosexuality, the trait of sociosexuality. No strings attached sex. Do I need to mention which direction it is? >> Uh yeah, yeah, yeah, yeah, yeah. Someone can intro it I guess. >> Yeah. So so men on average uh score higher. However you measure that trait, they score higher than women on that trait. The difference is there maybe though are not not as huge as people sometimes assume. Um we're looking usually at an effect size of uh you know, about Cohen's d equals one. So what what that means is there's about one standard deviation between the average for men and the average for women. Uh so so yeah, between eight and one. And that is pretty big. That that is big for a human sex difference. But there is still quite a bit of overlap. So there are plenty of women who have a higher sociosexuality than plenty of men. I guess an intuitive way to put it, a way to make it intuitive, would be to to say to imagine plucking two people at random, one man and one woman. With effect size of or or one, probably two-thirds to 70% of the time the man will score higher than the woman on that trait. Um so that is a majority. It's not an overwhelming majority though. In a significant minority of cases, you'd find that actually the woman scores higher than the man. >> Mhm. >> Yeah. >> Why? >> Why is that sex difference? That is getting right into this the central question of why there are any sex differences at all. >> we we we probably need to talk about like the evolution of sex differences, why they why they exist in the first place. >> Yeah, um so we should jump to that. Uh Can I just as an aside though, can I we we mentioned three of the six lines of evidence for innateness. Do we want to jump back and do the other three and then maybe get into the sort of thing. Um So, what are we what are we So, we had the developmental sex differences, we had the resistance to cultural pressure, we had the um persistence across time. So, another one is uh hormonal correlates of sex differences. And in particular, um you find associations between prenatal hormonal exposure and traits found later in life. Uh so, higher levels of testosterone in the womb for instance are associated with higher levels of aggression later, higher levels of risk-taking, lower levels of parental inclinations. >> Mhm. >> Uh and so on. So, a lot of >> regardless of sex. >> That is regardless of sex, yes. So, you can look at within sex differences as well. >> Mhm. >> And uh yes, so one actually very strong line of evidence for that claim is the fact that uh women who who when they're in the womb are exposed to very very high levels of prenatal uh testosterone uh due to having a condition called congenital adrenal hyperplasia or CAH. Uh they as girls and then as women, they they exhibit a lot of uh male-typical traits. Uh for instance, >> in playing with dolls. >> Exactly, yeah. Less interest in uh getting married and having kids, uh more interest in things-related professions as well. >> [clears throat] >> So, that's pretty interesting. >> them more likely to be bisexual or lesbian? >> Yeah, yeah, it does. It makes them more likely to be interested in in other women sexually as well, either as bisexuals or as lesbians, yeah. >> Wow. >> So, so like a wide range of traits seem to be influenced by testosterone. >> is is correlates with hormones? >> Yep. Uh the fifth one is uh cross-cultural universality. So, most of the key sex differences that we've been discussing so far, they are found either in every culture or in the vast majority. And if it were all just down to culture, you wouldn't expect that. You'd expect there to be more variation across cultures than what we found. Um but you don't you know you just always have like in every culture, you find that men are more aggressive than women, and you find uh at the extreme of aggression in particular, the differences are particularly big. And you find that the vast majority of homicides are perpetrated by by guys in every single nation for which we had data. Greater risk-taking, more accidental uh fatalities among men than women. Uh women across cultures are more involved in parental care, and so on and so on. And then last but not least, and maybe this is the one I find most plausible on its own, is the fact that a lot of these sex differences, you find them as well in in other species. You don't find them in all other species, but importantly you find them in species um that were subject to the same evolutionary selection pressures as as ourselves. Uh and actually the selection pressures in question uh bring us to the ultimate roots of evolved sex differences. Uh so, basically most sex differences emerge from the sex difference in in what I like to call the maximum offspring number, the male animals versus female animals can produce. And in most species, uh the males potentially can produce more offspring than females. Um that that average number of offspring has to be the same. At least in species where you have similar sex ratio, the average has to be the same, but the variance in the number of offspring produced can be greater in one sex than the other, and it's usually greater in males. >> Why does the average need to be the same if the variance can be different? >> Uh because it takes two to tango. >> Yeah. >> And so every uh offspring that's produced is produced by one male one female. And in most species it can be >> have one male servicing 20 females, why not have a 20 to one ratio? >> Well, that'll be a 20 to one ratio in terms of the number of parents. But the [snorts] average number for each sex will be the same. >> Right. >> Because you got the one male with 20 times more >> Mhm. >> uh than any female. >> Mhm. >> And then 19 and so that's already a high number. But then the other 19 bachelors who never get to have kids, uh that brings the average for males down. And then it's the same for all the females. So you average out across all of them and and the average is the same. >> I I get that. >> Sure. >> Maybe I'm being stupid. Why is it not the case given that men given that males are able to produce more children than women can and females can, >> Yeah. >> why is it not the case that there is a bias toward fewer males in the animal kingdom? >> Right. Right. That's a great question. Um and that is one of the sort of early mysteries of evolutionary biology. And if it were for the if selection acted for the good of the group, that is what we'd find. We'd find if if you only need one one male for every 20 females and selection were were for the good of the group, you get that because if you have 20 of each, >> Mhm. >> then the other 19 are surplus and they're using up these resources and they can uh competing with each other and fighting with each other. It's not good for the species as a whole. Uh but selection favors what's good for the individual. And for the individual, >> I could be the one. >> You could be the one, exactly. And and the average is the same. So the the Um it's I guess it's useful to think about Think about it from the parents' point of view. Like is it better to have to have sons or daughters? Um and if there were 20 females for for one male, it'd be much better to have sons because each son is going to just have There's going to be tons of females. And so that would mean that selection would slowly favor an increase in the number of sons. >> well, the [ __ ] you can't beat evolution. >> Exactly. And the reverse, if there's 20 20 males and on for every female, then it would be better for parents to produce daughters because then they get to pick the cream of the crop and and 20 males probably they're going to have a low number, so it's better to have daughters. So the equilibrium point is 50/50. >> Yeah, obviously as well, there's survival and not just reproduction. We're not living in this perfect hermetically sealed safe environment. >> Yeah. >> Males do other things than just reproduce regardless of whether they can do 20 to 1 or not. >> And they Yeah. >> Getting food, helping to protect, getting rid of other tribes, etc., etc. >> Yeah. Yeah, exactly. And you know, there are plenty of species where the male uh his his role in reproduction is just the reproductive act and then he then he's off looking for other females, but we're not one of those species. I mean, that does happen occasionally. There's occasional male that would do that. Uh but generally we're quite involved in child care. Uh yeah, so okay, so the big difference there is you you get this difference in the variance. >> Mhm. >> Um some males can have tons of offspring. Uh and they can have many more offspring than any female can. Where that's the case though, there's going to be some males that have no offspring um or maybe a few a few or none. And where that's the case, you get strong selection on the males to be one of the lucky few males that has many offspring >> Mhm. >> rather than one of the the few that has none. >> Yep. >> Or one of the many that has none. >> Yep. >> Um and so that selects for traits like greater aggression, within sex aggression to try to beat up other males for either directly for females >> Okay. >> or for the territories, the status, or the resources that are necessary to attract female attention. Uh a tendency to show off, a tendency to grow a great big tail. If you're a peacock, you might want to try that. Grow a great big flashy tail to seduce the peahens. Um, or just a tendency to seek multiple mates. And uh, and seek no strings attached sex, basically. So, that's the answer to your earlier question. Is that what That's why you have selection for like stronger selection on males than females for an interest in multiple partners and sex without commitment or that kind of thing. >> Did you know your gut controls your energy, your recovery, how well you absorb everything that you eat, and the one nutrient that keeps it all running properly is fiber? Well, it turns out that 95% of Americans don't get enough of it, which is why I'm such a huge fan of Momentous' Fiber Plus. Most fiber supplements are one-trick pony, one type of fiber solving one part of the problem. Fiber Plus is a three-in-one formula built to tackle digestion, gut barrier strength, and blood sugar stability all at once. I use this every single day. It is kind of hard to get enough fiber just through food alone. And best of all, Momentous offers a 30-day money-back guarantee. So, you can buy it, try it every single day for 29 days. And if you don't love it, they will just give you your money back. Plus, they ship internationally. Right now, you can get up to 35% off your first subscription and that 30-day money-back guarantee by going to the link in the description below or heading to livemomentous.com/modernwisdom and using the code modernwisdom at checkout. >> How does parental investment influence the evolution of sex differences? >> That is a major contributor. And the reason is that So, so this variance sex difference is mainly a a result of sex differences in parental investment. So, the reason that um, some males can have many, many more offspring than any female in in a lot of species is that females invest more in the young. So, in mammals for instance, to produce any one offspring, uh, a female has to have a have a long pregnancy, has to give birth to the young, and then has to nurse the young uh for for a while, whereas uh a male to produce an offspring just, in principle, only needs to um engage in in one sex act. >> Mhm. >> So, he can mate with multiple females and have tons of offspring cuz he invests potentially little in any given offspring. >> Mhm. >> Uh whereas the females on the other hand, they invest a lot in each offspring. That lowers the ceiling for the number of offspring they can produce. >> Therefore, you have to be choosier. >> You have to be choosier about your mates, exactly. Sleeping with uh or or mating with lots and lots of males less useful for females than for males. Um but so so parental investment is really the core um to >> Is that the Is that the key driver? >> Uh well, I think the key driver is the difference in the maximum offspring number or or the reproductive variance. >> Right. >> Because it's not just shaped by parental investment. >> Behaviorally, that shows up as parental investment. >> Well, that's a big part of it, yeah. So, the parental investment is is the major cause of the sex difference in in maximum offspring number. But other things do come into it in different species. >> periods too is like a biological imposition on parental investment, right? >> Well, look, is actually is is how long it takes to just make a baby considered part of parental investment? >> of parental investment, yeah. >> Right. >> And parental care is and nursing is >> Yeah. >> Um >> Obviously those two, but I wasn't sure whether or not it's classed Parental investment is classed as actually the making of the baby. >> It it is cuz it forecloses the option to make other babies. >> Understood. >> Yeah. Yep. Yep. Yep. Um but ecological factors come into it as well. So, one example of um effect other than parental investment that influences the reproductive variance uh is ecological factors. So, you'll have some species where the males where they're quite solitary. So, the males and females might pair up, and there aren't many other individuals around. Um even if the female invests a lot more in the young than the male does, their maximum offspring number is about the same because just simply cuz they're isolated from other uh members of the species, the males don't have many other opportunities to sow their wild oats, basically. >> What's Bateman's principle? >> Bateman's principle, so that is the idea that reproductive variance is greater in males than females in most species. >> Right. >> And then Trivers sort of refinement of that was that the main cause of that is parental investment. So so Bateman put put put a lot of it on anisogamy. He explained the difference in in reproductive variance in terms of the fact that um females invest more per egg than males invest per sperm. Um Trivers said, Robert Trivers, who died recently, he said it's not just that, actually it's it's all kinds of investment that you put into into the young, not just the gametes, but also gestation and parturition, which is giving birth, uh nursing, parental care, all those things um are what matters. And and I would just add that it's parental investment is the big one, but other things as well determine reproductive variance. >> What is the It's about 40% of males of human males ancestrally reproduce and about 80% of females, is that right? >> I have heard that number bandied about. I actually think that probably in our species, my guess is that it's not it's not that big. I've also seen other evidence suggesting that um it's called reproductive skew, >> Mhm. >> and suggesting that the reproductive skew in our species is quite a bit lower than you find in most mammals. And I think the reason for that is that >> So the 40-80 number you think is is wrong? >> Yeah. >> Right, okay. >> so. I think it's I think it's a small one. I well I think it's smaller and I think because males in our species very often invest quite a lot in the in the young. So it's not just the sex act. Um they often typically help out with the young as well. Uh and so we have we have high levels of biparental care in our species. That reduces the maximum offspring number for males relative to females and brings it down brings it closer to what we have for females. >> So if other animals have less of a reproductive skew but also have less male parental investment, how would the reproductive skew for us be so great if we have more male parental investment? Is that what you're saying? >> That that is what I'm saying. >> Bingo! I [ __ ] know evolutionary psychology, dude. Don't test me on this. I [ __ ] understand this. It's the only topic I understand. Um >> Yeah. >> So it's the variance in reproductive success. >> What >> What do you What do you reckon it was then if it's not 40/80? Feel free to just bro-science it. >> I think I I might >> [laughter] >> Um I probably shouldn't put a number. I I uh other than to say I think it's smaller. I think it was it was smaller. I know. I know. >> That's why I'm in the room, dude. Let me just [laughter] find and put this thing on for the rest of the conversation. Um >> Well, you've got these as well. >> That's also That's if you want to say something insane. >> Okay, cool. Well, I'll keep it here cuz I may well want to >> insane, you're allowed to put that on. It's actually saved me once already. I I got I got clipped talking about a slightly highly postulated theory. Put that on. It's going to be interesting on you because you already have the mustache and the glasses. >> It will indeed, yeah. >> Nothing's changed. >> [laughter] >> Yeah. Okay, so we've got a It's like an interesting I guess an interesting pivot on what people think. The That's sort of 40/80 number. As far as I was aware, like to actually So you think the skew is different? What I thought might be true is that the overall number might be different, too. That the whole To me, infant mortality >> Right. Right. Right. >> [ __ ] ruthless. So the only way that we can work out how many of our ancestors reproduced presumably is due to some kind of genealogy stuff. And that means that it's not how many reproduced, it's how many survived. >> Yeah, survived to reproduce >> yeah. The grandparent optimizing machine from your previous book, which is fantastic and everyone needs to go and look at. >> Um yeah, everyone has said the universe. >> 80% of women having grandchildren producing or 80% of women being grandchildren producing people >> Yeah. >> seems insanely high to me. >> Uh I guess the thing is that they would have had a bunch of kids and only about 50% would make it, but 50% would make it and so if they, you know, have sex for instance. >> That's what it is, around about 50% >> Yeah. >> that are born go on to reproduce. >> With unbelievably high, right? Uh what about 50% um infant mortality rate. So, like half of them didn't make it. Yeah. One of the great things I think about civilization is that we have lowered that number to very close to zero cuz that was I think a massive cause of misery throughout most of human history. >> Was it Darwin lost a bunch of kids? >> He did, yeah. He had uh What was it? He He had 10 and three didn't make it to adulthood, I think that's the number. Yeah. >> Is it your book or was it I think this might have been The Moral Animal Yeah. where Robert Wright talks about the fact that Darwin lost multiple children. But the one that was the most psychologically painful Yeah. was his daughter who was 12 or 13. >> Yeah. >> And the reason for that the evolutionary reason that Robert gives for it is that parents are able to detect the moment at which the life cycle of their child would have allowed them to just about become the grandparent optimizing machine that evolutionarily we're driven to be. And that if a child dies at two years old, that's horrible, but they won't they had a long way to go and many things could have occurred between now and being able to have kids. If a child dies when they're old, then they've had all of the opportunities to have had kids and that didn't didn't go well or maybe did go well. But if you are just on the cusp of being able to reproduce biologically and you die, that is from an evolutionary perspective the most painful. Am I making that up or is that the story? >> No, that is the story. Yeah. And there's pretty good evidence on it as well. That grief tracks reproductive value of the individual. >> No [ __ ] way. So this has been reproduced cuz that book's 30 years old now. >> Yeah. Yeah. Um yeah, go the grief average grief levels go up and up and up as reproductive value goes up as as kids move from the very vulnerable historically very vulnerable early infancy to childhood, it's kind of peaks at about the age that reproductive value peaks. So couple of years after puberty and then starts coming down again as people get older. >> [ __ ] fascinating. How is everyone not obsessed with evolutionary psychology? It's so cool. It's so fun. >> And sheds light on some of the most fundamental stuff in life. >> Yeah, I mean obviously it's very bleak in some ways too. It's very stark. It doesn't paint a particularly flattering picture of human motivation. Like the reason that Darwin was particularly sad about his 13-year-old daughter dying is that he had this weird algorithm running in the back of his mind. He's like, "Oh, so you're just saying that all the children are that produced for you to be happy to do things like I do that you you don't need to lord our ultimate evolutionary drives >> Yeah. >> in order to understand and respect them and accept the fact that they are important influences on our behavior. >> I completely agree and even you know, and I do feel the pull to what like it is a bit bleak. I remember when I was first reading about that grief theory, it does seem a bit a bit dark. But then when you think about it though, it's not very flattering exactly. I mean, I guess one thing is that um we don't actually we're not actually thinking about reproductive value. Uh we just we just have a built-in tendency to react as if we are. But we're not actually thinking in the back of our minds, this is sad because I this this kid was going to close [laughter] to having kids and then I wouldn't have been >> then. Well, this is this is sort of my least I don't know actually. I I I probably could write out a hit list of my least favorite internet rebuttals to anyone talking about evolutionary theory, but one of them is a lack of understanding about the difference between proximate and ultimate motivations for behavior. >> Yeah, exactly. So one of the big ones. >> Yeah, like the >> big misunderstandings. >> why you feel the desire to do a thing and the evolutionary advantage of you doing the thing. The fact that those two things are different. Um you eat food because it tastes good. But the reason for eating food is to keep you alive. You have sex because it feels good, but the reason to have sex is not the reason that it feels good. >> Exactly right. And and it's quite annoying, right, when people say, "So you're saying that um like sex and uh having like short-term relationships or long-term relationships is just about babies, but that can't be true cuz often the last people the last thing people want is to have kids." >> I don't want to have kids. I'd love to have sex. >> Yeah. Yeah, yeah, exactly. So it doesn't make sense. They've just misunderstood the idea cuz it's not a psychological theory. Uh like the the genes I view explanations the the evolutionary explanations those are not motivations. Those are just explanations for why we have the the proximate psychological drives that we do. >> Not the ultimate. >> Exactly. >> Yeah, yeah. And you know, with the the what's it referred to as that theory of the sexual not sexual value? >> Um >> of uh Darwin's daughter dying, what's the >> Oh, yeah. Our reproductive value. >> Reproductive value. No one is how horrible to say to a parent, "Well, it's actually Mrs. Thompson, the reason that you're grief Mrs. Darwin, the reason that your grief is so high is because of the reproductive value that your daughter almost didn't cash in on." Horrible, horrible thing to say. But it doesn't need to it doesn't need to be something that's in your mind to like go how could you claim that this mother is feeling that, thinking that at the time and that's contributing to a grief? No. >> Yeah. >> No, she just loves the kid. Yeah. It would would be the same it would be the same as going why is it that people get depressed when they're lonely? I'm not thinking about potentially being kicked out of the tribe. You go, "Well, yeah, like we're in a modern environment. Why do you think it is that depression and anxiety correlate with isolation?" >> Yeah. Yeah. >> If it didn't matter. Well, it does matter. It doesn't matter anymore, not in the same sort of a way, but that doesn't negate the fact that our system is basically ancient programming living in a modern world. >> Exactly. And even though it does seem bleak sometimes, I don't see that other explanations, socio-cultural explanations would be any less bleak, you know? If they were telling me >> I'm at the mercy of the memes and trends of the modern world. Some guy decides to start a new cool movement somewhere and then that completely sort of blows the wind of whatever it is that I'm supposed to care about. >> Exactly. Or or you might say, "Okay, the reason that you grieve this individual is just because you've been socialized to do so." How's that any less any less bleak? >> It's the same. This is why I think there's a lot of similarities between evolutionary psychology and behavioral genetics that if you start to strip away the science and the evidence underneath it, what you end up with is an equally or maybe even uglier perspective. No, if if for instance, if you deny that there are genetic influences on outcomes in life, >> Yeah. >> what you're left with is this world where everybody did start off equal. And you are exclusively at the mercy of the entire world. >> And and injustices. >> Yeah. Yeah. The the only reason that this didn't come out is all on your shoulders. All on your shoulders because you didn't try hard enough or your parents didn't try hard enough. >> Yeah. >> Horrible. Horrible. >> And I guess so the thing is that whatever hard truth and they're not all hard either, but whatever hard truths ultimately we just got to um accept what's true, whether we like it or not. As you know, sometimes it is positive. So so in natural selection has given us a whole range of less than noble traits, but it's also given us some really lovely traits as well. Like the capacity to fall in love and to love our children and to love our friends. >> Mhm. >> You know, these are all great things. Yeah. Yeah. Exactly. To be able to do stuff. >> Okay. So I guess one just to round out the We haven't even got into the sex differences yet, which is the meat and potatoes of this, but I don't care. Um Is it Are humans unique in this regard because we've got mutual mate choice mhm and we've got biparental care. So when we're talking about evolution of sex differences, parental investment, ability to produce children, volume of children across a lifespan, Bateman's principle, variance in reproductive success, but humans do seem to be somewhat of an outlier in mammals and especially in the animal kingdom. >> Yeah. Yeah. >> What wrinkle does that throw in? >> Uh well, yeah. So we are So the question, are we unique? Sort of yes and no. So the way in which we are unique, we're very unique among mammals. Like you say, in the fact that we have high levels of the tendency to pair bond, sort of fall in love and form relatively durable pair bonds and for both sexes rather than just the females to invest in the young. Um that is found in maybe 5 to 10% 10% at the most of mammals. So the overwhelming trend among mammals is that the females do all the investment in the young and the males are basically deadbeat dads. In birds on the other hand, they are an outlier family of animals among animals in general and that around 90% of birds form pair bonds and have biparental care. And so there's a funny thing I find this just very very interesting is that in our primary reproductive behavior, humans are more like the average bird than like the average mammal. >> No way. >> Yeah, that's cuz of our pair bonding and our biparental tendencies. >> Is a reinforcement that the parental investment is the key driver of sex differences. >> Yeah, exactly. And and of the difference in most birds hang on a second. So most birds are kind of like dinosaurs and humans are closer to birds than they are to most mammals, which means that humans are kind of dinosaurs. >> Yeah, so that's great. It's great. Do you want this or >> Yes, I don't need that. I don't need that. >> No, no, you don't cuz I I agree. So we we're mammals that are more like dinosaurs in terms of having the the primary reproductive arrangement of of today's dinosaurs. >> go. >> It's wild, right? >> Let's [ __ ] go. >> And so yes, so we're an exception among mammals in that respect. A way in which we're not an exception though is that the the same evolutionary principles that apply right across the animal kingdom apply to us as well. So the fact that sex differences emerge from the maximum offspring number, the the level of sex differences and reproductive variance that is true across the animal kingdom and the rules about that apply to us as well and the fact that we have we do have a sex difference and reproductive variance. Men do have and have always had greater reproductive variance than women, but it's relatively low compared to most mammals. >> Most people have no idea where their testosterone levels sit, but what if I told you there was a solution? Something that identifies low T faster than a high school bully, and it won't cost you all your lunch money. That's where Function comes in. Gives you access to over 160 lab tests including a deep dive into your full hormone panel. Every result is reviewed by clinicians. Anything out of range is flagged, and you get clear explanations with a personalized protocol with actionable next steps. So, if something's off, you know exactly what to do about it. Whether you just need to go to the gym more or you need to play Creed louder in your car, Function will tell you exactly where your testosterone and everything else stands. Normally, this level of testing would usually cost thousands, but with Function, it's $365 a year. That's $1 a day to stop guessing with your health and start knowing. And right now, you can get $25 off bringing it down to 340 bucks. So, get the exact same blood panels that I do and save $25 by going to the link in the description below or heading to functionhealth.com/modernwisdom using the code modernwisdom at checkout. >> Isn't there an interesting inversion of this in spiders where female spiders are bigger than the males? >> Uh actually, in most insects, it's that way around. And actually, there are more animals where the females are bigger than where the males are bigger. Um but that's not because of difference in reproductive variance. It's because um in a lot of species, the main driver of sexual dimorphism is just the number of eggs that you can produce. And females bigger females can produce more eggs. There's a selection pressure on them to get bigger and bigger and bigger. They're typically bigger than the males. The males don't need to be much bigger. >> need that much room for sperm. >> Uh yeah, exactly. Yeah. So, so the um gamete size difference, sperm are bigger than eggs, is reflected in the physiology of the species. >> so [ __ ] cool. That's so cool. >> we're the weirdos. We're so used to males being bigger than females, but actually mammals and other large vertebrates we're the exception to the rule. And the main reason for it is that um you still have the selection pressure on the females for producing more eggs. So, you know, they got certain size sort of push for them to be bigger. They got an even stronger push on the males to be bigger as a result of intersexual selection which is selection for the ability to be able to beat each other up basically. So, a lot of species bigger males do better in in fighting than than smaller ones. Males get bigger than the males get bigger and sometimes they get even bigger than the females. >> All right, meat and potatoes. Getting back to sex differences in sex drive. >> Yeah. >> What casual sex, sexual variety, cheating, what's going on there? >> Yeah. That's all about producing more offspring. So, um a male that is equipped with those motivations is going to be sort of like a heat-seeking missile going out to seek multiple partners and is therefore more likely to have um more offspring. If if he's successful than that, then he would if he just sort of sat back and wasn't wasn't interested in multiple partners. >> Right. >> And and you do find that in many species. Now, I don't think that the difference is as big in our species as in many others and I think that's a side effect of the fact that because we have biparental care the level of reproductive variance among males in our species is somewhat constrained. Still greater than among females, but because it's somewhat constrained, sex differences in our species have correspondingly come down as well. >> Mhm. >> So, we still have all the traditional sex differences that you find in in most mammals and many other species, but they're somewhat muted. So, you have the the sexuality sex differences, but they're somewhat muted. The aggression differences, but they're somewhat muted. Um Uh uh parenting differences is the main source of this. So, that, you know, is like uh the discrepancy in male investment in kids versus female investment has been massively reduced. >> And that's the driver. >> And that's the That's the driver of all of >> The biparental investment is the nerfing the reason for the nerfing of all of the others. Okay. Again, I I'm only going to make this [ __ ] disclaimer once. Uh but we said it we said it previously, but I think it's worth saying again. Just because we can explain using evolutionary logic the reason why men might be driven to cheat more than women is not the same thing as excusing why it happens. >> No, not at all. Anymore than um a sociocultural explanation would excuse it. That's a funny asymmetry. People seem to think if you explain it in evolutionary terms, that excuses it. But there's no more reason to assume that than to assume that if you explain it in sociocultural terms, it excuses it. >> of those, you are um outsourcing the culpability of the individual to something else. In one, it's it's evolution and ancestors, and in the other, it's culture and influence. >> Yeah, exactly. And all our behavior must have causes, right? So, if we're going to say that if we can identify the cause of a behavior, and it's an evolutionary cause, we're going to have to um not hold people to blame. We're going to have to say that for any cause. And we're going to have to say that for all behaviors, because all behaviors have some kind of cause, whether or not we know what it is. They have some kind of >> Whether it's evolutionary or cultural. >> Or or most likely a combination of both. >> Yeah. >> Yeah, yeah. >> that basically we the institution of holding people responsible we have to keep that institution cuz it's useful, regardless of the fact that of course people's behavior has causes, and it's not inexplicable. >> That's so good. Uh Ashley Madison, the cheating website, had 20 million active male users. >> Yeah. >> And 1,492 active female users, despite women getting free lifetime membership and men having to pay. >> Yeah, that's wild, right? That's a massive difference. >> 20 million 2,500. >> It's probably similar to that ratio we had up before that >> It's probably it's almost exactly the same, yeah. >> Yeah. Um, what about men being more turned on by visual triggers? >> Uh, yeah, that's another another big sex difference. Um, both sexes are to some degree, you know, both sexes are interested in good looks in a mate, but it's stronger in men than in women. And the main reason for that is that the traits that we consider good looking are associated with with youthfulness and fertility for both sexes. Um, but men place a greater weight on those traits because because of menopause, basically. So, the fact that um, that they place more weight on youthfulness in a mate because youthfulness is more closely linked to fertility in women than men because of the fact that women's fertility shuts off about you know, two-thirds of the of the way through the lifespan. >> Mhm. >> Yeah. So, yeah. So, men are much more interested in visual sexual stimuli, as psychologists call it. It's part of the explanation for the fact that um, men are much more avid consumers of porn than women are. >> What is the reason that women are much more avid consumers of romanticy and romance novels than men? >> It's it's an interesting one, isn't it? So, that's the the standard sort of differences in consumer preferences that we hear about. Men are much more into porn than women. Women are much more into romance novels. Um, now Now, it is interesting. We've talked about the fact that men on average are more interested in casual sex than women. And people often assume that the flip side of that is true as well, that women are more interested in long-term relationships than men. But actually, that's not the case. Uh, typically what we find is that men and women are about as interested as as each other in long-term committed relationships, in falling in love, in forming a committed bond with with a partner. >> So, you haven't reapportioned the sex drive relationship drive desire from short-term to long-term for women. It's just that they don't have this addition that men do of the one-night stand. >> Exactly right. But bearing that in mind Yeah. Yeah. Yeah. Bearing that in mind the the fact that women are so much more interested in romance novels is interesting and sort of slightly unexpected. You you might expect that both sexes would be interested in them. So so why is the case that women are more interested in them? I guess evolutionary speaking I don't know. They they do seem to be despite the fact that actually men do seem to be very invested in long term relationships. A bunch of papers have come out recently actually saying that in in a lot of ways men are kind of more more romantic than women. They are more likely to suffer after a breakup. They fall in love more quickly. They say I love you more soon. Exactly. Exactly. So why aren't they more into romance novels? I don't know. Maybe they're just too busy with the with the porn. But >> I true. Dude, I mean I sat next to a lady, lovely lady, floral dress, slightly slightly older lady on a flight a few months ago and she had a iPad up resting it and it was a big big [ __ ] off font and she was reading some romancy thing and she was getting to the good stuff. And I mean I couldn't I was like we have legalized we have legalized women reading porn in public and it's not I mean I it was she was having a she seemed to be having a wonderful flight and I got my When someone sits next to me and they've got an iPad I think oh that's that's great cuz it's going to or whatever the Kindle or something it's going to influence me to be not be a degenerate. All I wanted to do was put a pair of blinkers on. [laughter] Focus on some brain slop stuff. >> I've never I've never I've been meaning for ages as a sort of anthropological study to read >> you want dude. Excuse it however you want. >> I haven't got round to doing it. I'm going to do it. I'm going to read a romance novel at some point. I have heard that the general theme is boy meets girl. Boy is a bit of an [ __ ] Girl tames boy and then they live happily ever after. And they do involve sex, right? >> Well yeah, I mean, there is some sex in them. At least there was in hers. >> And the one that she was reading. >> Yeah, exactly. Um I mean, there's some interesting stuff, right? The number of uh if you have a single a sexual fantasy mental sexual fantasy, men will cycle through, I think it's between four and six different partners on average during the >> and six or 46? >> Four and six, I think, but it depends who you are. Yeah. Um whereas for women, they tend to have fewer or maybe maybe just one. Now, I don't know, but I'm going to guess that this would be reflected in romance novels. Uh in fact, I know that this is the case because I've been on the cover of a bunch of them. And during those novels, at least mo- I would say on average most >> Yeah. >> the women who are the protagonists aren't cycling through multiple male suitors. And if they are, even if you look at movies, movies like The Notebook or Titanic or whatever, >> Yeah. >> it tends to be a a pivot between two different life directions. >> Yeah. >> Um it's not a kind of ruthless conveyor belt that is closer to sort of the the typical male fantasy. Uh but yeah, the the men being more turned on by visual triggers thing, I think make makes makes an awful lot of sense. I remember in uh Bad Men, Buss's book, he talks about how there is an area of the brain that exists in men that lights up when they just see something that's remotely sexual. A a pair of rocks that look like boobs. >> Putting a coin into a vending machine. You're [ __ ] kidding me. >> Oh, that was a joke. I'm not sure there's actually research on that. But that kind of thing wouldn't surprise me. >> No, no, likewise. >> There is something penetrative about gambling. And it was on top of the risk-taking on top >> [snorts] >> That's it. Um overperception bias as well. Another great example that I learned from uh Bad Men by David. >> Yeah, yeah, and that's um uh research by him and and spearheaded by uh his former student Martie Haselton. Yeah, the sexual overperception bias. Yeah, that refers to the fact that, uh, men are more likely to infer sexual interest on the part of a woman falsely. Like like falsely infer it than women are on the in the case of men. That's so they're more likely to think, "Yeah, she's into me." When actually they're just, uh, in a little dream world, and that's not actually true. >> Men are more likely to think that women are interested in them than they are, and women are more likely to think that men aren't interested in them when they are. And I think that the data shows the level of attraction that men assume a woman has toward them is roughly equal to the amount of attraction that the man has toward the woman. >> Right. Right. Yes. Right. Yeah. Exactly. So, it seems to be maybe some kind of, uh, projecting yourself into the world kind of bias. >> Yeah. So, it's a failure of cross-sex mind reading, but it's also specifically in a in an overperception bias here, too. And this is smoke detector principle. If you as a man had the opportunity to potentially bag an available and attractive woman, and because you weren't sufficiently vigilant in detecting it, because you underplayed your potential success likelihood as opposed to overplayed it, >> Yeah. >> you are going to have an error of missing the opportunity as opposed to the error of an awkward and clumsy rejection. >> Exactly. >> And this, again, I [ __ ] I'm just going to have to keep saying it, does not excuse guys in the workplace with the receptionist in the printing room having an awkward fumble that she absolutely didn't give off signals for. >> Right. >> However, >> Yeah. >> this does explain how you get to that situation, or why it is that on average men seem to be, unless you're the CEO of Who is it? Procter & Gamble? Who is the one that that Indian dude made the whole [ __ ] um, uh, conspiracy theory about? It went insanely viral. I bet your fish-head Asian wife doesn't have these cannons. Do you remember that? >> Goldman >> Goldman Sachs. >> Right. >> Goldman Sachs. Yasmin's mom works at Goldman. We should get the inside scoop. Um Uh Yeah, my get my guest book his mom is like real real high up at uh at Goldman Sachs. And then there was that huge Did you see this thing kick off a couple of months ago? >> I don't >> or two ago or so. Uh it just It was a a guy me tooing a very very high up um >> Right. Okay. >> Exact. >> Yeah, a bit of a role reversal. >> at Goldman. But as soon as the proposed accusations came out, there was no >> I was >> rare. It was like the most It would have been incredibly extreme >> Yeah. >> for a guy to do. >> Yeah, yeah, yeah. >> And the fact that everybody intuited like, "Really?" >> Yeah. >> Sex differences. >> Yeah. Yeah, yeah. >> All right, how do um how do gay men and lesbians reveal what each sex wants? >> They do so in a very interesting way, which is that um gay men have more casual sex than straight men, and lesbians have less casual sex than straight women. Uh and the reason is that gay men and lesbians don't have to compromise with the typical sexual inclinations of the other sex. >> Mhm. >> And they can there- therefore their behavior is a like a clearer window onto the the sexual motivations of men and women in general. >> Unsullied by the other sex. >> Ex- exactly. Yeah. So, men are compromising by having less cuz basically women are thwarting their plans. >> Yeah. >> Whereas >> gatekeeper. >> Ex- exactly. And uh yeah, whereas straight women are compromising with men and they'll be having more than more uh casual sex than they would choose, uh at least as revealed by yeah, lesbian behavior. >> There's a an interesting study that Rob brought up, which was uh inside of marriages typically men say that they would like to have twice as much sex as they are having, and women say that they are happy with the amount of sex that they are having, which suggests that there is a compromise going on. >> Yeah. >> Uh but that the compromise >> The guy going, "Okay, fine." And she's setting she's setting the level >> more than he is. Uh I do think that there's kind of a And this is I mean, like, are we really going to say boo-hoo poor men not getting exactly what they want? But I do think that it's a a kind of compromise that might be invisible to women because sexual entitlement comes wrapped in some really ugly uh paper. But there is an argument that you can make there to say something like, "Look, men are doing a type of containment, a type of desire containment there that isn't a burden that is >> Yeah. >> that they are paying that isn't being paid in the same way inside of a marriage by the women. And huh, that's we Well done. Well done for doing that for for compromising what it is that you want." >> Yeah, indeed. And I guess uh >> [gasps] >> I guess it's more it's more I guess that um men are doing that more often. Like like some women are doing the same thing, no doubt, but it's just fewer women than than men in that situation. >> Yeah. Uh there's also more dead bedroom in lesbian relationships. >> I've heard that, yeah. There's what is the um there's some some phrase like that, isn't there? The there's been dead bed or something. Yeah, yeah. >> Okay, so mate preferences >> Yes. >> When it comes to mate preferences is it surprising how similar men and women are when it comes to what they look for in a partner? >> [sighs] >> Uh well, I guess it fits with the generalization that in a lot of ways we are quite similar. That we sex differences in our species are not as huge as as in some others. And I guess also just on a um everyday level, when when you hear about some of the sex differences that we have in common they're all things that I think it's it's obvious why we like them. Uh people tend to be uh, and women tend to want somebody, uh, who's pretty intelligent and who's kind and who loves them and who is attracted to them and who is pretty good looking, uh, and who's not, uh, like, mentally unstable. >> [snorts] >> Uh, both sexes want that, not just men, not just women. Um, there are some areas though where you do find sex differences in the strength of different preferences. So, both sexes want someone who's pretty good looking, for instance, um, but on average in long-term relationships, that's a bigger deal for men than for women. Uh, men put more weight on looks in a mate, um, than in a long-term mate than than women do for the reasons that I mentioned that I mentioned earlier. Uh, women on the other hand tend to put more weight on resources and status in a long-term mate, uh, than men do. Um, now now in neither of those cases is that the it's not like looks are the most important thing to most men. To most men, it's it's important, but other things are equally important or even more important. Traits like kindness. And likewise with women, um, uh, resources and status in a mate, they're they're important, but other things, like, again, like kindness, uh, tend to top the list of the things that are most important for women. >> Most people don't realize how much being dehydrated impacts their performance, which is why for the last 5 years I've started pretty much every morning with Element. Element is a tasty electrolyte drink mix with everything that you need and nothing that you don't. This orange salt in a cold glass of water is like a sweet salty orangey nectar and I really tell the difference when I take it versus when I don't. It plays a critical role in reducing muscle cramps and fatigue, helps to optimize brain health, and regulate your appetite while also curbing cravings. Best of all, they have a no questions asked refund policy with an unlimited duration, so you can buy it and try it for as long as you want and if you don't like it for any reason, they'll just give you your money back. Plus, they offer free shipping in the US. Right now, you can get a free sample pack of Element's most popular flavors with your first purchase by going to the link in the description below or heading to drinklmnt.com/modernwisdom. That's drinklmnt.com / modernwisdom. What's the evolutionary logic of non-physical mate preferences like wealth and status? >> It all comes down, I think, to the fact Well, there are two main explanations for it. So, one is that it's part of our evolution and other pair-bonding biparental species. So, a guy who is able to access resources, you know, bringing food, and and also has good standing within the group, that's going to be someone who is better able to invest in the young to co-rear the children. And that's the explanation, I think, most popular and most likely. There is also an explanation, though, that it's primarily a human equivalent to the peacock's tail. So, that any any male that is capable of bringing in resources and climbing the status hierarchy, that's a male who's got good genes and he's going to pass on whatever traits enabled him to do that to his male offspring. They're going to be able to do the same. They're going to attract more mates. So, those are two main explanations. I think it's quite possible that both of them shed light on it. That that is both a a fitness indicator, but also is actually useful in the context of biparental care. >> You mentioned this is to do with long-term relationships. >> Yeah. >> How does this change when it comes to short-term relationships? Do women place more or closer to equal uh weight on physical attractiveness in men? >> They do. They do, yeah. So, that sex difference in good looks, we sometimes hear it discussed as if that's the difference between men and women right across the board in every context. But, actually does just apply to long-term relationships. And when it comes to low-commitment relationships, um then that that difference basically evaporates. And women are at least as interested in physical attractiveness in a mate as men are. If not, you know, some research suggesting maybe even more interested in physical attractiveness. >> Why would that be the case using evolutionary logic? >> Because well, the the best explanation is that in a short-term context, that's likely to be um uh basically there's going to be no further investment, probably. >> Huh. >> Uh likely no further investment. The only investment is the genes that the male is going to be passing on. And therefore traits that are indicative of good genes are much more important. They they take center stage in terms of what what women are looking for. >> Mhm. >> And um and and yeah, with the the basic evolutionary logic that uh when you're reproducing, you are finding somebody to mix your genes with. >> Mhm. >> If you want your genes to go on in the gene pool, uh you got to mix them with a good set of genes from from another individual. >> And what you want, if it's you have a a short window to do this assessment in, you want the most obvious representation of those good genes as you can. >> Exactly. And and physical looks are the are that. >> I'm sorry, your ability to do non-kin altruism and reciprocal care and kindness and your ambition over time. It's like, yeah, great, but I don't have time to assess that in the same way >> Yeah, yeah. >> as I do your status and your resources. I suppose it's another one of the reasons. And both men and women if this sex difference didn't exist, if this preference didn't exist, why would it be the case that both men and women seem to play into a caricature of that in an attempt to get sexual access? Why is the caricature of dudes in Miami nightclubs wearing a Rolex and having a fast car outside? Well, that's a way to turn wealth, ambition, and status buying a VIP booth, status, into an immediately transactable and obvious advertisement in case there is some of this short-term mating that's going on. Why is it that women do more beautification when they go on a night out, etc., etc.? Like because you're playing into even if you don't intend on doing it, it's always nice to sort of be window shopped against, I suppose. >> Totally. And And it's interesting, right? Cuz these are human equivalents of the peacock's tail. And whereas in in peacocks and and every other species, basically their peacock's tails non-negotiable, that's just how they do it. Whereas we, cuz we're a cultural animal, we we always have our peacock's tails. We always have our way of showing off status and and whatever else, resources. Um But it varies from culture to culture and time to time. >> Why isn't it that women aren't turning up in a fast car with a an expensive watch outside? >> That's a very interesting question. And I guess that I guess cuz that's more indicative of of resources. And resources are more important to women than men. Um I don't know. There was this um the study where uh this guy uh it wasn't study actually. This guy in in his class, his evolutionary psychology class, he was uh showing a a photo of um this uh this amazing Rolex. And um people saying how how great it was and what what a great uh way of attracting a mate that it would be. And then he revealed the trick was that actually it was a woman's Rolex rather than a man's. And uh and and his point was that actually this goes both and in both directions more than we kind of think it does. >> Mhm. >> Yeah. >> Have you seen, I think it's Andrew Thomas that did this study. Have you seen the preferences that women state when it comes to sperm donors? >> Yeah. >> So this is [ __ ] fascinating. Cuz what's interesting is when you run a kind of a split test or you're able to separate out certain motivations from uh a behavior that people are typical with. So in order for you to do the I want to have kids with this person, typically you need to go through courtship phase and get to know them and or even if it's a one-night stand, be seduced by them. >> Yeah. >> But that means that you're optimizing for two different things. You're not just optimizing for the genes that your kid gets, you're also optimizing for the expression of traits that make you want to get into bed with somebody. But if you get rid of the seduction side of this, all you're optimizing for is what do I want my kids to have from a trait perspective. >> Yeah. >> And that difference of when you get rid of the need to actually be attracted to somebody, you can just optimize for what do I want my kids to be like. >> Yep. >> Kind of fascinating. >> It's really fascinating, right? And and just the same mate preferences emerge in that context as emerge in an actual uh interaction, social interactions. >> Mhm. There's that Clark Hatfield study as well, right? The on-street interview. >> Yeah. Yeah, that's the one where um uh basically, they got a bunch of good-looking guys, good-looking gals to go around a campus on a nice day, uh walk up to random people on the campus and just say, "Hello, how you doing? Um I've noticed you around the place lately and find you very attractive and I was just wondering whether you wanted to {dot} {dot} {dot}" and then they would finish that sentence with one of three options. Option number one was I was wondering if you wanted to go out with me tonight. Option number two was I was wondering if you wanted to come up to my room. And option number three was I wondering wondering if you wanted to go to bed with me. And they got men to ask women, women to ask men. And for the um for the first first question, the go out with me question, there in in the first study they did, there was basically no sex difference. So it was about 50% 50/50 likelihood of saying yes in both cases. Uh other replication studies have found that it's not a huge difference, but that actually men are more likely to say yes than women are. But then with the other two questions, the gaps get bigger and bigger. With question number two, which is would you want to come up to my room, um what was it? It was basically 60 In the first study, about 67% of men said yes. So, actually higher than the date rate. >> [laughter] >> More likely to go up to your room than I am to go on a date with you. >> Exactly. >> Hilarious. >> Uh, with women on the other hand, it uh sank down to I believe it was 6% said yes to that. Uh, and then the gap was even bigger for the last question, unsurprisingly. So, would you go to bed with me? 75% of men said yes uh to that offer. So, at even higher rate of men. Whereas uh exactly 0% of women said yes to the the kind offer. And not only that, but actually the the manner of the refusal differed between men and women. So, uh the um 25% of men who said thanks, but no thanks, well, they kind of said that. They were like polite about it. And uh some of them said, "I'm really sorry. I'm I'm meeting my fiance." or whatever. Bunch of them even asked for a rain check, apparently. They said, "I can't No, I'm very busy. I'm meeting my fiance or or whatever, but maybe we could postpone the sex till later." Whereas uh none of the women uh who were refusing were polite about it at all. They were more They were reacted more like, "Are you crazy? Um How dare you ask me that?" None of them um apologized and asked for a rain check. >> Why do you think that the manner of refusal was so different? >> Uh I think that it reveals Well, two reasons. So, one is there's this average difference in interest in casual sex. And of course men are more interested in it. They are more likely to be flattered by the request. Uh because men are much more likely to approach women than vice versa. Traditionally, uh women are much more likely to get sick of it and and have to, you know, uh push guys away. Whereas guys are much It's a rarer event for them, so they are more likely to be flattered and uh and hugely grateful on the rare occasions when it happens. Uh the other thing though, and the reason I think the difference is quite so big is because it's it's not just a reflection of sex differences and interest in casual sex. I think also in that situation like like if a woman were to go off with a guy that she doesn't know, she's at a greater physical risk than if a guy goes off with a woman that he doesn't know. So, the fact that the the difference was massive is partly due to that as well. >> Feels like a danger. >> Yeah, exactly. >> that emotional activation of hang on, I'm going to go with this person who I don't know, who is physically stronger than me. >> Yeah. >> Explosion. >> Exactly. >> As opposed to there's just way less of a It feels less of a physical threat to me. Those both make Those both both make complete sense. There's a an interesting wrinkle in this. Now, I'm I'm going to guess that when they did this, the Clark Hatfield study, they must have done some sort of rated assessment of the attractiveness of the man or the men versus the women to ensure that they were similarly high in terms of physical attractiveness. >> Yeah. >> Right? >> Yeah. >> So, something that I learned that I think is absolutely [ __ ] hilarious is one of the reasons why women, and I presume men would be too if women approached men at the same rate, one of the reasons why women are sometimes quite rude when guys come up to them is if they feel like there's too big of a disparity in mate value between them and the person doing it. Because they go >> Hang on. You think you've got a you've got a chance with me? >> Yeah. >> Oh my god. It's basically an insult. It's essentially an insult. If you as a woman think that you're an eight, nobody thinks like this. It's not the Whatever podcast. You as a woman think that you're an eight, >> Yeah. >> and a guy that you think is a three comes up to you, that is >> Yeah. >> it tests your own self-perception and you go, [ __ ] maybe this is how the world sees me." >> Yeah. Do you not think I'm an eight as well? Yeah. >> Yeah, and I think that that it feels like an insult. And the same thing like, "Fucking no, get away because rightly so, you're kind of pissed that this thing happened. >> I wonder if guys would feel the same in reverse. See, my my hunch is that they would be less likely to take it as a huge insult if the guy felt he was an eight and approached by a three. >> Well, preference for casual sex. >> Yeah. >> rarer approach in any case. >> Indeed. >> Um and because women are less likely to approach, I think that most guys would actually see it as closer to, "You know what? I'm so good looking that I got that girl to overcome >> Yeah. >> non-approach predisposition. >> Yeah. Yeah. Yeah. >> That's the power of my attractiveness. I think that's I think that's how a lot of guys would take it and I think that's why it is it is flattering. It's like um somebody running for a bus fast that they really, really want. You know, like, "Well, they must really want this bus cuz look at how fast they're going as opposed to how slow they would usually >> And guys tend to be more overconfident than women. >> Mhm. >> Yeah. >> What about sex differences in aggression? >> Sex differences in aggression very, very consistent especially for direct aggression, so face-to-face aggression and guys predominate. And a really interesting fact about the aggression sex difference is that it's it's for like verbal aggression it's there and it's significant. It's fairly modest though. So, the effect size might be about like a 0.5 effect size, so half a standard deviation between the mean for men and men and women. And maybe, you know, pluck two people at random, guy and a gal, two-thirds of the time the guy's going to be higher in verbal aggression. But as you go further out to more and more intense forms of aggression, the size of the sex difference gets bigger and bigger with every step. So, when you go to low levels of physical aggression, slapping, pushing, that kind of thing, that you have a larger sex difference, men doing it more. Then you get into serious physical aggression, violent crime, it's much more men than women. >> of who the victim is. >> Independent of who the victim is. It is, yeah. Um and then when you get to the extreme of one-on-one aggression, which is homicide, uh men vastly predominate. So, across different uh cultures, every single nation, uh every data set I've I've ever seen, 90 plus percent of homicides are perpetrated by men. Men are also they're they're the majority of the victims as well, and and almost all data sets that I've seen. Um but but yeah, the 90% plus perpetrators, very very strong effect. >> Yeah, uh men commit more than 90% of homicides in every society on Earth where data is available, and this gap is remarkably invariant across cultures, not just the absolute rates. In humans, males commit 95% of homicides, and are 70 to 80% of homicide victims. In chimpanzees, males commit 92% of chimpicides, and are 73% of victims, virtually identical numbers to humans. >> It's wild, right? Yeah. Now, they are more aggressive than us. I think some sometimes people hear that and they think that the claim is that we're just as aggressive as chimps, but they are more. But the size of the sex diff- difference in lethal aggression is the same, and the size of the the targets, the sex difference in the targets of aggression is about the same as well. >> Why? >> Uh that is a direct offshoot of the fact that um it it's the selection for getting to be one of the few males that has many offspring rather than the many that have few of them. And one of the ways that males do that is they compete with each other uh for status and resources, uh which increase their mating opportunities. And so you get selection in many many species, not just humans, selection for greater aggression in the males, and and particularly for greater male-male aggression, which is why you have this the skew toward not only do other males more aggressive, but the targets of their aggression tend to be same-sex individuals as well. For women and for female animals in general, they are capable of aggression in many species, but there's just less of a selection pressure. It's less It's less useful for them evolutionarily to engage in same-sex combat for status and resources because of the fact that the the ceiling offspring number that they have is lower. So, they can't vastly increase the number of offspring they have by fighting each other and getting lots of status, resources, and ultimately mates. You know, that that won't boost the number of offspring they have cuz the ceiling is lower. So, it's it's costly effort them. The costs aren't worth the risks. >> Yeah. Plus more fragile. >> Yeah. >> More easy more easily killed. Like just generally. >> Yeah, um but that's that's possibly just an offshoot of the fact that there's been less selection on them for aggression. So, there's been more more of that in males. >> up the defenses in order to be able Exactly. That's why we have a brow ridge. That's why we've got bigger hands. >> Exactly. Yeah. >> So, what's interesting, again talking to Andrew Thomas about this, he said why is it the case if violence is rightly so such a huge fear that most women have that lots of women are attracted to powerful men who are able to be violent? And Andrew's theory is that it's a perspective that a guy who is violent is able to turn it on and turn it off in service of the family unit >> Yeah. >> as opposed to violence being a trait that just is more global across the board. I think Is Andrew doing Krav Maga? He's into it martial artsy type stuff, I swear it. >> so, yeah. >> And uh he was explaining how many Krav Maga, this Israeli martial arts, very lethal, supposedly, martial art. Um, a lot of the guys that he trained with, unbelievably lethal physically. >> Yeah. >> And a lot of the training was them learning to turn it off, not turn it on. >> Interesting. >> Yeah. >> that that the number of men who are physically imposing and might seem like somebody that would be really great to be able to protect the family unit >> Yeah. >> that have done the work to be able to learn to turn that off >> Yeah. >> to the trigger that makes this person likely to be uh flash-in-the-pan, you don't want to [ __ ] with me, bro, guy. At least non-zero-ly are also going to have some triggers that will be more sensitive when it comes to interpersonal communication and domestic disputes >> Yeah. >> and things around the house. >> Indeed. It's It's interesting, isn't it? Having uh >> [sighs] >> that kind of temperament, violent temperament, and the capacity for physical aggression is a It's really a mixed blessing for women, you know? It's great if the guy's going to protect them, protect the family. But it's not so great because he can potentially turn that against them as well. And so, you know, you get the evaluation of those traits. It can increase attract- Like aggression itself, I don't think increases attractiveness. Protectiveness does. >> Yeah. >> Uh Muscularity and the like can increase attraction somewhat, but because it's a mixed blessing, I think women are also interested in the guy's character. >> Muscularity seems >> pretty reliable at improving attractiveness. >> Yeah. >> Yeah, and it's the probably the most easily modifiable thing that guys can do. >> Right. Yeah, yeah. >> I think In fact, I think William said that this is exactly the case cuz he's he's looking at his incel stuff. >> Yeah. >> Did you see Now, I broscience this. I put the I put the the captain of broscience hat on when Mack and came through last time, and I said, "I'm pretty sure that I've seen a study that says a woman would be would lose more attraction if her partner didn't protect her during a physical altercation than if he cheated on her. >> Right. >> And then the guys went and replicated it and >> And you were right? >> I was right. >> Excellent. >> I mean it wasn't my original insight because I found it in a study that I couldn't discover again. But this this the same insight being true, the protectiveness, the ability to protect. In fact, do you know what it is? It was the willingness to protect. >> Yes. >> Wasn't even the ability to protect. Yes. But I suppose willingness to protect is the most important part of protectiveness cuz you can be the biggest guy in the world, but if you're not prepared to step in between your misses and this potential assailant, doesn't mean anything. >> might as well not be. >> Exactly. >> Yeah, exactly. >> I wonder, do you know what it is? I wonder if this would be This is another new skew that the guy should do. >> Yeah. >> Um is it more or less attractive for a guy who could protect you to not than a guy who couldn't protect you to not? >> That's an interesting one. >> You know what I mean? I need to separate it out here. >> But in terms of the character trait, it would be less attractive >> Yeah. >> for the guy who could protect you but doesn't, right? >> Mhm. >> That shows uh a worse character. >> Yeah. >> Um but I guess it does also matter >> I just need to train him to be able to in the future. >> There is that, yeah. >> Yeah. Although I mean I need to teach him to be able to like be strong enough to be protective or need to be able to change his character in order for him to use his strength of potential protectiveness. >> Yeah. Yeah, but if he's definitely not going to do that, that's going to be very off-putting and you might just want the person who is not quite so good at protecting but is willing to do it. >> Mhm. >> If they if they can do it. >> That's what I mean. >> There's trade-offs though, right? >> Why is it Why is it that women care more about a man's height than women do? Is it playing to this? >> Uh I think probably yes. I think it must be. I think it's the within a cluster of traits that determine protectiveness and the like. Muscularity, height, they they're all part of the same package. >> Mhm. >> And it's interesting, right? That does seem to be really, really high on the list for women. Seems to be very important. >> You know why this makes the most sense? And it's the probably Yeah, I would I would go as far as to say it's the most commonly cited "Well, you bitches" internet kind of rebuttal that guys have around I think uh Tinder released as an April Fools' joke about 10 years ago mhm a height filter >> Mhm. >> that people could use. Like, "Wouldn't it be funny if we gave you a height filter?" >> Yeah. >> That's now an actual feature. >> actual feature, right? >> Yeah. Um and many women don't need to date or don't want to date men that are under 6 ft. Uh especially not men when you get sort of like 5'7, 5'6, 5'5, like very few would. And I had this insight, the tall girl problem, uh and it was born out of a friend whose sister is 5' 2. Uh sorry, her sister's 5'11. Um so, if she wants to wear heels on her wedding day, she's like a professional athlete. >> Yeah. >> And they were going around the supermarket and she saw this guy who was like 6'5, like tall dude, like you. Tall guy. And she sort of nudges her sister and says, like, "I got to go up I might go up and talk to him." And they round the corner and they say see him with this 5'2 Latina bombshell and she kicks off at her sister quietly and says, like, "This [ __ ] [ __ ] Like, she could date 5' 5'5, 5'6, 5'7. Why do you have to take a guy that's a foot and a half taller than her?" But the point here is if we're talking about protectiveness as the driver, >> Yeah. >> the fact that your chick is a 5'2 Latina, not a 5'11 American, does not make your height any more or less useful when it comes to protectiveness. this. I don't need to protect you less just because you're smaller. >> Yeah. Yeah. Yeah. Indeed. >> You know? And this is why I think you don't see much of a height compensation effect. >> Yeah. >> Other than I guess if you're 5'2, you can't really tell the difference. I don't Above probably 5'10, you it's all just up there. >> Yeah. >> It's just like it's all up there, you know? >> In the clouds, exactly. Yeah, my cousins are my cousins are quite tall cuz I'm I'm from a tall family and I know they were complaining often. I remember them complaining, female cousins, about guys, taller guys, dating much shorter women. But guess how short Guess how tall my wife is. She's 5'4. So >> [laughter] >> These bloody [ __ ] how dare they take the tall men? All right, sex differences in stalking. What about that? >> Uh women do a lot more of it. Joke. Men do a lot more of it. >> [laughter] >> Uh men do a lot more of it. It's I think it's just um an example of the the fact that men are more, you know, proactive seeking out mates, seeking out multiple mates, uh and stalking is the subcategory of that when it gets into extremely inappropriate examples of that. Um and also I guess uh yeah, it's also it's not just mate seeking, it's also when people get fixated on somebody. >> Yeah. >> And both sexes can do that. They can get fixated on somebody. >> Sort of limerence type thing. >> Yeah. Yeah. Exactly, limerence. Yeah. It's a sort of falling in love except that we call it limerence cuz it's in an inappropriate circumstance, i.e., circumstance where the other person does not reciprocate. Both sexes can do it, but men are more prone to aggression and risk taking and just bad behavior. And so they're more likely to do more of the those kind of behaviors in the context of uh limerence and being fixated on somebody. >> surveillance, surveilling of a partner, checking in because I could see two two reasons why either side might be doing it more. Male parental uncertainty, which we haven't talked about yet, but is super important. No woman has ever given birth to a child and wondered whether it was hers, but many men have looked at maybe even all men to some degree. In fact, it would be evolutionary useful for you the first time that you look at your kid to be so beautiful and those my eyes? >> Yeah. >> Yeah, I think they're my eyes. But given the fact that you have high male parental uncertainty >> Yeah. >> because you've got concealed ovulation and you don't have the same kind of sort of harem hermetically sealed sphere when it comes to men and women human men and women. Um stalking I could see a surveillance surveillance behavior mate guard could be a a part of mate guarding >> Totally. >> Uh to try and counteract that, but I could also see how it would be useful for women in order to ensure that their partner doesn't leave them high and dry because there's more of a dependency especially if we are going to have a kid or do have a kid. >> Yeah. >> Um the the man doesn't need the woman as much for survival. Uh but the woman doesn't need to check on the man as much to ensure female parental uncertainty. >> Yeah, that's exactly right. And both sexes do get jealous. Uh paternity uncertainty or you know, parental uncertainty is uniquely an issue for guys. But you're absolutely right that there is uh the danger of desertion for women. And so for different reasons both sexes have evolved to be to be jealous and prone to jealousy. And one way that that manifests so so jealousy drives mate guarding behavior and one subset of mate guarding behavior is surveilling and just keeping keeping an eye on what the person is up to and are they getting on too well with that good looking next door neighbor or the good looking guy or or woman at work. Um and then if you take that to an extreme, that's where it becomes surveilling behavior. Isn't it interesting that you have a an extreme insight of men about other men and an extreme insight of women about other women, but the failure of cross-sex mind reading still occurs even when you add other individuals in? So, when we're talking about surveillance, jealousy, mate guarding, etc. The I mean William put these stats up recently about how what the percentage is of men who would sleep with a female friend. >> Mhm. >> It's huge. [snorts] It's like 50% of relationships used to be friendships. >> Yeah, yeah, yeah. >> Uh so, that's like 50%. >> Yeah. >> Right, that's a huge amount and I think uh when you put all of this together, you end up with a world where inside of a relationship men are trying to explain to women what they see in other men that are around them and women are trying to explain to men what they see in the other women that are around them. And just because it's not them talking about themselves doesn't mean that they can explain it. A woman is no better at understanding another man than her own husband and a man is no better at understanding another woman than his own wife in these sort of more subtle hard to detect motivations. >> Did you say what? Um that those data that that William was talking about so so yes so like a lot of guys would be interested in sleeping with friends that they have, right? But it's not true in the other direction like fewer uh some women but fewer of them are particularly interested in sleeping with male friends that they have. >> Mhm. >> But because of the sexual over perception bias, the male friends in question would probably assume otherwise. >> Mhm. Mhm. >> What's the sex difference on sexual violence? >> Sexual violence men are much more likely to do it and that is just partly just an offshoot of the fact that men are more aggressive uh, aggressive. >> Mhm. >> Um, yeah, and the numbers are pretty big. So, sexual violence, um, is much more often perpetrated by men than by women. It's not It doesn't only go in in the one direction, though, but it is just much more common for men to do it. >> have any idea what the numbers are? >> Uh, I probably do. Let me have a think. Um, Okay, so I do have a few numbers coming to mind, but I'm not actually sure if they're the right numbers. So, I'm going to I'm going to again do the annoying academic thing. >> Directionally correct, specifically vague. >> in vague. So, directionally correct, and and I'll you know, I'll go to say that it is a big difference. >> Yeah. >> Um, I think the effect size might be something like, uh, two. So, like two standard deviations between the mean for men and women for the extreme forms of, um, of sexual violence and sexual assault and harassment and that kind of like. >> Yeah. >> Yeah. Yeah, another situation where it's kind of hard to talk about evolutionary explanations for bad behavior, like the worst behavior, right? Between this and homicide without sounding like you're excusing it as natural, but >> Exactly, but again, natural doesn't mean good. >> Yeah. >> I mean, you know, you can explain bad stuff without saying that actually the bad stuff is not good stuff. You It's still, uh, bad even if it has an evolutionary explanation. >> Yeah. Yeah. It's that, uh, analysis is not justification. >> Yeah. Yeah, exactly. >> Uh, you know, that's a [ __ ] Hasan [ __ ] quote. That's like a Hasan [ __ ] quote. >> Is that Is that right? >> Yeah, he got canceled He got canceled for talking about some stuff to do with the right wing. That is an absolute slammer of a line, analysis is not justification. >> Yeah. >> Uh, but you know, we can see sexual violence if men are able to procreate without having to do any investment, the ultimate form of that is to not even have to ask for consent as well. >> Yeah. Yeah, indeed. And, you know, it has been argued that the tendency in some men to do that, to take that path, does have evolutionary roots. Um And I guess really you just have to have two things. You have to have men's greater interest in sexual variety and casual sex. >> Mhm. >> Uh coupled with their willingness to use violence in certain uh you know, certain situations. So, because men are more interested in casual sex, it's going to be not uncommon for a man to want to have sex with the woman who doesn't want to do so. >> Yep. >> And because men are willing to use violence sometimes to get what they want. >> Mhm. >> Every now and then you are going to have that situation where those those factors add up and the man's going to try to force the woman to have sex. That's not just found in our species. Uh males in in many species try to coerce women females rather in into sex. >> Mhm. >> It happens in our species. It's also been argued though that because uh preserving female choice is so important across the animal kingdom including in our own species, so important to women uh that that helps explain why sexual coercion and rape is so upsetting to women. You know, it's not that we haven't just been socialized for it to be upsetting to women. It's very very deep in uh females' nature to be upset by it because it compromises female choice. >> Oh, that's interesting. >> Yeah. >> That's interesting because not not only not only is it [ __ ] heinous, but you know that because somebody because this male committed that behavior they've had to disregard the entire female-wide value that is supposed to be uh universally uh uh protected. >> Well, right. Well, I mean, she's evolved this tendency to be choosier >> Mhm. >> about who mates than men have. And she's got these mate choice criteria and uh that that's because she can have fewer offspring and therefore each offspring counts for more. So, she's got to be uh wiser in every mating decision that she makes. And this other male has come along and has just taken that away from her. Taken that choice away from her. Uh and has gone against the the so that she's evolved to be more to be choosy and and gone against that. >> I I I think that the inability of men to fully understand what fear of sexual violence must feel like >> Yeah. >> is one of the reasons why any guy who's seemingly sort of flippant or callous about any type of male-female aggression, even non-sexual violence >> Yeah, yeah. >> is treated with a very strong antibody response from from women. >> Indeed, yeah. And guys do you know, guys the idea of going to prison and being raped in prison obviously is is terrifying to a lot of guys. So, they they do get it to some degree. But, and I guess particularly when it comes to the sort of lower level stuff, like like I think in Buss's Batman book, he talks about research suggesting that men often will underestimate just how upsetting it is to women to be to be sexually harassed and to have stuff done to them against their will. And that's another very good example of a and a very important example of a failure of cross-sex mind reading where the guy just doesn't really appreciate just quite how upsetting it is for that to happen because if it would have happened in reverse if if it would have happened to him he might not like it, but he on average is not going to be quite so upset by it. >> It's interesting that people who denied sex differences seem to sort of not want to argue for parity that if women weren't so held back, they'd want to commit just as much violent crime as men do. >> Indeed, yeah, indeed. >> There's a directionality to the way that this analysis happens. >> Yeah. >> They're Why is it not that we've got 50/50 in terms of homicides? Like that we should do. >> Yeah, yeah, yeah. be free to commit as just as many killings as they want to. >> Yeah, and they've just been kept down the fact that they're not doing it. Yeah. >> Yeah, the patriarchy, the damn patriarchy. >> And I guess the thing is that they and then we all would want it all to come down. >> Mhm. >> And uh it's a good example of um how equality is not necessarily a good thing in itself. So So men are more aggressive than women. The solution to that is So So we want to kind of um reduce male violence. And in the process of doing that, we're going to reduce the size of the sex difference. >> Mhm. >> And And that's a that's a very good thing to do, but the reason it's a good thing to do is not cuz there's anything inherently wrong with the sex difference. It's because violence is bad. It's not cuz the sex difference is bad. It's cuz violence is bad. And we know that because another way to get rid of that sex difference and violence would be to increase the female level of violence. >> [laughter] >> And that would be big thumbs down on that, right? That is going to going to make the world a a worse place rather than a better place. >> [laughter] >> Point is, yeah, equality is not a good thing in itself. >> itself. Yeah, yeah, yeah, yeah. Okay, what about the differences in parenting? >> Differences in parenting, that's quite a controversial one, actually. Um that's one of the ones that people like least. The aggression sex difference, no worries about the parenting sex difference, people aren't so keen on. And that refers to the fact that in every culture, again, where we have good data, women do more of the direct parenting uh than than men do. Uh and they invest more in the young. They do more parental care. Um men in every culture do more than your average male chimpanzee or male walrus. But they they do less than women in every single culture. And it doesn't seem to just be because men are forcing women to do it. They do do seem to be average differences in terms of parental inclinations, with women being more interested in doing it uh than men are on on on average. And yeah, I guess the reason that it's controversial is that there's a concern that people are saying making up an excuse why you should do it. So So like the guys are using it as an excuse. It's just It's just natural that you should want to be changing the nappies and doing these things that coincidentally I would rather not have to do. >> Mhm. >> Um so that that I think is the concern. But in a way it's ironic. So, the fact that people consider it to be kind of an insult to say that on average women are more interested in parenting than men, um implies a negative valuation of parenting or doing more of the parenting. Because if it didn't imply a negative valuation of that, it would not be an insult to say that women on average are more >> one of my most one of my one of the best ideas that I think I've come up with over the last couple of years, which was the the soft signal of male expectations. >> Yeah, yeah, yeah. I think you mentioned that in when we met the first time, right? Was it? >> Yeah, yeah. Soft the soft bigotry of male expectations. It's It's like as if we treat the the male standard, what whatever men do, that's the standard of what what is right. And if women do it less, that's a bad thing and we should make them more like males. >> Mhm. >> But not so much not so much the reverse. Um yeah, and it is very ironic cuz >> It's really misogynistic worldview. >> It is, really, isn't it? It is. It is. And so to if we're taking a negative valuation of uh our parenting, which is what we are implicitly doing if we say that it's an insult to say women are more parental. We're implicitly uh if it is actually true that women on average are more parental by nature, then we're taking [snorts] a negative valuation of a more female typical trait and that is really sexist. >> Yeah. Yeah. What's the kibbutz experiment? >> Uh the kibbutz experiment So, there there there are um the there were these kibbutzim that they had in in uh Israel. So, these were these communes uh like highly egalitarian uh communes where they wanted to get rid of all traditional kind of structures including traditional male-female ways where the woman is expected to do all of the child care and the guys out of in the public doing the public stuff. She's at home doing the private stuff. So, what they did was they would um they would get all the kids and they would house them in communal houses. And then they would have dedicated adults within the group who'd be the primary primarily in charge of looking after all the kids. So, the kids weren't living under the the roof of their biological parents. They didn't think you know the idea was everyone should care for everyone rather than having this traditional what they they saw as uh as bourgeois uh approach where people are specifically interested in their own biological children. They want to get rid of that. Um they tried to they did manage to make it work for a while, but what happened was that just the parents hated it basically. The parents hated not having their own kids living with them under their under their roof. And they agitated and complained about it and and eventually it broke down. And [snorts] the interesting thing was that um although both parents hated it most of the the mothers particularly hated it. And a lot of the agitation came from the mothers more than the fathers. And it's a great example a great case study because we often hear that um that women are placed in the primary caregiver role by men. That men have kind of forced them into the into that role. But here was a case where actually uh the women in particular were rebelling against the male leaders to try to put themselves into that role instead. So, it's it's a another example of a very common phenomenon where you see certain behaviors and certain aspects of human nature that emerge and persist despite culture rather than because of culture. Culture's pushing in the opposite >> going against it. >> Exactly. >> Yeah. Yeah. I saw this really heartbreaking video of a woman on TikTok. Uh she was at work in a cubicle like like a sort of normal office cubicle and she had a screen up of maybe the daycare that her kid went to and she was seeing watching her kid say its first words or take its first steps. >> Mhm. >> And the it was just one of those ones with the caption over it that said uh like me being devastated that I'm at work while my kid is going through one of the most meaningful experiences at the start of its life and I'm missing it. >> It's tough, right? There's a real That's the uh the work family uh you know, clashing roles uh that that both sexes do experience, but it does seem to be um still a bigger deal to women than men. >> Yeah. It's not It's not It's certainly not something that people are happy to talk about matern- maternity leave and the lack of maternity leave as being kind of barbaric and I agree. I think it I mean the UK gives 9 months, which is still not enough, but feels at least remotely humane. >> Yeah. >> Um the US is basically once you're out of the hospital, you're back to work. >> Yeah. >> Uh but very few people I think it's not a big cultural conversation around what is missed by either the need to go back to work to keep yourself financially stable or the desire to go back to work because of expectations that have been adjusted on women about where their value comes from. This soft bigotry thing again. I don't want to be just a mom. >> Yeah. >> Uh but by being not just a mom, I'm also missing out on a lot of the joys of motherhood. It's a It's a very kind of It's kind of hard to win that situation. Women really don't have a good a good outcome there. >> Yeah, and people in general I mean in a way you know, there are there are these kind of trade-offs for everybody always and and choosing one option always does mean uh not choosing another one. I know that a lot of people solve that problem to some degree to the extent that it is solvable. A lot of women do by taking some time off you know, more time off, taking career break in other words when the kids are are young. >> Yeah. >> But then particularly when they go to school, then, you know, getting back on the uh career career horse. >> Yeah. >> What about differences between men and women in sexual jealousy? >> Um that's an interesting one. So, both are prone to it, like I mentioned. But for the reasons that uh you mentioned already, um men men's jealousy is more focused than women's on sex. So, a sexual infidelity, like like if you ask men, which would upset you more, uh your partner who you love going off and sleeping with somebody else, or just forming a close emotional bond with somebody else? Now, both of those are upsetting to most men, but men are more likely to say that the sex is more upsetting than just the bond. And pose the same question to women, and again, it's both of them are upsetting to to the vast majority of women, but they're more likely to say that the emotional bond, the sort of falling in love maybe falling in love with the other person, um that that's more upsetting than just sex per se. >> Huh. >> It's interesting, right? >> And it comes out of the fact that uh men have this this problem of paternity uncertainty. Like you say, no man in the history of the species has ever um no woman around the in the history of the species ever given birth and thought, "Now, how do I know that this is my kid and not some other woman's kid?" Whereas you know, for most men, more than likely it is their own kid. >> Huh. >> Um but there is always some non-zero chance that actually it's not, that it's the uh the good-looking next-door neighbor's kid instead. So, yeah, that's why sex is more important issue for men than women. Women are more likely to be left holding the baby, and that is not good for their fitness, >> Yeah. >> cuz it's going to reduce the time before they can have another kid, and uh just make things a lot more difficult for them. And so, the it's obviously not great if their partner sort of sleeps with somebody else. It's not great. They'd be very, very upset about it. Very often it destroys the relationship. >> But it's even worse for most women if the partner gets emotionally involved with somebody else because then the whether whether they want the relationship to end or not it's going to end cuz they're going to leave very likely going to leave and I set up shop with the other woman. >> I have an example that I heard about from a while ago that a a friend was on 23andMe or ancestry.com and one day in their 30s got an email notification saying you've got a new half-sister. >> Right. >> And it says, "How the [ __ ] have I got a new half-sister?" What it turns out was that 32 years ago the dad had had a one-night stand affair. That kid had never met the father, never been involved again. >> Right. >> But three decades later this situation unfolds and uh ob- obviously awful awful to try to live through. But I would have been fascinated to have done a study to work out what happens to what happens to sexual jealousy and intimacy jealousy and the fear of resources resource provisioning needing to be split >> Yeah. >> when you've gone past all of those things because you have this you know three decade as assuming that there's not been more infidelity this three decade example of someone committing to the family and raising the kids and doing the rest of the stuff and also the person that would have been the dependent is no longer in need of any of the provisioning. Do you understand what I'm getting at? To like separate out all of the typical areas trust infidelity all of those things obviously horrible but kind of kind of fascinating too. >> It is really fascinating and I wonder if this could be an example where proximate and ultimate could could just I thinking about the proximate and ultimate might solve the mystery cuz it's possible that cuz we don't necessarily think about we don't necessarily think it through well. We're not really necessarily thinking well, I'm going to lose this partner. He he's going to fall in love with her and he's going to go away and then I've got this baby and I'm going to have no one to help me with it. That's the evolutionary rationale, but it could just be a gut reaction like he's getting close to somebody else. I hate that. I feel jealous. I feel bad about it. And so that could kick him just as strongly 30 years down the line when it doesn't matter anyway. You know, like you say trust issues and those kind of things are going to kick him. Could kick him just just as strong even though evolutionarily the circumstances it doesn't matter anymore. The gut reaction that evolved might be might not discriminate those those details. >> Mhm. What do we know about sex differences in personality? >> Uh well, there are some and they're pretty consistent. They're not huge. Two of them are bigger bigger than the rest. Now if you're thinking about the big five personality traits. So so the ocean acronym, right? So openness to experience, neuroticism, extraversion, agreeableness, uh and uh conscientiousness. I got that in the wrong order. That wasn't ocean, but but those were the those are the five. So um the two sex differences that are largest and most consistent uh the sex difference in neuroticism, which is proneness to negative emotions like depression and anxiety plus emotional volatility. So ups and downs. Um and that is about a medium effect size. So I guess it's usually estimated between about 0.2 and 0.5 uh standard deviation between between men and women. There's that one and then the other consistent one is the sex difference in agreeableness. Uh and women on average score higher. Again, it's not a massive difference, heaps of overlap, but but again it's 0.2 to 0.5. I'd say it's a it's a medium small to medium sex difference. Uh as well. There are some sex differences in the other uh three big five traits. Um Often not always. You sometimes find that women score a bit higher conscientiousness, but but not always. Some studies don't find that. Uh extraversion, on average women slightly higher on extraversion, but but again, not always and it's it's a smaller difference if it is one. Uh and then uh Uh what's the other one? Conscientiousness? Openness. Yeah, openness slightly higher for for women as well or no difference. >> What's the explanation for why those would be the case? >> Uh well, I I don't think we know for sure, but my best guess so then neuroticism sex difference, so that's proneness to things like anxiety and depression, and I think women there's a general trend where women seem to be more self-protective than men. It's kind of the flip side of the fact that men take greater risks than women. They more risk-taky. I think that that evolved cuz that is um about trying to propel yourself up the status hierarchy. You got to take risks in order to do so. Uh and men have evolved to do that more than women cuz they have a higher maximum offspring number. But yeah, the flip side of of risk-taking is to be more self self-protective. Part of that is to be more prone to anxiety. Anxiety, the function of anxiety is to is the same as the function of the of the turtle shell. It's to protect yourself. It's about protection. So I think that's why women are more neurotic. Now, the agreeableness sex difference, so women on average are more agreeable. Um I don't have quite as strong an idea about that. I do think that Well, I guess I guess it could be the flip side of the fact that men are um sort of more more aggressive, more more pushy, and and that evolved like like we discussed to try to again get up the status hierarchy. Uh beat rival males to to go up in the world and achieve status and resources. Women have evolved to do less of that and one manifestation of that is the fact that they're more more agreeable, more friendly, more compassionate. Um and and just the way that women have evolved to form social bonds that does tend to have a high level of compassion and and understanding the other person. That seems to be more common in in women than men. >> What about the people versus things divide? >> Um so that's an interesting one, right? That is a bigger difference. That's actually quite a big difference. One of the bigger psychological sex differences and the effect size there is is like one standard deviation or even even a bit more when it comes to people people versus things. Very very consistent. I think there's a good case that it is not just due to socialization. So so one thing is that like I mentioned earlier, it has persisted for as long as we've been measuring it. Very very consistent. Even when the culture's trying to push against it and and get women more interested in things related professions traditionally male professions. Seems to be related as we also mentioned seems to be related to prenatal hormonal exposure. And one thing I haven't mentioned already is that it's also very very cross-culturally consistent. So there was one study that had about 200,000 people in it and found that sex difference in career-related interests. Found that in 53 out of 53 nations. And another one had half a million people and found that in 80 out of 80 nations. >> Wow. >> And that level is amazing, right? That level of cross-cultural uniform uniformity you just hardly ever find it in the social sciences, but you do find it for that difference. >> And this has been around for 100 years. >> Yep. Yep. >> First documented in 1911. >> Yeah yeah yeah, that's right. Yeah, that's when they first first documented it and it's been consistent ever since. It's one of the biggest differences and I always find that pretty interesting really cuz the kind of careers that we have today are evolutionarily novel. So you might not necessarily expect that to be one of the biggest sex differences. You know, interest in careers that just haven't existed throughout the vast majority of evolutionary history for our species. >> Yeah. >> But but it's there. And very consistent. >> And there's been some deliberate effects attempts to try and close it as well. >> Indeed. And they're ongoing. And it just doesn't seem to doesn't seem to budge really. >> Mhm. >> Yeah. >> Interesting that the the soft bigotry of male expectations happens with get more women into STEM as well. >> Yes. Yeah, indeed. As opposed to get more men into traditional female dominant Exactly. Exactly. But um you know, Richard Reeves who he's been on the show, right? And and [clears throat] he's he's trying to get more men into the into those kind of professions. >> He's trying to do it, but again I think the reason that there is a publicly lauded push toward getting more women into STEM is because of that soft bigotry. >> Agreed. >> And if you look I'm going to guess that if you look at the gender equality paradox, you're going to find that in more gender equal nations fewer women end up going into things-based roles. >> Yep. >> And more men go into things-based roles. >> That is exactly right. Yeah. And and just the interest in it is gets bigger in those in those cultures as well. >> Regardless of what you do, what you That's an interesting one to have to separate out what jobs are available to you and can you get from what ones you interested in. >> Exactly. And and both both expand. And it's really it is interesting. Now, I think that you were right that it does reflect the soft bigotry of male expectations. I think I think people who want to close those gaps also will typically point out that those kind of professions pay more as well. And that's that's another reason to try to close the gap. >> But that doesn't change the interest. >> It doesn't it doesn't change the interest. >> I mean, some people are interested in things because I I went to university and did business >> Yeah. >> because I thought I could get a job in it. >> Yeah. >> So I became interested, but it was a very transactional type of interest. >> Interesting. >> Yeah. So yeah, I how many people develop an interest in a thing because it's functionally useful for them to acquire resources in it? I I you know, not know people. I would say that in in a pretty wealthy society that more men than women do that. Now, in in poorer societies, I think it's more common for everybody to do that, you know? Some poorer societies you just think, well, I would love to do whatever it is, impressionistic dancing or whatever. But you get some in in high inequality and uh high poverty environments, you get some really interesting outcomes. You've seen Candace Blake's work on the female beautification. I I have, yeah. Remind me remind me the details there. They analyzed It was either Instagram posts or tweets and correlated them with the level of income inequality in the local ecology. And in areas with higher income inequality, women did more self-sexualization and more beautification. And supposedly, the proposed mechanism for that is when you see not only how high you could climb, but how low you could fall, you try to maximize your ability to be a assisted in being dragged out of that from a resource resource provision perspective. Yeah, it's it's it's really cool, but basically, it's just when material restrictions are in place, stuff gets warped and squirrely because people are concerned about survival. I mean, you've seen the um environmental security hypothesis as well about men are more attracted to bigger women in times of poor economy and more attracted to skinnier women in times of bad times of good economy. >> And and good Yeah, it's interesting, right? And there does seem to be pretty good data on that. I am not 100% persuaded of the evolutionary arguments for it, though. >> You could survive a famine, there's a famine imminent. You couldn't survive a famine, but it doesn't matter cuz we got loads of food. >> Indeed. And I mean, it does make sense. Like the the logic there does make sense, but I mean, is it the case that for a long enough fraction of human evolutionary history, Uh we had feast and famine feast and famines I'm sure we did have that, but with a feast periods big enough that people were actually getting bigger. I mean my impression is that hunter-gatherers they just didn't really get uh big enough that they would have been selected for that. >> very very very rare. It would have would have been almost impossible >> Indeed. >> before what 13,000 years ago. It would have been almost exactly impossible definitionally because you could only eat what you could carry. >> E- Exactly. >> no surplus at all. That's interesting. >> So I sort of feel like I can hear today we can [ __ ] grill him about it. We can talk about that, yeah, cuz he's a he's a fan of that, right? >> Yeah, he is. Well, he likes he likes the sort of behavioral ecology approach to things. He likes humans as plants as well as humans as as animals. So we grow toward the sun and how is the local ecology imposing and warping, uh but it definitely the the it's self-sexualization in high income inequality makes makes sense. >> Yeah. And I do agree with the general principle that uh we've evolved to respond to the ecology. I'm just not sure in that case it could have it could have evolved because of there weren't, you know, fatter people around the place for long enough. >> What about cognitive abilities? >> Cognitive abilities, um that's if anything is I would say that's probably the most controversial topic that I deal with in the book. >> Let's bury it 2 hours into the episode. >> [laughter] >> Yeah. >> Um so there are some, I guess, few things to say uh to avoid or try to avoid getting canceled is first of all that there are there are no sex differences in the cognitive ability that matters most to most people, which is IQ or general cognitive ability. Um there is basically zero sex difference in the average there. Um now people when when you say that some people will say but that's because IQ tests have deliberately been constructed to create equal averages. Um and that is true. Some of them have some of them have, but there are some IQ tests >> the sex difference? >> Well, that that's the that's the theory. And so some of some of them have been deliberately created that way, but some haven't. But even those ones that haven't been created specifically to give the same the same outcome and balancing spatial versus verbal and and that kind of thing. Um even when they haven't they they give basically the same averages with representative samples of people. Now, sometimes you'll get uh some studies that will have males doing slightly better on average, but uh I'm persuaded by the argument that that is because the very low IQ males are more likely to fall off the map, fall through the cracks, and kind of disappear and and not end up on the samples >> Right. And the low IQ women bringing down bringing down the female average. Because we do have a higher variance. >> Yeah, right. >> Yeah, yeah, yeah, yeah. In cognitive abilities there's higher variance, yeah. Average is the same. The variance is slightly greater in men than in women. >> More male geniuses and more male retards. >> That is exactly right, but uh important note that that's quite a small effect. Um and that is this is the controversial area and that's maybe the most controversial claim within that controversial area. Um so I always like to follow that up by saying So that that people hate that cuz it's a cognitive advantage that gives an advantage to guys, but there are also other cognitive um ability sex differences that give the advantage to women. So women on average um are better verbally. Um that is one. And another one is that among the minority people who are really really gifted at maths, the women are more likely than than the men to also be gifted verbally. So they're they're more likely to be a double threat. >> [laughter] >> That's cool. >> Uh So that's So no average differences in IQ. Where you do find differences, they're just as likely to favor women as men. Some of them So in some cases men are slightly better. Spatial abilities, that's an example. Verbal abilities though, women tend to be somewhat better. And then, most of the differences are small. So, the personality They're smaller than the personality differences. They're much smaller than the differences in interests. So, when it comes to cognitive abilities, we're much more alike than different. But, having said all that, there are these average differences in these specific abilities. Um and that, like it or not, that just is the the fact of the matter. And that's been measured for uh 100 years as well. There's There's tons and tons of data on it. Typically found across cultures. Very likely, I think, to be to be partly innate. You know, that it's shaped by culture as well. You can You can minimize it. Uh and and I guess also, in principle, you could increase it as well. But, yeah, I would be surprised if it's just due to socialization. >> What about physical health? >> Physical health, um there are some definite sex differences there. Uh one of them, and the one that's probably best known, is that men are more prone to cardiovascular disease. That women are more prone to heart attacks in particular. Um at least among you know, like like in '50s and '60s. Until until very old age, men are more prone uh to those. Women are more prone to immune system disorders. They're more prone as well to to pain disorders. Uh men are more prone to most forms of cancer, other than sort of reproductive cancers that only strike one sex or the other. Uh men are somewhat more prone to to cancers as well. And actually, one of the big ones is that men die younger, on average, than men in the vast majority of cultures. Uh including even most cultures where women have high rates of of death during childbirth. So, we drew the the short straw there. >> Eunuchs in the Korean Chosen Dynasty lived longer than intact males of identical social standing, demonstrating that testosterone has a direct biological cost to male lifespan. >> That is very true. So, I touch on that in the book in a billion billion years of sex differences. I write about how actually most people probably don't know this, but we do actually already have an intervention that we could in principle do, which would completely obliterate the the average difference in lifespan between men and women, and would extend men's lifespan, and that is castration. It's got to be um castration before you hit puberty though. So, you know, sadly enough if anyone wants to take that approach, if you've already hit puberty, it's too late. Uh but yeah, the fact that it it would work is it's interesting. That show that it's testosterone that is making us bigger, stronger, more aggressive, but also shortening our our lifespan as well. >> If male mortality rates were lowered to female rates, Randy Nesse, who did the evolutionary medicine studies, calculated we would save more years of life than if we cured cancer. If male mortality were at female rates, we would save more years of life than if we cured cancer. >> Yeah. So, we're so used to it, so used to the fact that men die younger, that we don't really think about it, I think. But then when you do think about it, yeah, you find that that is a is just a massive massive difference. >> And then we've got 88% of Darwin Award winners, which are people who die through spectacular self-inflicted stupidity, are men. But 90% of Carnegie Hero Awards, which are given to people who risk someone's life in order to save a stranger, also go to men. So, the risk sort of cuts both ways. It's almost exactly the same. 88% of people who die through stupid self-inflicted ways are guys, and 90% of people who risk one's life to save a stranger are also guys. >> Yeah. So, that is the trade-off there of of risk-taking, right? Is that and in fact almost by definition, taking risks can pay off big time, but can also kill you. >> Winners and losers. >> Yeah, exactly. And because men do more of that risk-taking, I mean, that's one of the reasons I think that um that you get more males than females will start a business that does really really well. Uh and people focus on that, and they think it's it's unfair, but it's it's also the other way around. Exactly, exactly right. Yeah, they're more >> likely to go in both directions. So, they're more likely to succeed cuz they take bigger risks, more likely to fail because they take bigger risks. Some people when they hear about that, they think, "Well, we should encourage women to take bigger risks." But the problem is that they are then to the extent that they do that, they're opening themselves up not only to greater chances of success, but also to greater chances of failure. >> Yeah, risk doesn't just cut one way. >> Yeah, well, totally. Exactly. And so, my solution there, I think, would be just tell everybody all the facts. Tell men and women all the facts. This approach to life, this risky approach uh cuts both ways. You could go up, you could go down. >> Yeah. >> Uh do do what you want with that with that knowledge. >> Mhm. >> And that's my approach to just uh a lot of gender gaps in general, right? So, like workplace gender gaps. Tell people all the facts. Try to get rid of I mean, just do everything we can to get rid of bias and barriers. But then, having done that, um respect people's choices about their own lives and how they want to live them and what careers they want to do. >> really interesting about that is if you try to compartmentalize the information that people see >> Mhm. >> and you don't give them full access to the information, >> Yeah. >> what you end up with is actually a world in which there's more likely to be resentfulness, and you need to do more compensation on the back end because people have made decisions under imperfect information. >> Yeah. Yeah, that's exactly right. And um some of the steps I think that people take to try to balance out gender gaps in the workplace, I think, can have exactly that effect, creating uh resentment. Um This is one of the dangers really, I think, of overstating the extent to which gender gaps in occupations are due to bias and barriers. >> Mhm. >> Um Uh you know, I do think it's absolutely essential to look at the extent to which they are due to those facts. But I think we just to to bias barriers, I think we also though need to look at um the extent to which they're due to preferences as well. >> [gasps] >> Cuz if we don't, first of all, if if we say any kind of gaps that you see are products of discrimination, first of all, it's going to create unnecessary resentment cuz you're going to say, "Look look at these gaps, that's because of men mistreating women." >> [gasps] >> Second, it's going to lead to like like costly interventions to try to eliminate the gaps. And those interventions probably not going to work because they're targeting things that are not the causes, the primary causes of the gaps in the first place. Then what happens is cuz they don't work, we start doing more and more coercive things to try to eliminate the gaps. >> Yeah. >> In some cases, we do anti-male discrimination kind of inadvertently just trying to eliminate the gaps. We get a bit more coercive and end up instead of getting rid of discrimination, which is what I think we should do, we end up reversing the direction of discrimination. Which I think is just creating It's not It's not undoing past injustices. It is just adding to the sum total of injustices. >> Exactly. Exactly. And reverse reverse ones. And then I can create a backlash among guys. And then also if we if we exaggerate the extent to which discrimination is behind those gender gaps. Um like in STEM, for instance, we say there's the the you have these gaps in STEM, more men than women go into it, and it's just because STEM is just riddled with sexism. It's a horrible horrible hotbed of sexism. That's going to put a lot of women off, girls and women off, who might otherwise go into it. So, ironically, this effort to try to to fight it could actually be, you know, create the the reverse. >> You touched on it earlier. What about differences in mental health? >> Mental health, so there's the neuroticism sex difference, first of all. Women are more prone to depression and anxiety, just sort of day-to-day depression and anxiety, um, than clinical levels of it. But, at the extreme of that distribution, they are also more prone to clinical depression and clinical anxiety disorders. >> Mhm. >> Uh, men are slightly more prone to schizophrenia. Men are much more prone to like antisocial personality disorders, sociopathy, psychopathy, um, more likely to be psychopaths. Mhm. What else is there? I'll tell you one that we don't find a sex difference is bipolar disorder. That is, I'd say in the book that that's the the least sexist disorder on record. Because it's basically the same, uh, across cultures it's about the same frequency in both sexes. >> What's your explanation for why we would have these differences in mental health? >> Well, with the depression and anxiety, I think that's just a, um, side effect of the neuroticism sex difference. So, at at lower levels, it's adaptive for women to be, girls as well, but especially women to be somewhat more anxiety-prone because they they protect themselves more and they're not taking risks, uh, in the way that is more adaptive for males. >> Mhm. >> Um, because of the higher maximum offspring number. Um, I So, it's adaptive at that level, but I think that cuz you have a distribution, it it means that inevitably some people are going to be the extreme of that distribution. I I I don't think it's actually adaptive out there. So, I don't accept adaptive explanations for clinical depression or clinical levels of anxiety disorders. >> Mhm. >> I think that that is the sort of, uh, non-adaptive or actually maladaptive, often, byproduct of sex differences. >> Kind of a spandrel, yeah. So, just a side effect, um, exactly, of differences that closer to the mean are adaptive. >> Mhm. >> The schizophrenia difference, I don't have a theory about that why that is and I don't think there is that there is a theory yet about why that is more common among men than women. >> Mhm. >> Uh, some that I didn't mention, actually, autism is more common among boys and girls. Uh ADHD is more common among uh boys and girls as well. Um so yeah, ADHD I think that again that's just a sort of offshoot of the fact that boys are kind of more active on average than girls and sort of less attentive and more likely to get distracted and run running around the place. And it's not a problem at in the usual I mean it might be irritating for parents and teachers, but it's not a big problem in the normal uh range, but at the extremes it is a quite a problem. And it's a problem more often suffered by males than females as an offshoot of the differences at the mean. >> Mhm. I think going through all of this, doing all of the the research obviously you've been deep in this for a long time. >> Yeah. >> And then doing the book, what happens or what's your fear when people don't respect sex differences or they deny them? What what's the sort of world that we live in if that happens? >> It's a good question and I think it's a particularly good question because we're always focusing on the dangers of exaggerating sex differences and and moralizing sex differences. I think there are lots of problems with doing that and we need to be careful not to do it. Um but where I think I disagree with a lot of folks is that I I think that there are also problems with doing the reverse. I think there are also problems with minimizing sex differences and denying them. Um so one thing is that just as in exactly the same way that some people who exaggerate and moralize sex differences, they try to push people into traditional gender roles. People who deny the differences or or massively minimize them, they're in danger of trying to push people out of gender roles. So kind of replacing one gender straightjacket with a with another unisex gender straight straightjacket or like a maybe reversed gender role reversed uh straightjacket. Um and then we've actually touched on another of the big problems I think with minimizing the differences, which is the fact that trying to explain gender gaps in society like occupational gender gaps, there's just a whole host of problems with doing that that we that we discussed. Um, other problems uh, with minimizing sex differences is that there are certain physical health problems and and mental health problems um, that so so not only do they frequency of the of different problems differ between the sexes, sometimes they um, symptoms differ as well. They they present differently. So like cardiovascular problems present differently for women than men. Women are more likely than men to have shortness of breath as as a as a symptom rather than sort of shooting pains down the arms and the other kind of classic problems like that. And if you don't focus on sex differences, you might be more likely to overlook the symptoms of heart attacks in women. Traditionally, doctors and people themselves have been have overlooked it for that reason because they've underestimated the sex differences. Uh, mental health-wise, same deal. So, even though autism is more common among boys and girls, there is a strong case that it's under-diagnosed in girls. And part of the reason for that is that it it presents somewhat differently in girls. It's less likely, for instance, to involve repetitive behaviors. So, people might not know if they don't if they're not aware of that sex difference, they might overlook it in girls. And that means girls won't get the help that they need. Uh, and yeah, likewise with um, social problems. Uh, if you're looking at social problems like intimate partner abuse, um, if we assume that all intimate partner abuse only goes in one direction, uh, like male-to-female, uh, then we're going to like underestimate the extent to which it sometimes goes in the in the other direction. Um, yeah, just so you know, >> of that is bidirectional, right? >> Uh, at at low levels it is, yeah. Sort of low levels, um, verbal abuse, pushing and shoving. And actually, in the West, there's even some data suggesting that like verbal abuse might be more common women toward men. Other cultures that's not the case and and it's more likely men to women. And when it comes to severe >> the equality paradox >> Indeed. When it comes to severe aggression though, even even in the West, men do predominate. But you know, it's not 100% >> And what are the harms of exaggerating sex differences? >> So one of them is trying to push push people into traditional gender roles and like if you just let people do what they want probably a majority going to kind of gravitate in the direction in traditional directions. But not everyone does. We cuz we don't have massive massive sex differences, somewhat modest sex differences. There always going to be some folks who are not going to want to go into the traditional directions and in my view, my let people be themselves view, would say well that's fine, just let them let them be themselves. It it doesn't matter. >> But if you exaggerate and moralize sex differences, you're unlikely to think that. You're going to think well no no, this is the way of nature. Any exceptions to the rule that is by definition a problem and we need to push people into into those roles. >> What else? Other problems with the exaggeration differences. If you exaggerate the frequency of cardiovascular health problems, you will say well you find them in men not women. So that's another reason that you might overlook them in women. Just because you just it doesn't occur to you that okay, she's got these symptoms. What would that be? Well, it's not going to be cardiovascular problems cuz that those are men's problems. Get the same thing with with mental health problems. If you're really fixated on the fact that depression for instance is more common among women than men, you might overlook it in men. Because you're exaggerating the size of the sex difference and you know, like a significant minority of people who suffer depression are men. You you a third of cases are guys. >> [snorts] >> Um so, if you exaggerate that difference, uh you might not be on the lookout for them. Anxiety disorders as well, so and social problems, yes, so social problems like um and interpersonal violence, sexual harassment, if you exaggerate the extent of those, you are more likely to focus on just the cases where men are doing it to women. And those are the majority of the cases, but there are cases the majority of the extreme cases anyway, but you do find the reverse. And the reverse is a problem as well, and it's problem that that we overlook if we exaggerate those sex differences. There's an irony there though, um how which is that uh the sex difference in sexual harassment, sex difference in interpersonal uh intimate partner abuse, the people who are most likely to exaggerate that and say it's all men tend to be gender role progressives, so people who generally trying to minimize and deny sex differences. In those cases, they actually, funnily enough, flip to the reverse and and adhere to them in fact just reverse it and and uh massively exaggerate those differences. >> Fascinating. Steve, you're the best. I appreciate you, man. You've done a wonderful job with this book. Everyone should go and buy it, Billion Years of Sex Differences. What else what else do you want to plug? >> Could I plug uh my Substack? So, that's the the thing I'm most excited about. >> nurture newsletter. Dude, I am a I am a Steve Stewart-Williams stan, bro. I mean, you're the AP wonders that the universe is in the five books that everybody needs to read for my first reading list. Had this one have been out, it would have been in the second one. Yeah, your your Substack rules, and everyone should go and check it out. I love it. The my favorite thing that you do is the link fest yeah yeah yeah breakdowns. Once a month, you just send like 40 or 50 different studies or insights that you find. You're the best, man. I I really appreciate you. Thank you so much for coming to see me. >> Thanks very much for for making this happen. This is great. >> I got you. All right, goodbye, everyone. >> Okay, later, folks. >> Deuces. Yes. >> All right. >> Nailed it. Nailed it. Nailed it. [ __ ] hell. it. >> Congratulations, you made it to the end of a full podcast episode. You are not so TikTok brained that you've completely dissolved into nothingness. >> [music] >> Why not watch another one? Right here. Go on. Press it.