What's happening, people? Welcome back to the show. My guest today is Machen Murphy. He's an evolutionary biologist at the University of Melbourne, a writer, and a podcaster. Why do people cheat? Is it just the allure of novelty, dissatisfaction in their current relationship, fear of being left, retaliation for their partner cheating? Machen's brand new study gives so many fascinating answers to all of these questions. Expect to learn what the evolutionary drivers behind men's and women's infidelity are, what this new science says about the dual mating and mate switching hypotheses, the top three reasons for why women and men both cheat, whether cheating is heritable, if there is such a thing as one and done cheating, the most common behaviors of someone who is being unfaithful, and much more. This episode is brought to you by 8 Sleep. I have been using my 8 Sleep mattress for years, and I literally cannot imagine life without it. Having a actively cooled and heated mattress is the game changer. Now, they have launched their newest generation pod, the pod 4 ultra. The pod 4 ultra can cool down each side of the bed up to 20 degrees below room temperature, keeping you and your partner cool.

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A little bit of drama. I try not to get in trouble, but certainly this last publication might be a little controversial within the field, sure.

What have you done? What's the current state of the leading infidelity infidelity hypotheses?

Well, I guess we've got time to get into it, but it is a bit of a long story. I would say that the background to know for someone who's just completely entry-level here and has not heard about the Evo infidelity debate is that there's been a long-running debate as to the evolutionary drivers of women's infidelity, female infidelity in humans. During the late '90s and the the early 2000s, and to an extent, the 2010s as well, I would say that most evolutionary psychologists would have said that the primary driver of women's infidelity from an evolutionary perspective is the powerful benefit of being able to obtain better jeans, better in a fitness sense, obviously not in a moral sense. We might end up saying the phrase good jeans quite a bit on this show, and every time it's always in It's always good in a fitness sense, but in any case, the mainstream idea was that infidelity is a conditional strategy that women sometimes employ in order to obtain better genes for their offspring. To pair the genetic benefits of one male with the parental investment benefits of another male. Everyone, when we're looking for mates, there are two things that they can give our offspring.

They can give our offspring genes, obviously, or they can give our offspring investment. And normally, women get genes and investment from the same person. But the idea was, is that women's infidelity allows them to get genes from one person and parenting from another. Let's say if they're with a mate who is very high investment. They love them, they've got lots of resources, but they don't necessarily have the heritable traits that a woman might want to pass on. So that was the mainstream idea for a very long time, almost 20 years. Then in the late 2010s, there was a bit of a reckoning, which stemmed from the fact that during the 2010s, the original suite of experiments that were used to evidence this idea, which from here on we'll call the dual mating hypothesis. In this case, there's a few ways to use that term. I'm using it to describe that specific strategy. There was a bit of a reckoning because the original support for the dual mating hypothesis was based on these ovulatory shift experiments. The idea was, and it was a very clever hypothesis originally put forward by Steve Gangestead and Randy Thornel, which is that if it's true that women's infidelity functions to pair good genes with good parenting, Well, women can only get pregnant during a brief window in their monthly cycle.

It would only really make sense for them to have affairs during that time. Because the risks of infidelity are evenly distributed We did. Infidelity is a very risky behavior. You could lose your relationship, you could be subject to retaliatory violence or social penalties. It would make sense for women to engage in the genetic strategy during their peri ovulatory phase and the parental investment strategy during the rest of their cycle. That was their hypothesis. The first tests, which were with And this isn't their fault, but small samples and relatively primitive methods, those looked quite positive. Then as methods got better, these effects either shrank or disappeared, depending on who you ask.

It seemed to be-Reanalyzing the original data?

No, not reanalyzing the original data, collecting new data with better methods. Although there has been some questions about the original data as well. So one example of this is that some of the early studies would determine when a woman was in her cycle based on self-report counting. So count since your last period. Method, essentially. That's not a completely inaccurate method, but it's not exactly high reliability. Then later methods that use more direct tests and just bigger samples and also preregistered in some cases. Just better methods overall. They made this ovulatory shifts sub-hypothes of the dual mating hypothesis. They made this look less good. Some scientists, led by David Buss, but it was quite a large number, said, Well, hang on. Maybe it's not just that ovulatory shifts aren't happening. Maybe dual mating isn't happening. So dual mating is something that we see in some other animals to an extent. We see, for example, that red winged blackbirds, the females will engage in infidelity with males who have more robust dust bodies. Fly catchers, another one where they've got nicer plumage, the affair partners, compared to the primary partners. So it's not something that's without precedent in the animal kingdom.

But other animals, like cockatiels, for example, when they have affairs, their affairs are geared towards something called mate switching. The affair is a way of cultivating and obtaining a new, and from a reproductive standpoint, probably overall better mate. They put forth this idea that, Hey, maybe humans are more like cockatiels than flycatchers. Maybe the underlying theory, so we've got dual mating, this good genes, good parenting combo deal. Maybe it's not a combo deal. Maybe it's a best whole package type situation. Maybe that's what female infidelity is geared towards obtaining. That was the history of the debate, and they put this alternative idea forward. It wasn't based on this new idea. It was a hypothesis that was put forward. It is a hypothesis that is put forward based largely on what we would call circumstantial evidence. It's drawing together a variety of facts from past studies and forming inferences about them, about what's happening from that. It's not that there was some experiment that showed mate switching was very common in humans. It wasn't that we collected It did some awesome data set and it showed mate switching. That's not what happened. It was just an alternative hypothesis.

Then after that, Brook Schelsa tried to test the mate switching hypothesis in her population, at least the trading up function of it. She tried to test it in her study population, the Himba. That's a group of agro pastoralists in Namibia. She didn't find evidence for the mate switching hypothesis. She found slight evidence for dual mating. Then she found evidence that a lot of women's infidelity in this area was geared towards obtaining additional resources from additional mates. So it has an additional function. This is a theme that we'll probably talk about more. There was a little bit of evidence for dual mating. Women seemed to have put a higher premium on physical attractiveness in affair partners. But the mate switching hypothesis camp, at least in what I read, they seem to, I won't say brush it away, but they seemed to interpret that as just applying to that population. It's like, okay, the mate switching hypothesis didn't work, but it's in this pretty unique population. I think that's fair enough because the Himba do have a unique relationship to infidelity. What we wanted to do is we wanted to actually set up an empirical design that directly pitted the predictions of the dual mating hypothesis against the mate switching hypothesis.

What did that design look like? Well, the mate switching hypothesis has quite obvious and intuitive predictions. If you're looking at the trading up function, some scholars, they would classify backup mating and breakup mating as part of mate switching, but we're looking at trading up. If women are cheating to obtain a better mate, then they should perceive their affair partners as better. Very simple prediction. Probably better looking, better as specifically as a potential co-parent, since that's who they want to switch to. Overall, mate value should be higher. Maybe a more attractive personality. I guess that could go both ways. What we did was we set up an experiment where we collected women and men. We collected a large sample of women and men who had actually had affairs because this was a problem with the previous literature, especially the literature in the mate switching, dual mating debate, not Berkshire's work, was that most of it was done on people who hadn't had affairs.

Where do you find people that have had affairs?

I wish I could say something fun like Ashley Madison or something, that we're recruiting on Ashley Madison, but that's not what we did. What we actually did was we put up a large survey that- Have you seated on your partner?

Come and do our survey.

Yeah, it was basically three questions. It was demographic questions. Then it was, Have you Have you ever been in a relationship that was sexually exclusive? In any of those relationships, have you slept with somebody else at any point? And would you like to do our study? And we sent that out to, I think it was 1,500 people. And quite a lot of people said, Yeah, I actually have had an affair at some point. But it was a relatively small subgroup, let's say, that actually wanted to go through all the way and do further research with us. And that final sample was 254 people, for those who are interested. Let's circle back to the predictions here. If the mate switching hypothesis is true, and we're looking at people who have actually had affairs, well, then women should rate their affair partners as more attractive in some way, but certainly more attractive overall, and more attractive as a potential co-parent. Those would be the things that you'd really expect to see if the mate switching hypothesis were true. The dual mating hypothesis has different predictions. The dual mating hypothesis would predict that there'd be this crossover effect where the affair partner is rated as better physically, physically more attractive, but But parentally, they should be less attractive.

If women's affairs function evolutionarily to pair good genes with good parenting, well, then the primary partner should have better parenting. The alternative wouldn't really make much sense.

I'm not sure. I don't quite understand that. Why would it be the case? Why would dual mating not predict better parenting as well?

Because dual mating is pairing the good genes of the affair partner with the parenting of the primary partner. So it's essentially a process where women will have an affair or female animals, other species, will have an affair and try to pair the genes of one male. And this is, None of this is meant to be conscious. We're looking at the subconscious evolutionary drivers of our behavior, the structured psychology underlying it. I guess to summarize, mate switching would predict that affairs function to obtain a mate overall, whereas dual mating would propose that female infidelity functions to capture, quote, unquote, better genes and pair it with better parenting, better investment. These are distinct hypotheses. I'll flag post here or signpost here that none of this is meant to be conscious per se. This isn't implying that anyone's deliberately trying to... In the same way that when we enjoy sex, we're not thinking consciously, Oh, this is great because I'm going to get to have kids. In fact, we might be thinking the opposite. It's more what psychological biases undergird our infidelity. We have very good reasons to suspect that infidelity did evolve. It appears cross-culturally. That's the first sign.

It appears this is something that your friend, Steven Stuart-Williams, likes to share, which is that if a behavior appears even where it is socially discouraged, it's probably not socially constructed. We see that infidelity is very harshly punished, and people still do it. Then also, humans are mostly socially monogamous mammals. If you look at other socially monogamous mammals and other socially monogamous primates, extra pair paternity has some degree of presence, extra pair copulation is documented with quite a high frequency. We have very good reasons to suspect that this has evolved. Given the dueling predictions that that the dual mating hypothesis proposes that it's better physical attract. Oh, and here, I actually, not to just over-caviate, but why would physical attractiveness be a sign of good genetics? I would say, listen to our last episode. Chris's last episode covers that in very high detail. But the short TLDR version would be that, one, a lot of the things that we find conventionally attractive are just cues to health. The things that we think are good-looking, the reason that they're conventional is because they signal heritable benefits such as good health. Then another idea is just that physical attractiveness itself offers benefits and is itself Good-looking people tend to have good-looking children.

It would make sense that given the tremendous benefits that come with being good-looking, you would want a partner with good-looking genes. Anyway, so different predictions. Mate switching predicts that the affair partner will be better overall and better as a coparent. Dual mating predicts that the affair partner will be better looking, but worse parenting. Yeah, worse parenting, really, it's the primary partner should have better parenting is the correct way to think about it. What we did was we took everyone in our sample and we had them rate their affair partner and their primary partner separately on valid and reliable scales. Our study was pre-registered. It's a very diverse sample and compared for differences. We had them rate their affair partner and their primary partner's physical attractiveness, parental attractiveness, mate value, their overall desirability, and also their personal attractiveness, although to be fair, that could have gone both ways. It would have been interesting, but not necessarily consistent or inconsistent with either hypothesis. And what did we find? Well, We found that affair partners were about two points more physically attractive on our scale on average, and primary partners were about three points more parentially attractive. So We had this crossover interaction between rating type and attractiveness, which was really the best case scenario for the dual mating hypothesis.

It's also very unlikely, just for those at home, it's very unlikely that you would find this structure by accident, because usually better-looking people, because of the halo effect and just positive perceptions in general, they're going to get better ratings on everything. It's very strange for one group to be better-looking but worse parenting. This is a very unlikely thing to see if there's no structured psychological adaptation involved. The dual mating hypothesis was I would say, strongly supported best case scenario, a preregistered study on actual women who have had affairs signaling this. The mate switching hypothesis, there was no difference in mate value. Overall mate value, overall desirability, even between affair partners and primary partners, no statistically significant difference, and no statistically significant difference in personality either. Our study ended up being the best case scenario for dual mating and the worst case scenario for mate switching. I guess we started this conversation with why would this cause controversy? Well, it seems like everyone has been a little too hasty in dismissing dual mating based on the fact that the ovulatory shift studies don't replicate. But the truth is that ovulatory shifts are just a sub-hypothesis of dual mating, and human sexuality is actually unusually stable across the cycle.

Maybe it was a... I mean, I still think it's a cool hypothesis, and maybe more complex methods will prove that there is something to human estres. But The truth is that dual mating doesn't need this hypothesis. It's just a sub-hypothes. The more important thing is that we do seem to have different priorities in our affair partners versus our primary partners. One thing that I'll flag, maybe we can talk about this later because it's more confusing and maybe the most interesting result from our study, is that men showed the same pattern. So men also, contrary to conventional wisdom, men also tended to cheat up in terms of physical attractiveness and cheat down down in terms of parental attractiveness. A lot of people responded to our study basically saying, I would have thought that men cheat down across the board, basically because it's easier. A man is only as faithful as his options, and most men have more options that are less attractive than themselves. That didn't really seem to be supported. Then in our qualitative data, we also didn't find any differences in novelty-based. I would say that the overall picture, the dual mating hypothesis traditionally has focused on women, but I would say that it's really a human strategy in the sense that humans in general, it's different what benefits are sought, but humans in general seem to prioritize conceptive benefits in affair partners and parental benefits in primary partners.

This is just one study, of course, and I did design the study to be persuasive to myself, so I am persuaded by the result, but there are other results that converge with us in terms of at least the physical attraction side of thing that affair partners tend to be more attractive and primary partners less so. I've spoken for quite some time, so I'll...

Not at all. What is the evolutionary function of men following that same pattern when it comes to infidelity?

It's a little confusing, right? I know that you've obviously had a pretty intense crash course in evPsych talking all the world leaders in the field, let's say. You would be aware of the fact that if you ask an evolutionary psychologist, why do men cheat? They're going to say, Oh, easy. More mates means more offspring for male mammals. They're going to talk about Genghis Khan, and they're going to talk about how the ceiling is basically unlimited for a man reproductively if he just has enough mates. Whereas for women, the ceiling, in theory, and if you believe the accounts of Valentina Vassiliev, this is a funny anecdote to illustrate the conventional outside view, Valentina Vassiliev was a Russian peasant, and I believe she had 60 something children all with her husband. Then her own husband, if it's true, she would be the world-record-setting mother as a woman, the most prolific woman in childbirth. Then her own husband, if you believe the gossip, her own husband outpaste her by having affairs, and he had like 80 something. The idea being that a woman can, in theory and potentially in practice, maximize her reproductive output with just one male, whereas a male can only maximize the reproductive output by seeking additional mates.

That's the unconventional wisdom in EVSEG. Our study, it's not inconsistent with that. We didn't design our study to test that hypothesis, but then we didn't find support for this hypothesis where we expected to find it. So one prediction that I think would be pretty natural from that idea that men's infidelity is purely quantity-driven. So the women's infidelity hypothesis, mate switching, dual mating, both of those are It's a quality hypotheses. Then the main male hypothesis is a quantity hypothesis. I think, that you'd expect to find that men cheat down to maximize their numbers, so to say. Then you'd also expect, when you ask men why they cheated, you'd expect them to report variety-driven motives at a higher rate than women. It could have been because of our study design. We also asked participants just straight up, Why did you cheat? I believe we've got certainly the Evo literature, maybe, I won't say this, but certainly one of the largest data sets on just people saying why they cheated from our qualitative data. And men and women both reported sexual boredom, a desire for novelty. There were no statistically significant differences in that area. Maybe a better design would find that.

But our study-There was no are sex differences in proximate reasons for why people cheat?

There were sex differences in proximate reasons, but not in the novelty area, and not in the boredom area, and not in the combined measures of both of those, not in the variety area, generally. But I think that that's just because... I mean, maybe I'm being too generous, but I think that we have to be really skeptical. I think our quantitative data is really good, really reliable. Our qualitative data has unavoidable shortcomings that come from just interviewing people. If you just ask someone why they cheated, people don't have perfect insight into their own motivations, and then they also aren't perfectly honest. Humans are storytellers. We like telling stories where we're the hero. We're going to downplay motivations that are unseemly or subconscious, and we're going to play up motivations that are flattering. I'll give you an example of this that's pretty stark. We asked women, What motivated you to have an affair? And about 5% of them said, Oh, it's because my affair partner was really hot. He was super attractive. That's part of the reason why I had an affair. So 95% of women didn't even mention it. But then in our quantitative data, women were 77% more likely to prefer their affair partner's physical attractiveness than to prefer their primary partner's physical attractiveness.

What a coincidence if that's not a motivating factor, right? So we have to be... I am happy with our qualitative data, but we have to be careful with it. I think the only thing that it really shows is strategic diversity.

How do you know that that's not just novelty seeking? It doesn't need to be better. It just needs to be different.

Yeah. So there was a bit of that. I would say that about one in 10 people in our... Again, our quantitative data doesn't really get at novelty, but it does suggest that it's not just novelty because from a physical attractiveness perspective, on average, it was better.

But that's the My point being that physical attractiveness is inherently a subjective. You're asking you, participant, what do you think about the rating of A and B, which I'm sure you can see as being open to just straight novelty itself. If, as you've said, we are not a clear pool of water that we can see down into the depths of. If you were to get people to say, Okay, show me a photo of both your affair partner and your main partner, then let's get other people to rate whether they think which one is more attractive and compare that to their answers, that would be fascinating.

That would be a very good test.

To see how much of a role... Can you send me a photo of the person that you're in a relationship with and the person that you cheated on them with, please? That would be great. Thank you.

The ethical nightmares that you've just designed. Oh, yeah.

And by the way, I'm going to show these. I'm going to show these to loads of people.

Yeah. So that would be a bit ethically fraud, but a good Genuinenly good study design. That would be a test of our hypothesis. I guess one, and I think that that's a legitimate limitation, it could be that novelty itself is causing more physical attraction. That seems plausible to me. But if it were just positive illusions associated with novelty, I think you'd expect higher ratings overall. It's weird that this is only happening with physical attractiveness. We all know that in the early stages of a relationship, we tend to have these very biased views, very positively biased views. They granted everything. Yes, they're wonderful, they're perfect. And so if that's what's causing the physical attractiveness gap, very peculiar that didn't happen for mate value, very peculiar that it didn't happen for personality, an extremely peculiar that actually reversed for parental attractiveness. So it's a legitimate critique, and I would be interested in... I would be very interested in the results of that study if anyone can get ethics approval for it.

Oh, dude, I'm the king. I'm the absolute king of coming up with studies that you can't do. I'm like one of those rock stars that never actually learned to play classically and is able to... I'll do it left-handed and upside down. It'll look awesome but sound terrible. That's my contribution to the world of Eve Psych and human-based oncology.

That and giving us cool terms.

Cool new names. I'm good at meeming. That's it. Meeming and coming up with studies you can't do. Dig into what else you learned from a qualitative perspective? What was interesting? What did men say? What did women say? And how does that tie in with your new reinforced perspective of infidelity?

Well, sure. The top The first thing to notice would be that the top motivation for men and for women was relationship to satisfaction in their stated motivations. The way we did this was we read. It took a very long time. We read all of the responses. Our data is public, by the way. Other people can also look at... If you want to read hundreds of reasons why people had affairs and get a gist, you can just access our data It's fine. We read through all of these. We coded them for themes. That's when you basically write down like, Oh, this one mentioned that the affair partner was hot, that thing. We coded them for themes, and then we went through and We found the themes that were repeating themselves. Then myself and a lab assistant went through, and we separately recoded these items to see which themes were occurring at rate. Then we ran statistical analysis to test for sex differences. That's our methodology. Relationship dissatisfaction was the number one stated motivation for infidelity in both men and women. However, it was a big sex difference as well. So only 30%-ish of men mentioned relationship dissatisfaction in their answers.

So most men, even though this was the most common response, most men didn't bring it up. Whereas about 65 % of women mentioned relationship dissatisfaction. So women were twice as likely to bring this up, essentially, over twice as likely.

Even though it was number one for men?

Even though it was number one for men, correct.

Does that mean that men had a flatter distribution of reasons in that case?

Not necessarily. That inference would be correct if we coded them one to one. But the way that we coded it was that one affair could have multiple motivations. So for example, a participant might say, I was in a long distance relationship and things weren't going well. She really wasn't treating me right. And my affair partner was just gorgeous. That would be a pretty reasonable answer. That would be the thing that we'd see. And then that would get coded as attractive affair partner, long distance relationship, and relationship dissatisfaction. It doesn't necessarily mean flattered distribution of reasons because we can recode variables in this way. But great question. Historically, the whole women are more likely to have relationship dissatisfaction when they commit infidelity. That's an expected sex difference. It's something that pops up in the literature quite a bit since the '80s.

Why? Why is it expected?

Well, it's funny because the original logic was that it was evidence for the mate switching hypothesis. Because it's like, Oh, if women are usually dissatisfied when they have affairs, that means that they want their relationship to end. Two reasons I'm skeptical of this. One, women often have higher relationship dissatisfaction anyway, given certain circumstances. They might be more sensitive to cues that the relationship is not going well. There also might just be a difference where they're more likely to express dissatisfaction, even if dissatisfaction levels are in actuality, even between the sexes. That's number one. Number two, and this is more important and more deeply theoretical, which is that infidelity, as we discussed earlier, is a very risky activity. It is especially risky for women. So Based on Martin Dauley's research, who I believe you might have spoken to.

No, I haven't. I'm lining up. I would have called him Daily, so I'm glad that you fact-checked me on that first.

It might be Daily. I've only read his name.

I mean, it's only your industry three, mate. Yeah, I can't get away with it. I'm speaking to Martin through a combination of Rob Kerspan and Steve. I think he'll be great.

Yeah, no, he surely will be. He's written just some of my My favorite stuff has been written by him, but some of his early research basically found that women's infidelity is more likely to result in relationship dissolution than men's infidelity. This is a funny way of thinking about this, but in F-Psych, it's pretty common to think of relationship satisfaction as an internal regulatory variable that partially tracks the value of your relationship. If your relationship satisfaction, if you risk your relationship every time you have an affair and your relationship satisfaction is low, well, then you're literally risking less than someone who's relationship- What are you giving them? Exactly. If infidelity is more likely to result in relationship dissolution for women than men, Then the risk is at a baseline higher. You should expect that women should be more likely to be attuned to whether they have the infidelity discount that comes with relationship dissatisfaction. This has been interpreted as evidence for the mate switching hypothesis. I think it's reasonable to say that someone who's relationally dissatisfied is more likely to be mate switching with their affair. Some Some people do mate switch. Several women in our sample, but only several, said that they were mate switching.

But I think it's reasonable to assume that they're more likely to be mate switching than someone who's really relationally happy. But I don't think it's reasonable to do the reverse inference, which is that because they're relationally unhappy, they want to mate switch. There are plenty of people who are relationally dissatisfied, having an affair, but also want their relationship to keep going. And that's also quite intuitive to me, this idea that sometimes relationships are unhappy, but you want to stick things out.

What do you make of the difficulty that women supposedly have in separating their emotions from having sex with a guy? That women will fall more when they are physically intimate with a man because there is a higher hurdle for this man to get over, that it is her being more risky. Would it not be the case for mate switching that women would be more likely to fall for that partner still, even if it's not... Sorry, for dual mating, even if it's not for the purpose of mate switching, while they're dual mating, would it not be more likely that they were going to fall for that partner in any case as a natural byproduct of the feminine desire to be emotionally intimate with someone?

That's very clever. I haven't considered that, and I have to think about it more Because you're familiar with the mate switching hypothesis, but what Chris is referring to here, I believe, is that there's a... One of the flagship pieces of evidence for the mate switching hypothesis is that women are more likely to fall in love with their affair partners than men are. What you're saying is that women are more likely to feel emotionally entangled with sexual partners in general, and so that also isn't That's not necessarily particularly good evidence. One thing that I will note is that we didn't find that love for affair partners was coming up much at all. We're talking like 1, 2%. I can't remember. It was sub 5%. Very few people in our sample, men or women, said that they were motivated by love for their affair partner. It just didn't come up very much. I'm a bit skeptical. I mean, maybe it is the case that women are more likely to be in love with their affair partner, right? But at least in their stated motivations, it doesn't seem to be a big factor in why they had the affair to begin with.

Even though that's my favorite evidence for the mate switching hypothesis, as you say, it might not have as much theoretical to it as it seems to at first glance. Then also, there's an inference involved there where it's like, if they love them, that must be their motivation. It's possible to be in love with your affair partner and have that be pretty low on the list of why you had an affair.

I remember Andrew Thomas talking about what women say that they want in terms of traits when choosing for sperm donors. Everybody's eugenicist, right? Everyone is, everyone is, whether you like it or not. And some people are more quantitatively and obviously eugenicists if they choose sperm donors or if they choose a... If they go through IVF with a donor for either side, I suppose. And one of the things that I thought was really interesting that Andrew brought up is women who choose sperm donors, it is the only time where the traits you want in your future child are divorced from the traits of the man that is able to get you into bed to be able to create that future child. So you have this weird territorial cutoff, which is, what do I want my future kid to be like? Without having to jump through the hoop of what is the thing that I find attractive that gets me into bed? So it's a much more sterile, controlled environment when it comes to doing that. And given that, that with regards to dual mating, it surprises me that things like personality didn't include in that, given that although you want sexy son hypothesis, presumably you want likable son hypothesis.

It's interesting. In our preregistration, we didn't make specific... I guess one thing that I'll note on the eugenics point is that I've heard a lot of people say the same thing of it's sexual selection is eugenics. I personally do see a difference between individual level, what traits do I want my child to have in the case of embryo selection, in the case of IVF and sperm donation, and then what traits do I want to be high frequency in society at large?

That's a good... You're perfectly acceptable to do that. There's a difference between Tubi's concern about that gene erosion thing, that scaling up, even though I think it's still largely ethical, that's more of a scaling up. That being said, the one conversation that I've ever had about embryo selection. I got called an actual Nazi for having. But it's okay. I'm over it.

I mean, I'm not someone who's super into science philosophy. I'm sure that someone's listening and just thinking that I sound like a bit of an idiot. But I will say that I don't see a huge difference between... I mean, maybe I'm just thinking about this wrong, but I don't see a huge difference between selecting an embryo and selecting a mate at the individual level. Where I would start defining it as eugenics and start defining it as ethically abhorrent to myself would be when people are telling other people what they do or when the government is getting involved and trying to adjust. Any top-down, trying to adjust the frequencies of genes in the population, I would see that as very bad. But at the individual level, I don't really understand. I mean, I also don't really understand embryo selection, to be honest. It's not my area. I'm an expert in very few topics, so we'll stick to those. It is interesting, of Anything else from the qualitative insights that you learned? Yeah, I think it would be cool to just go over the top three motivations for... Oh, actually, can I just ask, though, what was Andrew Thomas What was his actual conclusion on what traits did they want from sperm notice?

Because that's very relevant to the dual mating.

I can't remember. Let me see if I can pull it up. Andrew Thomas, the advantage of having 3,200 notes. Okay. Conducted an experiment where you asked ChatGPT for mate preferences. No, I don't actually have it on there. I certainly know that things like kindness were much more prioritized. It seemed to me to be softer skills, if you want to call it that, the soft skills of being a person. I think in there, kindness, humor, intelligence. Yeah, it was more prosocial stuff, I think, which maybe you would probably be able to predict pretty easily that you can look away from someone's dark triad adjacent personality traits because they're hot or cool or funny or something.

Interesting. As It's funny because sperm donation, embryo selection, all of these, it's hard to know if it's stated or revealed preferences. It's hard to know where to put it. There was a really cool study from Paul Eastwick and his colleagues. Just awesome, where they looked at... This is very recent. I think it's still in press, so it's not even fully published yet, but it is fully peer reviewed. It's going to be published as is. They looked at what people say they want in a partner, and then they looked at how what they say they want actually predicts romantic evaluations in practice. That stated preferences on one end, and then a version of revealed preferences on the other end. And there were some funny examples. The number one stated preference trait was loyalty. That's what people said. It's like, what do you want in a partner? Number one thing, loyalty. And the number one revealed preference was being good in bed, a good lover. So there's that.

I took that table from your Twitter. So, yeah, they said the first rank was loyalty. But to be fair, that ranked as number two.

It still ranked as number two. Yeah, that's the other thing, is that it only got suppressed a little. The main thing that was shocking was how much- A good lover jumps from rank 12 to rank one. I know. People don't... Again, It goes back to what we were saying about the people want to tell stories in which they're the hero. It doesn't sound great. If you're asked by a psychologist, what do you want in a mate? And the first thing you say is good in bed, you sound quite unhinged. But in practice, that might actually be more predictive of your romantic evaluations than anything else, and it certainly seems to be in this large sample. Then they also found that in general, I think the general gist of that table is that traits, physical traits, are much more important than people say, and they're especially more important than women say. So for men and women- Sexy jumping from number 19 to number 6. Yes. Yeah, that's a huge jump. Smells good. That's another just physical trait, whether you smell good or not. What was that? I know it jumped to number 4, but it was- Where the fuck it smells good?

Oh, number 15 to number 4. Attractive, number 16 to number 8.

Yeah. So if you want to contrast what people say they want and what people actually want, one of the main things that's going to come up over and over again is that people understate, and this doesn't necessarily mean they're lying. It could just be that we don't have perfect insight into what makes us happy, but we understate how important physical attraction is.

The black pill was right all along. You just need to smell nice.

Yes, the new black pill just dropped.

I'm smell-maxing. Smell-maxing. I'm so smell-maxing right now.

Yeah.

Okay, qualitative, the rest of the qualitative stuff.

Yeah, the rest of the qualitative stuff. That was a diversion, but a happy one. And one that's actually relevant because in a way, we found the same result. Again, 5% of women mentioned that their affair partner was physically attractive, and then they were 77% more likely to prefer their affair partner physically. What a coincidence. But top motivations for women. Relationship dissatisfaction, number one, and a high number one. Again, most women mention that. Second place, and second place by quite a bit, only 20%, that's still a high, 22%, mentioned that their primary partner was uninvested. This also illustrates an important point, which is that not all women's affairs are explained by dual mating. It seems that there might be a psychological bias towards the dual mating strategy. But many women had affairs with affair partners who they perceived as less attractive. 77% more likely is not... That's not an infinite gap. Then one of the reasons that many women cheated, one in five women cheated precisely because they thought that their primary partner wasn't invested enough. If it's pairing good genes and good investment, that doesn't make a lot of sense for those women. Then the third most popular motivation for women was revenge.

So 15.5% of women said that they were cheating to get revenge.

Did they say what on?

Well, in this case, the 15.5% figure is revenge for their partner's affair, specifically. I remember I spoke to a guy who was an unofficial marriage counselor in his neighborhood, and I asked him, Why Why do women cheat in your experience, what you see. He very flatly said, he said, Women cheat when men cheat. Now, that doesn't seem to be 100% true, but there's certainly some truth to it in our data in the sense that women were much more likely to cheat for revenge. You could interpret that as a genuine strategic difference. But since men cheat more than women, women have more opportunity to cheat for revenge, or at the very least, they have more opportunity to cite revenge as one of the reasons why they cheated.

Whether it was going to happen or not. Yes. What is the state of who cheats more, men or women?

Oh, that's a pretty open and shut case. Men cheat more. Men say they cheat more when you ask them. Men say they get cheated on less when you ask them. So women report getting cheated on more. And then women who are the third person Some people might say, Oh, well, maybe women are just understanding things. When you ask who's more successful as a mate poacher, women who mate poach tend to have a higher hit rate. There are three people involved in any given affair. There's the primary partner, there's the person who's cheating, and then there's the affair partner. You can do studies on any one of those three groups, and you generally find the same result, which is that the man is is generally more likely to have an affair. In some studies, it's not a big gap. In some cultural contexts, it's a huge gap. But that would be the overall state of the science there. The revenge difference, it may just be downstream of the sex difference in committing infidelity. They have more opportunity to have an affair.

What do you learn from a woman's concern about investment from their partner?

It's a good question. This is pretty consistent with... It's not consistent with the dual mating strategy, but it's consistent. It's actually a really good thing to illustrate that women cheat for many reasons. They cheat maybe for traditional variety-based motivations such as genetic heterogeneity or fertility backup. So some % of couples are infertile. And so if you're mating with multiple males, you're really lowering the probability that that's going to result in the end of your lineage. There are many motivations for affairs. Revenge. Being an uninvested partner, low investment, I would say that it signals... I would say It signals the traditional evpsych difference, which is that women's investment in offspring is largely physically obligate in the sense that women have to go through pregnancy and lactation. This is part of why women seem to be more careful about who they mate with, more choosy. A lot of men complain about women having high standards for their mates, but really, what do you expect? If you could get pregnant, surely you'd be pretty careful as well about who you mate with. And so women's investment is partially obligate, whereas men's investment is not morally, but pragmatically, entirely optional.

Men have the option to seduce and abandon mates. And so you'd expect, given that, that women would be very sensitive to cues that a man might seduce and abandon her and really try to avoid that as much as possible. And so if they're in a relationship and they think, Oh, my partner is not investing in me. He's not invested. Well, that's a huge signal that he's a low mate value mate, essentially. It's like, Oh, this isn't going to work. And maybe that's evidence for mate switching, but maybe it's also evidence for a breakup or backup or just lowering the cost of infidelity. Again, the discount an infidelity idea.

I was going to say this doesn't mean that no woman ever leaves her partner to get into a relationship with the cheating partner. Yeah, reliably, that does happen. And also, I'm going to guess that if you looked at the cohorts of women and you were to find the one that said, I was worried about investment from my relationship partner, that would probably result in more likely of a pivot to the new infidelity partner as a new relationship. I'm going to guess that that would probably be predictive of that because what am I sticking about for? If I'm going to have jeans and investment and I don't have investment, then I might as well try and get jeans and investment together. Yes, exactly.

So the dual mating, it doesn't explain all of women's infidelity, certainly. And we did see some mate switching in our samples. Several women in our sample were mate switching.

I'm wondering whether the era that we were in, instead of 2017, when we look at the mate switching hypothesis, the dual mating hypothesis feels a bit icky to me. When you think about it, when you think about, and maybe this is just me as a man, but thinking about some guy, male parental uncertainty, raising another man's children, whether this is or is not during a period of ovulatory shift where you're fertile as a woman, it makes me go like, you It's a little bit more Machiavelian, it feels like in that way. Whereas mate switching seems to just be, okay, you're monkey branching from one relationship to the other. People have backup mates. People have their friends, females, friends that are men often tend to have the attributes of the men that they would get into a relationship with, which has these weird quasi-orbiter backup mate things floating around a little bit. I wonder whether in a post-Me Too world, that was just a bit more It was a little bit easier to digest to have something that was a bit less like, Oh.

I know. I mean, I don't really... In terms of assessing theories, I don't really care about how icky they are or how... Yeah, it just doesn't affect my assessment of the facts. I just want to know what's true, whether or not it's gross. I would say that the evidence points to this idea that this is a part of human evolution. I mean, in modern populations, quote, unquote, cuckledry is quite uncommon. You know, one %, two %, three %. Those would be the sorts of estimates that you'd get from people who really understand the subject.

That would be of them, one to three % are men raising a child that they are unaware is not their genetic offspring.

Yeah, exactly. One, two, three % kids of kids are in a you are not the father type situation.

The male sensitivity to parental uncertainty, though, has to exist for a reason.

Yeah, exactly. If it never happened, Exactly. How could we have such concern with paternity certainty if there was no paternity uncertainty to be concerned about? That's number one. Number two, the modern percentages are based on They're based in a cultural context where infidelity has been highly suppressed socially, and they're based in a technological context where we can choose through contraceptives and whatnot, consciously, who you have kids with to some extent. There's much more control over it. If you look at populations with less contraceptives, well, then you start to see rates of 5%, 10%, among the Himba, 48%, really high rates of extra pair paternity. Some evolutionary psychologists have said, Oh, dual mating isn't true because it happens at such low rates. It's like, Well, first, reconsider that 2% number in terms of the 15% of women who have affairs, reconsider it as a hit rate as opposed to an attempt rate, and then also reconsider it in the sense that that's not nothing over millions of years, right, from an evolutionary time scale, but also it's not necessarily relevant to our understanding of our ancestry, given that we have contraceptives now and we really didn't then.

What about men's motivations? What did you learn from them?

Yeah, men's motivations. I guess I actually do want to say one more thing on the icky point, because I I think that there is a... And then I'll talk about men's motivations right after. I'll just go straight into it. I guess one issue from outside EvoPsych is this idea that the dual mating hypothesis is somehow, or the mate switching hypothesis or any of these, that it's somehow sexist to talk about the evolved psychological influences on human sexual behavior. The first thing that I would say to that is just that the evolved psychological influences on men's sexual behavior are also very unfavorable. The portrait that you can paint of men's behavior using evoPsych is downright dastrically. It's full of deception. Men's affairs, just as much variety as possible, completely emotionally detached. We've talked about the seduce and abandon strategy. All of this is very ugly. It's important that we have, if we want to reduce ugly behaviors, it's vitally important that we have a good understanding of what's actually happening instead of diluting ourselves that other influences are at play, more comforting ones. Another thing is that the primary advocates for the dual mating hypothesis, I mean, the senior author on our paper, Candice, who you've spoken to, she has a gender studies degree.

Everyone on our paper is a feminist. We all believe in gender egalitarianism. Some of the chief advocates for dual mating, Elizabeth Pillsworth, back the day, Marty Hazelton even today, these are women and feminists who are interested in this topic. So the outside evo-psych view that it's like, Oh, this is some anti-woman agenda. No, we're just interested in what's true, what's false. We're trying to take the politics out of it as much as possible so we can just buckle down and do good science. Yeah, we can talk about top motivations.

It doesn't paint women in a particularly flattering light, but we're talking about infidelity. We're talking about infidelity.

Most women don't cheat.

But But what this does show, I think, if you do get more pushback saying, This is unfair. This is you trying to control women's sexuality. This is you painting them as Machiavelian and all the rest of it. I think that what that betrays is the typical social expectation and interpretation of women's behavior, which is that sexually, women are not the protagonists, that they are almost always responding. It's actually low your key, quite a sexist perspective on women, that they don't have agency to go and chase down a new partner. It's the same people that will tweet, You're too good for him, Bay. Remember your value, queen, whilst also saying, No, women are never the ones that initiate. Women should never be the ones that so on and so forth. It's such a midwit take from people that pretend to be egalitarian between the sexes. It's not. It's not. It's like the soft bigotry of male expectations.

Yeah, it's so based, such a good point. It's incredibly patronizing how everyone's happy when you talk about men's evolved psychology. But then as soon as you talk about women's, it's almost as if the whole story is about men. And this is something that I see a lot in public discourse is that if you label everything as the patriarchy, let's say, well, then you're basically saying that men are the only ones with their hands on the wheel. That's a pretty patronizing view of women. Our lab views women and men both as active sexual strategists. That's a much more... I mean, politics aside, it's just a much more accurate view. I mean, it would be weird if women weren't active sexual strategists. But also, I think it's even less flattering to just say, to just pretend that women are always acted on as opposed to active agents in their own rights, actually. I can't tell if we're being woke or anti-woke here. We're doing something new.

I'm sure that we'll be accused of being both.

Yeah, the last five minutes of our conversation is going to be a Rorschach test online. Correct.

So we'll see. Dude, I've been using that all the time. Two Two memes that I'm yet to write into existence, one being an ideological raw shock test. So a good example of this was Trump getting shot in the head. That was an ideological raw shock test. That was either on one side, the Dems trying to take down the candidate that was going to win through purposefully stopping the Secret Service from protecting him, or that was Trump attracting crazies in a world where he's enabled everyone to have a gun. It was just pick. And the other one, the other meme being a thinking in superpositions. So you have these two worlds that both exist at the same time, and they collapse down into one. And it's interesting to see we talk about, okay, so are you saying that women don't have agency sexually? Well, no, of course they do. In fact, they need to have more. It's like, right, okay, so you're saying that they can make choices when it comes to their own infidelity? Yes.

And you would surely expect that they would make strategically prudent choices. What's the alternative?

So they're going to be culpable. They're going to be culpable for this thing. Yeah, it's so funny. Okay, men's motivations. What did you learn?

Yeah, that was a rich segue. This now feels relatively this now feels relatively lightweight by comparison. But again, top male motivation is relationship dissatisfaction again, but it's at relatively comparatively more frequency, comparatively lower frequency. That's the sense that I'm using relatively here. About a third of men, about 30% said that they were dissatisfied. About 16%, so significantly more than women, said that it was because they had an attractive affair partner. And about 14% of men said that it was motivated by sexual desire. Here, again, I just want to note that the qualitative data is qualitative, and so it's subject to these reporting biases, it's subject to these interpretation biases. Are we really meant to believe that only 14% of men's sexual affairs are motivated by sexual desire? Surely it was part of it for much more men. It's just that it's not particularly flattering or self-flattering to talk about those things. And so men are going to be wants to report that at a lower rate because it seems a little inappropriate. That would be my interpretation of that. But it is interesting that there's a sex difference there. And that actually was something that's consistent with the mainstream Evo takes on infidelity, that men's infidelity is somewhat more sexually driven, directly sexually driven than women's infidelity, because for men's infidelity, the only benefit really is sexual.

That's the mainstream take. It's not my take. I think that men cheat for a lot. Men and women both cheat for lots of reasons. Some men in our sample were mate switching. Some men in our sample had an affair because they wanted a new girlfriend. That happened at a similar rate to women as well.

What was the rate of men saying that their partner wasn't invested?

I think it was 5%.

That's interesting. We're going to get on to talking about jealousy shortly. But just to round this out, what are the exoplanets, the unspoken ghosts and potential obitors of infidelity hypotheses? Is there anything Anything else that's still lurking out there in the Ether that isn't dual mating, mate switching?

Oh, yeah. Multiple investors is the elephant. It has to be the elephant in the room. I mean, there's a few elephants in the room. One that I think you've talked to Jeff Miller, have you? Yes. Multiple times, yeah. Yeah, actually, I've seen clips. Jeff Miller had a hypothesis that didn't really get hardly any attention, which is that part of the affairs that we have are to gain information, to calibrate our own mate value, to gain skills in seduction. That theory has largely been brushed off, but it did pop up quite a bit that I can actually check the percentage here. It wasn't nothing. About one in 20 people said that they were cheating for some variety of information acquisition acquisition, right?

What do you mean information acquisition? Are they fucking spies? What's going on?

For example, one woman said that she basically wanted to obtain skills in seduction. She I wouldn't phrase it that way, but it was like, I wanted to be able to do this. I wanted to have this ability. That's a reason for infidelity that's strategically legitimate, where it's like, look, I don't really know my own mate value, or I don't really know how to get guys, or I don't really how to get girls. And that's a very important life skill. It's going to be important throughout my life. Let me go work on it, on the side. I wouldn't expect it to be the main motivation for infidelity, but it's a motivation. You can imagine someone who is, let's say, a college student. They're in their first big relationship. They're halfway through college, and they realize, I actually don't really know what I'm doing still dating, and I'm going to have to date my whole life until I get married, at least. So let me go get some skills here.

I said this about people who get into marriage with the first person that they ever have sex with. It's like being with your first ever therapist. I'm doing therapy at the moment, and a lot of people, it's the first time I've ever worked with someone for this long in person, etc. People go, What's your therapist like? I go, I think she's great, but I don't really know because I've got nothing else to compare it to. It's the same with that. I suppose you just don't know. Could I do better? Could I do any better? Is this really the best that I could do?

Yeah. There could be some mate value calibration that comes from engaging in infidelity to some degree. Multiple investors is worth talking about because most of the theories that we've been talking about for women's infidelity have have been, quote, unquote quality-driven theories. The difference is what qualities are being searched for. So again, mate switching is best overall whole package, whereas dual mating is the best combo deal. But both are quality-motivated. Multiple investors is a very interesting hypothesis. It seems to be the primary explanation of infidelity among the Himba of Namibia. It's essentially that if a woman can't get enough resources from one man, well, then she can obtain supplementary resources from additional mates on the side. This wouldn't be a quality-driven hypothesis. It would be a quantity-driven hypothesis. It's just that the quantity, or not necessarily quantity-driven, but it's quantity of resources, and that could translate to quantity of mates. I would have to talk to Shalza about it. But it's a very interesting hypothesis, and I think it does happen. We didn't find a lot of evidence in our sample unless you take the uninvested primary partner as evidence for it. Like, Oh, this guy's not invested in me.

Let me go get some investment somewhere else. But very anecdotally, I have at least heard of people having maybe maybe a sugar daddy character on the side who it's like, he's not particularly attractive, but you need to pay rent at the end of the month. And so this is something that you engage in. I don't think multiple investors should be expected to be at high frequency in high SES countries and in high SES individuals. But in situations where resources are scarce, that could very well be the main reason that women have affairs, to obtain additional resources.

Do Do you know The Wizard Liz? Do you know that YouTube channel?

No.

Right. So her channel is huge, but just has not come across my radar until recently. She got six and a half million subs on YouTube, hugely engaged Instagram as well. And she regularly does videos basically explaining how to get the princess treatment, which is how to make your man a man, a man, pay for your entire life, pay your bills, buy your car, pay your tuition, ensure that you're looked after, treat you like a princess. And if I was to speak to her, I would be very, very interested in asking what are the motivations for that? What do you think about using multiple partners? Like really trying to dig in. She's like super duper famous. And it's tangential to this boss bitch thing, but it's done in a very different a way because obviously it's not focusing on financial independence and not needing a man, it's a more, some would say, Machiavelian manipulative version of this to get the guy to pay for those things, for everything that you should be showered in gifts, that it's very important that you're showered in gifts, that you should set the tone. I was watching this video from her yesterday.

She says that you should lie to every new relationship that you're in and say that the guy in the previous relationship spoiled you because men will only work as hard as they feel like they need to to beat your previous boyfriend. So basically, if your last boyfriend beat and abused you and never cared for you, your next one will just think, Well, if I just don't beat and abuse her, then I'm better. So it's a Very interesting. Super interesting. I'll send you some of the videos once we're finished up.

I'll be interested to see if men start taking on that strategy because this is the first period in history where it's viable to be a boy toy or a- Dude, I'm an aspiring fucking trophy husband.

Have been for a very long time.

Unfortunately, you've got too much money for that. I still have hope.

I'm still hoping for an heiress to step out of somewhere. Okay, so what about the role? How does this fold into your new perspective on this? How does this fold into the discussion around jealousy, about sex differences in jealousy, about why men and women get jealous, its evolution function, et cetera?

Well, I mean, this is what's funny is that the dual mating hypothesis is more consistent with the evolutionary psychology literature on jealousy. I mean, it's quite conspicuous to me, but it doesn't seem to have been acknowledged generally. It's something that we've touched on earlier, which is just that if... Okay, well, to give everyone the down load if they don't have this information yet. On average, it varies the degree of the sex difference, the size of the sex difference varies, and it also varies what people care about. There are plenty of cultures where everybody cares more about sexual infidelity or everyone cares more about emotional infidelity. But the general difference is that within a culture, on average, men will be relatively more concerned with sexual infidelity, and women will be relatively more concerned with emotional infidelity. That makes sense if dual mating is the concern, because men aren't protecting against a woman leaving them for another partner. They're protecting against the potential that they will be, quote, unquote, cuckolded. They don't want... They're more upset by sexual infidelity because men can be cuckleded where women really, at least not in the same way, in a euphemistic way maybe, but not in a literal sense.

On the women's end, we've talked quite a bit about investment. They're going to be chiefly concerned, or not chiefly necessarily, but they're going to be more concerned than men with losing investment because women's investment is more obligate, men's investment is more, not morally, but pragmatically, optional. That's really the landscape in terms of sex differences and jealousy. It pops up everywhere it's looked for. I will note, though, that some people have taken it, some people have exported this F-Psych finding and said that, Oh, women don't care at all about sexual infidelity. Their main concern is emotional infidelity. As long as it's just sexual, it's fine. That doesn't pop up. Women are very upset by sexual infidelity. Then also on the other end, men are very upset by emotional infidelity. It's just that relative to one another, within a culture, you'll generally find the difference in that direction. This makes sense under a dual mating view because men are paranoid about getting cuckleded. Then it also makes sense from a traditional what women stand to gain from relationships in the view that it's like, well, if he is invested in her emotionally, then he might go off and raise her kids instead of mine, and maybe he's not invested in me.

Men have paternity uncertainty, women have investment uncertainty. That's how I'd summarize it.

A The consequence of this being accurate, dual mating being the leading infidelity theory, would be more men being cookholded ancestrally. Is that right?

Yeah, and I think it's very reasonable to think that that happened quite a bit. I mean, if you look at even like rural American populations, I've seen higher numbers, like close to 10% in terms of estimated... If contraception is low and infidelity is high, you're going to get a lot of men raising kids that aren't theirs. That doesn't happen a lot in modern America, in modern Britain, in modern Australia, where there's contraception and strong social norms against infidelity. We don't really see a lot of that. So it's not really something to worry about in a modern context. But in an ancestral context, I would say that this would be a real worry. I will also note that there's a great new paper, relatively new paper from, again, Berkshawza, called the Cuckoldry Conundrum, which is just pointing out that sometimes our conception of cuckoldry isn't necessarily exportable in the sense that, and this might sound strange, but sometimes you know that a child isn't yours, but it still makes evolutionary sense to invest in them. For example, among the Himba, there's tremendous status to be gained and social cloud from being a good father to your wife's affair partner's children.

Fuck me, that's prosocial in some ways.

Yeah, so it's like you would be Because... And you got to keep in mind that they've probably played both sides of the field here. So they've probably got eggs in other nests themselves, to use a metaphor. And so it's in everyone's best interest to be like, let's just invest in the kids that are in our nest. It's a free for all.

It's a pull. Well, this is like the human equivalent of the why female chimps mate with multiple males because the risk of infanticide gets reduced because each male is uncertain about whether or not that child might be his. I'm not sure if that's even true, but it seems to me this seems to be a more, I guess, socially enforced equivalent of that.

Yeah, I would call that a tangentially related hypothesis for sure. I don't know how high, and this is something that you should talk to Martin Dali about, actually, because his Cinderella Effect book is just the truth about Cinderella. Yeah, that is such a fun one about infanticide in humans. I say fun. Oh, my gosh. Don't clip that. Ruthless. Yeah, interesting. I really did mean it when I said, I don't care how gross the theory is. I just want to know if it's true. But I don't know how much infanticide has actually played a role in humans, but it's funny, and this actually relates back to the political conversation we were having earlier, is that some of the initial theories from Sarah Herdy on women's infidelity in humans were related to paternity uncertainty. Hilariously, given that, this is something that Louie Bichaud pointed out to me, which is that in the '70s, '80s, and '90s, these findings on women as sexual strategists, dual mating, paternity uncertainty, creation, these sorts of things. They were championed at that time as feminist ideas and pushed back upon by right-wing people who wanted women to... They had this archaic view of women as passive and not engaging in the sexual marketplace as active agents.

Now, today, we have the complete political reverse where it's the same set of scientific findings, but it's the the super-feminist groups that are saying, Oh, that's just not true. They're acting like the old right wingers. It's the really misogynistic groups, such as the tail end of incels and Dutch, who are holding up these same findings and saying they're great. I think that that's better evidence than I've heard for anything that these facts are neutral. If you have an agenda, you can collect a set of facts and spin them in a way that fits whatever agenda you like. The same findings that today we call sexist were originally championed by feminist scholars, and that's just the way the cookie crumbles.

Well, the horseshoe is very horseshoe-y, and it ends up being a total fucking circle eventually.

Yeah, it's more like a merry-go-around in the history of this debate. The same sexual findings that were considered liberal or now considered conservative. And if you give it another 20 years, it'll probably flip back. Meanwhile, we're just going to keep our heads down and try to figure out what's actually going on.

What are the predictors of infidelity? How can you tell if someone's going to cheat?

Okay, there's actually a long list here. The most obvious one would be, have they cheated on a past partner? Once a cheater, always a cheater. This lines up with our folk psychology. It's not exactly true in the sense that many people cheat on one person and then never cheat again, but it's true enough, let's say. There was one longitudinal study from Kaylanop that found that if someone had cheated in their last relationship, they were three times more likely to cheat in their next relationship.

Have you got any idea what the base rate is?

Oh, the base rate of infidelity? Yeah. It's difficult to find in dating couples. I'll say two things that I'm quite confident in. I would say that about a fourth of marriages will encounter infidelity at some point in their lifespan. I would say that about half of people, maybe a little more than half in men, a little less and a half in women, but somewhere floating around that mid-range, not like a super-majority or a super-minority, will cheat on somebody at some point, but that doesn't mean that they'll cheat on you specifically in one relationship. So for example, there are plenty of people who cheated on their college boyfriend or college girlfriend, and then they never cheat again for the rest of their lives. But given that most people have several relationships, and also given the data showing that most people report getting cheated on by somebody at some point, I would say that the inverse is also, though it doesn't logically necessarily follow, I would say that it is likely that about half of people will cheat on somebody at some point. But I would love to see better data on that. Unfortunately, the really good data has been collected on marriage and married couples.

And again, I would say that a conservative and reasonable estimate would be about a fourth of marriages will experience infidelity, and it's usually going to be the man who does it.

Okay, what else? Someone was a cheater in the past, that's a pretty good predictor that there might be in future. What else? Yeah.

Extra pair interest. We are naturally quite sensitive to extra pair interest. We notice it. So people tend to notice if their boyfriend is constantly checking other girls out. That seems to predict infidelity empirically. I believe there's even a study where they tested how long a man's eyes lingered on other women, and that was predictive of infidelity, which is funny. And extra pair flirtation, that thing, I would be attuned to that. There are people who are, let's call it laser-focused on their partner. Then there are people who you go to the social event and they just want to talk to all the hot guys or all the hot girls, that thing. That probably doesn't bode well. Narcism is another thing to look out for. That's another thing that I think people find quite intuitive. A general history of, and I don't say this in a loaded way, but a general history of promiscuity, I would say, would be something to look out for. If you're a woman and you're choosing between two guys, and one guy, he slept with over 100 women. He loves going to the club. He loves having one-night stands. He rarely has long-term relationships, and the other guy has had two long-term girlfriends and has never had casual sex.

If you're choosing between those two guys, which is more likely to cheat on you, I think it should be obvious, but it is statistically backed as well, that the guy who has more of a history of monogamy is going to be more faithful in practice. I've given you five things there, so I think maybe four, I'm not sure. That's quite a bit.

I seem to remember a line from one of David's books, maybe the evolution of... I can't remember. Where he said that the single biggest predictor of extramarital sex is premarital sex.

That's probably true. I love that line. I'm stealing it, but I'll have to check it.

I just wonder how true that I wonder whether it's the case. Is it just socio-sexuality all the way down? Oh, yes. That's such a driving force that the person who wanted to have a novelty in their teens and in their 20s How much of that is setting a particular type of habit? Damaged goods? How much are you damaged goods? How much have you set some lifestyle routine versus how much is this a natural growth of you and your nature as a person. You know what I mean?

Yes, I completely agree. I think that it's possible. I don't find it completely implausible this idea that it's like if you practice having one-night stands over and over again throughout your 20s, maybe in your 30s, it'll be hard for you to not do that when the opportunity arises. But I also think it's plausible, as you say, and this would be what I would think, is that it's socio-sexuality all the way It's like if you want novelty and you're just holding yourself back from it, I'm not sure that that actually will... Maybe the ritual of doing that will help you in a marriage, but maybe it won't. Also, maybe you want those things, you want to be sexually unrestricted restricted, but women just don't like you. When you're married, the first time that you get the opportunity, maybe that's the first time that you take it as well. I would say that if someone is... I think that, yeah, it's humans seem to exist partially on this spectrum. It's a construct, but it's a useful construct of sociosexuality. Some people are quite, let's say, unrestricted. They like to have sex without love. They like to have some casual sex.

And some people are quite restricted. And the people who are more restricted, the people who don't have sex with people who don't love them, the people who would feel uncomfortable getting naked in front of a stranger, those people are probably going to be more faithful to you. I think that's pretty reasonable. I think for all the Internet discourse, I know that every podcast, I want to put a moratorium, a ban on body count, because I've talked about it before so many times. But yeah, I would say that body count is a a dull proxy But it probably is a proxy for likelihood of committing infidelity, at least in the studies that I've seen.

Yeah, I suppose the reason the body counts an interesting discussion, the reason it comes up so much, is it's such a low resolution, rough-hewn signal in the same in a way as saying your bank account shows how hard you work. It's this odd singular figure that you can compare. Everybody has one. Everybody has a bank account. How much money is in your fucking bank account? How many people have you had sex with?

I would say that it probably isn't predictive. I think there was one... Actually, I won't quote it because I don't remember the exact stats. But I think it's pretty intuitive that if you got one person who's only slept with one person before you and another person who slept with 100, who's more likely what? They're going to cheat on you with the third person they've slept with or the 101st? I think it's pretty intuitive.

What are some of the common signs that a person is cheating?

Signs that a person is actively cheating? I mean, a lot of these aren't literature-backed, but you do hear them from relationship counselors and relationship psychologists and things like that. I would say that I don't think that you should be... I don't really have prescriptive claims. In my personal life, I wouldn't really want to be in a relationship where everyone's snooping on each other's phones all the time and accessing each other's technology. But conversely, anecdotally, you do see it a lot where people who get cheated on, they say that their partner became very digitally secretive, very protective of their phone. They go to the bathroom, leave the room, and they are sure to take their phone with them. Never leave their phone unlocked, never let you use their phone for any reason. I would say that that would be somewhat suspicious. I suppose there are plenty of reasons why someone might be digitally secretive that aren't infidelity, but it's also hard to imagine carrying out a full-blown affair in a modern context without keeping digital secrets. That would be very Stone Age in nature. I would say that... Yeah, I mean, a science that they're actively cheating are much more difficult because we don't have as much research on it.

Well, by virtue, The people who are actively cheating are trying to conceal it. So who's going to blow the Tom Cruise Mission Impossible mission whilst it's still underway?

Yeah, exactly. So, yeah, do you want to take part in my study that will completely expose you to unnecessary risk in your secret operation. But I would say that cautiously, millions of years of evolution has prepared your brain for this moment of detecting partner infidelity, potentially. Maybe it's only tens of thousands of years. It depends how deep monogamy goes in our lineage. But point being, I would I would say that trusting your gut to some extent is probably wise. If you think something's fishy, there might be. With the caveat that you got to look at your personal history. If you know that you're someone who's just morbidly jealous, you're really oversensitive to that thing, then play a cautious hand.

I was going to say there's thousands of people right now who are... Vindicated. The people who are adamant at all times that something's going wrong. There was this Interesting study that I saw on Cipost, the top four behaviors that signal commitment within relationships on social media. Number one, deleting dating apps. Number two, ignoring flattatious messages. Number three, indicating relationship status online. Number four, unfollowing potential alternative mates. Research has found that individuals with high attachment anxiety reported significantly higher levels of discomfort, worry, and jealousy when imagining their partner interacting with an attractive alternative on social media. This confirmed that such scenarios are particularly distressing for anxious individuals. Interestingly, the partner's high commitment behaviors on social media successfully increased perceived partner commitment and the perceived devaluation of alternatives, regardless of the participant's attachment style. However, these behaviors did not significantly enhance feelings of security or relationship satisfaction for anxious individuals as hypothesized. This suggests that while explicit commitment signals are important, they may not be sufficient to fully alleviate the deep-seated insecurities and fears associated with attachment anxiety.

You have to send me that. That's very cool. Also, I would say that it's modern, but that doesn't mean that it doesn't have some evolutionary roots. This broadcasting that you're in a relationship on social media. What it reminds me of most is I spoke to one of, if not the leading experts on gibbons on my podcast, Species, and we were discussing monogamy in gibbons. So gibbons are our closest socially monogamous relatives. And one thing that they do is they sing duets together. And part of that function, I mean, it's got many functions, but part of that seems to be to broadcast the pair bond. To basically say the gibbon pair will sing a duet, say, Hey, everybody, just so you know, we're still dating.

It's the relationship status update on Facebook.

Yes, exactly. And so whenever I see someone just put up their your girlfriend posts them, and then they share the story or vice versa, it's like you're doing a gibbon duet in the sense that you're both signaling, Hey, everybody, alternative mates, we're in a relationship, and we're doing well. So that thing, it has its roots, I would say, in a very basic evolved desire, even if the behavior itself is not evolved, obviously. There's no selection on Instagram posting, at least not yet. Not yet.

That will be soon. What have you learned about what counts as cheating?

That there's a major variety. I mean, it's hard to know because a lot of this is from the gray literature. If you're in an open relationship, for example, even sleeping with someone else is not necessarily cheating. So Then on the other end, some people who are in very, let's say, sexually restrictive relationships would say that pornography is cheating, or that even fantasizing about other people is cheating, or that light social flirtation with other people is cheating. There's a huge spectrum as to what's considered cheating, what's not, what's considered just disrespectful versus full-blown affair. For what it's worth, our study only looked, the study that we spent the first half hour or so discussing today, we just looked at sexual affairs. It's possible that if we... Women are more likely to engage in emotional affairs than men based on the existing data that we have on that subject. It's possible that purely emotional affairs are more geared towards mate switching. That would make sense to me.

Oh, that is interesting.

Yeah. What is the function of non-sexual emotional affairs? Like where a woman is daydreaming about her coworker crush but isn't actually acting on it or a man.

You're blowing my mind. You're blowing my mind because this You chose a particular bar to classify infidelity, and by design, that bar would lend itself toward the dual mating hypothesis more than it would lend itself toward the mate switching hypothesis.

That is correct. However, I will also say that- Cheeky. It's not cheeky. I wasn't rooting for the dual mating hypothesis. If anything, I was rooting for the mate switching hypothesis, but I tried to stay as emotionally neutral as possible. I was surprised by the results. I'll also say that to give the devil its due, advocates the mate switching hypothesis, they do think that Or they did think, maybe this research will change their minds, that the primary function of women's affairs, sexual affairs, is to obtain a new mate. So the sexual affair test, I think, was a fair one. Because look, we're looking at extra pair mating. We're not looking at extra pair flirtation, which can have even more functions. I mean, sometimes you'll flirt with someone who's not your partner, or one will flirt with someone who's not their partner just because they want to be more popular at work, or they want to get a raise, or they want the airport, they want going through the airport to be slightly smoother.

That's literally what I was about to say, if I want a second Lotus bisque off on a Delta or something, I better hope that it's one of the female air hostesses that comes around, because if it's that miserable-looking bloke with a beard, I've got no chance. If I can flood my eyelash She's in the right way at some lovely lady, then maybe I get a second biscuit. I'm so fascinated by that, by what constitutes cheating and the emotional infidelity versus the sexual infidelity. It's a term we haven't used yet, but monkey branching from one relationship to another.

The slang for maid switching.

Yeah, where you are dipping your toe in. Just how invested is this person? Just how funny is this person? Just how good are the two? How How good does he smell? Before we get to- How good of a lover is he? How good of a lover. Yeah, before we get to that. So I'll ladder up all the way before I get to that one. It's also, I suppose, the thing from an operational perspective, for want of a term that makes it sound less like a military fucking undertaking, it allows more culpable deniability for anybody. Did you sleep with him? Look, I haven't even touched anybody. Darling, I've never touched anybody. It's like, well, that's not what I was asking.

It's a much safer form of... An emotional affair is much safer. And so you're insulating yourself against the costs while you're engaging in it. I think that makes a lot of sense. I will also say that one of the strengths of the mate switching hypothesis is that because it is about sexual affairs, it's also about emotional affairs, but because it is about sexual affairs, is that it acknowledges something that's true, that Helen Fisher actually said this to me. She said, You learn a lot about someone between the sheets. There's a lot of mating relevant information that is obtained through having sex with someone. How conscientious they are, how much they care about you versus themselves, how athletic they are. You get a lot of information.

Is cheating heritable? Have you looked at that? The behavioral genetics of cheating?

Yeah, I mean, everything's heritable. I'm not a behavioral geneticist, but there have been studies on this subject, and it shows that... I mean, genes code for proteins and regulatory molecules that build and operate your brain. It would be bizarre if genes had no influence on any behavior. For a behavior to have zero genetic input would be peculiar. There hasn't been a ton of research on this, but there have been some twin studies, some candidate gene studies, and candidate gene studies are always a little more questionable. But the twin studies, I find that study... Again, I'm not a behavior geneticist. I do find that study design quite persuasive, and those indicate that, yes, cheating is heritable.

Hey, talking about a gene embryo selection, imagine if you could... I'm going to select for a scoundrel Chad of a son. I'm going to have him just absolutely decimate Stockton on T's in the northeast of England.

Well, the reason that that's... I mean, that's very funny, but I suppose the reason that that is... And the reason that I think, I don't know why embryo selection is coming up so much, but I guess the reason that I think that this whole project might be a little unlikely is that the genes that affect one's propensity to cheat, it's not going to be one cheating gene. It's going to be thousands of genes that each do hundreds of different things. In all likelihood, at least by my understanding, it's going to be the influence of one gene that has a tiny effect on risk-taking propensity, another gene that has a tiny effect on socio-sexuality, another gene that has a tiny effect on honesty. Just all these genes that have tiny effects on things that are good in some contexts and bad in others. And so in order to genetically adjust someone's probability, what does someone who has a zero % of the cheating genes look like? Maybe they're super boring.

Yeah. Have you seen this new, I think it's Jacob or Jacob Jakub Fort, examining the fraternal birth order effect and sexual orientation insights from an Eastern European population. Jakub Fort and colleagues examine the fraternal birth order effect, why by men with more older brothers are more likely to be gay. This seems at least slightly relatively robust. Analyzing data from Croatia and Slovakia, they find that the fraternal birth order effect exists for lesbians, too. Women with more older brothers are more likely to be lesbian.

Strange. I mean, so not my area, but very interesting.

Fascinating, dude. I thought that was so cool. I mean, I had Dr. James Cantor on the show, and he's spicy, and lots of people really don't like him. But for his area, parasexuality, is that it? The one where it's all sorts of weird sexualities. He's just the best. He taught me very much. He's gay, and he taught me a lot about the birth order effect. But the fact that it occurs for lesbians, too, I thought it was fascinating.

Yeah, a bit confusing. And also, I would just love for there to be a really... This is something that I don't know if we'll ever get it because it might not be adaptive. But it would be so cool to get an adaptive story of homosexuality that works. But at the end of the day, it just matters what's true. And I haven't heard an a psych story that one, makes a lot of sense, and two, actually has good data behind it.

But it's also not my area. I can't give you the data, but I can give you one that's got a good story. But it only works as guys. It really doesn't work for females. And this female thing throws a huge spanner in the wrench, the works of it, which is if you have had multiple males go through the same woman, your mom, it likely that the sex ratio is going to be skewed toward men, which makes it less likely that you, as a man, are going to be able to find a female mate.

And so you become a kin helper, essentially, and invest in your brother's offspring?

I think so.

Yeah. I mean, that's, again, very interesting. Doesn't fit with this new finding on feelings at all. Absolutely.

Totally fucking pointless. Why would the lesbian... No, we need more of you. We need really the men, all of your brothers. Well, maybe not your brothers.

Yeah, it seems more of a... I think that it seems like more of a spandrel. That would be the hypothesis where it's like there's selection. Again, this is so not my area, but I've heard stories about maybe certain strong selective biases select for genes that also, at a low dose, they lead to certain things that are very selectively advantageous. But if you get a high enough dose of them, then you become purely same-sex attracted, and the buck stops there. I guess my favorite hypothesis that might have been true in our ancestry, just doesn't seem to be particularly true now, would be this idea that it would be this kinselection idea, that it's like in some circumstances, because we see this in other animals, in some circumstances, it makes more sense to invest in your kin's offspring than your own offspring because they share 50% of your kin's share.

Born basically to be an alloparent.

Yeah, born to be an alloparent.

It's a little early warning detection system about the sex ratio and then down the street from that.

I met an evolutionary biologist who liked that, and he called it, I don't know if this is his name, but it's such a funny one. He was gay, and he called it the Rich Gay Uncle Hypotheta. It's just hypothesis. No, perfect. I was like, It is true. I looked it up and it's like, Oh, yeah, gay guys do tend to make more money, and they do tend to invest a lot in their nephews. I was like, This is cool. But it doesn't seem to be. Again, it's just hypothesis, and I actually don't think it's true. I think it's more likely that not everything is explicable by evolutionary psychology. Yeah, but it's fun. I wish it was. It's fun, which is what's most important. That's Evzeig's biggest hurdle, is that it's so fun to come up with stories that we tell too many. You have to be very conservative with your hypotheses and test them rigorously.

We've spoken about people that are consistently being cheaters, the culprits. What about people that are repeatedly victims. Is there such a thing as a repeat infidelity victim? Some people always get cheated on, other people manage to sail through completely smooth.

If I'm remembering correctly, in the Calinop study, People who were cheated on in their last relationship were twice as likely to be cheated on in their next relationship. And some people hear that and they think of it as like, Oh, that's just lightning striking the same spot twice. Oh, my gosh. But the truth is that lightning does tend to strike the same spots because there are things that affect the probability of where lightning hits. So this isn't victim blaming, but it's possible that someone is very low-skilled in mate guarding, let's say. They just don't do that effectively, and so they consistently get cheated on. Or another thing, we often see that people are attracted to narcissists. We know that narcissism co-varies with infidelity. And so if you're someone who finds super cocky really sexy, well, you're going to pick those guys over and over again, and then you're going to end up picking... You're picking a trait that co-varies with infidelity, and so you become repeatedly victimized to it. Again, not victim blaming, just stating the reality that sometimes people's strategic decisions have an influence. Another possibility, though, is that this is based on self-reports.

Did you get cheated on in your last relationship? Did you get cheated on in this one? It's plausible to me that some people are too suspicious and overreport infidelity, or some people are just really good at catching cheaters. They've got a skill there. Maybe the rate of getting cheated on is relatively evenly distributed between the two groups, but the group that gets cheated on a lot are constantly catching it. It's plausible to me that if you're someone like myself, for example, who wouldn't go through their partner's phone, I would just feel like that was a gross thing to do. I can Certainly imagine, I'm not going to say I've never done it or that there wouldn't be circumstances where I could, but just that it would... Generally, that would be something that I would find very aversive. There would need to be some really legitimate reason. Well, then maybe I'm more vulnerable to infidelity, but I'm also just more vulnerable to not noticing it. So there is this effect where people who get cheated on in the past are more likely to get cheated on in the future, and people who haven't been cheated on in the past are less likely to be cheated on in the future.

So winners keep winning and losers just lose more. That seems to be the case. But it could be a detection bias. It could be, as you like to say, a skill issue, just not good at-It is a skill issue, man. Yeah, not good at detecting it or not good at picking mates. But It's an interesting phenomenon. I'd love to do more research into it, but it's not my research.

That's fascinating. The consistent themes that you find throughout your life, if they continue to come up, have to have something to do with you.

Maybe it's you.

Yeah, it has to have something to do with you. And maybe it is that you're unbelievably good at detecting. But given that not everybody cheats all the time, maybe it's that you're good at picking cheaters. Maybe that's That's a good skill.

I think the most likely explanation is that you're attracted to traits that co-vary with infidelity. So if someone says to me, why does everyone cheat on me? The first thing that I would ask in a less callous way, why do you keep dating cheaters? Yeah.

What is it that you're predicting?

Yeah. What are you attracted to that's causing this problem? Because if you think narcissistic bad boys are super hot, well, problem solved. Maybe not. And if you're- Misstry over. Yeah, Yeah, Sherlock Holmes over here. I've solved it. And vice versa for men, if you're a man and you're attracted to really dark, triad, sexy, flirtatious women, maybe maxing out on that. And it could also be a prioritization issue. So let's say you're the guy who puts physical attractiveness above all else. You don't pay attention to personality. It's just who's the hottest girl that likes me? That's who I'm going to date. And then it's like, why do they all cheat on me? It's like, well, maybe you should have considered shared values.

You weren't selecting for loyalty.

Yeah, you didn't select for loyalty. So bit of a skill issue, but we won't victim blame too much.

What does With this new study, this new insight, how does it inform your perspective on how natural or unnatural infidelity is, ancestral mating strategy, monogamish versus serial monogamy versus polygyny. Does it adjust your worldview at all?

No, but I'm so glad you brought this up. One thing that I will say is that, again, I want to emphasize that my study is just one study, and I look forward to more research, hopefully research using the same paradigm where we look at actual people who have had affairs that try to investigate women's infidelity more. Then also that even though the top-line conclusion is a pre-registered win for the dual mating hypothesis, best case scenario, and worst case scenario for mate switching, we also found that some women mate switch and women cheat for a variety of reasons, including obtaining additional resources, getting revenge, et cetera. How does It didn't affect my view? Really not that much. I thought that mate switching would be much more common, and I found David Buss's arguments very eloquent and persuasive for the mate switching hypothesis, and I'm a huge fan of David Buss. I thought that maybe this would be a win for the mate switching hypothesis. I was surprised it wasn't. I guess it changed my view in that sense. But it didn't change my view as to whether we're naturally socially monogamous mammals. Because most socially monogamous mammals engage in extra pair mating, and most have some degree of extra pair paternity.

The idea that we, a socially monogamous mammal, also engages in extra pair mating and also has some degree of strategic evolution in the context of extra pair paternity, neither of those things were particularly surprising. A lot of people hear the word monogamous. The way that folks at home use the term monogamous is different from the way biologists use monogamous. Generally, when we talk about monogamy, we are distinguishing between genetic or sexual monogamy and social monogamy. Most species that are labeled monogamous are only socially monogamous. So there's some degree... Plenty of them don't cheat, but many of them do. One example, and this would be a very unethical study to perform in humans, our closest socially monogamous relative, the gibbons, There was a study in the 1990s, the scientist named Rykard, he or she, I can't remember. They went out into the field and just watched Gibbons having sex and tried to tabulate how often was it with the primary partner and how often was it cheating? And a full 11 to 12 % of the time, it was not the primary partner. So that's not 11 to 12 % of gibbons cheating. That's that number of gibbons.

That's gibbons having sex with other partners at that rate. So usually with the primary partner, but very oftentimes not. Some people are going to hear this and think naively because they don't have, and there's nothing wrong with this, but because they don't have the biological, anthropology context, they might think think, some people might think, Oh, Mackin's infidelity research suggests that humans aren't naturally monogamous. I would say, on the contrary, it's completely consistent with us being socially monogamous. And given that, again, most women do not execute a dual mating strategy in this way. Most women get their genes and parenting from one partner, both in terms of their psychology and the psychological mechanisms undergirding their behavior and in terms of their actual behavior. But in any case, some of you are going to hear this and think, Oh, this means that we're not naturally monogamous. It's consistent with us being socially monogamous. It's just a question of how sexually monogamous we are.

It's fascinating stuff, man. It's so interesting. I'm going to throw a little bit of money into the ring that there's something missing with the The way that the studies are being done for ovulatory shift, it seems too unlikely to me that we could have all of these converging. It would be so useful for ovulatory shift to happen for it to not actually have an effect. Because it seems to me that each time that it comes up, it sounds really cool and it's sexy explanation, and then it doesn't replicate, or there's something in the data that does whatever. It just to me seems like such an obvious mechanism for evolution to take advantage of the original pill, the original pill, the original contraceptive control for women, concealed ovulation with behavioral change that occurs during that period of time. No one knows, maybe not even her. And it would just be... I don't know.

I feel the exact same way in the sense that I think that maybe more sophisticated study designs that look at partner qualities and look at relationship qualities as mediators, maybe those end up validating the ovulatory shift hypothesis. But I will note again and emphasize that the dual mating hypothesis does not need ovulatory shifts. For example, one might intuitively think that in monogamous relationships, fully sexually monogamous relationships, it would only make sense for a woman to have sex at ovulation because sex has risks, and that's the only time she can get pregnant. But instead, we see that there are benefits to having sex outside the cycle, outside of that part of the cycle. It's possible that there are benefits to having sex with one's affair partner outside of that part of the cycle as well, in terms of seduction, in terms of mate acquisition. I mean, it's funny. I was talking to a couple of ovulatory researchers at a conference, and one of them said offhandedly, but it was so clever, they said, We'd have more success testing a weekend, weekday shift hypothesis because so much more cheating happens on the weekend versus the weekday. That really puts the That really puts the cycle shift effect sizes into comparison.

It's not like humans are werewolves, and depending on what part in our hormonal cycle, there's noticeable changes. Part of being human, part of the defining characteristics of our species or the suite of defining characteristics, is that we exhibit remarkable sexual stability across the cycle. Even if we exhibit dual mating, it's not inconsistent that that stability translates to infidelity.

Hell, yeah. Mac and Murphy, ladies and gentlemen. Dude.

Chris Williamson.

I really appreciate you. Your work's fascinating. I love the fact that you can communicate it this well. And I'm excited to see what you do next. I will be seeing you in Australia in only a couple of months time when I'm out there for my tour. So are you still going to be there?

I have got tickets to your Australia concert of sorts.

Oh, yeah. I'm going to come out and play the Banjo.

So if anyone is going to Chris This is a Melbourne show, I'm sitting in one of the regular seats. It's going to be a very easy opportunity to meet me as well. I'll be doing an unofficial meet and greet in the aisle.

Where should people go? They want to keep up to date with your work. What is it? Podcast, all of the things. Where do you want them to go?

If you Google my name, everything comes up. My podcast is Species. The app that I have for couples is Cupply. I've got a course on human evolution. If anyone wants to learn about those topics. I bought it.

Very good. Highly recommended. I bought it. Go and buy it if you want to learn more about this.

Thank you, Chris. And so there's a few ways to get more time with me, but all of them can be found through Google.

Oh, yeah. Maken, I appreciate you, man.

Chris, I appreciate you. Thank you so much for having me back on.