Modern Wisdom - #520 - Robin Dunbar - The Evolutionary Psychology Of Love

Episode Date: September 1, 2022

Robin Dunbar is an anthropologist, evolutionary psychologist, head of the Social and Evolutionary Neuroscience Research Group at the University of Oxford and an author. Love is something that people have been trying to describe for thousands of years. Beyond asking what love is, is the question of why humans feel something so strange in the first place. Why would evolution have exposed us to this extreme sensation with huge potential for catastrophe and pain? Expect to learn how love is adaptive, why humans need to have more sex than almost all other animals to get pregnant, why ancestral men who hunted big animals were only doing it to get laid, how the length of your fingers can tell you how promiscuous you are, whether Robin thinks humans were ancestrally monogamous and much more... Sponsors: Get over 47% discount on all products site-wide from MyProtein at https://bit.ly/proteinwisdom (use code: MODERNWISDOM) Get £150 discount on Eight Sleep products at https://eightsleep.com/modernwisdom (discount automatically applied) Get the Whoop 4.0 for free and get your first month for free at http://join.whoop.com/modernwisdom (discount automatically applied) Extra Stuff: Buy The Science Of Love - https://amzn.to/3wyJsW6 Get my free Reading List of 100 books to read before you die → https://chriswillx.com/books/ To support me on Patreon (thank you): https://www.patreon.com/modernwisdom - Get in touch. Instagram: https://www.instagram.com/chriswillx Twitter: https://www.twitter.com/chriswillx YouTube: https://www.youtube.com/modernwisdompodcast Email: https://chriswillx.com/contact/  Learn more about your ad choices. Visit megaphone.fm/adchoices

Hello, everybody. Welcome back to the show. My guest today is Robin Dunbar. He's an anthropologist, evolutionary psychologist, head of the social and evolutionary neuroscience research group at the University of Oxford, and an author. Love is something people have been trying to describe for thousands of years. Beyond asking what love is, is the question of why humans feel something so strange in the first place? Why would evolution of exposes to this extreme sensation with huge potential for catastrophe and pain? Expect to learn how love is adaptive, why humans need to have sex more than almost all other animals to get pregnant, why ancestral men who hunted big animals were only doing

it to get laid, how the length of your fingers can tell you how promiscuous you are, whether Robin thinks humans were ancestral immunogamous, and much more. This episode absolutely blew my face off. It is so interesting. I adore evolutionary psychology, especially from someone like Robin who understands it in the wider context of anthropology, of primatology. This is absolutely great. I really, really hope that you enjoy this as much as I did. And if you do, don't forget to hit subscribe. It's the best way to support the show, and it makes me very happy. I thank you. But now, ladies and gentlemen, please welcome Robin Dunbar. Robin Dunbar, welcome to the show.

Great pleasure to be here. Do you ever find it annoying to be so well known for one landmark concept like Dunbar's number? I have to say sometimes, but you know, there are only about 10 people who have a number named after them and I'm the only one that's alive. No way. Something like that. Wow, which is a bit worrying. Oh, well you think that they're killing off the people that numbers are named after? Who knows? Yeah, you never do know.

So originally I wanted to talk about friendships, but we're gonna do that another time. You have a book that explains very interestingly from an evolutionary psychology basis, what is happening when we fall in love, what happens when we fall out of love? So it's just an absolute primer, how do you define love? What is it?

Well, I think humans have spent the last umpteenth thousand years trying to figure out how to define love and the answer is it is very difficult. It's clear that something weird goes on in the brain. In fact, the brain goes completely crazy. And we kind of become fixated if you like, it's what effectively happens on a particular person. And it's kind of easy to describe the appearance of somebody in love, I mean, all the great poets and Shakespeare and etc etc kind of do it extremely well, essentially you know they sort of dreamy appearance and they can't get

the person out of their mind and they want be near the person, all these kind of things, but trying to understand what is actually going on inside the mind really has been a bit of a nightmare. But the reality is all cultures have or experience are something very similar on these lines. That's not to say that every person in the given culture experiences some people are constantly falling in love. And like every time a new person comes in the room, they fall in love with them. And other people don't fall in love particularly with anybody. They get on fine with them and maybe have babies with them, but you know, they're not, it's a bit give or take, you know, as you might say, they're not, they don't have that sort of commitment.

So I suppose there is a sense in which there's a feeling of commitment of rosy sunglasses, this person is the most wonderful person I've ever met. All these kind of cliches, cliches are true based on observation of fact. What makes us fall in love with somebody then? Well, how can we reliably fall in love with someone? Oh, I don't think you can. I think it just overwhelms you when you least expect it. And sometimes it can happen if you like after the event. So, one of the characteristic things, people who have been arranged marriages will tell you is you know you get ordered by your parents to marry this person and you think

oh my god and then you know learn and behold a little way and you kind of just fall in love with them and it just seems to work like that. We kind, you know, we kind of prefer to fall in love first before you marry people. Well, you know, that doesn't always work out either. So, you know, there is no rule that's universal to these things. It sometimes happens that sometimes it's hard to say, I would figure anyway, hard to say why it happens in particular cases. Often we don't really know.

It really is one of the great mysteries of the universe. And it's a great trauma very often. Well, that's the thing, right? It's not just an enjoyable experience. It can often cause the worst psychological pain that many people will go through in their lives. Oh, yes. I mean, if you look at you know all the great love poetry from the wonderful stuff the Persians produced and the Arabs produced, right the way through to the modern day even in the

poetry love poetry of other you know sort of non-Euro, Middle Eastern cultures elsewhere in the world. It's all very similar. It's the trauma of unrequited love that it really carries the weight, as it were, you know, sort of. What do you think's happening evolutionarily there? Is that somebody lusting after someone and fearing that they are being

told their genes are not good enough? That sounds very cruel. Look, I'm trying to break it down into your language here, probably, unless you want to start pontificating about some romance language poetry stuff. language poetry stuff. Well, the great mystery is why we have this kind of falling in love for Norman. And we might think of it in terms of Peirbon because what it does is create this very intense, emotionally intense, peirbon between two people. And that's is kind of unusual. It's certainly very unusual in mammals to have those kind of one-on-one anonymous relationships. The only group of mammals that is 100% monogamous in that sense, that's actually the dog family, so the wolves and the foxes and all that a lot. foxes and all that a lot. Most mammals aren't there, promiscuous, or they have kind of harem type mating systems, families, male and several females. And females, sorry, humans

have this very peculiar halfway house, which is something that looks like monogamy in the sense that you've got this very strong pair bond that holds two people together but unlike all the proper properly monogamists, mammals like dogs and gibbons and various other species of monkeys that are going for this kind of thing. You know, these relationships aren't lifelong. Humans have a form of serial monogamy in which people tend to move from one relationship to another on average as it was. It's not say that some people don't have lifelong relationships. Any more than some people have no relationships at all. On average, most people probably go through a number of these relationships, some of which are just teenage crushes phase and then you end up marrying somebody and maybe you part company and go off and marry somebody else and that may

go off and marry somebody else and that may happen to all three times and it can happen a lot in some un-togaddlerous societies where they may have eight or ten partners in a lifetime, each partnership, each romantic partnership if you like to think of in those terms is quite robust and it lasts for a number of years and then they get fed up with each other I suppose. they don't last for a number of years, and then they get fed up with each other I suppose. Thank you. We've on. Is serial monogamy what you would guess and cestrally is this sort of, I guess,

natural state of affairs on average? No, not really. For humans, it appears to be something more chimpanzee-like, which is polygamy in some form, either promiscuous polygamy as it kind of is in chimpanzee. Can you explain what that is? Well, I suppose just think in terms of the way chimpanzee society works, the males fight it out of us themselves, and the top dog then gets to make with all the females.

This doesn't mean to say that the males further down the hierarchy don't occasionally make with females they often do. They try and sneak them off into the bushes where nobody is watching. But they don't have a sort of permanent relationship. The females rear the they're offspring unadid, mother males, and males may be contributing by defending a territory or something like that or keeping other males, strange males away from the group. But the males aren't really particularly involved in, in childcare and child rearing. You might get some relationships that last longer. There's a tendency for these kind of systems. You see this in the gorillas, particularly

where several females are locked on to one male. So the males in those sort of contexts are functioning as kind of sumo wrestlers, if you like. They're the big thugs that keep everybody off your back. It's sperm donor and bodyguard. Absolutely. And this is sometimes known as the bodyguard hypothercyst. And we kind of see that in humans too, a little bit. But by and large, most human societies are actually polygamists that say you have

a male with several wives. Have you got an idea of the upper bound of that? Well, if you look at some of the famous amoeas of Morocco places or or the emperors of the Mughal state in North India can run into a rocking Solomon ispairs is the other famous example running to many hundreds if not thousands of wives and concubines between them. But the problem is that if you have a few males doing that, that means there's an awful lot of males at the bottom of the hierarchy who don't get a wife period. Unless they go around stealing them from other cultures, I think they're both.

And either of those? Either of those make for a pretty unstable society. It makes for a very unstable society. It makes for a very unstable society and one of the consequences of this in almost all these societies historically is when the Grand Old Man dies, he's got like a hundred sons, all of whom are gunning for each other, to take his place as the next emperor. So there's an absolute bloodbath usually of rivals. Because to the victor the spoils. To the victor all the spoils.

And the spoils are very, very rich indeed in these cases. It's not unusual. I mean, that's basically what happened under the Saxon kings in England and it happened in Scotland with the Scottish kings really quite late running through into the 12th or even 1300s. You would just end up with an almighty mess basically as different families fought over who was going to be the next king. Sometimes while the king

previous of us still alive and he didn't survive much longer once they'd sorted out who is going to be tough. You've got to prepare, you know. It's like getting ready for a night out. The event is coming. We might as well make sure that we're all set. Given the fact that you were of the opinion that polygamy is typical Ancestrale or at least on average would have been not uncommon How on earth is it that we have managed to wrangle anything close to a monogamous society even if it's serial monogamy? Okay, I mean, I think it's it's important to see this in the context that whatever it is Which is mostly

to do with the length of the finger bones, just quite a good measure of how promiscuous society is, all our ancestral species going back to the astrology of the scenes seem to be polygamists. They show a strong anatomical signature of polygamists, only modern humans. That's what's known as the 2D4D ratio, the ratio of the index finger to the ring finger. Talk to me about how you can tell the dating preferences of a society based on the ratio of their fingers?

It sounds bizarre, doesn't it? But it seems to work quite well, and this was established both in animals and in humans. It works quite well in primates. But it seems that the genes that control the lengths of the fingers, and particularly the second and the fourth digit. So you're indexing it in your ring finger, determined by or influenced during development by testosterone load in the womb. So the fetal, the load that the fetus has of testosterone from the mother that the fetus is exposed to. The higher that is, the shorter the index finger is. So, more testosterone is shorter index finger.

Yes, shorter index finger means that you are on the home more likely to be promiscuous and it's kind of indicative of high testosterone levels, both internally to you. So some male babies, because they're obviously switching over from being a kind of generic non-sex. So a female body form is the default. Yeah, I remember I got to interject there. There is a I think it's called Gone Girl, which was a movie, kind of a thriller movie a few years ago. I'm pretty sure that the line was in that. And the female protagonist in it is very manipulative. And she uses this line that would have slipped under the radar for a lot of people, but she points at the guy and she says,

the male form is an aberration. And that's so cool, right? Because it's the reason that men have got nipples, right? You need to be born with all of the elements, all of the individual bits that could make a woman. And then you turn from a kind of nothingness that could be a woman into a man. And then that was why she said she pointed out him and she says the male form is an aberration. Yeah, well, this is also what's known as the race to be male because it depends on how fast the fetus grows.

So it's a combination of having a Y chromosome and how much fat the baby lays down. And that switches the brain over from this kind of generic female brain into a male brain, which is clearly missing lots of bits to be there as a result. Okay, so what you were saying before, the finger length, that isn't the determinant of the dating preference.

That is simply a manifestation of testosterone levels, testosterone is, so you're saying shorter index finger, more testosterone, it would appear. More testosterone also correlated with shorter monogamous partnerships. synagogumist partnerships? Normally it would be either totally promiscuous mating systems or mating systems in which males compete with each other to monopolize groups of females. So what sometimes there is a harm based social system where you have one male and a number of females and they're offspring. So species like Gibbons, which are obligately monogamous, very occasionally they might have two, maybe even three females,

exceptionally in their little group, but you know, 98% of Gibbon groups in the world are strictly monogamous and the pair stays together effectively for life. Very long index fingers. No, they're very equal. And if you look at the polygamous species of primates, they then tend to have both sexes will have index fingers which are shorter than the ring finger, but the more promiscuous sex will have relatively shorter index finger compared to the female. So the males who tend to be the more promiscuous sex will even in promiscuous species will have a more deviant

finger ratios than the females. You do see that in humans as well. Just tens of thousands of people right now looking at their hands. Yes, I know. And working out. They're on not there. Whether or not the digits justify their desire to cheat or to go out and have sectored somebody tonight. Yes, well, you have to be a little bit careful

because the padding of the flesh and the muscles around the finger bases disguises the point where you should be measuring from. So you need to find the joints between the bottom finger bone and the top end of the first hand bone, if you like. And the differences are very, very small. They would be hard to tell by eye, although I have seen some males with spectacularly short index fingers, which is just blindingly obvious. And you take one look at them in their behaviour and you go, yes, you're an absolute bastard, basically, not just in the world of romance, but in the world of work. You know, just to test us, we're uncoicing through them. Yes, yes, I mean, just fizzing.

Okay, so let's get back to love itself. I'm still not sure about how love is adaptive. Like is it just ratcheted up attachment? It seems odd that we've evolved to feels something that's so weird and has so many downsides. Well, this is where it all gets a bit murky because it's not really obvious why humans should have these kind of peabonded, if you like, the think of them as semi-monogamous. I think the fact that we have this capacity just going back to your earlier question is what makes it possible then to have monogamous arrangements imposed on us because if you look at the 8,000 or so societies around the world, that's about 8,000 languages in each language of different society. The vast majority are

polygamous and you know sort of a few minutes at the top. Right now? Yes, well even now yes, unless they've been Christianized. The point is the society is that aren't polygamous that pursue a monogamous family structure or either hunter-gatherers and so the differences between males aren't very great for the females to choose between there's one can maybe hunt a bit better than another but you know by and large the differences are quite minimal or they're primarily being subjected to Christianization, which is imposed strict monogamy or attempted to impose strict monogamy. If you look at, well, I guess the answer is it doesn't work very well because we just

have serial monogamy instead, which is effectively the same thing. And of course, there are some Christian cults, I think of some of the Mormon breakaway cults and the original Mormons first started it. Are still polygamous? Blend off the same. Well, yes. The issue, though, is what seems to drive polygmy in human societies is when you've got massive, wealth differentials. This is why you get the King Solomon's type of, you know, or the Great Cans or, you know, the, I mean, there's this extraordinary statistic from the genetics, which tells us that 1% of all the males alive today are the descendants of Genghis Khan or his brothers.

And within the area of the Mongol Empire that he and his brothers, his generals, conquer it's 7% of all living males are their descendants. You know, well, you know, it's easy to see why, it's because every time a city refused to capitulate to them, they overran them very quickly. They killed all the men and they took the women into their harams and that was the end of that. So they inevitably produced huge numbers of descendants. But it's remarkable that we can still pick that signature up now.

You know, sort of, what is it? Six, 700 years later. It is seems strange that we've got the, if we're leaning towards polygamy, as soon as we have the surplus resources to be able to afford a stratified hierarchy of men and men to be able to support many women and stuff. It kind of is strange that we've got the mental faculties for love to be such a compelling, overbearing emotion for men as well, right? Yes, that's true, but it's just

And it's just kind of worth pointing out at first though, that these polygamous societies are all ones with very, very wide spread of wealth. They've got very, very rich people, very, very poor people, and the rich people, the rich males, become attractive to the women which and the rich people, the rich males, become attractive to the women because of what they have to offer, not for themselves, but in terms of wealth, because the big problem all human societies face, but particularly so once they're kind of into the agricultural game, as it were, no longer hunters and gatherers, is that the better off you are, the more likely your children will survive. We know that from our societies here in modern Britain, it's absurdly still the same.

If you come from the poor and the society, your children are much more likely to get ill and much more likely to die. So the issue, the trade-off, the kind of women all around the world are operating with, is is it better to be the second wife of a very, very rich man and therefore have a big cut of, let's say, the land for you to grow crops on, then be the first wife of a very poor man. The interesting thing about falling in love and romantic relationships generally is the extent to which people are willing to compromise on their ideals in order to just get the best job they can get under the circumstances

they face. In other words, you know, everybody wants to marry Mr. Darcy, but unfortunately there's only one of him and 500 of you. So, you know, what do the rest of you do as Jane Austen with her acute observation of the foibles of humans observes is you hang on and you hang on, you hang on, hoping to catch Mr. Darcy or one of the other rich land headers until you get to is the point of no return where you go, if I don't marry soon, I'm gonna be told I have children who's basically what it is. So you marry the curate, right? You wouldn't have looked at him twice,

but it's the best you can do, and at that point, the whole system will flip in, and you fall in love with him. So you're completely mad. This is what you were talking about kind of early run to do with the arranged marriages, I guess, that, well, two things may be happening here. First is that subconsciously, woman's programming is reacting to her ecology and her biological age and kind of this ticking

time clock to adjust her attraction levels based on basically scarcity. And another element is it would seem like closeness, physical closeness and familiarity can breed love. That's what it seems comes from the Indian arranged marriage. You literally do not know this person. And the very well, the matchmaking job may have been done perfectly and you may have fallen in love with this person. But I would guess that tons and tons and tons of people in arranged marriages fall in love more out of familiarity and closeness than some predestined sense of compatibility. Yes.

Yeah. I'm absolutely sure that's the case. But the issue then is why you have, what you have, if you like, is the generic system for you. It seems to be a form of polygamy. That's almost a default. Why would you have this romantic component to it? This very strong pair bond, because you get that in polygamous marriages.

That's what happens when a new wife is taken on. It's not because, or sometimes it's because the first wife who has always becomes the chief wife, says, you're boring, go and find another little one to play with. I mean, literally that, you know, is the kind of thing that happens. Or the husband actually falls in love with somebody else and wants to bring this new wife younger,

or it's always younger, into the household. And then it's a trade-off for the first wife. Or the third wife for the first two wives as to whether they're happy with that arrangement or whether they just shrug their shoulders and go, we can live our lives quite happily without having to be bothered by the husband as it were. So it's still a mystery in that sense. So the question then is, you know, what's underpinned the evolution of this kind of romantic falling in love component? So the classic answer has always been, well, it must be the need for biparental care. Human babies are born absolutely premature by a whole year.

That's why they're all kind of floppy and useless and don't even smile at you. Never mind. Be, behave in an engagingly human way. You need something to sort of persuade you to keep investing in it until it's completed its growth that all other monkeys' names do before birth and starts to, if you like, become more seriously human. And that is so taxing for the mother that having somebody else around, why not the male, to help out is absolutely necessary. And you kind of go, well, that sounds awfully like a American culture to me in my real life. You know, wearing the world does that actually happen in the answer? Well,, well, sometimes in other societies,

the men dandel babies on their knees and do things like that, just as all men everywhere do, change the old nappy here and there, but they're not really that good at helping out. They're much better when the kids are old enough to fire a bow and arrow and learn how to do these kind of useful tasks. So I deeply suspect that the amount of eternal care that humans give despite desperate efforts to claim that it's part of our nature simply isn't the reason at all.

And that's because in the end, the people who are most valuable to the mother, in almost all societies, and just as much in ours as anybody else is, is the grandmother and the sisters and maybe your female best friend. These are the ones that really make the business of particularly those early years possible if you like, less trouble-free than they might do on your own. And, you know, sort of, yes, males are useful if they're own land that you can farm and produce, you know, lots of crops to feed your children on and all those kind of things. I mean, no, that's important. We know from historical demography data, for example, from Europe, that in the 18th and 19th centuries, that women whose husbands were landed peasantry, so they only had a few acres.

They weren't the nobility, they weren't even middle class, they were peasants, a bit like crofters, you might say, in Scotland. Yeah, and they've got five acres of land or something like that, and they can get a graph. You know, the more land the husband had, the better the survival chances of the wife's children were. And of course, you know, for landless peasants who were day laborers that day, were, and of course, you know, for landless peasants who were day laborers that they, they're in the only way they could earn a living was to hire themselves out by the day to help with other people's farms. You know, their wives, you know, had high mortality rates because when they needed to go to

the doctor, they didn't have the odd fiver to spare for the doctor's fee. They, you know, if they couldn't, didn't have any money, they couldn't buy any food. All these kind of things piling in on them, the same old story that we even now, you know, still have to cope with. So, you know, yes, once you have agriculture, once you have wealth accumulating then the males can contribute indirectly, but that comes late. That doesn't happen until 8,000 years ago with an nearly-cagricultural revolution. Prior to that for several million years, our lineage had just tonned together as So those kind of issues don't necessarily come work out.

And, you know, typically, anyway, you might say, well, maybe a husband who's a particularly good hunter is the equivalent thing. And the answer is not really in hunter-gatherer societies, because if he's a good hunter and he can bring down mammoths instead of, you know, a chicken, always in those societies, those big prey that are hunted are shared with the whole camp. It's only small things that you eat within the family of the hunter on their own. So, seems to me there really isn't all that much evidence. This is what the claim that this romantic relationship is there for biparental care as such, as the technical term is. And the only obvious answer seems to be,

this is a hard gun problem. So what it, in effect, is happening is that the females are wanting to attach themselves to a particular male, essentially for protection. And in the kind of size of societies we lived in, this is only going to work terribly well if you've got both sexes locked onto each other. So the male has to be prepared to, has to in effect fall in love as well at the same time. And the reason for saying that goes to recent evidence, to recent evidence, there's only just been published, that for mammals in general, I say, all mammals from your humble local mouse and vol, right the way through to humans, the bigger the group, you live in the lower the fertility of the females. Now, in mammals in general,

it's a very linear decline. So if you look at things like voles and rodents of various kinds, then the bigger the social group, the more females in the social group, the lower the fertility, but what's not species, as you might call them, like lions, primates, monghis, that live in intensely bonded social, stable social groups, and have formed coalitions are able to do a shift that decline in fertility towards a bigger group size, so that they can live in bigger groups for protection, mostly against predators. The offset of the big group with extra protection is better than it would be if you were able to have tons of people. But what happens is, you know, there's only so far you can push that effect over to allow

you to live in bigger groups because in the end that declining fertility catches up. What you see in those species is an inverted U-shaped relationship between female fertility, average female fertility and the size of the group. So if it's the groups two small females do rather badly. These species, indicating these species, it pays to be in groups because that solves an ecological problem for you, but there just comes a point where these negative effects on facilities start to overwhelm the positive effects. Now the question is what's or who is causing those effects? Well, for 40 years, I confess, I've been studying various mammals, thorough goats in particular because they go crazy in the mating season.

In the belief that, therefore looking for evidence and explanations for the fact that males going crazy during the rut as Red De Deer do and Farrell goes to, and so on, many other antelope do, is so stressful for the females that it causes infidelity. So the assumption is here, it's the motorbike gangs roaring around the village midnight that's kind of making everybody jumpy and stressed.

And that's what I mean, know that psychological stress suppresses fertility. The menstrual endocrinology in mammals and women are no different is incredibly sensitive. Any level of high levels of stress, and this is partly in order to ensure you don't stress. And this is partly in order to ensure you don't have a menstrual cycle while you're lactating, right? So that's because that would mean you're having to gestate and lactate for babies at the same time. Oh, so there's an adaptive reason for why babies make you stressed? Yes. Well, not make you stressed. The system is just designed so that baby sucking shuts down the menstrual cycle. Right. I learned from, I think it's Christian Jarrett personality psychology is not long ago,

that women who are toward the bottom of their social hierarchy can be so downtrodden in terms of status that they can shut off their reproductive cycle as well. Yes, well this is exactly what's driving the thing because when we looked at the data for primates, it turns out that it's nothing to do with males at all. Sometimes males can be quite useful. But what's driving it is something going on between the females. They're squabbling amongst themselves and it's that stress. So this is not fighting. This is just what I sometimes describe as the London commuter experience.

You know, you're just being jostled and hassled. Right. On the undergross. You're very sensitive of status, but the issue being that because it still takes nine months to birth a child, a woman who is maximally fertile still has a relatively limited number of children. So it's not like the woman that is at the top could give birth to so many that the group size could be unlimited. You still have a limit on the top. And then the women that are toward the bottom, if the group size gets too big, there's too much hierarchy, there's too much infighting, too much squabbling, too much social pressure, that's causing a drop in the, that's fascinating.

And the problem is that once you push group size limits, you can see this in species after species after species of primates. And you see it in lions, you see it in, as I've said, in some of the social monkeys, for example. If the further you push group size or the number of females in the group is the correct thing, the bigger the effect on everybody, so even though the top ranking female is still pumping babies out, the other 9 or 10 are being pushed so low that the group actually can't replace itself. And this is what seems to cause or perhaps causes groups to split because it's the female is kind of wanting out from a context where they're just being pressured. Now, I mean, we've known about these effects for a very long time.

It's been known in generally that stress affects fertility in women and in humans. There's the classic work that was done on the Marmer's Etnum, here's the Caledatricians from South America, which shows that if a daughter stays in the group, she doesn't even go through puberty because she's being harassed so much by her mother. Right? Take the mother out or put the female with the sub-adult female with another male, and within a month she's gone through puberty and she's cycling and she'll conceive. It's absolutely extraordinary how fine-tuned this mechanism is. It's like plants.

It's the way that plants respond to their local ecology. This is true. Yes, it's crazy. Well, species that have to be able to combat varying circumstances, whether it's, you know, your local ecology as an environment as a plant, or the vagaries of the world in general or if you're a complicated memory like a primate, you know, flexibility of that kind is the key to its success And primates of particular is that, now the issue here is, if you're having these stresses,

the problem for humans evolving away from our common ancestor, the common ancestor of the chimpanzees and the gorillas, the great ape, South Africa. So sometime around about seven million years ago, give or take a bit. They're pushing out eventually. Actually, during the Astralopithecene phase, they were kind of okay. They were really operating in a kind of cheap, chimpanzee type of environment or rather impoverished chimpanzee environment, but they don't see any signs of increasing group size, but once you get the genus homo appearing

sort of humans, if you like, proper two million years ago, so, or lineage really taking off, what's driven, what's driving that is a move, or what that's associated with, it's a move out into a much more nomadic lifestyle outside the forests in less protective environments. And at that point, you see evidence in terms of brain size for dramatically increasing

group sizes. Now, what these species are all facing, right? The way through to modern humans is a need to live in very large groups with lots of females in the face of this pressure suppressing you. So if you're going to be able to live in these big groups, somehow you have to solve the fertility problem pressure. Now primates have been doing that for 60 million years. You know, every time they, you know, you get a new lineage

ink that's sort of increasing group size because it's occupying more predator-risk habitats, that's sort of increasing group size because it's occupying more prejudicial risky habitats, the cacks, the boons, ground-dwelling species like that. They're having to solve this fertility problem, the way they're doing it, predominantly, is through female-female coalitions. So you form a within the group close bond with a best grooming partner and the two of you act as a buffer. So you end up with the benefits of a large overall tribe and you ameliorate the effect of the infertility by having a small flat hierarchy little microcosm within it. So are you saying that women, females,

ancestrally, and maybe even today, need to take care of their status, of how statusful they are, and how they're feeling in terms of respect and pressure? No, actually, no, they're much less worried about status and risk. I was using status, I was using status as a proxy, I suppose, for like psychological, oh, okay. turbulence or whatever it was that presumably the women that would have the most psychological turbulence would be the ones that were the most downtrodden. Yes, I guess so. That's about how it is. But the issue at this point is, you see that have two choices,

is to either form coalitions with other females, who, if you look at the boons of the cacks and the like, almost always close female relatives, they're little matrilineal groupings, mum and two daughters or three daughters, maybe a kind of arranger. Or you might choose to lock onto a male. So in gorillas, you have all the females locked onto a male.

They don't really relate to each other at all. But most of the time, it's female female bonds. Now, in some species, you get a bit of both. Now, the gelada purgoon seems to be one of the few which operates both systems simultaneously, and that's because they live in such big groups. So what they have is little Haram-based groups where the females are locked onto the male,

which buffers them against living in these very large grazing herds of sometimes several hundred monkeys milling around and treading on each other's toes. And then of course that's exacerbating the stresses within the little subgroup, harm subgroups. So what they do there is they buffer themselves against those by forming these little female female coalitions except for the female that's got left out because she has no sisters or mum or daughter to do it with and she locks onto the male. Yeah, so you've got two potential solutions here.

That's right, and they treat the male exactly like he was a female in this social sense. Oh, I'm trying to say. I think what's happened with humans, this is is kind of a guess as it were. I'm still trying to figure out how you can improve it. What's happened is as the group sizes have increased, it's become increasingly necessary for females to lock onto males as hired guns because females are no good as hired guns. They're no snob. What do you mean when you see good guns?

Protectors. Cool, bodyguard. Bodyguard, yeah. Is it not... Okay, so if it wasn't for the fact that you need the physical protection of a male because males are typically bigger, more aggressive, more capable of doing stuff.

But there is one caveat to this, is not necessary that the bodyguard, as indeed is the case when females are forming these coalitions and in these other species with other females, female relatives, that this is a kind of defensive pact by the military, full machine AK-47s pointing outwards. It's passive protection. It's just that I know that when I am about to tread on your toes, that your best friend is five yards away. And if you go out, I'm in trouble because I don't have to contend just with you.

I'm going to have to contend with your best friend as well. And at that point, primates is not. They know the odds are just not worth fighting. So they're just detour slightly round. Right. So it's a, it most of it is passive debate. Now and again, all passive defense has to be proven at some point by by by genuine fisticuffs if you like otherwise it it doesn't really work but most of the time it's just passive protection it's having another partner that everybody else knows that's your buddy so just don't mess and this you really know you're going to win. Is there a potential argument that this reliance on? Is it alloparenting? I think where you have it's sort of distributed between women,

people, women looking after multiple children that are not necessarily that. If it wasn't for the bodyguard issue or the hide gun element of having a male partner. Could females not just have been vegetarians, not decided to go chase something down, it seems like, you know, with menopause, you do end up having a surplus of women to be able to look after children. It's difficult to do that. But I can't remember what it was in your book or somewhere else that I read that potentially the hunting part of hunter gatherers for men was more about judging male reproductive fitness of whether he's a good hunter, more so than the nutrition that he derived.

If that's true, that is one of the wildest things I've ever heard. No, this is, this appears to be absolutely so, that if you look at the economic returns of hunting, hunting males like to go hunting big dangerous animals in all these cultures. The energetic returns on hunting big dangerous animals are not that good, not least because they're just dangerous don't and you have every chance of not coming home yourself. Right, you actually do better energetically to just shoot rabbits. But there's no demonstration of skill. So if you look at male courtship strategies, if you like, it's all about demonstrating how good I am. And by good, I mean, how good my genes are.

So if all the kinds of things that young males do, racing each other, climbing them, stupidly high cliffs for no other purpose than to say I've done it. Playing vigorously brutal games where basically you're just bashing heads together. All these kinds of things, it's argued, are essentially displays of just watch me, I can afford to take these risks because my genes are so good, they're the ones you want. And of course there's no point in kind of making vague claims, these things have to be proven. And the result is teenage males have very high mortality rates by comparison with teenage girls because they take so many

more risks. We've actually done a study on this as a crossing in the middle of Liverpool, watching when people cross against the lights. What seems to happen is, so we've got a very nice measure of how risky it is because we can measure how far away the oncoming car is. If there are women present in the crowd of people waiting to cross, males are much more likely to cross on their own, especially if the car is close. especially if the car is close. Right? This is just advertising. And it really is a case of chicken

because you, it doesn't work if some people don't pay the price because they get it wrong. So these pressures then seem to be spill over into to honey. There's the show off explanation hypothesis for hunting law. That's what it's called the show off explanation hypothesis for hunting log. That's what it's called the show off hypothesis. Wow. I mean, that is absolutely spectacular.

Think that it might not be a utilitarian while you go out, like, Robin go, Robin stab, Robin bring back. It's not about that. It's about, look, Robin competent. Case with Robin. Yes. Robin got very good genes. Yeah, yeah. You'll build genes build very good body. Yes, yeah.

Robin strong. Robin's son will be attractive as well. Fast brain. Yeah. Fast muscles. Okay, so going back to the pair bond stuff. What is commitment in your mind then? Is it hard to fake signal of authenticity that sort of encourages trust?

Basically, yes. I think that's a lot of... I mean, the problem this is a two-way game. This is not a game played by one sex, and the other sex just as it's there and does nothing. There is a caveat to that and I'll just detour for a moment because it does kind of sum up the asymmetry of this. So we were looking at a huge national telephone database. So this is all the phone calls made on one provider in a very large European country, 20% of the entire country. So we're talking about tens of millions of subscribers and something like 6 billion phone calls over the course of a year. Now we're looking at the over the course of a year. Now, we're looking at the person they called most,

each person called most. And what you see is looking across the age span. So, as is always the case, we don't know what happened below 18 because that becomes minor, and is a whole nother ethics issue. So, nobody ever bothers about it. that becomes minor, and is a whole nother ethics issue. So, nobody ever bothers about them. But from 18 onwards, what you find is that the girls start very quickly calling a particular number

who is, when you check who that is, it's a male of similar age. It takes about three years before the male starts to reciprocate and put a female at his age in that pole position. So in other words, the girls have made up their mind long way beforehand as to who they want and they call and they call and they call and they make sure they're there when the guy comes around the corner, all these things. And to eventually, even the most stupid male goes, oh, goodness me. She's interesting.

Interesting. The game is the over-perception and under-perception bias. In this context, meaning? The fact that it's just their phone calls. I suppose so, but men or at least David Bus in his new book, he was talking about the fact that men tend to over perceive attraction from women and women tend to under perceive attraction from men. Yes.

You would have thought that like how how high do you need to waive the flag? Yes. Mentured have already been. Yes, but that's absolutely, it appears to be absolutely true, but men don't pursue that for very long, I think, is the answer. But they think, oh, you know, she's showing an interest in me and then they go, oh, no, she's not actually. Because the women are being very choosy about their responses to the males.

They make it very clear. Sorry, you're going to go away. Don't ring me. Don't want to. But the one they want, they will keep phoning. But what's interesting is, and this bears back on some of the other stuff we've been talking about, is if you look at what happens after that. So this is a late marrying population. They average age of marriage is about 29 in that particular population at that particular time. So they really, they've got this lead in, in which the girls start very, very early, focusing on this one male, the boys eventually halfway through our right and then they get married. And then about 20 years later, almost exactly, suddenly, the wife switches, the girl switches

to a female one-generation younger. Grandchild's just been born. But the male has long since already switched out. He's no longer phoning his wife with the same frequency as C. So the female carries on phoning and phoning the same person. But the male only lasts about seven years, you know, with her in poor position. He then gets, if you like, it gets bored and he starts phoning other people. If you like it gets bored and it starts phoning other people. And what this looks like is very intense female choice going on. They're the ones that really decide. You know, okay, you can kind of force them to marry you in some way or another, socially or otherwise. But it's a bad deal if you do that because you have a very grumpy wife to put on

the wife who didn't want to be there and probably isn't going to stay very long. If you respond to the natural rhythm of the thing, and let them choose, then you're into a good deal because you've got real you know, real focus and lock on. But it seems the guys just drift away in their social world as it were much much earlier than the women do. It's just so conspicuous and you see it in the phone calling later. What's the lesson that you take away from that? Oh, well, one level is the choice is being made by the women, and it will work better if you just live on to it. The difficulty, of course, is back to Jane Austen.

She was such a good observer of human behaviour. People are being left out. Mr. Darcy is getting all the girls and you know, the curates getting non, except the desperate. And you know, because Mr. D'Arcy is getting such a lot of attention, there are a whole bunch of guys who aren't getting any wives at all, which is effectively what happens in polygamous societies. So you have to have a way of managing them. And you can see all sorts of interesting strategies through history and across cultures and how that problem is managed. The one suggestion has been, this explains why the Portuguese started their

explorations in the 15th century because they had reconquered Portugal from the Moors, they'd taken over all the more-issured states. The nobility that were created in the aftermath of that had enormous states they were able to divide their states equally between at least their sons and their daughters probably got a bit of a share too. And you know everybody was happy because they got a decent amount of land, but the came at point all over Europe this happened in fact, where estates started to get carved up into the ever smaller pieces to the point where they were no longer economic. So when this happened in Portugal, who were the first people to really show this, they switched to primogeniture, oldest son in herits everything.

So before that, all sons had inherited equally. They switched to primogeniture. That meant the oldest son got the lot. The youngest sons kind of looked very grumpy, started being useless. And basically, they were riding around them in motorcycle gangs through the villages playing maim and beating the peasantry up and on these kind of things that people will insist on doing. So some some bright sparks said, listen boys, you know, why do you get a boat when you go exploring? And what you find is that it led to this huge exploration and

conquest of the new world and the east. And what you find is the oldest born son dies in Portugal, the second and the third born son die in the empire, Morocco or somewhere else, like just get them out of the system, go and make your own way. So you're saying that when the demand for potential mates outstrips the available supply, but you have a surplus of resources, you can basically pay men to go off and have an adventure, find some more women, find their own little kingdom that they can go somewhere. So you can control single, disgruntled nuisance-causing men by using the thing that you do have a surplus of, which is resources and money. You don't necessarily need money. I mean, you just say go, because this is how the Venetians

solve the problem. They never have this problem, right? They maintained equal division of the family wealth between all the sons, I mean, for centuries, because they were traders. Right? The more sons you have, the more trading you can do. The problem with land is it's a fixed commodity. And you see this very nicely illustrated in the Tibetans. So, traditionally, the Tibetans, one of the few societies that practice polyandry. They have one wife and many husbands. The husbands are all brothers. And this is a strategy to prevent, so what you're dealing with here is very high

altitude, very poor quality land and not much of it at that and every time you divide the family estate up between all the sons, you know it very quickly gets down to one field of peace and that's not enough to keep anybody going. So their solution is to marry all the brothers to one girl from another family. And the strategy works because the brothers of different ages says, you know, when four or five brothers marry a girl, the oldest will be 21, 22, something like that. The youngest will be five. They all go in as and they're all treated as husband by the wife, but because of the age differentials, they kind of operate a, what's effectively a former serial monogamy because by the time the next brother gets old enough to go,

oh it's the first one's bored. He's bored. Oh my god. Except for except for number two. Right? Because number two is 18 when they get married. It's older brothers, let's say 22. The next one is 17 or 18. Now these, he's on the right on the the hinge as it were of getting interested in girls. So what do they do? They stick him in a monastery. So all these, this is wider to better than have this huge, monastic culture. Part of it is to absorb the excess suns, who are always the second born sun. Wow, so you really didn't want to be the second born then. That was a bad, but it depends on how much you like the monastery, I suppose, and whether you want your older brother's ex-wife

as your future partner, I suppose. The interesting thing is you see exactly the same thing happening in Ireland. So we showed looking at the seminary records, for one major seminary in Ireland through the 19th century, that the seminaries were filled with the younger sons of big families. They're all farmers, they're all petty farmers at one size or when the family got too many

boys in them. Girls who can always marry off, right? It's no problem. When you've got too many sons, you've got competition for the land. So if they were a family with a lot of sons, then, you know, the excess sons were persuaded to career in the church. You're not going to get as disgruntled in the parish, perhaps, if you've decided to commit yourself to God. Okay, so you looked at it. You know, they live very well, you know, the church looks after them, they get to travel, you know, they might go to Rome and become incredibly rich as a card or all these kind of things, or all these attractions to make it. But the losers here in these kind of systems, sticking to the defense system is the other daughters because you're only

marrying one daughter out of each family into another family. So you end up with surplus of daughters and for better or for worse, they end up as drudges in their sisters or their brothers, households, literally a servant in leading a very miserable life. But the Portuguese had that problem too. They ended up because they wouldn't allow their daughters to marry out of the duke class, the top-nabled class of dukes. You've got a big constraint on the supply. Yeah, that's right. Now, what do you do with all these surplus girls? You put them in an

unnery, and these girls went in with the title of Brides of Christ, that's what they were called. They went in with a dowry, and if their older sister died, before marriage or soon after marriage before she'd produced an heir, the next girl could relinquish her nunnery vows, to reclaim her out and go back and replace her. I can imagine that if you're... Parents, you know, they're awful. They're so manipulative. They are. I can imagine that if you were a disgruntled, unwilling nun, that knowing that if your sister died at some point soon, your older sister died, I imagine that that could create some perverse incentives down the road if you were a

particularly why worry why really little none okay so one of the things that i thought was fascinating that you looked at was kissing the use of human kissing what's what's the explanation for that explanation for that. It's one of those things again for which there has never been really a satisatchy explanation. One of the interesting things about kissing though is in mouth to mouth kissing. I mean, not all cultures do it, so it doesn't necessarily work everywhere, but it seems that it's as close to a universal as anything that might be in the large numbers of cultures actually do it. The key to it is your exchanging information on your essentially your immune system. So it's reckoned a five-minute kiss results in the transmission from one person to the other of tens of billions of chemicals and bacteria and all sorts of other things that belong to your insides to the other person.

And it's giving them a very direct measure of the quality of your immune system. So if you think about falling in love, courtship in other words, as a process of assessment, so it starts, since you enter the room and your eyes lock across the room, and you go, poor ducks, a very attractive one, that fills, ticks all those kind of physical attraction boxes,

I shall go and explore further, and you go closer and engage in conversation, and so then you're picking up all sorts of cues about, you know, that cultural background, if you like, how they think and psychological background in the conversation. And then if you're still happy, at that point you kind of go through a point of reappraisal, do I like what I see or do I pull out now, but I still can or do I go to the next level.

You go to the next level is a bit more sort of physical. So you have a grapple and a dance. And at this point, you can get a good sniff of the other person. Smell what they're sniffing. It's very important in human. Very important. Very important. Because the same genes that determine your smell are the ones that determine your immune system. What you're looking for is somebody who has the different immune system. It seems that what you're looking for is somebody who kind of looks like you in all sorts of ways. So it's keeping a good bunch of genes together from your extended family, if you like.

There's what's known as optimal inbreeding, or optimal outbreeding. Why would you waste the fact that history of mating in your ancestors produce this perfect person that is you? Why would you waste all that by dispersing it, by marrying or mating with people who are not so perfect as you, right? So the answer is you look for people who are similar to you, H.L.E. and all these kind of things, look like you as much as possible because that's indicative of

the fact that you probably have common ancestry. And of course, in village societies that would work really well. And it probably doesn't work so well for us because we don't actually meet people really look like us very often these days. But in village society, you can tell it, tell it of a village

from that village they just look different. And that's not just how they come their hair physically. Did I see that you said that men can actually smell when women are ovulating? Yes. So this is the point that, well, I'm looking at MacThowes, I just finished the make-choice bit is that the one thing you want looking for somebody to be similar to you is in the immune system. Because what you want is your child to have as diverse an immune system as possible. You did the narrowly it is. So, in breeding is bad for all sorts of reasons. But one of them is you end up with no variability in their immune system to resist diseases. When you say immune system to resist diseases.

When you say immune system, what do you mean? The body's natural immune system. This is what produces all the white blood cells and stuff that attack and cannibalize. Okay. Genetically viruses. Genetically, people have a predisposition to be what robust against certain types of viruses and bacteria, but maybe not all of them.

So the goal is to kind of spread the risk across. Okay, okay. Yes, it's not necessarily particular resistance but bacteria or what have you. But a very strong immune system, which is, because immune system is very adaptive to what's thrown at it, right? It learns to recognize foreign bodies that have invaded you. And this isn't just genetic, this is something

which is going to be influenced by if you were an adventurer, if you'd been away. No, no, it's the genetics of the immune system itself, this capacity for the capacity for essentially the white blood cells to identify the natural killer cells, the NK cells, to identify foreign bodies in your system and seek and destroy as it were. And, you know, what you, I mean, there will be an element probably from different exposures in terms of lineages that have, you know, that have produced some genetic adaptation to particular kinds of viruses maybe, but the essence of it is you want as much diversity as you can get there. And smelling somebody is as the semi-distance queue is the best way to find that out.

And in famous cases, our eskimos and Maury is rubbing noses and we all think they're rubbing noses. They're not. What they do is they put their noses side by side and they sniff and take in a deep breath. And it's called, I forget the term, use how it's translated, but essentially it's breathing in the spirit. Is that the equivalent of the European air kiss on both cheeks? Yes, exactly the same thing. And this is why people pick babies out and sniff them. If you've ever watched newborn babies when they're being sort of passed around, everybody

goes, holds them up to the sort of passed around. Everybody goes, holds an up to big whiff of the baby. And pretend not to be sniffing, but they sniff the question of that. So, and we get a lot of cues from, much more cues from smell than we really like to think. And we're actually quite good. I mean, mothers can tell their offspring from other people's offspring by their smell alone. The big issue really in this context is perfume,

right? Perfume billions of dollars are spent every year on perfume billions of dollars and everybody thinks it's to cover up your natural bad odors. And it's not. What you're doing is you buy perfume that exaggerates your natural, your personal natural odors. That's why there are so many different perfumes. It was just covering it up. We just have one perfume and everybody, you know, like old spires out of the shape. It's loaded up. No, not with women. It's very carefully chosen to, and this is kind of how they build up these perfumes, so they kind of match different smell

characteristics, they're sniffers extremely good at decomposing the smells in different perfect mixes, the people that do it for them. But what it's doing is actually exaggerating your natural smell. Of course, it helps to cover up some of the bits you don't want to smell of, but it's actually really upon pass of the courtship strategy. And that's why it's been, since time time immemorial women in particular have done that or used it and not say that men also don't but it's much much more important in the case women but you'll finally say you've had a good sniff while you're sort of grabbing the girl in the vaults or something like that or pretending to dance very close in the club. But the final

point really comes with kissing because that actually is direct experience of in saliva. Slyvers just full of immune system stuff as well as digestive stuff. So it gives you a really clear message as the best you could do. But that's your final, because that's invasive. That's obviously the final step in it. So courtship is like this series of steps, starting way out the distance cues, to largely visual getting closer and closer and closer into, literally, into taste at the end.

What do you think is going on with non-reproductive sex then, if you're using contraception? Well, I mean, sex is designed to make you keep doing it. Sex is designed for all animals, never mind humans, to be a pleasurable experience, and therefore make you keep coming back and doing it. What's interesting about humans is it's clearly geared to reinforcing the pair bond because the amount of sex that has to be done to conceive is just outrageous, no sensible primate, whatever, wasted so much time in sex, just to conceive and offspring.

It looks like it's very, very quick, three cycles and primary and the female will be present pregnant. It seems to take much longer in humans and the only explanation for that is simply to prolong the pleasurable components of sex to reinforce the pair bond. Because what happens, right? You have to remember it's all bonding, and all our bonding comes essentially through the endorphin system in the brain, which is part of the brain's management system for pain. It's an opiate, an opiate-way, technically.

So it's rather similar effect to morphine. It makes you feel very relaxed and woozy and peace with the world and trusting of whoever you're doing the activity with and and for primates that's done by social grooming, leaving through the fur triggers in the receptors and the skin which trigger the endorphin system in the brain, specialised that a receptor. Now we still do that, that's why we go around hugging people and patting them on the shoulder and stroking their arms and things like that. But a lot of what we do, because we live in big groups, bigger groups, and any primate

would ever think of grooming me. In other words, it's intimacy, you know, you don't do it with everybody, you only do it with the close ones, but you now want to bond a bigger group. Then a lot of the things that we part of the social toolkit, so the laughter, singing, dancing, eating socially together, feasting, telling emotional substories, all these things trigger the endorphin system and make you feel bonded to the people you're doing it with. So you say that the difficulty of human females

to get pregnant, the fact that it does take many attempts, let's say, in order for that to happen, and maybe concealed ovulation as well, or the fact that it happens without us being able to tell when a woman is like equivalent of in the heat. Yes, yes. That is evolution making it purposefully more difficult or rarer to occur, to encourage the man and the woman to have more sex, which is already reinforced through the

pleasure of response in order to increase the pair bond. Yes. Yes. Yes. It's so cool, but it's so cool. Because after all, as soon as the woman is pregnant, you know, it's, it's, John's done. John was done. Well, you know, I mean, the, yeah, okay, early stages of pregnancy, you can, obviously, can still have sex, but later on, you know, it starts to become so if every woman got pregnant, the first mechanically tricky, if every woman got pregnant the first mechanical tricky if every woman got pregnant the first time that she had sex with a man it would be very unlikely for them to form the sort of robust pair bond that they

would need in order to be able to raise the child that is I mean that is absolutely fascinating and it's because the reason this is working is a two-fold mechanism, in this particular case, because the physical stimulation of the skin, all over the body, the hairy skin, as opposed to palms of the hands and the sole of the feet, well, we used to think there were no receptors in there. There's some doubt about that now, but all the sort of hairy skin, the arms, the body, the hair, and what pednolar, legs, are full of these endorphin receptors, or the system that sets the endorphins off in the brain. And so the stimulation that's given during sex, all the massaging and so on and so forth is triggering

the endorphin system like crazy. And in addition to that, you've got a secondary system kicking in, which is the oxytocin system, which is designed around, or what it exists for. Well, oxidism started, I think, fishes as a mechanism for maintaining water balance in the body. So the body, the complete sun, let's complete sun's to me. But in mammals, it had the opposite. It was adapted to keep the water in rather now. And therefore, it became very important into as a lactation. Right. So it plays an extremely important role in the course of lactation to ensure that the woman has enough liquid to create milk without killing herself.

And therefore, it's kind of been adapted into a hormone that causes mother infant bonding and then seemingly from that it's been adapted to cause bonding to the romantic part, because of all the stimulation, both of the breasts and of the vagina, the trigger oxytocins as well. Tocins are very short-acting. They don't last very long, but they're very high, it's like a very high hard hit, whereas the endorphins are long and slow. So, line of cocaine, not the tab of LSD. Yeah, exactly. I'll speak in language.

I understand that. I wouldn't know, officer, but. So, is cuddling the same? Is that the same response? Hold it, right, okay. Did I read in your new book, Friends, which we're going to talk about another time, that the speed that you rub somebody with needs to be slower than one and a half inches per second that you're moving across the skin in order

to get the optimal endorphin response. And this is some vestigial grooming picking bugs out of the fur thing. Yep, it's three centimeters a second. If you go substantially faster than that, it doesn't trigger the receptors in the skin. And that's about the speed with which the hands move across the fur, parting the fur during grooming in monkeys. So they're looking for bits of rubbish and stuff in the fur. So they're constantly parting the fur with both hands. And it's that movement deforms the skin and triggers these receptors.

And it's been shown with babies, newborn babies, that if you stroke them at exactly three centimeters a second, it calms them down when they're crying and makes them, if they've got to have, as they do, pin prick for the test that they do with newborn babies, they're much less bothered by, they don't sort of go, ouch, make it up, make a big scene.

I wanna get back, right. But if you do it at 30 centimeters a second, it has absolutely no effect. I don't know how you rub a baby which is probably only about 50 centimeters long at 30 centimeters a second. I don't know what it is. It's the rate. It's the rate. Yeah. It only 3 centimeters a second like three centimeters. Thank you. Thank you for correcting me there. Right, so here's a question. And this question came from interstellar the film.

It's by Christopher Nolan. It's spectacular. And it's this question that stuck with me for a long time. Does this lady who has a felt sense that someone on a different, a distant planet is still alive? They're doing this journey to try and find a new world for humanity to live on or something like that. And in it she brings up this question about why it is that we love people, we continue to love people that have already died.

And if love exists to encourage child bearing and child rearing, why would we love people after they're dead? Oh, I think that's because the difference between platonic love and romantic love is almost paper thin really. They're both based on the same framework or obviously wanting incorporates a sexual element, which is very specialized because what happens with a sexual element, which is very specialized because what happens with, in the context of falling in love, is the brain shuts down interest in other people. Obviously, this doesn't happen every time, but if you fall in love properly, then you lose interest in alternative possibilities. It's only some time years later that you come out of that rosy sunglasses phase, that you begin to become interested in other individuals. It's very, very focused.

Friendships are very similar and interestingly enough, and this bears back to the earlier discussion we had about females best friends. This best friend forever phenomenon, BFF phenomenon, which is very characteristic of women and very uncharacteristic of men, seems to be really important for women. This goes back to your moral and emotional and physical support mechanism that they need when they're in moving from one society to another and you know everybody's related to the husband and you're on your own

you know your support mechanism is another woman girl who's in the same boat as you so you so you know you can form an alliance and then they're very important then in helping each other with through the business of birth and child early child rearing. Those friendships of very characters that nearly always women, very occasionally made about 15% of women's best friends forever are actually a man, which must cause all sorts of interesting dilemmas, which means, well, you need not go into. But the great majority, 85%, almost all women have one and the great majority of those are another woman.

And the interviews that have been done with women about these by the social psychologists they just say I need somebody who's on the same emotional wavelength as me, many useless for that kind of thing. That's why I build these relationships where I'm sure it's much more to do with the kind of forming these little coalitions to buffer yourself against the stresses of the rest of the group and to provide childcare support. And that kind of remains constant right the way through life. And indeed your social networks are a very, very gender bias. 70% of men's social networks, their friends and family,

are men and 70% of women's are women, and that number figure remains constant in the age of 5 to the age of 85, doesn't bat an eyelid. You just don't see that same kind of emotion and intensity in men's friendship. If you ask them, have you got a best friend, male friend, I'll kind of go, oh yeah, go drinking with Jimmy a lot, you know. But the truth is, if Jimmy moves away, you know, and goes and lives in Thailand for the rest of his life because he's fed up with wherever you live. As you do, you know, you

kind of shrug your shoulders and say, well, it's too bad. I'll go and see if Steve's available. Men's friendships are much, much more club-like in that sense. So for women, their friendships are personalized and dietic and very focused on the individualists and individual men's friendships are kind of more casual. They may involve a lot of time doing stuff together, but they're very casual and they're much more club life. Why would that be adaptive for each sex? Well, I think in the women's case, it's precisely because they're typically they're moving between communities on marriage to an environment where everybody in the group, the community is related to the husband. Yes, because the woman was the thing that was passed around or given, the woman was the one that was expected to move, she needed a steady rock that would go with her. Yeah, well, she doesn't necessarily go with her, she just has to be able to find somebody

in that new environment. Of course, all the young girls will also be in the same boat, so they'll share lots of things they can't. And what's characteristic of friendships is you form friendships with people who are very similar to you in all sorts of different aspects, including you know, how they view the world, they live in and the support kind of elements that they need. Whereas I think the male issue simply goes back to the fact every single hunter-gatherer and well, the name of horticultural society, in fact I suppose, still in

in a 40-cultural society, in fact I suppose, still in industrialized Western societies, the male's most important function, the young male's most important function is defense. So they all have these warrior grades, certainly once you're into the agricultural phase, you have these warrior grades where young men bonded as groups and they formed very intense friendships but it's a friendship with a group, all the guys who are circumcised together all the go however they, you know, whatever the process of going from childhood to manhood is always involves pain, some form, and frightening experiences. So I'll take them out into the jungle in the night and all the older men will creep around in the bushes and make howling noises and scare the wits out of these booklets. But the result of that is that utterly bonded.

It's exactly what you see in the military even today, right? Guys are being shot at, it's terrifying. Forever afterwards, you're deeply bonded to those guys. Is the reason for the male friendship being able to be swapped in and out to account for the fact that you're going to have casualties then? I guess so, yeah. Yeah, interesting. That you don't get Yeah, yeah, interesting that you you don't get so attached to an individual that You're in my mind you're mind is to go to the job. Yeah. Yeah. Yeah. Yeah. So one one thing that I just thought about You mentioned mail-and-female bonding during relationships oxytocin and endorphins

I Learned last year about vassupressin and the role that it has for men particularly I'm less convinced. Oh tell me tell me more Well, it was yeah, vasopressin plays a very similar role To oxytocin in the sense it was involved in water balance in somewhere originally in the sense it was involved in water balance in some way originally. It's certainly been banded about as the male equivalent of oxytocin, certainly in the early literature when they were talking up oxytocin as the love hormone and the cure to the secrets of the universe. Of course, oxytocin is primarily present in females, we're talking about female mammals

in general. So it was the argument was, it's what creates mother offspring bonding in mammals so that they will invest, they don't nurture and cuddle this wretched little squirming thing. You know, it's not going to survive. It's not built as a vibe, I'm saying. You have to have something that makes the female just kind of focus on being completely altruistic and nurturing this little thing until it's old enough to stand on its end to feed. And then they were left with the thing, well, you know, what happens in the case of males,

you know, you need something else if you're going to have males in monogamous social systems. This is all done on voles, you know, the difference between polygamous and monogamous voles. So what partly the story was that Oxytocin played a stronger role in monogamous, in males of monogamous species of vols than was the case in polygamous promiscuous ones. But then somebody lit on to face a press in and there was some nice Swedish work on twins showing that males with high levels of face-to-pressing were more reliable, essentially, in their romantic relationships. So males with the wrong allele for face-to-pressing tended to be here today and gone tomorrow and they would act first and think afterwards. But it's not clear that

it's really playing a very strong role. We've done a huge genetic study. It was all done in Britain. So quite a different people. But it showed no signature at all for face-oppressing in any gun. We looked at three different levels of socialities. So your social predisposition, your romantic dyadic romantic relationships and your embeddedness in the wider social network. And you know dopamine plays a very strong role, oxidation plays a very specific role in the context of romantic relationships and endorphins, again play a very important role across the board. But there was absolutely no signature at all, no difference. So I'm a little skeptical of the literature. People tend to latch onto something, get very excited about it,

and then of course the media gets excited and it all gets playing out of water. And the object lesson here is the vol studies, because it was all based around the difference between monogamous vols and polygamous vols in terms of oxytocin essentially, oxytocin genes, except that when somebody did a study of, and that was comparison of two vol species. When somebody did a comparison of the oxytocin genetics across all vol species, there was no correlation at all with monogamy versus promiscuity, and then somebody else's point discovered that actually you can explain the polygamy, promiscuity versus monogamy difference between the original two, the all species, American voluose species on the basis of endorphine genes,

anyway. So all the vasocressing got wrapped up within the existing framework and it wasn't needed. Look Robin, you are absolutely spectacular. Thank you very much for coming on today. We didn't even get onto betrayal. We didn't even get onto the book that I meant to bring you on to talk about So I'm just gonna have to drag you back so you can have another glass of wine and spend an evening with me

If people want to keep up to date with the stuff that you're doing either out of your work or online Is there any way that they should go? Visually the best place is the books actually the books are written for the best places there, the books actually. The books are written for the laymen, they're me thinking out loud really, trying to pull the big story together out of all the research we and others have done. And I hope they're a pleasure to read as well as being informative, they're meant to be informative. So I'd go there, it's much less place, but it's been great fun talking to you. Robin, I appreciate you very much. Thank you. Thank you.