The Evolutionary Psychology Of Love - Robin Dunbar

1. 0:00 – 1:01

   Intro

   1. RDRobin Dunbar0:00

      The length of the fingers and particularly the second and the fourth digits are determined during development by the load of testosterone from the mother that the fetus is exposed to. The higher that is, the shorter the index finger is. Shorter index finger means that you are, on the whole, more likely to be promiscuous. (air whooshing)

   2. CWChris Williamson0:20

      Do you ever find it annoying to be so well known for one landmark concept, like Dunbar's number?

   3. RDRobin Dunbar0:29

      Um, I have to say, sometimes. But, um, you know, there are only about, I'm told, uh, 10 people who have a number named after them, and I'm the only one that's alive.

   4. CWChris Williamson0:44

      No way.

   5. RDRobin Dunbar0:46

      (laughs) Something like that.

   6. CWChris Williamson0:47

      Wow. Well, that's i-

   7. RDRobin Dunbar0:48

      Which is a bit worrying.

   8. CWChris Williamson0:50

      Oh, well, you think that they're killing off the people that numbers are named after?

   9. RDRobin Dunbar0:53

      Mm, (laughs) who knows?

   10. CWChris Williamson0:55

       Yeah, you never, you never do know. So originally I wanted to talk about friendships, but we're gonna do that another time.

2. 1:01 – 7:59

   Defining Love

   1. CWChris Williamson1:01

      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, uh, an absolute primer. How do you define love? What is it?

   2. RDRobin Dunbar1:17

      I, well, I, y- I think humans have spent the last umpty thousand years trying to figure out how to define love and the answer is, it is very difficult. Um, it's clear that something weird goes on in the brain and, in fact, the brain goes completely crazy, um, a- and, uh, w- we kind of become fixated, if you like, is what effectively happens on a particular person. Um, and, uh, um, I mean, it's k- it's- it's easy to describe the appearance of somebody in love. I mean, all the great poets and Shakespeare and et cetera, et cetera, kind of do it extremely well, essentially, you know, they, it's sort of dreamy, uh, appearance and- and they can't get the person out of their mind and they want to be near the person, all these kind of things. But trying to understand what is actually going on (laughs) inside the mind really has been a bit of a nightmare. But the reality is, all cultures have or experience, uh, something very similar along these lines. That's not to say that every person in a given culture experiences. Some people are constantly falling in love (laughs) and like, mm, 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. Yeah, they get on fine with them and they maybe have babies with them, but you know, they're not... It's a bit give or take, you know, um, uh, uh, a- as you might say, they'd better not, they'd have that sort of commitment. So I suppose there is a sense in which there's a, uh, a feeling of commitment, of, um, rosy sunglasses, this person is the most wonderful person I've ever met, all these k- kind of cliches. You know, cliches are true, based on observation of fact. (laughs)

   3. CWChris Williamson3:18

      What makes us fall in love with somebody then? Or how can we reliably fall in love with someone?

   4. RDRobin Dunbar3:24

      Oh, I don't think you can, but I think it just overwhelms you when you least expect it. And sometimes it can happen, uh, if you like, after the event. So one of the characteristic things there of people who have, um, been in arranged marriages will tell you, is, you know, you get ordered by (laughs) your parents to marry this person and you think, "Oh my God." Um, and then, you know, lo and behold, a little way in, you kind of just fall in love with them. It- and it- it- it just seems to work like that. And, you know, w- we, uh, kind of prefer to fall in love first before you marry people. Well, you know, w- that doesn't always work out either. (laughs) So, you know, there is no, no rule, uh, that's universal to these things. It- it sometimes happens, it sometimes doesn't. 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's- it's- it really is one of the great mysteries of the universe, and it's a great trauma (laughs) very often.

   5. CWChris Williamson4:30

      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.

   6. RDRobin Dunbar4:39

      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, um, right the way through to- to- to the modern day, even in- in- i- the poetry, love poetry of other, um, you know, sort of non-Euro Middle Eastern cultures elsewhere in the world, it's- it's all very similar, and it's the- it's the trauma of unrequited love that it really carries the weight, as it were, you know, sort of.

   7. CWChris Williamson5:13

      What do you think is happening evolutionarily there is that somebody lusting after someone and fearing that they are being told their genes are not good enough?

   8. RDRobin Dunbar5:23

      (laughs) That sounds very cruel. (laughs)

   9. CWChris Williamson5:28

      Look, I'm- I'm trying to break it down into your language here-

   10. RDRobin Dunbar5:31

       (laughs)

   11. CWChris Williamson5:31

       ... Robin, unless you want to start pontificating about some romance language poetry stuff.

   12. RDRobin Dunbar5:36

       (laughs) Well, eh, uh, the great mystery is why we have this kind of, uh, falling in love phenomenon. And we might think of it in terms of pair bonding because what it does is create this very intense, emotionally intense pair bond between two people. And that n- uh, is kind of unusual. It's certainly very unusual in mammals to have those kind of one-on-one monogamous relationships. The only... group of, um, mammals that is, uh, 100% monogamous in that sense are actually the dog families. So the wolves and the foxes and all that lot. Um, most mammals aren't. They're promiscuous or they, you know, have kind of harem-type, um, mating systems, families. There are male and several females. And females... I'm sorry. Humans have this very peculiar halfway house, which is something that looks like monogamy in the sense that it's, you've got this very strong pair bond that holds, uh, two people together. But unlike all the, um, proper, properly monogamous (laughs) mammals like dogs and gibbons and various other species of monkeys that go in for this kind of thing, you know, these relationships aren't lifelong. Um, humans have a form of serial monogamy in which people tend to move from one relationship to another, on average, as it were. This is not to say that... Some people don't have lifelong relationships, um, any more than some people have no relationships at all. Um, on average, you know, most people probably go through a number of these relationships, some of which are, uh, just, you know, sort of teenage crushes phase, and then, you know, you end up marrying somebody. Um, and maybe, you know, you, you part company and go off and marry somebody else. And that may happen two or three times. I mean, it can happen a lot in, in some untogetherer societies where, you know, they might have eight or ten partners in a, in a life- lifetime. Each partnership, each romantic partnership, if you like to think of it in those terms, is quite robust and it, it lasts for a number of years. And then they get fed up with each other,

3. 7:59 – 13:12

   Were Humans Always Monogamous?

   1. RDRobin Dunbar7:59

      I suppose, like we all do, (laughs) move on.

   2. CWChris Williamson8:01

      Is, is serial monogamy what you would guess ancestrally is the sort of, I guess, natural state of affairs on average?

   3. RDRobin Dunbar8:11

      No. Uh, not really. Um, for humans, it appears to be something more chimpanzee-like, which is, uh, polygamy in some form, either promisc- promiscuous polygamy as it, it kind of is in chimpanzees, but-

   4. CWChris Williamson8:26

      Can you explain what that is?

   5. RDRobin Dunbar8:27

      Um, well, it, it... I suppose just think in terms of the way chimpanzee s- uh, society works. The, the males fight it out amongst themselves and the, the top dog then gets to mate with all the females. Now this doesn't mean to say that the males further down the hierarchy don't, uh, occasionally mate with females. Uh, they often do. They try and sneak them off into the bushes where nobody's watching. Um, but they don't have a sort of permanent relationship. Um, the females rear the- their offspring unaided by the males, and the 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. Um, you might get some relationships that, that, um, last longer. There's a tendency for these kind of systems, you see this in the gorillas particularly, where several females are locked onto 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, off your, off your back. So it's, it's...

   6. CWChris Williamson9:44

      Sperm donor and bodyguard.

   7. RDRobin Dunbar9:46

      Absolutely. And this is sometimes known as the bodyguard hypothesis. Um, uh, and we kind of see that in humans too, uh, a little bit. Um, but by and large, most human societies are actually polygamous. That's, say you have a male with several wives.

   8. CWChris Williamson10:03

      Have you got an idea of the upper bound of that? Do you think...

   9. RDRobin Dunbar10:06

      Um, uh, well, if you look at some of the famous (laughs) , uh, um, emirs of (laughs) Mo- Morocco places or, um, you know, the, the, um, uh, emperors of, uh, um, the Mughal state in, in, in north India. You can run into... Well, King Solomon, I suppose, is the other famous example. Run into many hundreds, if not thousands, of wives and concubines between them. Um, but on the whole, the problem is that, you know, if you have a few, 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. Um, unless they go round stealing them from, uh, you know, other cultures, as it were.

   10. CWChris Williamson10:51

       And either of-

   11. RDRobin Dunbar10:52

       Other tribes.

   12. CWChris Williamson10:52

       Either of those make for a pretty unstable society.

   13. RDRobin Dunbar10:57

       It, 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 100 sons, all of whom are gunning for each other, um, to be- take his place as the next emperor. So there's an absolute bloodbath usually of, of rivals.

   14. CWChris Williamson11:22

       Because to the victor, the spoils.

   15. RDRobin Dunbar11:24

       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, um, the Saxon kings in England, and it happened in Scotland with the Scottish kings really quite late, running through into the 12, uh, or even 1300s. Um, you know, they, they would just... You would just end up with a- an almighty, um, mess basically, as different families fought over who, who was going to be the next, the next king. Sometimes while the king previous on was still alive (laughs) , and, uh, he didn't survive much longer (laughs) , once they'd sorted out who was, who was going to be top dog.

   16. CWChris Williamson12:08

       You've got to prepare, you know?

   17. RDRobin Dunbar12:10

       Yeah. (laughs)

   18. CWChris Williamson12:10

       It's like getting ready for a night out. The event is coming, we might as well make sure that we're all set. Right, so given the fact that y- you are of the opinion that, uh, polygamy is typical ancestrally, 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?

   19. RDRobin Dunbar12:33

       Okay. Um, I mean, I think, it, it's, it's important to see this in the context that what evidence there is, um, which is mostly, um, uh, uh, to do with the length of the finger bones, which is quite a good measure of how promiscuous a society is, all our ancestral species going back to the australopithecines seem to have been polygamous. They, they show a strong anatomical signature of polygamy. It's only modern humans, that's the s- what's known as the 2D/4D ratio, the ratio of the, um, index finger to the ring finger. Right, now-

   20. CWChris Williamson13:11

       Talk

4. 13:12 – 19:08

   Telling Dating Preferences by Finger Length

   1. CWChris Williamson13:12

      to me about how you can tell the dating preferences of a society based on the ratio of their fingers.

   2. RDRobin Dunbar13:21

      Um, it, it... (laughs) It sounds bizarre, doesn't it? But it seems to work quite well and, and this was established, um, uh, both in, in, in animals and in, in humans. It works quite well in primates. Um, but it seems that the genes that control the length of the fingers, and particularly the second and the fourth digit, so your, uh, index finger and your, uh, ring finger, are determined, uh, by, uh, or, or are influenced during development by testosterone load, uh, in, in the womb. So the fetal, uh, the load that the fetuses have, testosterone from the mother that the fetus is exposed to, um, the higher that is, um, the, uh, uh, shorter the, the index finger is. So, um-

   3. CWChris Williamson14:09

      More testosterone is shorter index finger?

   4. RDRobin Dunbar14:12

      Yes. Shorter index finger means that, um, you, uh, are on the whole, more pr- likely to be prom- promiscuous. And they, and it's kind of indicative of high testosterone levels then, both internally to you. So some, uh, male babies, because they're obviously switching over, uh, from being a kind of generic, um, non-sex, so, so a female body form is the default body form, right?

   5. CWChris Williamson14:38

      Yeah, I remember. I don't, I got to interject there. There is a, um, 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, the female protagonist in it is very manipulative, and she uses this line that would've slipped under the radar for a lot of people, but she points at the guy and she says, "The male form is an aberration."

   6. RDRobin Dunbar15:03

      (laughs)

   7. CWChris Williamson15:04

      And that's so cool, right? Because it's the reason that men have got nipples, right?

   8. RDRobin Dunbar15:07

      Yes.

   9. CWChris Williamson15:07

      You need to be born with all of the elements, all of the-

   10. RDRobin Dunbar15:12

       Yeah.

   11. CWChris Williamson15:12

       ... individual bits that could make a woman.

   12. RDRobin Dunbar15:15

       Correct.

   13. CWChris Williamson15:15

       And then you, you turn from a kind of nothingness that could be a woman into a man.

   14. RDRobin Dunbar15:20

       Correct.

   15. CWChris Williamson15:20

       And then that was why she said, she pointed at him and she says, "The male form is an aberration."

   16. RDRobin Dunbar15:25

       Right. Yeah, well, th- this is also what's known, um, 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, how h- how much fat the baby lays, 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 that should be there as a result. (laughs)

   17. CWChris Williamson15:55

       (laughs) Okay, so-

   18. RDRobin Dunbar15:56

       Um-

   19. CWChris Williamson15:56

       ... what you were saying before, the finger length, that isn't the determinant of the-

   20. RDRobin Dunbar16:02

       No.

   21. CWChris Williamson16:02

       ... dating preference. That is simply a manifestation of testosterone levels.

   22. RDRobin Dunbar16:05

       Yeah, yeah.

   23. CWChris Williamson16:05

       Testosterone is-

   24. RDRobin Dunbar16:07

       Yeah, yeah.

   25. CWChris Williamson16:07

       So you're saying shorter index finger, more testosterone, it would appear.

   26. RDRobin Dunbar16:11

       Yeah, yeah.

   27. CWChris Williamson16:11

       More testosterone also correlated with shorter, monogamous partnerships?

   28. RDRobin Dunbar16:18

       Um, normally it would be, uh, either totally promiscuous mating systems or mating systems in which males compete with each other for, to monopolize groups of females. So, um, what's sometimes known as a harem-based, um, social system where you have one male se- a- and a number of females and their offspring. So species like gibbons, which are obligately monogamous, very occasionally they might have two, maybe even three females, e- exceptionally, in their little group, uh, but, you know, 98% of gibbon groups in the wild are strictly monogamous, and the pair stays together for, for, effectively for life.

   29. CWChris Williamson17:00

       Very long index fingers.

   30. RDRobin Dunbar17:02

       Um, no, no, they're very equal, right, uh, uh, and, and if you look at monogamous specie- sorry, polygamous species of primates, they then tend to have both, both sexes will have index fingers which are shorter than, uh, the ring finger. But the more promiscuous sex will have relatively shorter, um, index finger, uh, compared to the female. So the, the males who tend to be the more promiscuous sex will, will, even in, um, promiscuous species, will have, uh, sh- a, a, a, a more deviant, um, uh, finger ratio than the females will.
5. 19:08 – 25:38

   How Love is Adaptive

   1. CWChris Williamson19:08

      love itself. Uh, I, I'm s- I'm still not sure about how love is adaptive. Like, is it just-

   2. RDRobin Dunbar19:14

      Yeah.

   3. CWChris Williamson19:14

      ... ratcheted up attachment? It, it seems odd that we've evolved to feel something that's so weird-

   4. RDRobin Dunbar19:21

      Yeah.

   5. CWChris Williamson19:21

      ... and has so many downsides.

   6. RDRobin Dunbar19:23

      Well, this is where it all gets a bit murky, because it's not really obvious why humans should have these kind of pair bonded s- if you like to 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, uh, arrangements imposed on us. Because if you look at the 8,000 or so societies around the world, that's, uh, there are about 8,000 languages, and each language a different society, um, the vast majority are polygamous, and, um, you know, sort of a few men at the top.

   7. CWChris Williamson20:06

      Right now?

   8. RDRobin Dunbar20:07

      Yes. Well, even now, yes. Uh, ex- unless they've been Christianized. The point is, the societies that, um, aren't polygamous, that pursue a monogamous, uh, family structure are either hunter-gatherers, and so the differences between males aren't very great for the females to choose between. Doesn't, you know, there's, one can maybe hunt a bit better than another, but you know, uh, by and large, the differences are quite minimal. Or they're primarily being subjected to Christianization, which has imposed, um, uh, strict monogamy or attempted to impose strict monogamy. Um, if you look at, uh, uh, uh, at, well, and 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, think of some of the Mormon breakaway cults, and, and the original Mormons, uh, first started it, um, are still polygamists and, and operate on-

   9. CWChris Williamson21:11

      Blending the two.

   10. RDRobin Dunbar21:12

       Well, yes. Uh, (laughs) and, uh, the prob- the issue though is, or what seems to drive polygamy in, um, uh, human societies is when you've got massive wealth differentials. And this is why you get the King Solomon's type of, uh, um, uh, you know, or the great khans or, you know, they, I mean, th- there's this extraordinary, uh, statistic from the genetics which tells us that 1% of all the males alive today are the descendants of Genghis Khan or his brothers.

   11. CWChris Williamson21:47

       (laughs)

   12. RDRobin Dunbar21:48

       (laughs) And within the Mon- area of the Mongol Empire that he and his brothers, as generals, conquer, it's 7% of all living males are their descendants. You know, well, and 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, uh, harems, and that was the end of that. Uh, um, you know, 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, uh, what is it? 600, 700 years later.

   13. CWChris Williamson22:27

       It does seem strange that we've got the, if, if, if we're leaning towards, uh, polygamy as soon as we have the surplus resources to be able to afford a stratified hierarchy of men, and men to be able-

   14. RDRobin Dunbar22:39

       Yep.

   15. CWChris Williamson22:39

       ... to support many women and stuff.

   16. RDRobin Dunbar22:40

       Yeah.

   17. CWChris Williamson22:41

       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?

   18. RDRobin Dunbar22:52

       Yes. Um, uh, uh, that's true. But, um, and, and it's just kind of, um, worth pointing out, uh, first though, that, um, these polygamous societies, uh, are all ones with very, very, um, widespread of wealth. They've got very, very rich people and very, very poor people, which, and the rich people, the rich males become attractive to the women because of what they have on- 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, and no longer hunter ing- hunters and gatherers, is that the better off you are, the more likely your children will survive. You know, we know that from our societies here, in, you know, in modern Britain, it's s- you know, absurdly still the, still, still the same. If you come from the, you know, the poor end of society, your children are much more likely to get ill and much more likely to die. Um, so the issu- the issue, the trade-off to, uh, uh, kind of women all round 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, of, let's say, the land for you to grow crops on, um, uh, than be, you know, the first wife of a very poor man? And the interesting thing about, um, 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, t-Everybody wants to, uh, marry Mr. Darcy, but unfortunately (laughs) there's only one of him and 500 of you. So there's, uh, you know, th- what do the rest of you do? Well, as, as, um, uh, Jane Austen, with (laughs) her acute observation of the foibles of humans, uh, ob- observes is you hang on and you hang on, you hang on hoping to catch Mr. Darcy or one of the other rich landowners. Until you, the point you get to is the point of no return, where you go, "If I don't marry soon, I'm gonna be too old to have children," is 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. (laughs) So it's-

   19. CWChris Williamson25:35

       Yeah, so this is-

   20. RDRobin Dunbar25:36

       ... completely mad.

   21. CWChris Williamson25:37

       ... this is what you were talking

6. 25:38 – 36:18

   Love in Arranged Marriages

   1. CWChris Williamson25:38

      about kind of earlier on to do with the, uh, arranged marriages.

   2. RDRobin Dunbar25:42

      Mm-hmm.

   3. CWChris Williamson25:42

      I guess, that, well two things maybe are happening here. First is that subconsciously a woman's programming is, um, reacting to her ecology and her biological age-

   4. RDRobin Dunbar25:53

      Yeah.

   5. CWChris Williamson25:53

      ... and kind of this ticking time clock, to adjust her attraction levels based on, um, basically scarcity. And another element is, it would seem like closeness, physical closeness and familiarity can breed love.

   6. RDRobin Dunbar26:10

      Yes.

   7. CWChris Williamson26:10

      That's what it seems comes from the Indian arranged marriages. Like, you literally do not-

   8. RDRobin Dunbar26:15

      Yes.

   9. CWChris Williamson26:15

      ... 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, uh, 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.

   10. RDRobin Dunbar26:33

       Yes, yes. Yeah. I'm, I'm, I'm absolutely sure that's the case. Um, but the (laughs) uh, the issue then is, why, uh, you have ... You know, you, what you have, if you like, is the generic system for humans seems to be a f- a form of polygamy. That's the def- almost the default. Um, uh, why would you have a kind of, this kind of romantic component to it? This, this very strong pair bond? Because you get that in polygamous marriages, you know, that's what happens, um, when, when a, a new wife is taken on, you know. Um, it's not because, or sometimes it's because the, the, the, the first wife who is always becomes the chief wife says, "You're boring. Go and find another little one (laughs) to play with." Um, uh, I mean, literally that, that, you know, (laughs) uh, is the kind of thing that happens. Or, um, the, the husband actually falls in love with somebody else and wants to bring, bring this new wife, younger, always, always younger into, um, the household. And then it's a trade-off for the first wife or if this, this, this is the third wife or the first two wives as to whether they're happy with that arrangement or whether they just shrug their shoulders and go, "Well, we can live our lives quite happily without, uh, uh, uh, uh, h- having to be bothered by (laughs) the, the, the husband," as it were. Um, so, uh, it, it's still a mystery in that sense. So, the, 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 bi-parental care." Human babies are born absolutely premature by a whole year, um, that's why they're all kind of floppy and useless and, you know, don't even smile at you, (laughs) never mind any, be, you know, behave in a, an engagingly human way. You need something, uh, to, to, to sort of persuade you to keep investing in it until it's, uh, ha- completed its growth, that all other monk- monkey sapes do before birth, um, a- and starts to, if you like, become more seriously human. And it, that is so taxing, uh, for the mother that having somebody else around, why not the male, uh, to help out is, um, absolutely necessary. And you kind of go, "Well, that sounds awfully like American culture (laughs) to me in our real life." Uh, um, you know, where in the world does that actually happen? And the answer's, well, you know, sometimes in hunter-gatherer societies, you know, the men dandle babies on their knees and do things like that just as all men everywhere do. Um, change the odd nappy here and there, but they're not really that good at, um, helping out, you know. They're much better when, when, when the kids are old enough to, you know, fire a bow and arrow and learn how to do these kind of, uh, useful tasks. So I deeply suspect, uh, the amount of paternal care that humans give, despite desperate efforts to, uh, claim that it's, you know, part of our, uh, nature, uh, simply isn't the reason at all. Um, uh, and, and, 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's, is the grandmother and the sisters, and maybe your female best friend. That these are the ones that really make e- the, the business of particularly those early years, um, uh, uh, possible, if you like, less trouble-free than they might be, uh, do on your own. And, and, you know, sort of, yes, males are useful, um, uh, if they're...... own land that you can, you can farm and produce, you know, lots of crops to feed your children on and all those kind of things. And we know that's important. We know from, um, historical demography data, for example, um, from Europe, that in, in the ei- 18th and 19th centuries that women whose husbands were landed peasantries, so they only had a few acres, you know, they weren't the nobility, they weren't even middle class. They were peasants, you know, a bit like croft- crofters, you might say, in, in Scotland. You know, they've got five acres of land or something like that and they can, they can grow a few... The more land, uh, the husband had, the better the survival chances of, of the wife's children were. And of course, you know, for landless peasants who were day laborers, that the only way they could earn a living was to hire themselves out by the day to, 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, uh, if the, 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, we even now, you know, still have to cope with. Um, so (sighs) you know, yes, once you have agriculture, uh, once you have wealth, uh, accumulating, then, then the males can contribute indirectly, but that comes late, you know? That doesn't happen until 8,000 years ago with the Neolithic agricultural revolution. Prior to that, for several million years, our lineage, um, you know, were just hunter-gatherers. So those kind of issues don't necessarily, um, come, uh, work out. And, you know, typically anyway, you might say, well, maybe, um, a, 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 (laughs) instead of, you know, a chicken (laughs) , uh, always in those societies, those big, um, prey, uh, that are hunted are shared with the whole camp. It's only small things, um, that, that you eat within the family of the hunter on their own. So, you know, it seems to me there really isn't all that much evidence to support the claim that, uh, this romantic relationship is there for, um, uh, biparental care as such, as the technical term is. And the, the only obvious answer, uh, seems to be, this is a hired gun problem, right? So what 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 gonna work terribly well if, if it, 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. Um, and the reason for saying that, um, goes to, um, the fact, recent evidence, um, that's only just been published, that for mammals in general, let's say all mammals from, you know, your humble, uh, local mouse and vole right the way through to humans, uh, the bigger the group, uh, you live in, the lower the fertility of the females. Now, 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, um, the lower the fertility. But what smart species, as you might call them, like lions, primates, uh, mongeese, that live in intensely bonded social, stable social groups and form coalitions, are able to do is shift that decline in fertility towards a bigger group size, so they can live in bigger groups for protection, mostly against predators.

   11. CWChris Williamson35:23

       The offset of the bigger-

   12. RDRobin Dunbar35:25

       Yeah.

   13. CWChris Williamson35:25

       ... group with extra protection-

   14. RDRobin Dunbar35:26

       Yeah.

   15. CWChris Williamson35:27

       ... is better than it would be-

   16. RDRobin Dunbar35:29

       Yep, yep, yep.

   17. CWChris Williamson35:29

       ... if you were able to have tons of kids.

   18. RDRobin Dunbar35:30

       But, but what happens is, you, you know, there's only so far you can push that, that effect, uh, over to allow you to live in bigger groups, because in the end, that, that, that declining fertility catches up with you. What you see in those species is a U- is an inverted U-shaped relationship between, uh, female fertility, average female fertility, and the size of the group, right? So if it's, the group's too small, females do rather badly. These species, indicating to 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 fertility start to overwhelm the positive effects. Now, the question is, what's or who is causing those effects? Well,

7. 36:18 – 48:00

   Female Primates During Maternity

   1. RDRobin Dunbar36:18

      for 40 years, I confess, I've been studying various, uh, mammals, uh, feral goats in particular, 'cause they go crazy, uh, in the mating season. On, in the belief that, and therefore looking for evidence and explanations for the fact that males going crazy during the rut, as red deer do and feral goats do and so on, many other antelope do, um, is so stressful for the females that it causes infertility.Right? So, you know, so the assumption is here it's, it's, it's the motor might gangs roaring around the village at midnight that's kind of making everybody jumpy and stressed. And that's what... And we know that psychological stress, uh, suppresses fertility. The menstrual, uh, endocrinology in mammals, and women are no different, is incredibly sensitive. Any lev- high levels of stress, and this is partly in order to ensure that you don't ha- have an, a, a, a, um, a menstrual cycle while you're lactating, right? So there's the... Because that would mean you're having to, to gestate and lactate for, uh, babies at the same time.

   2. CWChris Williamson37:35

      Oh, so there's an adaptive reason for why babies make you stressed?

   3. RDRobin Dunbar37:38

      Yes. Yes. Well, not make you stressed. The system is just designed so that baby suckling shuts down the menstrual c- cycle.

   4. CWChris Williamson37:44

      Right. I learned from, I think it was Christian Jarrett, personality psychologist, 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.

   5. RDRobin Dunbar38:01

      Yes. Yes. Well, this is, this is exactly what's driving the thing, because when we looked at the data from primates, it turns out that it's nothing to do with males at all. (laughs) Sometimes males can be quite useful. Um, but what's driving it is, 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 on the Underground, you know?

   6. CWChris Williamson38:34

      Right. 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 basically be, be unlimited. You still have a limit on the top.

   7. RDRobin Dunbar38:54

      Yes. Yes.

   8. CWChris Williamson38:55

      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...

   9. RDRobin Dunbar39:04

      Yeah. Yeah. Yeah.

   10. CWChris Williamson39:04

       That's fascinating.

   11. RDRobin Dunbar39:06

       That's right. And the prom- 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, in, in some of the mong- social monkeys, for example. The, if, if you... The further you push group size or the number of females in the group, uh, uh, is cor- the correct thing, um, the bigger the effect on everybody. So even though the top-ranking female is still pumping babies out, the other nine or 10 are being pushed so low that the group actually can't replace itself, right?

   12. CWChris Williamson39:45

       Yes.

   13. RDRobin Dunbar39:45

       Um, and this is what seems to, uh, cause or perhaps causes groups to split, because it's the females kind of, uh, wanting out from a context where they're just being pressured. I mean, you know, we, we've known about these effects for a very long time. It's been known in, uh, uh, generally that stress, um, affects fertility in women in, in humans. There's the classic work that was done on the, uh, marmoset monkeys, the callitrichids, uh, from South America, that shows that, um, if a, if a, a daughter stays in the group, she doesn't even go through puberty because she's being harassed so much by her mother, right? Uh, take the mother out or put the female with, uh, the subadult 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, how fine-tuned this mechanism is.

   14. CWChris Williamson40:47

       It's like plants. It's the way that plants respond to their local ecology.

   15. RDRobin Dunbar40:52

       This, it's true, yes. Yeah.

   16. CWChris Williamson40:54

       It's crazy.

   17. RDRobin Dunbar40:54

       Well, you know, you know, species, species that have to be able to combat varying circumstances, whether it's, you know, your local ecology as a environment as a plant, or the vagaries of, uh, the world in ge- in general, if you're a, you know, complicated mammal like a primate, you know, flexibility of that kind is the key to its success.

   18. CWChris Williamson41:18

       So-

   19. RDRobin Dunbar41:19

       And primates are particularly so. 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 gr- um, gorillas, the great apes of Africa, so sometime around about seven million years ago, give or take a bit, um, they're pushing out eventually. Actually during the australopithecine phase, they were kind of okay. They were really operating in a kind of cheap chimpanzee type of environment, a rather impoverished chimpanzee environment, but, you know, they, they don't show any signs of, uh, increase in group size. But once you get the genus Homo appearing, sort of humans, if you like, proper, two million years ago, so our lineage really taking off, what's, what's that, what driven, what's driving that is a move, or what that's associated with, is a move out into a much more nomadic lifestyle outside the forests, uh, in less-protected environments. And at that point, you see evidence in terms of brain size for incr- dramatic increase in 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, it's, uh, every time they, you know, you get a new lineage incr- that's sort of increasing group size because it's occupying more predator-risky habitats, macaques, baboons, ground-dwelling species like that, um, uh, they're having to solve this fertility problem. And the way they're doing it, predominantly, is, uh, through female-female coalitions. They form a, a within the group close bond with a, um, uh, a b- a best grooming partner.

   20. CWChris Williamson43:23

       Oh.

   21. RDRobin Dunbar43:23

       And the two of you act as a buffer. And it-

   22. CWChris Williamson43:25

       So you end up, you end up with the benefits of a large overall tribe-

   23. RDRobin Dunbar43:29

       Correct.

   24. CWChris Williamson43:30

       ... and you ameliorate the effects of the infertility by having-

   25. RDRobin Dunbar43:33

       Yeah.

   26. CWChris Williamson43:33

       ... a small flat hierarchy, little, uh-

   27. RDRobin Dunbar43:36

       Yeah.

   28. CWChris Williamson43:36

       ... microcosm within it. That's-

   29. RDRobin Dunbar43:38

       Yeah.

   30. CWChris Williamson43:38

       So are we (clears throat) , are you saying that women, females, ancestrally, and maybe even today, need to take care of their status, o- o- of how statusful they are and how they're feeling in terms of respect and, uh, pressure?
8. 48:00 – 52:17

   The Show-off Hypothesis

   1. CWChris Williamson48:00

      argument that the, this reliance on... is it alloparenting, I think, where you have-

   2. RDRobin Dunbar48:05

      Mm-hmm. Well-

   3. CWChris Williamson48:06

      ... uh, it's sort of distributed between women-

   4. RDRobin Dunbar48:08

      Yeah.

   5. CWChris Williamson48:08

      ... multiple women looking after multiple children that-

   6. RDRobin Dunbar48:10

      Yeah.

   7. CWChris Williamson48:10

      ... not necessarily that... If it wasn't for the bodyguard issue or the hired gun, uh, 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, uh, menopause, you do end up having a surplus of women to be able to look after children.

   8. RDRobin Dunbar48:31

      Yep.

   9. CWChris Williamson48:31

      It's difficult to do that.

   10. RDRobin Dunbar48:33

       Yep.

   11. CWChris Williamson48:33

       But it, I, I can't remember whether it was in your book or, or somewhere else that I read that potentially the hunting part of hunter-gatherers for men was more about judging male reproductive fitness-

   12. RDRobin Dunbar48:45

       Yes.

   13. CWChris Williamson48:45

       ... of whether he's a good hunter-

   14. RDRobin Dunbar48:47

       Yes.

   15. CWChris Williamson48:47

       ... more so than the nutrition that he derived. If that's true, that is one of the wildest things I've ever heard.

   16. RDRobin Dunbar48:55

       (laughs) No, this is (laughs) ... This appears to be absolutely so, that if you look at the economic returns of hunting-Hunt- hunting, males like to go hunting big dangerous animals in all these cultures, right? Um, the energetic returns on hunting big, um, dangerous animals are not that good. Not least because (laughs) they're just dangerous to hunt. And you have every chance of, uh, not coming home yourself. Right? You actually do better, energetically, to just shoot rabbits. Um, but there's no demonstration of skills. So if you look at male, um, courtship strategies, if you like, it's all about demonstrating how good I am. Uh, and, uh, by good, I mean how good my genes are. So if, if, if all the kinds of things that young males do, racing each other, climbing stupidly high cliffs for no other purpose than to say, "I've done it." (laughs) Uh, playing vigorously brutal games (laughs) 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, right? And the result is teenage males have very high mortality rates by comparison with teenage girls, because they take so many more risks. I mean, we've actually done, (laughs) done a study on this at a crossing in the middle of Liverpool. Watching, uh, when people cross against the lights. And, and what seems to happen is, so we 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, right? This is just advertising. Um, and, you know, it really is a case of chicken, because you, you know, 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 in- into, to hunting. There's the show-off, uh, explanation, hypothesis for, for hunting large, large...

   17. CWChris Williamson51:41

       That's what it's called, the show-off?

   18. RDRobin Dunbar51:42

       Show-off hypothesis.

   19. CWChris Williamson51:43

       Wow.

   20. RDRobin Dunbar51:44

       Yeah.

   21. CWChris Williamson51:44

       I mean, that, that is absolutely spectacular.

   22. RDRobin Dunbar51:48

       Yeah.

   23. CWChris Williamson51:48

       To think that it, it might not be a utilitarian, "I go out," like, "Robin go, Robin stab, Robin bring back."

   24. RDRobin Dunbar51:57

       (laughs)

   25. CWChris Williamson51:57

       It's not, it's not about that. It's about, "Look, Robin competent."

   26. RDRobin Dunbar52:01

       Yes.

   27. CWChris Williamson52:01

       "Date with Robin." Yes.

   28. RDRobin Dunbar52:03

       "Ro- Robin got very good genes."

   29. CWChris Williamson52:05

       Yeah, yeah, yeah.

   30. RDRobin Dunbar52:05

       "Build genes, build very good body." Yeah.
9. 52:17 – 1:06:08

   What is Commitment?

   1. CWChris Williamson52:17

      what, what is commitment in your, uh, mind then? Is it a hard-to-fake signal of authenticity that sort of encourages trust?

   2. RDRobin Dunbar52:27

      Y- ye- I, basically, yes. Uh, I, I think that's a lot of ... I mean, the problem is this is a two-way game. This is not a game played by one sex and the other sex just sort of sits there and does nothing. Um, uh, there is a caveat to that. And, and that, and I'll just detour for a moment, uh, because it does kind of sum up the asymmetry of, of this. So we, we were looking at, um, a huge national telephone database. So this is all the phone calls made on one provider in a very large European country. It's 20% of the entire country. So we're talking about, um, uh, tens of millions (laughs) of subscribers, uh, and something like six billion phone calls over the course of a year. Right? Now, we were looking at the person they called most, each person called most. And what you see is, um, looking across the age span, so as, as is always the case, we don't know what happened below 18 because that, that becomes minor- minors, and is a whole 'nother ethics issue, so nobody ever bothers about them. (laughs) 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 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, uh, when the guy comes around the corner, all these kind of things, until eventually even the most stupid male goes, "Oh. Goodness me." (laughs) "She- interesting." Right?

   3. CWChris Williamson54:28

      Ah. Interesting. But you...

   4. RDRobin Dunbar54:30

      Uh...

   5. CWChris Williamson54:30

      Doesn't this run against the...

   6. RDRobin Dunbar54:32

      But the problem is...

   7. CWChris Williamson54:32

      ...the, the over-perception and under-perception bias?

   8. RDRobin Dunbar54:37

      In this context, meaning? (laughs)

   9. CWChris Williamson54:39

      The fact that...

   10. RDRobin Dunbar54:39

       This is just their phone calls.

   11. CWChris Williamson54:41

       I suppose so, but men, men are... Or at least David Buss 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...

   12. RDRobin Dunbar54:49

       Yeah. Yeah.

   13. CWChris Williamson54:49

       ...attraction from men.

   14. RDRobin Dunbar54:50

       Yes, yes.

   15. CWChris Williamson54:50

       You would have thought that like, how, how high do you need to wave the flag?

   16. RDRobin Dunbar54:53

       Yeah.

   17. CWChris Williamson54:53

       Men should've already been...

   18. RDRobin Dunbar54:55

       Yes. But, but, uh, you know, uh, that's absolutely, appears to be absolutely true. But, m- m- men don't pursue that for very long, I think is the answer. They think, "Oh, you know, she's showing an interest in me," and then they go, "Oh, no, she's not actually." (laughs) ... uh, because the women are being very choosy about their responses to the males. They make it very clear, "Sorry, you know, go away. Don't ring me. (laughs) Don't w-" But the one they want, they will keep phoning. And, and, 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. Um, so this is a late marrying pop- population. Um, they, uh, average age of marriage is about 29 in that particular population at that particular time. Um, (clears throat) so they're, they're really, they're, they're, um, got this lead in, as it were, uh, in which the girls start very, very, very early, focusing on this one male. The boys eventually, halfway through, go, "All right," and then they get married. And then about 20 years later, almost exactly, suddenly, uh, 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 he's h- So the female carries on phoning and phoning and phoning the same person, but the male only lasts about seven years, you know, uh, with her in pole position. He then gets, i- if you like, he gets bored and he starts phoning other people. Um, uh, and, and, and what this looks like is very intense female choice going on. They're the ones that really decide. Um, you know, okay, you can kind of force them to marry you in some way or another, socially or otherwise, um, but you, it's a, it's a bad deal if you do that (laughs) because you're gonna have a very, uh, grumpy wife to put up with (laughs) who didn't want to be there, and probably isn't gonna stay very long. Uh, if you, if you respond to the natural rhythm of the thing, um, uh, uh, then, and let them choose, then you're into a good deal because you've got, you know, real focus and lock on. Um, but it seems the guys just drift away, uh, in their sort of social world, as it were, much, much earlier than, than the women do. Um, it's just so conspicuous, and you see it in the phone calling data. (clears throat)

   19. CWChris Williamson57:34

       What's the lesson that you take away from that?

   20. RDRobin Dunbar57:36

       Oh, well, uh, uh, one le- (laughs) level is, the choice is being made by the women, and it will work better if you just leave them to it. (laughs) Um, uh, the difficulty of course is, is back to Jane Austen. She was such a good observer of human, human behavior. You know, people are being left out. You know, Mr. Darcy is getting all the girls, and you know, the curate is getting none, except the desperate. Um, and you know, because Mr. Darcy is getting such a lot of attention, there are a whole bunch of guys who aren't getting any, any, uh, um, wives at all, which is effectively what happens in, in polygamous societies. So you have to have a way of managing them. And you can see all sorts of interesting strategies, um, through history and across cultures, in how that problem is managed, and the... One suggestion has been this explains why the Portuguese started their explorations in, in the 15th century, because they had reconquered Portugal from the Moors. Uh, they'd taken over all the Moorish estates. The nobility that were created in, in the aftermath of that, um, had enormous estates. They were able to, uh, divide their estates equally between at least their sons, and their daughters probably got a bit of a share too. Um, uh, uh, and, you know, everybody was happy because they'd got a decent amount of land. But there came a point, all over Europe this happened in fact, um, where estates started to get carved up into 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, um, they switched to primogeniture, oldest son inherits everything. So before that, all sons had inherited equally. Um, they switched to primogeniture, that meant the oldest son got the lot. The youngest sons kind of looked very grumpy, started to be a nuisance, and basically they were riding around, them in motorcycle gangs, through the villages playing mayhem and beating the peasantry up and all these (laughs) kind of things that, that people will insist on doing. Um, (clears throat) so some, some bright spark said, "Listen boys, you know, why don't you... Here's a boat, why don't you go exploring?" And what you find is that, A, it led to this huge, uh, exploration and, and conquest of, of, you know, the New World and, and, uh, the East. Um, and y- what you find is the old, oldest-born son dies in Portugal. The second and the third-born son die in the empire, Morocco or somewhere else (laughs) . They just get them out of the system, "Go and make your own way."

   21. CWChris Williamson1:00:22

       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...

   22. RDRobin Dunbar1:00:38

       Yes. Yes.

   23. CWChris Williamson1:00:38

       ... find their own little kingdom that they can go make somewhere. So you can control single disgruntled nuisance-causing men-

   24. RDRobin Dunbar1:00:48

       Yeah.

   25. CWChris Williamson1:00:48

       ... by using the thing that you do have a surplus of, which is resources and money.

   26. RDRobin Dunbar1:00:53

       Yeah, but you don't necessarily need money. I mean, you just say, "Go." You know, 'cause this is how the Venetians solved the problem. They, they never had this problem, right? They, they maintained, uh, equal division of, of the family wealth between all the sons for, you know, for centuries, because they were traders, right?The more sons you have, the more trading you can do. (laughs) The problem with land is, it's a fixed commodity.

   27. CWChris Williamson1:01:18

       I understand.

   28. RDRobin Dunbar1:01:18

       And you see this very nicely illustrated in the Tibetans. Uh, so the Tr- traditionally, the Tibetans are one of the few societies that practice polyandry. They have e- uh, 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, uh, and not much of it at that. Um, and every time you divide the family estate up, uh, between all the sons, you know, it very quickly (laughs) gets down to one field apiece, and that's not enough to keep anybody going. So their solution is to marry all the brothers to one girl from another family because, uh, and the strategy works because the brothers are different ages. So, you know, w- 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, (clears throat) uh, they kind of operate what's effectively a form of serial monogamy. Because by the time the next brother gets old enough to go, "Oh, it's a girl-"

   29. CWChris Williamson1:02:34

       The first one's bored.

   30. RDRobin Dunbar1:02:35

       He's bored. (laughs)
10. 1:06:08 – 1:16:01

    The Use of Human Kissing

    1. CWChris Williamson1:06:08

       so one of the things that I thought was fascinating that you looked at was, uh, kissing, the use of human kissing. What's, what's the explanation for that?

    2. RDRobin Dunbar1:06:18

       Ah, it, it, it's one of those things, again, for which there has never been really a satisfactory explanation. Um, 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, it seems that pretty much it's as close to universal as anything, uh, might be in that, you know, large numbers of cultures actually do it. The key to it is you're exchanging information on your, essentially your immune system. So it, it's reckoned a, a, a five-minute kiss results in the transmission from one person to the other of tens of billions of, um, uh, uh, uh...... chemicals and, uh, you know, sort of bacteria and all sorts of other things that, that, that belong to your insides (laughs) , um, 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 once you enter the room and your eyes look across the room and you go, "Oh, that's a very attractive one. That, uh, feels, ticks all those kind of physical attraction boxes. I, I should go and explore further." And you go closer and engage in conversation and, uh, so then you're picking up all sorts of cues about, you know, their back- cultural background, if you like, how they think, and psychological background in, in the conversation. And then if you're st- if you're still happy, at, at that point you kind of go through a, a point of reappraisal. "Do I like what I see or do I pull out now while I, I still can, or do I go to the next level?" You go to the next level, it's a bit more sort of physical, so you, you, you have a grapple and a dance. Um, and at this point you can, you can get a good sniff of the other person, uh, smell, uh, what they're ...

    3. CWChris Williamson1:08:29

       Is sniffing important in humans?

    4. RDRobin Dunbar1:08:31

       Very important, very important. Because a- again, the same genes that determine your smell are the ones that determine your, um, immune system. Right? And what you're looking for is somebody who has a different immune system. It seems that what, 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, is what's known as optimal inbreeding or optimal outbreeding, you know. The, the, you know, why would you waste the fact that history of mating, uh, in your ancestors have produced this perfect person (laughs) that is you? Why would you waste all that (laughs) by disbursing it, by marrying, uh, or mating with people who are, uh, not so perfect as you, right? So the answer is, you look for people who are as similar to you facially and all these kind of things, uh, look like you as much as possible, because that's indicative of the fact that you, uh, probably have a common ancestry. Um, and of course in village societies that would work really (laughs) well. It probably doesn't work so well for us because we don't actually meet people (laughs) that really look like us very often these days. But in village society, you know, you can tell, tell our village from that village. They just look different. (laughs) Um, uh, uh, uh, and that's not just how they c- comb their hair, physically. (laughs) Um-

    5. CWChris Williamson1:10:03

       Did I see that you said that men can actually smell when women are ovulating?

    6. RDRobin Dunbar1:10:07

       Yes. Yes. Um, so, so th- this is the point that ... Well, uh, we can come back to that. I was just-

    7. CWChris Williamson1:10:13

       Yes.

    8. RDRobin Dunbar1:10:13

       ... just finish the, the mate choice bit is that the one thing you aren't looking for somebody to be similar to you is in the immune system. Because what you want is your child to have as diverse a, uh, an immune system as possible. You d- the n- narrow it is, so inbreeding 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.

    9. CWChris Williamson1:10:40

       When you say immune system, what do you mean?

    10. RDRobin Dunbar1:10:42

        It, it ... The body's natural immune system. This is what produces all the white blood cells and stuff, that, that sort of attack and cannibalize-

    11. CWChris Williamson1:10:49

        Okay. And genetically-

    12. RDRobin Dunbar1:10:50

        ... and destroy viruses and ...

    13. CWChris Williamson1:10:51

        Genetically, people have a predisposition to be, what, robust against certain types of, uh, viruses and, and bacteria, but maybe not all of them, so the goal is to kind of spread the risk across?

    14. RDRobin Dunbar1:11:04

        Yes.

    15. CWChris Williamson1:11:04

        Okay. Okay.

    16. RDRobin Dunbar1:11:05

        Yes. Or, or it's, it's ... It not necessarily particular resistance, particularly of bacteria or what have you, but a, a very strong immune system which is ... 'Cause the immune system's very adaptive to what's thrown at it, right? It, it learns, uh, to recognize, uh, foreign bodies that have invaded you-

    17. CWChris Williamson1:11:26

        Ooh-

    18. RDRobin Dunbar1:11:26

        ... and, and find them

    19. CWChris Williamson1:11:26

        This isn't just genetic. This is something which is going to be influenced by if you were an adventurer or if you'd been away. If you-

    20. RDRobin Dunbar1:11:32

        No. No, it's, it's the g- it's the genetics of the immune system itself, this capacity for the wh- essentially the white blood cells, uh, to identify, and the natural killer cells, the NK cells, uh, to identify foreign bodies in your system and seek and destroy, as it were. And, uh, you know, what you ... I mean, there, there will be an element probably from different exposures in terms of lineages, uh, that have, you know, sort of 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, uh, s- smelling somebody is, as the sort of semi-distance cue, is the best way to find that out. And, and, you know, the famous cases are Eskimos and Maoris rubbing noses, and we all think they're rubbing noses. They're not. (laughs) What they do is they put their noses side by side and they sniff and take in a deep breath, and it's called, uh, I forget the term, uh, used, how it's translated, but essentially it's breathing in the spirit.

    21. CWChris Williamson1:12:41

        Is that the equivalent of the European air kiss on both cheeks?

    22. RDRobin Dunbar1:12:45

        Yes. Yes, exactly the same thing. (laughs)

    23. CWChris Williamson1:12:48

        (laughs) At first. At first.

    24. RDRobin Dunbar1:12:50

        And this is why people pick babies up and sniff them. If you've ever watched newborn babies and they're being sort of passed around, everybody goes ... Holds them up to-

    25. CWChris Williamson1:13:00

        Get a big whiff of the baby.

    26. RDRobin Dunbar1:13:02

        ... and pretends not to be sniffing. But they sniff. There isn't a question about it. (laughs) So, um, a- and, you know, we get a lot of cues from, uh, much more cues from smell than we really like to think. I mean, we're, we're actually quite good. I mean, mothers can tell ...... uh, their offspring from other people's offspring by their smell alone. Um, uh, the, and the, the, the, the big issue, uh, um, 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. You're, 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. If we were just covering it up, we'd just have one perfume and everybody, you know, like Old Spice aftershave (laughs) just gets loaded on. No, not, not, not with women. Uh, it's very carefully chosen to, uh, and that, this is kind of how they build up these perfumes is, you know, so they kind of match, uh, different, um, uh, smell characteristics, as it were. They're sniffer's extremely good at, at decomposing the smells in, in different perfect mixes, um, the, h- the, the people that do it for them. Um, 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 (laughs) to, to, to, to, to smell of, but, but it, it's actually, you know, really part and parcel of, of the, and that, you know, courtship strategy, and that's why it's be- be- been, you know, since time immemorial, um, women in particular have done that or used it. Not to say that men also don't, but it's much, much more important, uh, in, in the case of women. But your final... So you've had a good sniff while you're sort of grabbing the girl in, in a waltz or something like that (laughs) , or pretending to dance very close in, in, in the club. Um, but the final, uh, point really is, comes with kissing, because that actually is direct, uh, experience of, of, um, in saliva. Saliva is just full of, uh, um, you know, sort of immune system stuff as well as digestive stuff. So it's, it gives you a really, uh, clear, uh, message, as it were. It's the best you could do, but that's your final, 'cause that's invasive. That's obviously the final step in this. So courtship is like this series of steps starting way out with distance cues, which are largely visual, getting closer and closer and closer into, literally into taste at the end, so.

11. 1:16:01 – 1:24:01

    Optimal Rubbing Speed

    1. RDRobin Dunbar1:16:02

    2. CWChris Williamson1:16:02

       What do you think is going on with non-reproductive sex then if you're using contraception?

    3. RDRobin Dunbar1:16:10

       Uh, well, I mean, it's, it, you know, sex is designed for, for all animals, never mind humans, to be a pleasurable experience and therefore make you keep coming back and, and doing it. Um, 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. You know, no sensible primate would ever, you know, uh, uh, waste so much time (laughs) in sex, uh, just to conceive an offspring. A lot of it's very, very quick, three cycles in, uh, primarily, and, and, and the female will be pre- pregnant. It takes, seems to take much longer in humans, and the, the only explanation for that is simply to prolong the pleasurable components of sex to reinforce the pair bond, because what happens-

    4. CWChris Williamson1:17:08

       Oh.

    5. RDRobin Dunbar1:17:09

       ... right, in, it, it, you have to remember, it, it's all about 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, or an opioid technically, so it's rather similar effect to morphine. It makes you feel very relaxed and woozy and at peace with the world and, uh, you know, trusting of, um, uh, of whoever you're doing the activity with. And, and, and for primates that's done by social grooming. Heathen through the fur triggers endo- uh, the receptors in the skin which trigger the endorphin system in the brain, a specialized set of receptors. Now we still do that. That's why we go around hugging people and patting them on the shoulder, stroking their, uh, arms and things like that. Um, but a lot of what we do, uh, because we live in big groups, bigger groups than any primate would ever think of grooming with. (laughs) Uh, in other words, it's intimacy, you know, you don't do it with everybody, you only do it with the, with the close, close ones. But you will now want to have- bond up a group. Then a lot of the things that we, part of the social toolkit, so laughter, singing, dancing, eating socially together, feasting, telling emotional sob stories, all these things trigger the endorphin system and make you feel bonded to the people you're doing it with. So-

    6. CWChris Williamson1:18:31

       So are you saying that, are you, are you saying that the difficulty of human females to get pregnant, the fact that it does take, uh, many attempts, let's say, uh, in order for that to happen, and maybe concealed ovulation as well, or the fact that it, it happens without us being able to tell when a woman is like in-

    7. RDRobin Dunbar1:18:48

       Yes.

    8. CWChris Williamson1:18:48

       ... the equivalent of in heat?

    9. RDRobin Dunbar1:18:49

       Yes. Yes.

    10. CWChris Williamson1:18:51

        That is evolution making it purposefully more difficult or rarer to occur to encourage the man and the woman to have more sex-

    11. RDRobin Dunbar1:19:03

        Yes.

    12. CWChris Williamson1:19:03

        ... which is already reinforced through the pleasure response-

    13. RDRobin Dunbar1:19:06

        Right. Yep. Yes.

    14. CWChris Williamson1:19:07

        ... in order to increase the pair bond?

    15. RDRobin Dunbar1:19:09

        Yes. Yes. Because-

    16. CWChris Williamson1:19:10

        (laughs) That's so cool. That is so cool.

    17. RDRobin Dunbar1:19:12

        Because after all, as soon as, uh, the woman is pregnant, you know, it, it's, um-

    18. CWChris Williamson1:19:18

        Job's done.

    19. RDRobin Dunbar1:19:19

        Job is done. Well, you know, I mean, the, you know, okay, you know, early stages of pregnancy-... um, uh, uh, it, you can, you obviously can still have sex. But later on, you know, it starts to become-

    20. CWChris Williamson1:19:31

        So if every woman got-

    21. RDRobin Dunbar1:19:32

        ... mechanically tricky.

    22. CWChris Williamson1:19:32

        ... pregnant the first (laughs) mechanically tricky. If every woman got pregnant the first time that she had sex with a man-

    23. RDRobin Dunbar1:19:40

        Yeah.

    24. CWChris Williamson1:19:40

        ... it would be very unlikely for them to form the sort of robust pair bond that they-

    25. RDRobin Dunbar1:19:44

        Yeah. Yeah.

    26. CWChris Williamson1:19:44

        ... would need in order to be able to raise the child?

    27. RDRobin Dunbar1:19:45

        Yeah. Yeah.

    28. CWChris Williamson1:19:46

        That is, Robin, that is absolutely fascinating.

    29. RDRobin Dunbar1:19:48

        And it's because of the, the reason this is working is, is a, a twofold mechanism in this particular case, because the stimulation, uh, physical stimulation of the skin, um, all over the body, the hairy skin, uh, as opposed to the palms of the hands and the soles of the feet, um, 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 on what, head and all that, legs, uh, are full of these endorphin receptors or the system that sets the endorphins off in the brain. Um, and so the stimulation that's given during, uh, sex, all the massaging and, and so on and so forth, is triggering the endorphin system like crazy. Um, 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, oxytocin started life in fishes as a, a mechanism for maintaining water balance in the body so the body-

    30. CWChris Williamson1:21:00

        Makes complete sense. Makes complete sense to me.
12. 1:24:01 – 1:31:33

    Why We Love People After They Die

    1. RDRobin Dunbar1:25:27

       and this bears back to the earlier discussion we had about females' best friends. Uh, this best friend forever phenomenon, BFF phenomenon, which is very characteristic of women and very uncharacteristic of men, um, seems to be really important for women. It's- this goes back to your moral and emotional and physical support mechanism that, that they need when they're in, uh, moving from one society to another and, you know, everybody's related to the husband and you're on your own. Uh, you know, y- your support mechanism is another, uh, woman, girl, who's in the same boat as you. So you can, you can form an alliance. And then they're very important then in helping each other with, through the business of, of, uh, birth and child, early child rearing. Um, those friendships are very characteristic. They're nearly always, uh, women, very occasionally men, about 15% of women's best, best friends forever are actually a man, uh, which must cause all sorts of interesting dilemmas between... (laughs) Well, need not go into. But the great majority, 85%, almost all women have one, and, and the great majority of those are another woman. And it, 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. Men are useless for that kind of thing." Uh, I, you know, that's why, you know, I, I, I build these, these relationships. But I'm sure it's much more to do with the kind, forming these little coalitions to buffer yourself against the stresses of the rest of the group, and to provide childcare support. Um, and, and that kind of remains constant right the way through, uh, life. Um, and indeed your social networks, uh, are, are very, very gender biased. 70% of men's social networks, their friends and family are men, and 70% of women's are women, and that num- figure remains constant from the age of, uh, five to the age of 85. Doesn't bat an eyelid. Um, you just don't see that kind, same kind of emotional intensity in men's friendship. If you ask them, "Have you got a best friend, male friend?" They'll kind of go, "Oh, yeah, I 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, 'cause he's fed up with wherever you live, as you do, um, you know, you kind of shrug your shoulders and say, "Well, that's too bad. Um, I'll go and see if Steve's available." (laughs) It, men's friendships are much, much more club-like in that sense. So for women, those friend- their friendships are personalized and dyadic and very focused on the individual as an individual. Men's friendships are kind of more casual. Um, they may involve a lot of time, uh, doing stuff together, but they're very casual, um, and they're much more club-like. And it's the-

    2. CWChris Williamson1:28:44

       Why would that be, why would that be adaptive for each sex?

    3. RDRobin Dunbar1:28:49

       Well, I think, I think in the women's case, it's precisely because they're, typically they're moving between communities on marriage to, um, a, a, an environment where everybody in the group, the community is related to the husband.

    4. CWChris Williamson1:29:07

       Yes, because the woman was the thing that was passed around or given.

    5. RDRobin Dunbar1:29:09

       Yeah.

    6. CWChris Williamson1:29:09

       The woman was the one that was expected to move.

    7. RDRobin Dunbar1:29:11

       Yeah.

    8. CWChris Williamson1:29:11

       She needed a steady rock that would go with her.

    9. RDRobin Dunbar1:29:14

       Yeah.

    10. CWChris Williamson1:29:14

        Yeah.

    11. RDRobin Dunbar1:29:14

        Yeah. Well, she, she doesn't necessarily need to 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've got. 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, how they view the world (laughs) they live in and the support kind of elements that they need. Um, whereas I think the, the male issue is simply goes back to the fact every single hunter-gatherer and, well, you know, horticultural society, in fact, I suppose still in, uh, industrialized Western societies, the male's most important function, 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 are, are bonded as groups, and they, they form very intense, uh, friendships. But it's a friendship with a group. Uh, all the guys who are circumcised together will go, however they, you know, whatever the, um, uh, process of, of going from childhood to manhood is, it always involves pain, some form, and frightening experiences. You know, so they'll take them out into the jungle in the night and, and, and all the older men will creep around in the bushes and make howling noises and scare the wits out of these poor kids. But the result of that is they're 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, to those guys.

    12. CWChris Williamson1:31:02

        Is the reason for the male friendship being able to be swapped in and out to account for the fact that you're gonna have casualties then?

    13. RDRobin Dunbar1:31:09

        I guess so, yeah.

    14. CWChris Williamson1:31:10

        Yeah. Interesting.

    15. RDRobin Dunbar1:31:10

        That, that you, you don't get so attached to an individual that, uh, your, your mind-

    16. CWChris Williamson1:31:18

        You're in apathy while you're supposed to go hunt something.

    17. RDRobin Dunbar1:31:20

        ... drifts off the job.

    18. CWChris Williamson1:31:21

        Yeah.

    19. RDRobin Dunbar1:31:21

        You know?

    20. CWChris Williamson1:31:21

        Yeah, yeah, yeah, yeah. So one, one thing that I just thought about. Y- you mentioned male and female bonding during relationships, oxytocin and endorphins.I

13. 1:31:33 – 1:35:49

    Men’s Vasopressin Reactors

    1. CWChris Williamson1:31:33

       learned last year about vasopressin and the role-

    2. RDRobin Dunbar1:31:36

       Yeah.

    3. CWChris Williamson1:31:36

       ... that it has for men particularly.

    4. RDRobin Dunbar1:31:39

       I'm less convinced.

    5. CWChris Williamson1:31:40

       Oh, tell me, tell me more.

    6. RDRobin Dunbar1:31:43

       (laughs) Well, it was, uh, eh, yeah, vasopressin plays a very similar role, uh, to oxytocin in the sense that it was involved in water balance i- in some way originally. Um, it's certainly been bandied about as the male equivalent of oxytocin, certainly in the early literature when they were talking up oxytocin as the, uh, love hormone and the cure to, you know, the secrets of the universe. Um, of course, oxytocin is primarily, uh, present in, in females, we're talking about female mammals in general. Um, you know, so it was, the argument was, uh, you know, it, it, it's what creates mother-offspring bonding in mammals, so that they will invest, they, you know, they don't nurture and cuddle this wretched little squirming thing, you know, it's not gonna survive, you know, it's not built to survive on its own. So you have to have something that makes the female just kind of focus on, on, uh, being completely altruistic and, and, and, and, uh, nurturing this, this little thing until it's old enough to stand on its own two feet. And then they were left with the thing, well, you know, what happens in, um, uh, the case of males, uh, you know, you need something else if you're gonna have males in monogamous social systems, this is all done on voles, you know, the difference between polygamous and monogamous voles. So what, uh, partly the story was that, um, uh, oxytocin played a stronger role in monogamous, in males of mono- monogamous species of voles than was the case in pol- polygamist promiscuous ones. But then somebody lit onto vasopressin and there was some nice Swedish work on twins showing that, uh, males with high levels of, um, vasopressin were more reliable, essentially, in, uh, their romantic relationships. So males with the wrong allele, um, (clears throat) uh, for vasopressin tended to be here today and gone tomorrow, and, you know, they would sort of not vary, they would act first and think afterwards, let's say. Um, but it's not clear that, that it's really playing a very strong role. I mean, we've done a huge genetic study, um, and it was all done in Britain, so it might be different with other people, um, but it showed no signature at all for vasopressin in any kind, we looked at three different levels of sociality, so your, your social predisposition, your romantic, dyadic romantic relationships, and your embeddedness in, in the wider social network. And, you know, dopamine plays a very strong role, oxytocin plays a very specific role in the context of romantic relationships, and endorphins, again, play a very important role across the, across the board, um, but vasopressin, there was absolutely no signature at all, no difference. So wh- 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 blown out of the water, um, and the, the object lesson here is the vole studies because it was all based around the difference between monogamous voles and polygamous voles in terms of oxytocin essentially, oxytocin genes. Uh, except that when somebody did a study of... and th- that was a comparison of two vole species, when somebody did a comparison of the oxytocin genetics across all vole species, there was no correlation at all with monogamy versus promiscuity, and then somebody else point, discovered that actually you can explain the polygamy, uh, promis- promiscuity versus monogamy difference between the original two vole species, American vole species, on the basis of their endorphin genes anyways. (laughs)

Episode duration: 1:36:58