Robin Dunbar on Evolution

anyone who believes in indefinite growth on a physically finite planet is either mad or an economist we don't want to focus Politics on a notion that involves the rejection of principles around which a large majority of our fellow citizens or organize their lives we are not as endlessly manipulable and as predictable as you would think if you pick up the average human evolution book it's all about stones and Bone seems to me the really crucial thing that is the social and cognitive evolutionary history that underpins the stones and Bones so I'm going to sort of give you a little Glimpse uh partially of that and sort of put it in terms really of um why it is that that humans aren't just great a what really happened that that made that difference and if you like to think in cognitive terms and we're quite used to sort of seeing all this kind of fancy stuff that monkeys and apes are able to do kzy here in fact talking with her Handler there this is sort of nothing terribly exciting I don't think and you know it's the kind of thing you might expect of very smart animals but it leaves open the question of what is it exactly that's the difference between us and and let's say uh the other great apes the the other members of our immediate biological family and I will put it to you really and that's kind of my theme if you like that what it's really about is is what goes on in our minds what we can do in the virtual uh space of our minds and it comes down really to these two things at the top here essentially religion and storytelling that's the outcome that's how where where we finally arrive at and that part of that story is about these two activities which although not necessarily entirely unique to humans certainly uh as far as laughter is concerned nonetheless are used and exploited among humans in ways which other animals certainly don't do so at the end of the day we do these things and they don't the question is why and how did we get get there well a starting point really is this relationship here the social brain hypothesis as it's known uh an explanation for why primates have very large brains the argument is they live in uh very complex social systems if you plot something like social group size here as a measure of a very simple measure of social complexity against some measure of brain size here the relative size of the neocortex you get this General nice relationship but here the AP sitting out here the family to which we belong if we plug Us in so this is essentially a ratio of the neocortex to the rest of the brain the subcortical brain about 80% of our total brain is neocortex if you read up and plug us across you get this mystical number as I like to say dunbar's number so anyway the question is is that really true do we really go around in groups of that size the answer seems to be yes here's just some casual observations of different kinds I kind of like to point out the Doomsday Book this is the historians estimates nothing to do with me they did this a long time ago of the average Village size in in English and Welsh counties and county after County after County the average Village size uh from the Doomsday Book census is about 150 you're very very close to 150 and I I kind of like to uh uh remark on this one because they clearly did not know the theories they had no way to predict that that's what they should get but more more usefully here are Census Data from hunter gatherer societies mainly and if you census hunter gatherer societies like any good modern human or primate Society they're multi-level they have lots of layers of inclusivity as it were these are the typical size of bands these are the typical size of Clans or Regional groupings Mega bands and tribes and this layer of grouping very characteristically referred to very often as something like a clan uh has the average uh very very close to 250 there's obviously some variance around that if you try and ask people to list out all their uh friends and relations that are part of their social network and here's one example uh just asking people to list out all the recipients of their Christmas cards that's say all the people in the household again it comes out very close to 150 so if you like this is where we appeared from The ancestral uh most complex Apes as it were and here's where we ended up and and we can use this relationship to figure out what community sizes were at different stages through human evolution we can just plug in the one thing of course the pale anthropologists give us beyond all measure is cranial volumes we can figure out from CR volumes what their neocortex ratios are and plug those figures in here and read off how group size has changed through time not necessarily progressively it may have gone up may have gone down uh after all many species of uh homins went extinct but the point is we can make a very good prediction because these these relationships turn out to hold up extremely well in monkeys and apes generally in fact it turns out this is not just a a clump here but a series of grades which are actually very tightly bunched so the question is from our point of view however is how on Earth do did our ancestors manage as they pushed Community sizes up and up and up towards what they are now in modern humans how on Earth did they keep them coherent because the whole issue with primates is that they live in what is essentially an implicit social contract they essentially solving the problems of success survival and reproduction collectively and in order to do that you have to engage in effectively a tradeoff with everybody else to make sure everybody else gets their fair share and if you if you take more than your fair share the whole thing falls apart the whole social contract and effect falls apart so somehow you have to create this sense of community and bonding that allows you to do that monkeys and apes as I'll show you in a minute do this through grooming um uh but the the key is grooming is limited in the end in the amount of time you can do it for now in terms of how primates create their social relationships it's actually a two process mechanism part of it involves grooming here uh that's produces a massive release of endorphins in the brain dorphin are part of the pain control system uh but and they give you this kind of opiate like Li headedness and alls well with the world and you feel very warm towards those you're doing whatever with uh and that in a sense sets up a kind of psychopharmacological platform of which the second component which is the cognitive component can then be built and that's where the social brain bit comes in and what it's doing is essentially allowing you to build up relationships of reciprocity uh and obligation and trust and so on and and in doing so you create these large uh uh or by primate standards large uh social communities so I'm going to talk you through very quickly through each of those two two elements the the we'll start with the cognitive component the key to that probably we think is this kind of stuff it's known as mentalizing or uh mind reading the ability to understand what another individual is thinking and certainly from the point of view of human evolution this is crucial uh it it forms a naturally recursive hierarchy of embeddedness really known as the levels of intentionality from the philosoph of Mind Jack hears in first order intentionality he believes that something's the case about the world Jill hears in second order she believes that Jack believes that something is the case this is what's known as theory of Mind formal theory of mind which children acquire at age five pretty much uh but you adult humans can go keep going and in fact it turns out that the limit that normal adult humans do is about fifth order so this is sort of just the data from one of a series of studies where we've try to look at what the limits are natural limits are for adult humans uh you can probably forget the tale end really these are probably artifactual uh from the way we have to do these things which are as little vignettes and asking about what's going on in the in in these little stories but the the key is the fact that the the this this very strong mode at fifth order intentionality now if you ask people who've done this uh and you now know what their score is on these tasks if you ask them to list out their at least their inner Circles of of friendship you get this kind of picture uh and a very nice significant relationship that your click size your inner core social click correlates with your performance on these mentalizing tasks so it's it's really like playing mental juggling as it were the better you are on these tasks uh the more balls you can keep in the air at the same time the more friends you can manage to keep uh coherent as it were because obviously you don't do silly things like say things which are uh kind of uh upset them or inappropriate to the circumstances um there's a lot of scattering these data um inevitably perhaps but we know what some of it is some of it's us sex differences some of it's due to personality differences but the the key is that there is a nice significant relationship and we've repeated this with many data sets now uh and this is really a very robust effect now if you think about it what we've got here is some software we've got some Behavior some output uh number of friends you've got we've got some software here cognition the uh your performance on these mentalizing tasks uh and it made us wonder how these two then relate to the third element in the story which is the size of your brain and that took us off into looking at uh brain Imaging and we've now done a whole series of these and it turns out that both of these two variables correlate with the size of this part of your brain in particular that's the bit over the uh the eyes um uh so it's a sort of three-way correlation the bigger that bit is the better you are at mentalizing tasks and the better you are at mentalizing tasks the more friends you can handle and keep keep us a coherent unit and that seems to be the causal structure to that uh this is all part really of what's known as the theory of Mind circuit neural circuit in the brain which involves again these areas up here in the frontal lobe but also these areas on on the temporal lobe here so there's a sort of uh connection through there and again we pick that up uh it's the size of that those connected areas again correlates with the number of friends you have and how good you are at um mentalizing so what this does now is is essentially allow us to see both how you get this relationship between brain size and group size in effect but more importantly uh allows us to figure out what the mentalizing levels of different species of homins are at least uh uh uh coming up to to modern humans now the other side of the story and I'll back to that in a second the other side of the story is is the grooming component so these These are data from uh different species of monkeys and apes it's plotting the total amount of time daytime the percentage of daytime devoted to social activity against average group size for that species and uh in general there's a a nice linear relationship the bigger the group The more time you have spend socializing although it kind of tails off this is really under pressure from time budgets because at the end of the day all the rest of that time has to be devoted to uh feeding and foraging and and so on so so you've got this kind of limit impressed on it um what's interesting about this actually is that even though as group size increases it doesn't necessarily mean that when you have more social time you're grooming with more people what tends to happen is they actually groom with fewer individuals but devote more time to each of those in other words they're trying it seems to make their social relationships work much more effectively uh as living in bigger and bigger groups imposes more pressures on them just the commuter problem that you face of constant harassment and bumping up against other people and it's these close core uh grooming partners that protect you against that but what we're interested in is where humans fit on this so we know where humans sit we sit in our groups of 150 there if we just plug them up there what you get is some something in the order of about 45% of the day would have to be spent doing grooming if we were to bond our groups uh by that uh mechanism the same mechanism that all other primates use in fact we don't these are data from an average of seven uh studies of human time budgets from all over the world turns out that on average we spend about 20% of our total daytime in social activity social interaction so we're using the the same limiting amount of time as monkeys and apes do but somehow we must be using it more efficiently to bridge this enormous Gap and just to put this in the context of the fossils and how big that Gap is this is the predicted grooming time for individual populations of fossil hominins right the way back to Luci and her lot down here the aalines uh three million years or so ago so this is simply interpolating through a series of equations starting with cranial volumes uh figuring out what community size would be off the back of that and from the monkey and ape equation what grooming time would be required for that here's the 20% uh limit uh the styop theine sitting very nicely round it they're just jobbing Apes really nothing more but here we are up here and here's this long trajectory going up uh when the demand for grooming time is increasing steadily and putting their time budgets under incredible pressure because we know the aalines were already at the limit they had no uh spare capacity in their time budgets we we've modeled their time budgets and that's what on the basis of what other primates do that's what they tell us there's absolutely no spare capacity so if if these successive populations indeed species of our ancestors up to us are having to find this amount of time it's pushing them way above what time budgets they actually have and what we think happened was they introduced or we successively introduced these three steps to fill that Gap and we think they came in we now think they came in that these particular points here laughter uh with the appearance of early homo allowing that jump up that you see very dramatically here through the haby lines here up to homo gasta uh singing and dancing essentially uh with the appearance of archaic humans and finally the rituals of religion but very late and and we suggest that simply because religion in that sense that you have rituals requires language and we think language is extremely late probably not before 200,000 uh years ago the appearance of anatomically important humans and language as we know it may have been later still may have been as late as 100,00 years ago uh just at the point when finally anatomically modern human brains acquire their modern size and just before everybody starts dispersing all over the place within Africa and then Out of Africa the reason these three in particular seem to work in the way they do is they're all incredibly good releases of endorphins uh I'm not going to talk about these particularly at the moment uh but I'll show you some evidence at least for this we've been doing a lot of stuff on dancing and and essentially we get the same story but this is this is how we go about it uh we we're interested in in endorphin release endorphins are part of the pain control system but they don't cross cross the blood brain barrier so you can't measure them very easily directly uh without going to putting people to an awful lot of uh trouble and pain so what everybody does in the pain industry is they uses uh pain thresholds as a proxy for that so we take a pain uh threshold measure something like an oldfashioned um uh blood pressure monitor on your arm how long can you stand it uh you do an activity watch a video or do an activity might be dancing or singing or something and then retest for pain if there's an increase in pain threshold across here is because you have had endorphins uh released and so here's a summary of six different experiments we've done with laughter these they all involve an experimental group that watches a comedy standup comedy video so we have somebody like Michael McIntyre here and they always do it in groups of four uh because people don't laugh when they watch the stuff it's amazing you get people are 30 times more likely to laugh at the same video if they watch it in groups of four than if they watch it on their own it's an incredibly social thing laughter and then we want to have a control group which is completely neutral produces no laughter uh uh so what we found is the best one of the lot is golfing instruction videos you never get any laughter most of these are done in the lab except for this one I I really love this because we did it live at the Edinburgh Fringe Festival so this group were watching standup comedy shows and this lot of watching little playlets little drama LS non-humorous but as you can see in general all the groups in which were watching comedy laughed a lot pain threshold increases here's zero no change all the ones watching neutral videos no laughter pain threshold is either unchanged or is dropped uh is negative so and we we've shown the exactly the same thing with dancing uh and and in fact now singing we're just running it a an experiment on singing at the moment so here's the mechanisms that we seem to have come in sort of captured if you like to produce this effect but if we go back to where I started which is the two big things that differentiate between us and the at least the great apes in particular is our nearest and dearest name the world of the imagination storytelling and religion um uh essentially you can think about these as the product of mentalizing without these mentalizing skills you could not imagine this extraordinary World in of fiction in your mind as it were um and it turns out indeed we just finished the study on Shakespeare Shakespeare is absolutely extraordinary in his handling of the mentalizing demands on his audience and I'll show you what I mean in a minute um but the point is that the more complex your mentalizing ability the more complex this spiritual world or fictional World in your that's in your mind that you can create it's rather difficult got to to think through this in terms of religion it's blindingly obvious in terms of fiction so think about what's going on here with with the old Bill shaky uh thinking up one of his plays so we'll take orell as an everyday uh story of deception but we've got an audience here watching the main characters and what the audience is effectively doing is believing that Iago intends that orell believes that Des demoner is in love with somebody else well at this point I put it to you we have a jobbing airport novelist right this is a racy story but by the you can and you can have fun reading it on the plane but you Chuck it away it's not that interesting what makes the difference between Shakespeare and a jobbing uh uh airport novelist is this that the airport novelist can own because he or she is limited to five orders of intentionality as the norm uh they can only push the audience up to fourth order intentionality so you can only have three characters essentially on this story uh what Shakespeare does because he can go one level beyond that is bring in in effect bring in Casio into the story which makes the relationship between Casio and desona much much more threatening until desdemona's apparent love for Casio is reciprocated by Casio why should orell have cared you know he he needn't have it's not a big issue but the fact is he's made to believe that in fact they're an item at that point the audience is working at fifth order intentionality but to do that Shakespeare has to be able to go One Step Beyond to sixth order fewer than 20% of the population can do that so this is my pitch for why we can all enjoy a great story because we can be pushed to our limits uh and taxed if you like in mentalizing terms but very very few people can actually write a novel uh a good story because they have to be in this exceptional bracket but these are the core things really that have been hugely critical in allowing us to bond these very big groups because this is what all about shared knowledge shared worldview it's having the same perspective and that turns out to be fundamentally important just to to give you a sense of of of how this might have developed uh here's intentionality now measured estimated off brain size using our our equations for the for the various hominins here's the ear aalines anatomically modern humans up here all the early aalines are jumping along very nicely at second order intentionality just where the great apes are and then it takes off with the appearance of of uh uh early homo and Rises very sharply till we get up to us but the key thing is look where the Arches are and this is exactly where the neander tar sit as well as with the hdle bgs they're only at fourth order intentionality whatever they could do in terms of language and religion and storytelling the best they could do was a Jeffrey Archer Noel not a Shakespeare

Channel: RSA

Views: 13,052

Keywords: The RSA, Royal Society of Arts, RSA Events, Robin Dunbar, anthropology, human, behaviour, science, evolution

Id: 7HHejf9Q8Lg

Length: 22min 45sec (1365 seconds)

Published: Wed May 14 2014