How We Became Unique Animals | Lecture by geneticist Adam Rutherford

[Music] hello everyone it's my pleasure to warmly welcome everyone to this special event which is jointly sponsored by rapper rabid reflexive Radboud University and the Max Planck Institute for psycholinguistics here in Nijmegen my name is Simon Fisher and I'm one of the directors of the Max Planck Institute and I have the honor of introducing our distinguished guest speaker for this evening dr. Adam Rutherford in a time when scientific thinking and the virtues of expertise knowledge and objective evaluation are all coming under threat we need now more than ever talented scientific communicators who can reach out to the public to engage infuse inform and excite Adam Rutherford is one of the very best of these valued ambassadors of science with an impact that goes across diverse media including writing articles for newspapers and magazines presenting programs on radio and television giving lectures for a range of audiences authoring multiple critically acclaimed popular science books and acting a scientific adviser for major movies and music projects among others we greatly appreciate that Adam has been able to make time in his extremely busy schedule to come and talk to us tonight now Adam is himself a scientist he obtained a degree in evolutionary biology at UCL University College London during which time he carried out a project that involved feeding rotting sweet corn to a curious creature known as the stalk eyed fly he went on to complete a PhD in genetics at the Institute of Child Health studying the molecular basis of retina development and genetic forms of childhood blindness in humans and following this Adam was an editor at the journal Nature for more than a decade responsible for all their published audio video and podcasts Adams written extensively for journals and mainstream newspapers such as the Guardian on topics of science religion and film sometimes all three at once he's a seasoned broadcaster presenting BBC Radio 4's flagship science bro insidescience and co-hosting with with mathematician Hannah fry the curious cases of Rutherford and Frey highly recommended listening if you get a chance he's written and presented many other radio programs on inheritance of intelligence MMR and autism human evolution astronomy and art science and cinema scientific fraud and the list goes on his BBC two TV documentaries include the cell the gene code the beauty of anatomy and playing God now that's not all as a self-confessed movie geek adam has been scientific advisor for multiple projects his contributions contributions to cinema span an extraordinary range all the way from a cartoon for preschoolers The Cat in the Hat knows a lot about that through to the brad pitt zombie apocalypse action horror blockbuster world wars ed via Biophilia live a science influenced film from icelandic musician Bjork and most recently Adam was apparently responsible for teaching Natalie Portman the fundamentals of good molecular biology lab practice for her role as a kick-ass geneticist in the superb science fiction film annihilation but how does Adam keep himself busy I hear you ask by writing books of course eloquent witty accessible perspectives on some of the most fascinating questions of modern science his first book creation approached the mysteries of biology from opposite ends with one part folks focusing on the origin of life while the other part discussed synthetic biology providing a prequel and a sequel to our evolutionary story he followed this with a brief history of everyone who ever lived in which he argued that the DNA of your cells is an epic poem an incomparable sprawling unique meandering saga that captures the history of you as an individual and also Homo sapiens as a species his latest work the book of humans tackles a central paradox of what it means to be human providing a compendium of that which unequivocally fixes us as animals but simultaneously reveals how we are extraordinary and I won't say any more on that since this is a topic that Adam will cover today and we should avoid spoilers now before we move on I'd like to tell you more about the structure for this evening so first Adam Rutherford will give his talk which will last about 45 minutes then we're joined by expert discussant might h on our he philosopher and communication expert at our tears she's chaired lectures and discussions on many topics from current affairs and culture to religion science and film and after about 20 minutes of chat between our speaker and discussion there will be ample chance for you all to ask your own questions so all that remains for me to do is to thank Paul backer and colleagues a wrap out reflects for helping to arrange this and now I pass on to Adam Rutherford to tell us all about how we became unique animals thank you very much that was an extraordinarily generous and about 70 percent accuracy but biography of me just just to sort of balance out that wonderful introduction I I need to tell you why I'm standing here today because the last book I wrote the one the one before him weren't the one I'm going to talk about today which is called the book of humans the last book the book before that was called a brief history of everyone who ever lived and in fact in both this book and the last book I feature quite prominently a lot of the work of Professor Simon Fisher and we hadn't met even though our world had being very closely aligned academically due to his research in my interest more generally in in the field that he was working in linguistics and genetics and out of the blue about six months after a brief history was published I go this is email from Simon Fisher and it came into my own books I thought oh that's great because I've been writing about him we've never met and in that email he was extremely praiseworthy is extraordinarily generous and polite man and he pointed out 19 errors that I'd made about his work and if you want to know - the right way to address an author whilst simultaneously pointing out the stuff that they've got wrong the Simon's was a master Carson in productions and 18 months later I'm standing in front of you introduced by the man himself so that that book a brief history was about it was about using DNA using our genomes as a way to tell stories about our own evolution over the last million years or so and and it was predicated on the idea that we've begun to understand genetics so much with so much greater sophistication than at any time in the past but also because we've we've created the ability to extract DNA from people who've been dead for thousands or hundreds of thousands of years in some cases and allow that the combination of understanding genetics better and the fact that we've got genomes from dead people to to revisit our evolutionary and and history its itself and this this book is in a sense it's a sequel to that so I cover about a million years worth of human evolution it's focused on genetics there's very little genetics in this book but it's much more about our own cultural development now son said it is the sort of central question at stake is well what makes us human now I'm not going to talk about the whole book I'm just going to talk about some of the key ideas in in the book it's not a very long books about sixty thousand words tell your day and a half to read it and they're on sale outside so after the talk so some of the things they cover are things like tool use communication violence and there's a lot about sex and one of the ways I'm looking at humans is as someone said you know comparing us as an animal are we special what is different about us we as we remain animals so there is lots of weird animal sex in it I I didn't really want to spend a book talking about weird animal sex and just not that kind of writer I just happened to have written a book which has a lot of weird animal sex in it I will touch upon it in this lecture but it's a very different lecture when I really get into the details of how awful dolphins and otters actually are so this question what is it that makes us human so this is obviously a question that people have been asking for thousands of years and indeed entire careers are made on stating that something one one particular thing is the thing that makes us different from other animals entire careers are based on that that sort of notion that there were triggers that there were singular events which turned us from one beast into the the creature that we recognize today in all of my work in all of the things that some very generously described just a minute ago I have tried to avoid that's what I think is a trap because I I don't think time nor evolution or biology the complexities of our own journey it's really defined by those singular sorts of triggers there isn't one thing which makes us human and and or in all of my work I like to talk about and revel in the complexity of of biology and our evolutionary story so I like to avoid those very simple clear narratives that tell you what the answer to those types of questions ah there is a simple answer to the question of what makes us human and it is having two human parents and having a human genome but that's an incredibly uninteresting answer and it doesn't say anything about what is really interesting about being human which is the human condition why we are the way we are so there's a sort of central paradox of of being human we are animals and yet we are special animals we have exactly the same biology as every organism that's ever existed same DNA the same proteins the same metabolism we're on the same tree of life as every other organism that's ever existed and yet we can do stuff like this right in a way that no other animal can we've we've surpassed if you want a hierarchy almost every other creature on earth in all in so many capabilities so that's a that's the paradox that's the central question that I'm exploring though possibly not answering and in this book this is an idea that was described by Charles Darwin in 1871 in his second best book The Descent of Man in which in his typically beautiful prose he says with our godlike intellect penetrated into some movements of the solar system man using nineteenth-century language man still bears in our bodily frame the indelible stamp of our lowly origin you know there's the central conundrum now Darwin is is I think the most important human who's ever lived and he's a pretty good writer but it turns out that that exact same sentiment was expressed about 250 years earlier by a better writer than Darwin and that was Shakespeare so the soliloquy from Hamlet what a piece of work is a man in action how like an angel the apprehension how like a god the paragon of animals there was a point when I was writing this book that I wanted to call the book the paragon of animals and my editor told me that that was way too pretentious but he goes on in that soliloquy to say well what is this quintessence of dust and there is the central idea we are we are animals and yet we have godlike behaviors in action like a like an angel and and yet we are just matter like everything else now yeah it has been mentioned that I am a film nerd and I adore movies and I'd written a sentence in the last book towards the end of it where I was describing this sort of phenomena in a slightly different way and I wrote this sentence down and I when I sent the copy off to my editor she wrote back saying oh I liked that film quote you put in the final chapter and I was unaware of it so I wrote back saying what film quote and this was the quote so everyone is special which is another way of saying nobody is special what's that from there you go it's - from The Incredibles ten points to that person up there so in the first two pages of this book I quote Darwin Shakespeare and - so I'm personally very proud of anyway so the story here is about human evolution but but so much has changed in human evolution in the last 10 years due to the things I was mentioning earlier about ancient DNA that I'm just going to give you a quick recap so this is a version of the is my version of the Tree of Life for humans where we start 1 million years ago to the left and and this this is us today and downing in yellow at the bottom are Homo sapiens modern Homo sapiens asks we've divided geographically up into three regions Asians Europeans and Africans but we also know that there was a earlier out of Africa migration that happened 120 hundred forty thousand years ago we're Homo sapiens versions of us also had migrated Out of Africa and they know they went extinct and they leave no genetic trace to this day we also all know about the Neanderthals they're now divided into Eastern and Western Neanderthals they were a European species but the more we look and more we find them in sort of Central Asia at least so we divide them up like that and a few years ago you might remember in 2010 I think it was that a finger bone the distal tip of the little finger and a tooth that molar were found in a cave in Siberia a cave named after a Christian era mite who lived there whose name was Dennis and those two bones were but one bone one tooth had not enough to categorize a new species of human but because of our new ability to extract DNA from ancient remains the entire genome was extracted from this teenage girl as it was and it was not the same as Homo sapiens us and it was not the same as the anti tolls for whom we've got a genome a couple years earlier and so it hasn't been officially designated as a new species but it effectively is and we call those people the Denisovans of which there are less than five physical physical remains bones and teeth but we have their entire genome and indeed we see their entire genome in living people today now that's the simple picture but of course as I said I don't like these nice clean narratives because they're not accurate they're not an accurate description of human evolution so what we now know as a result of looking at the genetics looking the genomes of all of these humans over the last hundred thousand years or so is that well it goes like this the Western Neanderthals interbred with the people who'd become Eurasians we also know that the Western Neanderthals interbred width and a second occasion with people who were just Europeans in genetic genetics is which is effectively the study of sex and heritance we have lots of euphemisms so we refer to these as gene flow events so we also know that the eastern mountains had gene flow events with the archaic modern humans they're both now extinct and we know that the Denisovans had gene flow events with the Eastern Neanderthals and with the people who had become Asians there's this an over 18 lecture because I I was struggling to think of the right metaphor to describe this in the in the book and I well I stumbled upon a phrase that you might familiar be familiar with from a beat poet from the nineteen sixties in America I described this as a 1 million year now you might have noticed that there is a branch at the top there as well which I haven't mentioned yet so when we add up all the genomes and compare all the genomes of Homo sapiens with the old Homo sapiens archaic ones home in the and silences the Denisovans they don't quite square up and so we're aware of the presence of genetic material in modern humans that is none of the others none of the above and so we've actually got to the stage where we are aware of a gene flow events between a human that we don't know anything we don't know who they were we've got no idea who this human was that I mean a species of human they may be known to science but we don't know them we only know them in this case based on their genetics and I think that's a bit of science which is so incredible that it's almost magical there's a phantom species within our gene pool so that's that's the that's the sort of updated version of where we are with human evolution in terms of genetics and old bones now the interesting thing about this is that you know when we look at Soma sapiens the the date of the earliest Homo sapiens is now about 300,000 years ago and it's not in the east of Africa as it has been for a few decades now but it's actually in Morocco and a site called geobella root and the jevla Rhodes Homo sapiens were dated as being about 300,000 years ago two years ago so that was a big that was another big shift and it wasn't done using genetics it was done using traditional paleoanthropology the the key thing about this is that if you were to take any Homo sapiens from the last say two hundred thousand years or a quarter of a million years and you gave them a haircut and you tidied them up and put them in some nice clothes and sat them in this audience you would not be able to identify them right they physically are basically the same as all of us today and that's a quarter of a million it's a long time to be physically the same from the genetics there haven't been any major genetic transitions during that time either I mean I've definitely been regional adaptations and plenty of changes but nothing so significant that you wouldn't be able to reproduce quite happily with a man or woman there's a quarter of a million years old so we've been stable physically through time for a quarter of a million years and yet something massively significant did change within the last hundred thousand years and more specifically the last 50,000 years which is we started doing stuff like this right and in the archaeological record there's very little evidence of the ability to create culture and art works sculptures with such sophistication until 50 to 40,000 years ago this is the lion man of Hohenstein startled which is found in the 1930s in a cave in Germany and it's a 12-inch figure with seven strike marks down its arm it's carved out of a tusk and it is a man's body with a lion's head so it's an imagined being this is an incredibly abstract thought that has resulted in this in this sculpture so what this is showing is so many facets of our behavior which are what we recognized today so we think of this as the we call this behavioral modernity but basically the person who created that was fundamentally no different in terms of their cognition and their intellectual abilities than we are today it shows great skill great abstract forethought planning all those sorts of things and creativity things that we associate with with modern human behavior few years after that we have the first the earliest of a series of small statuettes which are collectively referred to as Venus's they're all female they're they often have exaggerated sexual characteristics and for that reason anthropologists over the years have speculated that they were fertility charms fertility amulets and there's been plenty of fairly pseudo scientific analysis of what the significance of these dolls is but the truth is I don't care if they may have been dolls they may have been toys they may have been fertility amulets they may have been pornography we don't know the important thing about the existence of these statues is that they again show behavioral Maternity this is the depiction of the female body it shows again enormous amounts of skill the ability to think abstractly 9,000 years ago and this is in also found in southern Germany and then by about twenty twenty five thousand years ago we have cave paintings in places like Lascaux in the South of France now this is all very Eurocentric so far because most of the research about human evolution has been centered around Europe for the last 150 years or so but that all changed a couple of years ago when there was the dating of artworks such as these so these are hand stencils where red ochre has been blown through hollowed out bones and created a stencils about 14 of these you know sort of large plates inside a cave and Sulawesi in Indonesia and that date still about 39,000 years ago as well so it's quite clear that behavioral modernity was simultaneously occurring well at least at two different locations at approximately the same time now this next slide is not in the book because it came out the week that the book was published which is what you know one of the unfortunate things about writing books is that they they have to exist for longer periods of time than the scientific literature remains accurate and in November last year the earliest piece of figurative art had moved from being the lion mane of whole inch town startled to a cave in Borneo where there's the depiction of this what we think is a Banting so a local cow as a horns up there and there's two legs there and they're States to a minimum of 40,000 years ago so again we have in multiple locations all around the world we have the emergence of behavioral modernity but that are thousands of miles apart is something had happened globally between a hundred thousand years ago and forty thousand years ago which meant that we were doing things like creating art now I said that it started off being Eurocentric and now we have to think about this as being a global phenomenon I've also entirely been speaking about Homo sapiens us and that changed last year as well because now the earliest figurative arts which was read ated in 2018 feb 2010 tabria and this is some art that's been known since the 1960s but it was read 8 as at beginning this year and it comes out at about sixty four thousand years ago the only people in Europe sixty four thousand years ago and not Homo sapiens there and many and silences right so the earliest depictions of creative processes that reflect behavioural modernity and not even in our own species are there in a they're in a another species of human in the and atolls this is all part of the vision of Neanderthals so the idea that the Neanderthals were sort of oh fish cave people that were unsophisticated grunting idiots he's now something we have to completely put to bed as far as we can tell Neanderthals were effectively indistinguishable from us in terms of their the sophistication of their tool use their behavior their arts their clothing their tattooing all of these things we have good evidence for and they did look slightly different from us they tended to have larger barrel chests and a different skull shapes likely slightly larger brains on average but you know whatever looked like they weren't so different that your ancestors didn't have sex with them okay so that's just sort of set up to how we got to where we are bodies the same for a quarter of a million years and then something has happened now I said at the beginning I didn't like these sort of triggering these ideas of triggering events but and when we talk about something happens some people call it the cognitive revolution you know it probably took 20,000 years I think revolutions need to happen in shorter time periods in 20,000 years but at least something significant happened all over the world now of the things that we have traditionally or over the years thought of as being human specific so it's just just us characteristics which are definitionally human and not shared by other animals the things that make us unique let me talk about tool use first because humans are obligate tool unit users this was the first stone tool discovered in the 1960s associated with ancient human remains in Olduvai Gorge in East Africa and it is a it's an obsidian stones or glass volcanic stone that has been chipped to create a a sharp edge now these were discovered by the Leakey family in 67 I believe it was alongside the bones of this human and their habilis which at the time is the earliest member of the genus Homo which is what we refer to as humans Homo habilis means handyman right so this is a species of human that is presumably on our evolutionary trajectory which is defined by tool use now that's you know that's that's 2 million years ago so we have been using tools in some capacity for 2 million years since before Homo sapiens actually existed it turns out in the 1990s another species of which there's only one sample called Kenya anthropos platy ops was discovered it's about 3.2 million years and roughly the same location but that was also identified with exactly the same technology the old one chocolate so in fact we now have obligate Tullius within hominid line which is at least 3 million years ago we've been using tools ever since the old Irwin tool set remains static through time for at least a million and a half years and gets replaced by a slightly more sophisticated set of tools which are referred to as the issue lien tool certain they tend to be bigger they tend to have two faces sharper and and more variety in them and they say to stable through time for about a million years so if a 95% of the history of humans being obligate tool users there's only two types of technology massively stable through time and then only into the last hundred thousand or so years the tools get so much more sophisticated than than just these these simple axes so the question then becomes and this is something that Darwin speculated on maybe it's tool use maybe we are the obligate tool users and that is what makes us definitionally human well you've all watched nature documentaries and you know that the answer to that is quite clearly no lots of animals use tools and the ones you know about like orangutans Zoar chimpanzees or gorillas that's always very impressive what's really interesting about tool use in the ER and the rest of the nonhuman animal kingdom is that it spans nine different classes of animals and reading mollusks Oh octopus sea urchins my own personal favorites is this this is the well it's called the boxer crab so it's about 40 different species of boxer crabs and what they do is they pick up see it stinging seein enemies and they use them to fight other cn enemies and for that reason they get called the pom pom crab and the truth of the matter is I could actually just do the rest of the lecture on this animal because I mean that's that's that's my favorite one I'm just gonna leave that up there I know you won't listen to me well that's on the screen so that's that's that's one example of the many examples of the 1% of animals that that use tools now that one of the key ideas that humans do very naturally and not exclusively but we do it all the time and very few animals do it systematically in the same way which is the idea of not biological evolution via genetics but what's known as cultural transmission so it's it's how we pass on bits of information units of information to other humans that are things that we know how to do that other animals other members of our species don't necessarily know how to do and it's not transmitted in the genetic way it's what we're doing now it's what we're doing it what we do every time you know anyone opens their mouth and speaks to someone else that's what teachers do in the book I argue that's many animals learn that humans are the only species that teaches and that is not a sentence that is that is not without qualification but it's a good line but I want to give you a couple of examples one specific example of a brilliant example of cultural transmission in non-human species so in the 1980s a pod of dolphins that were being studied in Shark Bay in Australia bottlenose dolphins it was observed that a proportion of them were swimming down to the bottom to the seabed and working a sponge onto their beaks onto then their rostrum and they were using these sponges to protect themselves when they were foraging for food on the rocky sea floor which and they things like crab probably probably pom-pom crabs so this is a is is a really cool phenomenon this is one animal using a second animal to eat a third animal so on it so that is an amazingly cool piece of of tool use of technological use by an animal here is a is a an actual photo of them um it gets so much more interesting when they continue to study them and look at the genetics of these of these sponging dolphins as what they're referred to the first thing is that it's only females who do it right so no males have ever been observed attaching sponges to their nose we don't know why they do that that doesn't appear to be any loss of reproductive Fitness between the males who don't do it and the compared to the females who who do do it so that's a weird thing in itself the second thing is when you sample the genetics of the animals that do the sponging behavior females that do the sponging behavior they're not particularly closely related to each other they're not in one kin group and so the assumption is quite reasonably that they're actually teaching this behavior to all the females in the local vicinity regardless of how related they are to each other so this this is a really really interesting example of of cultural transmission of a specific tool and a further crown to how interesting it is is when you trip when you when you look at all the individuals doing if and compare the genetic the relatedness using genetics between those individuals it tracks back to an individual who started this behavior and we know the generational time of dolphins and we now think that this behavior was instigated by a single female in about 1850 and we refer to that animal as sponging Eve now I was going to cut the next two slides out but I'm going to leave them in because I am quite childish and biology is quite funny sometimes and I I there's a huge section in the book about brain size and how how our cognitive abilities are measured of which there have been many attempts over the years brain size itself is not a brilliant metric because brains just scale with size of the animals that blue whales have much bigger brains than than we do we do have large brains but nothing you know we're top ten in terms of size Oh so Darwin suggested that brain to body size ratio is a much better metric that is also not quite we're not top of that that list in fact it was Darwin who pointed out that shrews and ants have a higher brain to body size ratio than humans so this is all part of the I'm not going to talk about this maybe we can talk about in the question session but it's all part of the rejection of simple narratives in to explain complex behavior such as intellectual cognitive ability the only reason I'm talking about this now is because when I was looking up the animals with the lowest brain to body size ratio it's this fish which is called a Cantona some artists and as a gift to someone who is both quite childish and interested in in in biology the colloquial name for this fish is the bony eared ass fish which I just think is funny okay so one of the things we don't think about quite writes in in biology sometimes is how much of our biology isn't it has been selected by nature is an adaptation and how much of it is just stuff that happens just stuff that happened to you know is happenstance according to the environments in which we were raised which which we evolved and there's there's a phrase that some of you might be familiar with because lots of writers have talked about it over the years which is the idea of evolution as a tinkerer alright there's there's a different version which I came across which is not talking about evolution at all but it comes from Teddy Roosevelt which i think is a really really useful way of thinking about how evolution works do what you can with what you have where you are right now this is a really important idea because no matter how much we talk about the sophistication of dolphins or pom pom crabs or whatever there are fundamental limitations to the evolutionary trajectory of those animals because each eeveelution research actually is unique for each species alright so you know a totally obvious example is that well dolphins are always going to be limited in their tool use because their front limbs are paddles which are adapted for swimming very fast and they're very good at swimming now we know everyone who teaches evolution uses dolphin fins as a good example of evolution because they have almost identical bones in their fins as we do in our hands but dolphins can't do that because they do this right so they're never going to be able to you know play the violin or or do things which require complex to just dexterous use you know digital use and in a similar way and this is a very clumsy link to the next section dolphins are never ever going to be able to create or control fire because they live in the sea right so that puts a fundamental limits on the types of technological developments that those particular animals I'm not having a go at dolphins but the the trajectory that they can be on which will be different from us so let's talk about fire for a bit so that was another thing that Darwin suggested was one of the most significant aspects of human behavior which was probably unique to us which was our ability to control fire it's difficult to gauge when fire use becomes a staple of human evolution when we become obligate fire users or pyro files but again this has been suggested as the single thing that made us what we are there are lots of reasons for this now in fact it turns out that dozens of animals are pyro files as well including chimps on the Savannah in in Senegal who have an incredibly sophisticated understanding of fire such that they can stand very near the annual fires wait for them to go out and and then forage foot for cooked food with within the the land that had just been burning but again I talked about the Neanderthals about revising our thoughts about Neanderthals when I was talking about tool use those stone tools well they're the ones that get preserved of course that isn't the entire tool set because our ancestors were using those stone tools to craft other tools made of biodegradable material which doesn't preserve very well there are a very few example of examples of wooden tools that have that have lasted more than you know few tens of thousands years of tops here's one which is about a hundred eighty thousand years ago found in a site in Tuscany in Italy and due to the conditions of the soil it has been preserved the Buddhist boxwood which is very hard and so this is an example of a Neanderthal wooden tool has been crafted partially by stone tools that we're aware of but also it shows very very clear evidence of having been deliberately burnt on the outside in order to possibly take away the the small branches on the club itself so we now know that it's not just limited to us Homo sapiens control of fire we know that Neanderthals and chimpanzees and a bunch of other organisms also have a sophisticated understanding and reliance and an evolutionary sense on fire however we are the only organism that can start new fires right wrong right until this time last year when a paper was published out of Australia first time it's been described in the scientific literature but in fact had been known about by Aboriginal Australians for possibly thousands of years we're not quite sure but the observation that three different types of birds of prey of Raptors in Australia where they have repeated some fires were seen hanging around near the edge of forest fires and then picking up twigs that were burning or sometimes dropping dry sticks into the fire and then picking up when they were burning flying away over natural or man-made fire barriers and then dropping them into dry bits of of forests starting a new fire and then they sit up in the trees and they wait while all of the tiny animals run away from their fiery death and into the hungry claws of all of these birds that are hanging around waiting to feed off them so maybe this is unusual I mean this is the only other animal we think that can start fires they can't start fires from scratch like we can with a with a lighter but again it's another example of a characteristic that was once thought of as being unique to humans which we now know is widely used amongst many animals other species of humans and indeed birds now as well I think that the thing is that the more we look the more we're going to find examples like this which erode us from our a pillar of of uniqueness how long have I got left 10-15 minutes ok great ok I'm putting up a picture of their cover of the book because the next bit I'm going to talk about is is sex and you don't need to see those pictures so right here's a thing so I was whilst whilst thinking about the ideas of human uniqueness I came up with the way I can come up with I copied the idea of Richard Dawkins in the first pages of The Selfish Gene where he imagines an alien scientist coming to Earth to look at us to study us as a species now I did a different version of this for my purposes which was that if if an alien anthropologist came to came to the earth and watched us for not even a very long period of time they would notice very soon that humans devote an enormous amount of time and effort and resources into touching each other's genitals now if you were that alien species then the next question as a scientist would be well why do they do that now everyone knows why we do that alright sex is for reproduction we have sex as all sexual species do in order to make small versions of ourselves and it's been like that for probably 1.2 billion years that alien species would observe us trying to have sex you know pretty much all the time in many different ways so I decided to look at the stats of sexual behavior in humans and I work with a statistician called David Spiegel halter at Cambridge and we worked out that right this is so this is euphemism time again but you're super liberated Dutch people it's much more difficult doing this talk in front of English people so of all the sexual acts that could result in a pregnancy yes point one percent actually does this is a UK stats so that's one in every thousand acts of heterosexual penetrative intercourse results in a pregnancy and that includes sponte abortions and terminations 0.1% is what statisticians refer to is not significant right so if you were that alien species observing all of this sexual activity and you were trying to work out why they why they were doing that why we're doing that you would never come to the conclusion that we have heterosexual sex in order to make babies because statistically it just doesn't even chart now if you add on top of that all the sexual behavior that cannot result in a baby then the primary purpose of sex is massively dwarfed by the volume of sex though that we have right so the question then becomes half humans decoupled sex from its primary purpose which is reproduction are we that is that the thing that is definitionally human we have sex almost always for reasons that are not to do with reproduction so you asked the question do any other animals have non-reproductive sex and the answer is yes all the time and we've been quite reluctant as naturalist over the last few centuries to actually admit that our observations about all these sexual behaviors and tons of animals are basically not doing it in order to make new ones and many of these sexual behaviors and animals look familiar to us some of them therefore do share in evolutionary origin with us many of these behaviors are look similar but are nothing to do with the same behaviors in us there's quite a lot of euphemism in this section of the talk and some of those some of the behaviors we understand very well because they fit very easily into our own understanding of evolution others are totally mysterious let me just go through a couple of examples do you get David Attenborough documentaries out here did you see blue planets last year there was this amazing sequence of marine iguanas and the Galapagos being pursued by snakes and in just just this little clip doesn't show that that that little iguana actually gets away from from the grip the grip of the snake it's an amazingly dramatic brilliant piece of nature a documentary as you would expect from BBC and David Attenborough what they don't show in that amazing documentary is a very interesting aspect marine iguana sexual behavior which goes like this right so here's some basic facts about marine iguana sex lives the females are only fertile for one day per year the male's take exactly three minutes to ejaculate the males are stratified by size basically say have alpha males and smaller males and if a smaller male a beta male mounts the female during this very very precious one day of the year when she's fertile then a bigger male will come along and simply rip him off before he's had his full three minutes okay so that's just pretty standards in evolutionary sexual selection but the iguanas have evolved a strategy to cope with this which hits that the beta males masturbate before they mount the females and say take the sperm in a little sort of bundle of spermatophore it's called and they've got a pouch under their arms which they tuck it into so then they mount the females they don't need three minutes anymore they can just jump on the back I sorry about the action there so there's an example of one of the literally hundreds of thousands of species that engage in acts of solo sexual behavior for reasons that we we clearly understand because it fits very nicely into an evolutionary paradigm that we do we understand Cape ground squirrels this is another example incredibly promiscuous Cape ground squirrels and they have you know dozens of sexual partners all the time every day males tend to masturbate after they've had read but they've had sex with a female which is a nice trick if you can do it but we think they're doing it because there's such a high prevalence of sexually transmitted diseases particularly chlamydia that's their there they're trying to effectively flush out any potential infection because they've had sex with so many different individuals in a small period of time oh to be a Cape ground squirrel so there's tons of examples of sexual behaviour that we sort of recognize and they exist for known reasons his a is a giraffe obviously and giraffes are of great interest to evolutionary biology for a number reasons the primary reason being that they are the tallest animal and for a long time we've wondered why giraffes have such long necks and this appearance is a sort of staple of teaching biology for a long time it was thought that as in this picture giraffes are actually stretching to the tallest leaves originally it was thought that the act of stretching makes their legs next longer now we know via Darwinian natural selection that it's longer necks if this were true longer necks would be selected over generational time and that's how they got their long necks but in actual facts simple observation tells us that that is not correct because you're asked don't forage in the tallest leaves they forage at neck height so we don't think that giraffes have long necks because of foraging for the juiciest acacia leaves at the top of trees we think that it's actually probably more likely to be a sexual characteristic a little bit like the Peacocks tail you know something very exaggerated and characteristic in order to attract females or rot rather in order to compete with other males that females can then choose now here's an interesting thing about giraffe behavior they are sexually segregated almost all of the time so gestation in a female giraffe takes about 21 months they have male herds their female herds the males and the females only really hook up for the for a couple of days every year or so where one male will try and follow a female around for about four days until she either rejects him outright or she gives in they've got this amazingly nonchalant tactic for not being mounted the females which is they walk forward right so if the main four male is trying I'm gonna do the action now if a male is going to mount then the female just simply moves forward and it's sort of it's sort of it's quite impressive how casual like it is anyway so that doesn't happen very often but the males are in herds almost all of the time in in one group now again you might seen this one David Attenborough documentaries what they do with their necks is a behaviour which is known as necking which is when males fight with each other like this and it's a you know what an incredible thing that that they do to see this in in nature and they do it a lot now what they do not show in David Attenborough documentaries is that in about 60% of these types of interactions between males the males are wrestling or necking with unsheath erect penises right they you don't see that in David Attenborough because it's on Sunday night at eight o'clock and we're British so that's that's one thing you don't see and the second thing is that in almost all cases where they are doing this behavior with unsheathed erect penises the winner will mount the loser and pennant penetrates him alright now when we look at the stats of this so he's only been about three studies that observed this over the last twenty years or so but this bit is about three thousand hours worth of observation at three locations in Africa and three different parks game parks and the numbers come out like this 94% of giraffe sexual encounters are male to male and penetrative 94% right during during that same three-year period about 19 calves are born with a perfectly healthy set of car so it's they're not exclusively homosexual but about 94 percent of the time they are we don't know why they do this right we just don't know why they do this there was a suggestion this is this is a hierarchical thing we're very bad in evolutionary biology at its accepting the possibility that animals are enjoying themselves there's a couple of reasons for that that one is that we we try not to anthropomorphize we try not to put our own feelings onto animals no matter how familiar they look to us another reason is that if you say you like something and someone else says they like something we can put a we can put you in a brain scanner now and if there's a similar reaction and you trust it you're saying that you like something we can agree that you like you would just enjoyed that thing we don't do that with animals we haven't the capability of assessing pleasure in animals really but and so there's been a great reluctance in animal behavior over the last forever of actually saying maybe they do this because they like it we don't know if any of you've got dogs or cats it's pretty uncontroversial to suggest that they are enjoying themselves if cats purring or a dog's wagging its tail but it's it's something which is quite hard to scientifically assess the point is in this case is that well we don't know why they're doing this maybe they like it maybe it's a reason that we have no idea about for 500 years the Christian Church has decreed that homosexuality in nature homosexuality is contra nurturance against nature and and that is still believed all over the world and many places and homosexuality is is still criminal in many places and gay men and women are prosecuted and persecuted it's clearly not contrary to serum wherever we look in sexual behaviors in animals we see homosexual behaviour and again sometimes we understand why and in the case of the giraffes we have no idea and that's fine right now that's that's enough about sex there's tons more in the book but let me let me just get back to the idea of cultural transmission because one of the key idea the thing that I think is really the central thesis in the book which is a relatively new idea which hasn't been talked enough about and it's it's back to the idea of cultural transmission so there's a particular very few people studied this and they've studied at using archaeological remains and statistical techniques where you plug into large computers now but also mathematical modeling and the idea is that cultural transmission the effectiveness of cultural transmission is dependent on population size and this is an idea known as demographic transition so it's primarily led by some of my colleagues it's in the genetics department UCL but also some researchers based in in Harvard and it's the it's the idea that populations above a certain size maximize optimize the efficiency of transferring ideas from one individual to another now that sounds very highfalutin but the a simple way of explaining it is that we are a species of experts there is no other species where our talents are so unevenly distributed amongst the populace and so what do you do if you want to learn how to do something you ask someone who knows how to do it now it appears that we've been doing this for a long time tens of thousands you know fifty thousand years maybe and from these new mathematical models the implication seems to be that when a population is below a certain size the efficiency of the optimization of that of that transfer of information is low but above a certain size and it's not really a number so much as a sort of a concept of population growth the the transfer of that information is optimized and populations can subsequently grow and sort of bud off now we see this in the archaeological remains what we see is that spontaneously apparently spontaneously it's sort of temporarily associated with climate changes which allow populations to grow in size we see it in us we see it in Europe we see it in Africa we see it in Australia at different times between 40 and 20 thousand years ago but at each of those times we see a population expansion and then we see all of those sophisticated tools that I saw that I showed you at the beginning and that's the first time we see them and we see them continuously from that point on and so that's that's the central idea that it is population size this idea of demographic transition which is crucial in the emergence of behavioral modernity so it's again that idea we teach right we are we are a species that teaches and it's it's not just unique to us it's absolutely essential to our development in terms of modern human behavior there's a cap there's a flip side argument to this which supports the same idea and it concerns fishing because well you can spear fish but a hook is much better as any fisherman will tell you all right a hook is much better for catching fish because it win it won't wriggle off this is the earliest example of fishing hook it's from Java for about twenty four thousand years ago it's actually the bottom of a shell that's simply been cut off and it's still sharp enough to cut me to this day so twenty four thousand years ago we have the beginning of shell technology like this by ten thousand years ago and this is now in Europe we have incredibly sophisticated fine bone and carved harpoons which are much better that's it's capturing larger fish and going out further out into the ocean enriching our diet now there's the counter example though I want to talk about is very briefly because it's now the end is Tasmania so this is a slightly culturally sensitive idea to talk about I just talked about the facts so Tasmania was attached to mainland Australia until the end of the last ice age so when the last glacial maximum ended the waters of the sea the ice melted and the seas rose and Tasmania became an island for the next 11,000 years there are people and there are people distributed across that land until it's separated you have been Tasmanians and Australians mainland Australians who are separated for the next 10,000 years and there's not really any evidence that they ever um they ever met again until European colonial eyes colonists arrived in the 17th 18th century now during that time so what we know from the archaeological remains is that Australians when they were when Tasmania was joined to Australia they they had a few dozen tools in their tool set including things like this by the time that Europeans arrived in Tasmania in the 17th century on mainland Australia their tool set has gone up to something like 120 and Tasmania has gone down to around about 12 right now what we think is that the population size was inherently restricted and therefore the flow of information and expertise was simply lost over time so good examples of this are that they stopped fishing beyond the shore and returned to foraging at the shore looking for sessile non non moving animals like crustaceans and probably the pompon crabs again but at the same time the the the ability to share information widely across a much larger population in Australia their technological development continued now maybe the Tasmanians were particularly happy with with that as a development but their population doesn't grow which in general is a good measure of evolutionary success so that's the idea right so you've got these examples of how suddenly the emergence of behavioral modernity occurs in Africa in in some Europe but also in Indonesia and in Australia and all these things happen at roughly the same time through this process where we are teaching and sharing ideas in an optimized way due to due to the size of our populations that is the new idea which is not really talked about much in the scientific literature although it is the theory that I am most happy with about the emergence of behavioral modernity now I just end with one last quote because I say this as new this first paper was published in this field in 2010 and there's been a handful of papers I'm like I said it's the idea that I'm most wedded to who first suggested it well it was Charles Darwin who came up with exactly the same idea albeit in a short paragraph in 1871 where he alludes to exactly the same idea with this quote which I'll read out as humans advance and civilization and small tribes are united into larger communities the simplest reason would tell each individual that he or she ought to extend their social instincts and sympathies to all members of the same nation though personally unknown to them and that's all we are a species that is social we are a species of experts and we are a species of teachers thank you very much right Thank You Adam for this very elaborate and insightful lecture I told you already it's a bit of a deformation for a philosopher but the first question I'm gonna ask is why why did you feel it was so important to address this specific question what it is that it makes us human and what it is that makes us unique what I think it's the most fundamental question that humans always be asking and you know I've given a scientific perspective on this but of course philosophers and artists and writers and poets have been attempting this question I think with much more insight than scientists until the relatively recent past and then we've been asking that question for you know thousands of years I think that it is part of my mission that I mentioned that beginning to steer us away from very simple straightforward linear narratives about how you know why we are the way we are because it's it's I've given you a solution which I think is the correct I think it's the most accurate description of what we know based on the evidence but it's not definitive so and well because about this mission you talk about these singular explanations which are always insufficient and proven wrong as well and just to be clear how is this idea of cultural transmission not one thing because it's a very fair point because it it under writes everything else that we do that is either unique to humans or we do better or differently from other animals so things like so the idea of cultural transmission via this bit specific model what emerges from that are all sorts of things that we are we legitimately say are unique to us or sort of unique to us or kind you know all the things I talked about and many many more but I think that what the cultural transmission by demographic transition idea does is it puts down a framework a sort of base layer which says this is a behavior which appears to be something that no other creature has done and as a result of that this is this is the place from which all the stuff that we do happens so and let me ask you do you attach any value to this because the background of my question as to why you're asking this question is because it always makes me quite uncomfortable because in philosophy for example a lot of the biggest reason on asking why are we human and what makes us human is to prove that we are not a mere ape or that we are God's creatures or that so there's always a special value attached to this uniqueness so we're a higher evolved species versus lower evolved species I'm quite sure you're not thinking along those lines well that's do you attach any value - no because that's why you're a philosopher and scientist no no I'm joking because because it's quite clear that I don't think that as well and also you know we don't we don't I think what's most interesting about this question is that we are a paradox because we now accept that we are animals we don't talk about higher and lower species anymore well we try not to all species are as evolved as all other species we do have a set of behaviors which which are very unusual we've managed to spread ourselves around the world in a way that is very unusual we talk about us being the dominant species well yeah that really depends on how you measure it because there are bacteria have been around for four billion years and will be around for another four billion years after we're gone and they are by far the greatest type of organisms by mass and by cell count but by biomass so you know it kind of depends on how you measure these things we're not meant to be into sort of hierarchies and in in science and I I know that this slide has I don't know where this was deliberate or not but this is one of my least favorite images in the history of science well this is a version of it and thank you for putting it out because it gives us an opportunity to talk about what's wrong with this page right and I've got a at college I've got a lecture which is entirely based around this image so this is this will be very familiar to you to most people it's it originally appeared in a textbook and a French textbook in the 1960s and it's called the march of progress and this is a modified version of it of course but it's meant to be describing the evolution of humankind but it actually represents evolution in two very specific ways which are really really counterproductive in terms of understanding how we think about evolution in general the first is it implies direction to our evolution it's got a a monkey like creature on the far left and then there's it gets more upright and then you've got some sort of cave creature and and the traditional version is it ends up with a a white anglo-saxon man with a beard and a spear and he's always got his left leg his right leg in front of his left leg so you can't see the way that all of this happens right so that's the first thing it implies direction there is no direction to evolution there is no inevitability about our sophisticated tool use or cognitive capabilities III think consciousness and intellectual abilities are an emergent property from our evolution so that implies it PI's direction and there is no direction to evolution the second thing is it implies that we know that root and we do not I think you know twenty years ago in the textbooks when I was growing up we knew every single we we knew every single step between you know the last common ancestor of us and gorillas and chimpanzees and us today and now we know none of them and that's really cool that's how science should work you know when when when you're confident about stuff in science and that's the point when you should be thinking have I got this right and the more you look the more the more we've studied human evolution and the more bones we found the less sure we are about the picture and that's great because it means like people like me and Simon genetics departments all around the world I've got an infinite amount of work to do and you you're not worried that your book will be interpreted in terms of these like as a proof that we are unique and that we are better maybe then I I hope not I [Music] I mean I'm quite I tried to be quite clear that the conundrum is that we are special and we're not at the same time and I'm sort of happy with that as a as an idea that it's we can celebrate how awesome humans are mm-hmm without being without putting us at the top of any sort of chain you know we can do tons of stuff that loads of animals can't do but you know a mantis shrimp can see in seventeen different wavelengths of light including polarized light and a mantis shrimp an octopus doesn't give a monkey's know that's a weird phrase an octopus doesn't care at all about you know this and they seem quite happy yeah yeah but the fact is we care that's one of the things that makes us that is that is the thing that is worth celebrating in us is that we are the only species that has actually asked the question we think maybe they just don't care yeah maybe they know the answers and we don't understand it's just not that interesting you know rotifers abandoned males deloitte rotifers abandoned males about 5 million years ago I think they seemed to be doing fine ok just one more question about your book the title is the book of humans the story of how we became us yeah and you haven't really addressed the hole in this in fact in the paperback version we've changed the subtitle publishers this question sorry no no no it's a good question but it's all part of the learning process of writing because you know this is a crowded market for writing about humans and there are some good books and some bad books out there so how do you distinguish yourself in that field it's a tricky question and one of the ways you do that is by talking about weird animal sex but but you know yet the other thing and I think this is the like I said a couple of times the thing that I try to do more than anything is embrace the complexity and revel in the beauty of unending stories and non-linear narratives i know that humans need and love stories and our stories are beginnings middles and ends and they tell us trajectories and they tell us about how we change and that's good and i love stories but that's not that's not how evolution works and it's not how life and time works and we should be able to do both things we should be able to talk about talk accurately about the science and the evolutionary trajectory of life on Earth without needing to rely on linear narratives that result in the hero's journey going from place a via place B and getting to play C because that's just not how this stuff works so I'd rather be honest about that and and sort of celebrate that that complexity yeah but still then is there no room there for answering the question how we became so because I'm not asking why we became us or what I'm not asking for a direction yeah but do you have funny any ideas as to how we develop this skill and this well yeah I mean it is through social interactions so it is through its through the random chance of of in our environment changing which means that for you know whatever reasons we reproduce more successfully we have more access to food and so we have reproductive success and our communities got bigger and at the same time seen you know there isn't a linear version of this of this this story in itself lots of different things contribute to being the development of behavioral modernity maybe we should just random you know some of the which will have a genetic basis others won't they will have social basis one of the things I think is interesting about why we don't talk about this idea more I think is because it is you know there is one interpretation of it which is anti-darwinian there's a specific technical reason for that it's not anti-darwinian but it looks like it could be and that's to do with the gene-centric view of evolution which is that which is the correct one which is the you know the idea of The Selfish Gene which is that the unit of selection that that nature operates in is the gene and we are merely husks are animals all organisms are merely husks for the most effective way of transmitting one gene to the next generation in concert with a bunch of other genes right now that that model is correct for a long time whilst this was an idea being developed there were arguments within the scientific community about whether what was the unit of selection was that the gene was the individual was it the family was that the group was it the species now the evidence suggests that it's the gene and none of the rest of those things the idea of demographic transition by cultural transmission it's very demographic what's the main idea of my book transmission yes is it looks like it's group selection so it looks like it's a cultural selection rather than individual genes there isn't a significant genetic change that results us in being able to make statues or to do arts all right we haven't even talked about communication and speech which is absolutely central to this and this is there's plenty of it in in the book but again that's a that's another extraordinarily complex trajectory of multiple lines of very complex aspects of of biology which include neuroscience motor skills just physical anatomy of our tongues and jaws and lips and bones and our you know larynx and pharynx and so over the years people have suggested that it was a single trigger which has taken us from being apes that don't speak into Apes that can do this and again I reject that Chomsky thinks that Chomsky things from there is oh there is a I don't know why I'm saying this because the man who knows most about this on earth is sitting right there so this is it's slightly ridiculous and I'm saying this in front of in front am i doing no back ok you'll send me an email later so ever you mentioned mentioned that but but again you know all of these things are essential so you know the ways our brains develop to recognize other minds so that's a sort of loose way of thinking about consciousness they're the evolutionary advantage of being able to try and work out what you're thinking which I'm thinking desperate for a drink now make this stop why is he still talking things like that but but also you know things that you might say are not obvious things to enhance reproductive success like you know we started doing music doing art I think things that don't have an immediate benefit may be it may be the ability to carve a flute and play the flute you know you know in a group of people does make you sexually more attractive well it works for guitarists and bands and not for drummers so there's certainly something in that but you know the idea that we sort of loosened the shackles of natural selection by all the cultural stuff that we do that we that we began doing fifty to hundred thousand years ago you know these are all aspects of evolution which are underwritten by biology by genetics but not entirely dependent on them then much more so here's an analogy which I haven't used in the book but I use elsewhere actually including this in the new book if you think about us as a sort of in in sort of computer terms right you've got the hardware which is our biology our genetics and and you've got the software which is our culture now more than any other organism I think is I think this is right fair to say more than any other creature we have shifted the significance of the software which is our culture away from the hardware which is our genetics both are still massively important that we are we are so dependent on our non-genetic facets or evolution more than more than any adequate are now looking to you for for acknowledgement it's a it's it's it's not it's not a perfect analogy but I think I think the idea that we've we've transferred to we've transferred the importance of the away from the hardware into the software is did you like that could I then say that your mission maybe is to move away as a geneticist that your mission might be to move away from this gene centric view and have a look at humans in a more cultural no well yes and no the gene centric view of evolution is correct there's it will be a famous scientist who get who's demonstrates that that is not the main mode of evolutionary change he just did that guy just disagree so much he's just walked out but well we can be both right I mean with it with that that is that is all creatures are we tend not to use the word cultural but a you know influenced by environment and their own behavior how it interacts with the environment some of which has a genetic basis and some of which doesn't so it is both of those things but again you know it's the same idea it's combining these things to try and understand the complexity you the thing that we do that we fail to appreciate the reason we get evolution wrong so often is just a staggering amount of time that it has had that life on Earth has had to get to this point in us or cuttlefish or octopus or bonobos or whatever they it's unimaginable time that has allowed this process to be enacted in so fundamentally the same way but in so many different varieties evolution is the most creative force that has ever existed and it is a combination of a gene centric view of evolution and everything else that isn't genes so that's so you know nature and nurture we used to say nature versus nurture that which is not a useful way of thinking about biology nature via nurture is a is an is a phrase that the writer Matt Ridley came up with which is better nature is genes nurture is everything that isn't genes and it's not just whether your parents coddled you when you're a kid or read your books although that is part of it it's random stuff like the orientation of the embryo in the womb or you know the the cellular activity around the embryos or all things which aren't primarily genetically moderated counters the environment and the complex interaction between the environment the nurture bit and nature well that's that's that's about that's what makes a life as an individual but that is also the trajectory that there's there is fundamental to evolution [Music]

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Many animals learn. Only humans teach. Our intense social bonding and our desire to share ideas make us different from animals. This states the British geneticist Adam Rutherford in his research on what it means to be human. Come and learn from Adam Rutherford how cultural accumulation and transmissions set us apart.