What Makes Us Human? - with Adam Rutherford

What Makes Us Human? - with Adam Rutherford

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[Music] now the question at stake here is really what makes us human now this is obviously something that is that people have been pondering for several thousand years and to my mind never really coming up with a satisfactory answer and you know careers are made and continue to be made by people talking about individual single things single triggers that made us human so things like speech or language or our ability to control fire Darwin thought that was that was the case or you know
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more outlandish things like hallucinogenic drug taking that is genuinely a theory out there of the switch that made us human and I think they're all right and all wrong and that's what this book is about and I suppose in all of my work as a science communicator I've tried to embrace the idea of complexity because evolution is messy and and has taken place over a long period of time so there's individual triggers I don't really buy into those ideas of single thing single
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narrative satisfactory stories that make us as complex as we are today so I've always shied away from those sorts of stories and I encourage I'd like to encourage people to embrace reality the reality of biology which is that this stuff is complex I you know what makes us human well the fundamental answer is having two human parents and having a human genome but that's an incredibly dull answer and it's not very informative and the real question
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interesting question is about the human condition now this this question of the human condition is what makes us special the question of are we special and and if so what is it that makes us special and it was as all my work ends up starting with with Darwin who is my intellectual hero and I think the greatest thinker that that humankind has ever produced and he was the first person to initiate this
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this idea of the conundrum of human existence and this is in 1871 from the descent of man and that that quote is is just one one little sample from the descent of man of him thinking about this and thinking about us in terms of our own evolution so he says without with with our godlike intellect which has penetrated into the movements and constitution of the solar system with all these exalted powers man Victorian language but I think it means humans still bears in his bodily frame the indelible stamp of his lowly origin
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lowly origin that's a sort of value judgment which was appropriate in the 19th century we no longer think about evolution in terms of higher or lower beings we are we are as equally as evolved as any bacteria but there there is the key idea that we are an ape that has descended from other Apes and a few years earlier it outlined the rules of evolution in what I think is the most important book ever written the Origin of Species so we are an ape descended from other aids but at the same time we are special now this is such an important sentiment is such an important
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question within the study of evolution it was in fact expressed more beautifully about 250 years earlier in Hamlet's famous soliloquy on what a piece of work is man you know this this line is so so beautiful noble in reason how infinite in faculty in action how like an angel in apprehension how like I got the paragon of animals and I love that phrase the paragon of animals because it says it encapsulates that in that conundrum in one beautiful
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Shakespearean phrase in fact there was a point where I wanted to call the book the paragon of animals but so Jenny my editor said that was pretentious do Cherie and I think she was probably right to be honest he goes on to say a few lines later but what is this quintessence of dust so we are mater but we are special we have had the powers of gods but we are merely animals and in fact the genesis of the whole idea for this book
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came from a line when my head came from a line that I wrote in the final chapter of my last brief history of anyone who ever lived what was it a brief history of everyone who ever lived and it was it was it was this line everyone is special which is another way of saying that no one is it's a slightly different idea but very closely related and in fact when I wrote that and I sent the first draft around to the core team and it was well Francis my my history agent he said I really liked that film quote that you put him in the final paragraph final
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chapter and I said what the line about everyone being special I said what I thought I'd made that up and he said no no it's actually for does anyone know what it's from no it's not Fight Club it is Incredibles so you might know that I'm quite a film obsessive but I managed to quote films without even actually noticing which is which is a little bit tragic so these questions all of these questions are about the paradoxes of uniqueness you know what what are the attributes which are ours and ours alone I think
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fundamentally it's fair to say that we are the only species that has ever held ourselves up to the light and asked that very question and then the answer paradoxically is both yes and no all right so I mentioned that I want to throughout my work as a science communicator I want to embrace the complex as a quote which I refer to all the time from the journalist HL Mencken which where he says for every complicated problem there is a solution as simple direct understandable and
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wrong so the whole story of human evolution has radically changed in the last two decades in the last moreso in the last ten years and continues to evolve and that's primarily what the last book was about it's mostly to do with the fact that we've introduced ancient genetics into the study of only evolution the ability to extract DNA from people have been dead for thousands of years so I want to do a quick recap to bring us up to speed with the last million years of human evolution because that's really what this story is about so this is a
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schematic of evolutionary tree for the last million years involving us and so the yellow at the bottom there is extant living humans broken up into broad ethnic groups Asians Europeans and Africans there was an earlier archaic modern human Homo sapiens which whose lineage died out and of course we all know about Steve Neanderthals which are now divided up into eastern and western and then you'll know presumably about the Denisovans so another type of human not designated as a species but only
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known from a very few samples but their entire genome primarily a human that lived in Siberia and and further east and we also know of a mystery human a human which is only identified due to the discrepancies in the total amount of DNA in homo sapiens Neanderthals and us so that's the tree of life as it stands today but we also know that the mystery humans interbred with the denisa ones that Denis Evans interbred with the eastern Neanderthals the denis ins also
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interbred with the lineage that would become modern Asians and the Western Neanderthals interbred with with those guys and those guys and I mean what's the sort of age on this just an over 18 talk yes so in the book I described as described the last million years of human evolution as an enormous and I stand by that so there's there's the tree as it stands today in terms of the number of human
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species that have existed in the last hundred thousand years all of which interbred with each other which challenges the whole notion of a species but it also challenges the idea of our own uniqueness in terms of our our behavior and our evolution so when the grand scheme of things so this is the most recent version of the Tree of Life so the origin of life some what do I have a pointer I do the origin of life somewhere around there almost all life on Earth it's bacteria the second biggest chunk is things that look a lot like bacteria but are qualitatively different and then there's all the eukaryota which is
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everything which isn't in the first two categories and we are somewhere down there so this is reinforcing the notion that we are evolved right we are part of evolution unquestionably we have the same type of DNA we have the same proteins we have the same types of metabolism we have the same cell structures as almost as every organism that has ever existed as far as we know so we are an evolved being but then when it comes to thinking about Homo sapiens and how Homo sapiens sits within human
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evolution there is another interesting I said a conundrum in within here so this is this is now the the earliest Homo sapiens specimen that were aware of it's from Morocco Jeb Olerud and was dated last year as being about three hundred thousand years old now by about two hundred thousand years old we have Homo sapiens that truly resemble us physically they were like we are today
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if you found one alive and gave them a shave or a haircut and put them in modern clothes we would not be able to tell the difference between a two hundred thousand year old Homo sapiens and any one of us today and this is a conundrum because we haven't physically changed significantly for the last two or three hundred thousand years but in terms of behavior are we have radically changed and only within the last well the numbers are a bit fuzzy on this but definitely within the last hundred
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thousand years and most significantly the last fifty thousand years and we sometimes talk about this as being the emergence of behavioral modernity or sometimes the full package of behavioral modernity so basically organisms which are recognizable in terms of behavior and and their physical presence as we are today sometimes it gets called the cognitive revolution I I dislike that phrasing phrase intensely because I
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think revolutions should probably take place over shorter time periods than 10,000 years but also it implies that there was a switch again and I reject the notion of these these single triggers where one day with one thing and the next day we're not that is not how evolution works but we do know this is what we looked like 300,000 years ago and by 50,000 40,000 years ago we have things like this so oh I forgot to mention so there are illustrations in the book and the illustrations are done
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by Alice Roberts who as well as being one of one of our greatest science communicators and a brilliant scientist is also annoyingly talented as an artist as well it's just annoying to be honest and of course she's going to be standing here in December doing the Royal Institution Christmas lectures so you have to get your tickets for that and I think I'm going to be standing here for at least some of it anyway so here Alice has drawn several illustrations for the book and one of them is of this figure so this 12-inch figure carved out of a
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mammoth tusk The Lion Man of Poland Stein startled and the states around 40,000 years ago and it is ice it's a stunning piece of art it's an imagined being so it's a man with the head of a cave lion we think and it has seven stripes on its arms which have some symbolism which we cannot possibly know [Music] or try this for size so round about the same time thirty-eight thirty-nine thousand years ago the venus of hohle ii felt so found found also found in
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southern germany from approximately the same time this is one of several venus figurines they call the first one was found in the 19th century was called the Venus in pewdie k-- because it was deemed a bit rude it has a very pronounced vulva now people over the years scientists and and otherwise have tried to assign meaning or value to these these venus figurines a lot of people talk about them as being fertility amulets because
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they often have exaggerated sexual characteristics in this case very big boobs but the truth is that we cannot possibly know what the motivations of those artists were why they created these these statues and it is just speculation to say it's a fertility amulet it may well be a toy it might be pornography it is impossible to know but the key thing about this is it is possible to know that it indicates very clearly these these pieces of art indicate clearly
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that the minds of the people who created them were not significantly different from our own they show intellectual curiosity show great skill great dexterity as well but also foresight and abstraction of thoughts and this is a this is the first the earliest depiction of a human body the lion man the earliest depiction of a of a chimera and then you know by 20,000 years ago we've got the cave paintings that were very familiar with so this is an example from the Lascaux caves in southwest France my favorite example
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there the one in the middle is the great Irish elk Megalosaurus now this is all based in in Europe so we're talking about the emergence of behavioral modernity which is so far I've only talks about as being at this time in Europe but it wasn't just in Europe at all and so if we go out to the Sulawesi caves in Indonesia we have this this artwork so 14 hand stencils so blown we think through a bone pipe with red okra dye around the hand and that also dates
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from 40,000 years ago to about the same time as there as the Lion Man and we also know very well of these types of examples of Bailey or modernity within within Africa too so you see at approximately the same time the relatively sudden emergence of a whole suite of characteristics which are very familiar to to us today now again you know we have to think about our uniqueness here because one of the key ideas and I think the key idea in the book is that humans are accumulators of
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culture all right so we are a species uniquely that is capable of acquiring culture and passing it on and accumulating it and passing it on in a non genetic way and this this is one of the key ideas in the book but in terms of you neatness of human species well from February this year a cave painting in Cantabria in northern Spain this is a cleaned up version because it's not very visible on the rock anymore was read ated and dated to
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around sixty four thousand years ago now we know that sixty four thousand years ago the only humans in europe and in spain were Neanderthals now this is this clearly shows all of the same attributes of behavioral modernity as the other Homo sapiens arts there's a sort of bovid you know some some sort of cow like animal popping out here and the back end here and this is rather beautiful again we can't know what the motivation of the artist for creating such such a piece was but it also it
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clearly indicates that the behavioral modernity that we think is unique to us was also shared by Neanderthals at a time before Homo sapiens arrived in Europe now one of the things that I do in my work as well as they try to make it as up-to-date as possible um and during the last stages of both this book and the last book I kept really annoyed my editors by saying like we have to include this paper which has come out just you know just just this week and you know managed to jam it in and the most recent paper referenced in this
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book is from July which you know I'm proud of the fact that it is as up-to-date as it can be and that this this research is from February at six o'clock tonight a new paper was published which puts the date of the earliest known to fiction of an abstraction almost arts in South Africa in the Blum boss case 74,000 years ago so literally on the day of publication on 10,000 years out
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thank you scientists anyway so we got that we got you know multiple sites around the world of the emergence of behavioral modernity full package and so when we think about those attributes I'm gonna go back to some of those key ideas that I talk about in the book so humans are obligate tool users right we know that this it's obvious we cannot operate without extending our abilities with external objects that we have called
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tools now we've been like this for millions of years this is a the earliest known example of a type of technology called the old wooden chopper or not the old one tool kit and it was it was discovered in the 1960s alongside the remains of of a new human identified at the same time approximately the same time which was known as Homo habilis Homo habilis means in Latin it means handyman so this is an example of humans
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defined by our tool use right and and you know again at the time thinking about how would these definitional characteristics that make us human well the suggestion was well we are the you know obligate tool users and this is the first incident of tool use in in homo sapiens Darwin thought that too he thought he described some examples of tool use and animal particularly weapons in baboons but primarily said that you know this is a thing that is ours and ours alone Homo habilis States to around 1.9 million years ago but then you know
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as science does its thing we now have discovered an earlier type of human that isn't categorized in the in the genus Homo but is called Kenya anthropos Plassey ops there's only one specimen of this and it's just around the corner in lamech we intend and Tanzania and it states the 3.3 million years ago and also within those remains are found examples of the older land toolset now it's it's a relatively simple form of form of stone tool used for cutting and
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slicing primarily they tend to be this sort of size and tend to be made from volcanic glass like rocks like obsidian and and we see them all over the world I overheard which last more than a million years what's truly and incredible about the older one toolkit is its stability through time once this had developed and spread all our all around the world in multiple species of humans it just stayed like that for a very long time after about a million years or so it gets replaced by another type of tool heads which we refer to as
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the Chilean tool sets now first discovered in dis in Norfolk I just I'm from Ipswich so I have nothing but contempt for people from Norfolk but nevertheless a biggest set was discovered a few years later in there in the northern French town of Center Xu I think I'm pronouncing that right but please do correct me and that's the name that it acquired but this is a more complex tool it's by faced it's got more
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more cuts to it so you can shape they tend to be pear shapes bigger as well up to 20 centimeters and again what's fascinating about this is you see them all over the world and they're basically static for about a million years with no significant development or change in the nature of the Julian axe heads for a million years so what that means is we've got two sets of tools the older one choppers and the Assyrian axe heads that are static for two million years without significant change spread all over the world that represents 95
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percent of the total amount of time that humans have been using tools so the question then is well are we is that unique to us are we unique and I in our command of extending our abilities via tools and the answer is well categorically no certainly in terms of complexity and scale yes we have our tool use is more sophisticated than any other organism but about 1% of animals also use tools and there are dozens of examples of this and they
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spread across families and across taxer which indicates that it is unlikely that there is a single origin for tool use and all subsequent users of tools that arrive from a single origin is what Daniel Dennett refers to as a good trick right so if extending your abilities via tools is useful then it's a good trick for all organisms to have it or as many organisms as possible I give you you know dozens of examples all of the great apes use tools many many monkeys use stones and sticks the fun goalie
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chimpanzees they do an interesting thing they sharp and they choose sticks that are about three or four feet long and they sharpen them with their teeth and their main food supply is bush babies bush babies sleep during the day and they tend to sleep in hollows in trees and if you break open a tree it makes a lot of noise and the bush babies wake up and they run away so they get these Spears the fungi lead chimps they get these Spears and they rapidly stab them down and pull the bush babies out I could go back and eat them off the stick but it's not you know we think I've told you some things like great apes as you
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know not that surprising but loads of other animals do too my favorite is the this is a boxer crab although no one calls him boxer crabs anymore they call them pom-pom crabs which is way less hardcore but of them the many species of pom-pom crabs they they pick up poisonous anemones and use them to wave off predators as they come in towards them and whilst to another crab it looks terrifying to us it looks like they've
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got pom-poms which is a shame but again this idea of cultural transmission is not necessarily something that we see in these type in most of the animals that have used tools there are few and far between examples of non-genetic non-biologically encoded tool use that is transmitted from generation to generation inevitably we must talk about dolphins because there is one good examples and the cetaceans which is the Dolphins the
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bottlenose dolphins in shark bay they they they work sponges on to their rostra that beaks in order to protect their beaks whilst they're foraging around in rocky baits for you know for food for crabs and and sea urchins and things like that now that's pretty cool right I mean that's a really cool technology it's one animal using another animal to eat a third animal which i think is the only example of that in nature but there's a much much more interesting aspect to this story which
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is that only females do this and from genetic studies we know that the females are not necessarily closely related to each other so this is not necessarily a characteristic which is passed down from well from mother to daughter it appears to be laterally transferred between females of bottlenose dolphins and from the genetics we can also tell that there was an originator we referred to as sponging Eve which was probably five or six generations ago so probably in the middle of the 19th century a female
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dolphin decided for the first time to nurdle a sponge on her onto her nose and that worked out as being a really cool way of getting food now we think that there's cultural transmission in this man Oh in some birds particularly Caledonian crows and there's a lot of talk of Caledonian crows and in the book but I think what's interesting about this is that whilst we've been over the years being trying to work out what what it is that bestows this amazing these amazing characteristics upon us one of the things that we have to think about is brain size right because we have very
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large brains and over the years there have been many attempts to account for the amount of brain power that we actually have what's been very interesting about this is that almost all of the attempts to do this have tried to put humans at the top and we're at the top of none of those categories so they include things like what brain size is the obvious one obviously we don't have the biggest brains because brains in general scale with the size of the organism and then we looked at number of neurons well we're we're sort of about fourth in that African
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elephants have about four times more neurons than us and then what Darwin in fact first so thinking about a better metric which might be brain to body size ratio so the proportion of your body that is actually made up of of brain but you know who wins that ants and shrews and again we come we come in about 56 behind a lot of whales and the ants and shrews incidentally and this is only including this and it's only included in the book for what will become a very obvious joke
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the lowest ratio of brain to body size is in a fish which is called I'm not making this up I mean that that is its name it's called the bony eared ass fish and when I was looking this up you know I thought this has got to be a joke but sometimes science is just a gift we even introduced two different metrics in the 1960s as an attempt to put us at the top of a top of the pile again which was called EQ and capitalization quotient and we did come top of the pile there and it looks like a better
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predictor of cognitive ability relative to size until you take humans out in which case size is a better predictor in the great apes so it's clear again that there isn't you know there isn't one thing it's not just brain size it's not just brain complexity we now know that although birds many the cognitive abilities of birds are being better and better understood and there and they're jolly impressive in many cases but their brains tend to be much smaller only last year did anyone actually work out that should scan the brains of birds and it turns out that the density of neurons is
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much higher for equivalent apes that have similar sort of cognitive abilities so again you know this is evolution working in working as a tinkerer which was what some the famous molecular biologist Francois Jacobs said in the 1940s evolution is a tinkerer I do love that phrase but there's a there's a better why not better one is one that I prefer which comes from Teddy Roosevelt and nothing to do with evolution but this idea to do what you can with what you have where you are and this is I
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think a very important sentiment when talking about evolution in general and the differences between natural selection adaptation and evolution overall evolution is simply change over time adaptation is the effect of natural selection on our changing bodies and those two things are you know adaptation is part of evolution but not everything that is evolved is an adaptation and it's the reason I think it's important to reference this at this point is because yeah a very simple but
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obvious thing to say that I think doesn't get said enough when we think about evolution dolphins are never going to evolve hands because they need paddles to swim with and so they're always going to be limited in terms of compare comparing our tool use and re-evolve tool use with things that swim because they need to swim with them and so you know it's just a good example of how no matter what the cognitive abilities of dolphins might be
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if they're in the water they have a different set of evolutionary pressures to us and for similarly obvious reasons dolphins are never going to create fire which I know sounds funny but it's not insignificant and thinking about their cognitive abilities of of whatever organisms we're talking about if they're never going to evolve fire there's not a lot of wood in the ocean that means they're never going to smelt anything
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and and so just you know remember this idea that's the for evolution for whatever you're talking about within evolution you have to make do with what's available to you in in front of you so let me talk about fire that was that was an unintentional but quite good link there I might use that again so this is another Darwin thoughts as well so darn said some incentive man II thought that a long side language perhaps file was a thing that separated
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us from other organisms we are obligate fire users as well and we have been for hundreds of thousands of years very difficult to date the origin of fire use because the archaeological remains are well we see evidence of fires outside of caves but it's very difficult to tell whether they deliberately started or naturally-occurring or wildfires compared to in more recent histories in the last hundred thousand years but it is it's not unreasonable to say that within the last hundred thousand years we have a commanding control of fire but fire has been part of our ecological makeup for a long long
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time as it is you know to this day in Africa and in Australia and in various places around around the world we talk about tool use and I've mentioned stone tool use we the era's geological eras are defined by stone tool use the Paleolithic which means old rocks and a nearly new rocks and the Me's oolitic which means medium rocks of course this is the stuff that survives but we mustn't make the mistake of thinking
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that the the stones we were using they were that that was the complete tool set because of course those Julian axe heads and and Buren's were used to carve wood but wood doesn't survive particularly well I've got very few examples of wooden tools that have survived over any significant amount of time here's one this was published last year and this is from a site in in Tuscany and this is one of several sets of Spears or sticks which are wood and particularly hardwood
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boxwood but also that have been crafted using fire right so they not only have been carved using stone tools but it looks very much like the outsides of them had been burnt off using fire now the date of these puts the creators of these as Neanderthals not the same sapiens again this is pre Homo sapiens arriving in Europe so again indicative that another human species way before us had similar level of cognitive ability the cognitive understanding of something as complex and as dangerous as a fire now
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there are other animals that interact with fire in a very sophisticated way vervet monkeys do this in in Africa and when wildfires happen which happens in an annual cycle they hang around near the fires and they wait for the fires to go out and then they they go in and they forage and same chimps that do the kabah being of the of the the bush babies also do this they hang around like weirdly close to fires and that shows something very important about their cognitive
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abilities that they understand something as dangerous as fire which can change very quickly and is very very lethal that they have an ability to understand in process that with sophistication enough that they can stand close wait for them to go out within minutes they will go in and what happens in in there's a couple of advantages to to hanging around Savannah fires the first is that it clears the plains which means you can see for much longer and we know this because grazing animals graze for much longer on planes that have been
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burned down they do when their grass is this high or so but also you've just got a smorgasbord of kooks food and so they go in they cruise in and they and they look for small critters that have been burnt to death and so that's what the fun gayly chimps do in the vervet monkeys do there's a strong interaction a recognition of fire as a danger but also a source of ecological an ecology that these animals closely interact with now of course we are the only animal
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capable of creating fire from scratch and we've been doing that for probably a hundred thousand years but a paper published this year in January this year was just a just a beautiful beautiful revelation and it concerns three types of raptors three types of Hawks all from Australia is one of the illustrations this is a a black kite an australian black kite and what the kites do and these two other two other raptors is they they stand syn
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in a tree near a wildfire and they go to the edge and they pick up a stick which is smoldering or burning and then they fly away with it in their beak I know I realized this picture looks a bit like that birds having a it's carrying a burning stick and we know this is deliberate behavior that we see them we see them drop the sticks when they're quite hot and may go back and get another one and then what they do is they fly off to an area often beyond a natural or man-made fire barrier and they're going to an area of dry brush and they drop the stick in there and
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they create a new fire and then they fly up to a tree and they watch all of the small animals run out from the burning fire and they go down and they eat them all so sort of moving a moveable buffet and this is we think the only other example of deliberate fire starting in any other organism it's it's true it's beautiful and it's truly impressive it is also something that Aboriginal Australians have known about for a long time and and is part of is referenced in
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some of their Dreamtime ceremonies it's called jerilyn and it's an interesting sight I mean it's a footnote in the book but I think it's worth mentioning that it just shows the value of local knowledge interacting within indigenous say expertise because they've known about it for centuries and may have been significant in in Australian control of wildfires which are cyclical and happen every year it may even be and they cease speculation but it's interesting
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speculation is there's one book that cites that suggests that observation by Aboriginal Australians observations of the fire Raptors the fire Hawks was the inspiration for them doing exactly the same thing now if that is the case that is a gorgeous example of cultural transmission between species from birds to humans which is just a lovely idea um there are many other examples so that's that's fire dealt with I've done tools have done fire there are many many
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examples of other characters that are familiar to us but aren't necessarily behaviors which have been that we have inherited from a common ancestor and that's again you know a key idea that sometimes we fall into the trap of thinking that because another organism does one particular thing and it seems familiar to us and that is why we do it one other example mostly because I just like showing this picture and telling this story this is Julie
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Julie is obviously a chimpanzee and in 2007 Julie picked up a stick one morning and stuck it in her ear and we don't know why Julie did this but that's what she did and within a few days her son and best friends it was called Kate I don't know who names these it's quite possible that the she didn't refer to herself as Julie but within a few days her son Jack and her best friend Kate we're also sticking twigs in the same here always the same if they put it in
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the other ear they took it out and put it in the same way and within a few weeks and then a few months about 12 out of 15 members of this particular tribe were also wearing sticks in their ears now Julie died in 2012 I think it was but the last time these chimps were observed some of them are still wearing sticks in their ears and to other tribes that are not genetically related to Julie's tribe are also wearing sticks Americans now we don't know why they're
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doing that this I think is the this is fashion this is the only example any reasonable example I'm aware of where an animal is doing a particular decorative behavior which doesn't appear to have any direct reproductive benefits and of course fashion is very important to us so this following that we do we think about a lot and spend a lot of time signaling on right let me crack on I told your head and time this it'll be slick one day now there's another aspect to this which I mentioned so I'm going
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to mention but I'm not going to dwell on and that is our sexual behavior so the way a frameless in the book is to think about this is a Richard Dawkins trick is - if aliens were to come to earth and to observe us as as if we were as a naturalist and to look at human behavior one of the things that be very striking is that we spend an enormous amount of time and energy and resources trying to touch each other's genitals and then the
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question becomes well what is the purpose of of sex obviously sex is to reproduce I did some some of the stats on this with David Spiegel Hall to the statistician at Cambridge and we worked out that phrase this very carefully we worked out that of the the sexual behaviors this is for Britain alone of the sexual behaviors that could result in a baby about point one percent does
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now I'm just turning to my mathematician wife here how does that rank on on statistical significance pretty low yeah all right so there are very few statistically insignificant number of sexual encounters that could result in a baby that actually does and if we pile on top of that all of the sexual behaviors human sexual behaviors that cannot result in a baby it is absolutely dwarfed so the primary function of sex in order to reproduce is absolutely insignificant compared to the
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amount of sexual behavior that we engage in right so we have effectively decoupled reproduction from sex so then you ask the question well maybe this is unique to us maybe this is the thing that evolved alongside our behavior that we decoupled sex from reproduction maybe that is not something that other animals do well no not in the slightest bit and I'm showing the cover here because some of the organisms on this cover represented by their footprints only
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some of them are some of the tails of weird animal behavior sexual behavior which are potentially familiar to us was not being related to the similar behaviors that we see in us we ran a competition on Twitter the other day to identify all these organisms the top one is me because those and there's a the Nike dunks they're the types of shoes that I wear not today the next one is chimpanzee of which we can talk about there's much in
40:19
the book about next one down anyone mammal otter it's a sea otter now sea otters are super cute as you well know in the hold hands when they sleep to stop themselves drifting apart and they crack by vowels on their tummies with with stones and that's super cute male sea otters in Seattle also drown females and then use their bodies to copulate with up to two weeks until the bodies fall apart so there you go a Bruins sea otters for you necrophilia weirdly is was only outlawed
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in this country in 2007 and is universally seen in all human cultures it is generally regarded as a paraphilia I don't think it's a very controversial thing to say but again the idea that actually there's quite a lot of necrophilia in the animal world but to suggest that otter behavior it relates to human para pathologies psychopathologies is stretching it a little bit and if you're interested in thinking about human behavior particularly human sexual and gender behavior and using animal models to back that up then you've got to pick your
41:25
examples very carefully that that is almost impossible to explain that alter behavior is almost impossible to explain using standard models of evolution right it doesn't make any sense the fact that they also do it to harbor seals a different species just is absolutely baffling so there is an example of a behavior that we simply do not understand what is the one below that it's a two toed ungulate any one giraffe someone said giraffe it's a giraffe only gonna show you the picture that you're after Alice did because it's such a
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beautiful illustration giraffes are very interesting for evolution of course because they are the tallest animal they have that amazing neck for a long time we thought that the neck was an example of a sexually of an exaggerated trait in order that they could reach juicier leaves for foraging actually that's not true because from observation we know that giraffes mostly forage at shoulder height so they tilt but we do know is it's involved in sexual selection because males so giraffes are mostly sexually segregated most most of their lives and
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mail packs spend almost all of their time together and they do this thing called necking which is you've seen it on David Attenborough amazing documentaries they do this wrestle to in order to establish status what those documentaries don't show that in about 60% of those necking encounters at least one of the males has an unsheathed erect penis and the winner ends up having penetrative sex with the loser now according to the best observations this
43:00
isn't very well studied this but several thousand dollars worth of observation across several regions in Africa indicates that 94 percent of sexual encounters in giraffes are between males now during the same period that these observations from maze 22 calves were born so they are still engaging in heterosexual sex because that would make a lot of sense if you want to survive as a species but the majority of sexual encounters are homosexual in giraffes now we do not know the reason for that
43:30
we do know that I'm asexual homosexuality in the animal world or homosexual behaviors are close to universal in in most sexual species and again sometimes we can work out the answers though the reasons for them and in other cases there are giraffes we cannot I'll just do one more and from the bottom to see this is what I mean about not to spending the next two years talking about weird animal sex I'm just doing it now on tie the bottom one is marine iguanas remember on the last issue so dove the last series of blue
44:02
planet they had there's amazing sequences marine iguanas in the Galapagos running away from snakes it was just you know Donna Shanice of natural history marine iguanas are a socially stratified by patriarchal social stratification so there are alpha males and sub alpha males and the females are only fertile for one day per year it takes a male iguana exactly 3 minutes to to ejaculate you can insert your own joke there it's fine but if a smaller male mounts a female then the
44:32
chances are the Jermel will come along and physically rip it off its back so the small amounts have evolved a strategy which is that they masturbate before they mount the females and they can't they have a little pouch where they put the sperm into spermatophore and they mount the females and they pop the package in so they don't need the full three minutes so there's an example of a of an animal behaviour which may sound familiar to us very sorry about this but he's unrelated and it's one that we can understand from evolutionary for evolutionary reasons
45:03
because it makes a lot of sense from an evolutionary point of view but for giraffes or sea otters they're things that we simply don't understand we mustn't make the mistake of assuming that behaviors that seem familiar to us can explain or explain away human behaviors all animals are evolved along their own trajectories to fit in with their own ecological niches to do what they can when they can with what they have o transactional sex and the dealy penguins is on my notes there I think I just leave that so I can crack on right
45:33
now things are pretty much run out of time I am the the this the the idea that I think is most interesting in the book and relates to this this concept of cultural transmission is has been talked about for a long time but in the last few years has undergone a sort of minor renaissance and this is largely the work of Mark Thomas my colleague and friend at UCL I think is here mark I know so if
46:04
you got any questions about this then ask him but a significant factor in the emergence of behavioural modernity in us emerges from looking at the archaeological records and processing them into mathematical models and asking the question well what is it about this structure of a population which coincides with this suddent the relatively sudden in geological terms emergence of all of this suite of modern human behaviors that we recognize that
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the so called full package and there's a thing that emerges from these mathematical models and from the observations that occur in multiple locations around the world at the same time which cannot have had a central origin from which they emerge they effectively emerge at the same time in different locations is something which i think is very largely ignores in evolutionary biology which is population size and population structure and just this idea that when populations
47:07
reach a certain size the amount of information and the quality of the information that flows between individuals is optimized the larger populations get the better the transfer of that information is we are a species of experts right we are a species that I think has the most uneven distribution of skill sets of any organism everyone's an expert in something and what we see from these types of models and from the archaeological record is that that expertise is most efficiently transferred when populations grow so the
47:39
model sort of goes like like this that when you see you see a change in climate as a result population expansion and as a result you see better and more efficient transfer of these sorts of skill sets and it is in those sort of networks and that that's that transfer of information that you be the coincides with the emergence of these behaviorally modern characteristics that we're that we're so interested in it may be and this is speculation we think that Neanderthals were never very large populations it may be that they're our
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success over theirs once their populations never became big enough that you see this maximization of this this flow of expertise and I think it's a very powerful idea I'm interested in why it's not discussed more I mean I I I think it's correct i I looked at the work and studied the word and talked to mark about this a lot I think it's probably correct I wonder why it's not a more popular idea and I think it may be to do with the fact that it it recognize
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it represents a type of evolution that we have been taught and groomed away from for the last 50 years or so which is this the when we talk about natural selection we have to talk about what is being selected now since the 1950s and the work of George price and Bob Trivers and all those sort of titans of evolutionary biology in the middle of the 20th century the question of what was being selected well is it what is it is it the individual is it the group is it the species well no it turned out to be the
49:13
gene right the gene is the unit of selection and this is correct and this is a pillar of evolutionary biology today you know popularized by the concept of The Selfish Gene the gene centric view of evolution it is correct and as a result of that we are rightly taught and movement to to to not ignore but to reject other units of inheritance units of selection and especially away from group selection but in fact this idea of demographic transition and that
49:43
being a cause of a primary cause of the emergence of the full package it is an effect a sort of version of group selection it is we're talking about a cultural group and thus the size of the group determines how that population will evolve from that point on I think I don't know I'm get I think that may be why it's or not it's not a more popular idea than it is but I think you know in this book I'm trying to get that idea out there so that we could talk about it more widespread there's a the reverse we think is also true as well and there are
50:15
a few examples of this but one significant is in the evolution of [Music] Tasmania so Tasmania was attached to mainland Australia until about 11,000 years ago at the last glacial maximum and then when the Seas rose and the ice ages melted it became an island and it's been an island ever since now before it separated we counts something like 50 to 60 tools in the tool set of the people around this area then it becomes
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separated and over the next several thousand years the people of Tasmania isolated from a larger community on mainland Australia systematically lose almost all of the tools that they had before the separation and so when we now think that that in the time where mainland Australians generated about 124 to by the time Europeans arrived in Tasmania they were down to the Tasmanians we're down to about 20 and so
51:16
we see this this is a Javanese fishhook carved from the bottom of a flat bottom shell and this dates from about 24,000 years ago but by the time you get to about eleven thousand years ago in there in the neolithic we've got incredibly precise beautiful fine bones harpoon heads and sophisticated fishing of cartilaginous fishes and what we see in the archaeological record in Tasmania is a slow loss of this type of technology and in fact their diets change and they stop fishing cartilaginous fish and
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return to being hunter-gatherers of sessile organisms so you know stuff on the sea shore and they lose their hunting ability and return to being gatherers and so that fits in with this this model of demographic transition as being a driving force behind barrel modernity now I'm gonna stop there so that we can get to questions but I just want to say one last thing I might have mentioned that Charles Darwin is my intellectual hero the amazing thing about this whole story and this idea which is only now being talked about in
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the last few years I think is correct is that here's the guy who comes up with it in the first place and it's in the descent of man his second best book he it's just a clue to it but this is this is the quote which is worth thinking about again this is 19th century language and he excludes 50% of humans as man advances in civilization and small tribes are united into large communities the simplest reason would tell each individual that he'll to extend his social instincts and sympathies to all
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members of the same nation though personally unknown to him this point being once reach there is only an artificial barrier to prevent his sympathies extending to the men of all nations and races and and with that he's ceding this idea that population structure is absolutely essential to the birth of our minds to our cognitive abilities as we see them today and so that's it that's what we do that's what humans do that is what we're doing right now that is why
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we write books and why we attend lectures and watch television and go to school and go to universities and talk to each other because we are the products of evolution and when we took those tools that evolution provided us with the genes and the brains and the bodies and we became something different thank very much [Applause]

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