2017 Paul D. Bartlett, Sr. Lecture - What Darwin Didn't Know: Evolution Since the Origin of Species

[Applause] uh it really is a real pleasure to be here uh for a while it look touch and go and I didn't know about the sing-song option I was thinking I was thinking of me sitting in the departure Lounge at Logan FaceTiming you guys and it was it was not going to be good um it's a real pleasure and a real honor uh to be here uh a real honor to be um giving the Paul D Bartlett senior uh lecture I really appreciate the invitation um and I'm not blaming you for my misery this afternoon so what Darwin didn't know Darwin knew a lot of things and I'm going to give you the the punch line right away uh it's actually absolutely remarkable and my science evolutionary biology I think differs from all other Sciences in this regard that our Founding Father our parent Charles Darwin has remained completely opposite completely on point so to speak despite everything an enormous advances have been made in biology that's the message he wrote a book what 158 years ago On the Origin of Species I still have my students in this is not a history of science class this is an evolutionary biology course I have them read the Origin of Species partly because they get to see how to construct an elegant powerful effective argument but also because there's so much really great science and that it's not it's not like it's become Dusty and Victorian the science that Darwin is discussing in the origin that science remains today vital important and interesting so that's the punch line Darwin's still hot as hell okay um but having got the punchline will now sort of back up and we'll get there so and this and I think it's really remarkable that he devised an idea he wrote this great book which is robust to all the developments that have happened since and this I'm a biologist so I'm biased but man what a lot has happened over those 150 plus years right and yet because he's stuck to what he knew and that he was confident in he stuck to his facts he didn't go overboard with his speculation what we have is something which is completely robust to this day that every virtually every word in that book is still as true today as it was when he wrote it but what I'm talking about are the things he didn't know okay and of course there were lots of critical things uh and and I obviously don't have time I I only have 45 minutes I I begged and weedled give me three hours I said um no they said secretly hoping that my flight would be even more delayed um uh so what I'm going to do is I'm actually only going to highlight two of these topics but I do just want to give you a very brief sense of some of the key things that have happened since a huge a huge one is this one here's Gregor Mendel natural selection is an explicitly genetic theory it's about the preferential survival of certain genetic variants okay and in order to understand that you really have to have a good model of genetics Darwin didn't have a good model of genetics you really didn't and it's sort of one of the great tragedies in the history of science 1859 1866 Mendel's Publications but Darwin wouldn't have understood them if he did read them two hated reading German and um three probably didn't have access to them so that marriage never happened but I mean what's happened since man we've moved into the genomic era and that's one of the things I want to talk about um and with that we now really understand I think the most I still think is the most remarkable thing in all of biology which is a transformation of a single cell a fertilized zygote an egg Meats sperm into you 50 trillion cells it's extraordinary and there's just a string of information it's that genome that drives that process cell division after cell division after cell division and you've got this amazingly choreographed beautifully orchestrated organism that is you and we actually have a pretty good idea in the in the basics at least certainly the early phases of that how that works this kept poor Darwin awake at night no wonder he looks so traumatized um social insects social insects business um wasps um they do this weird thing and it's absolutely it's a No-No in Darwin land okay a worker bee is sterile she does not reproduce now think about the logic of natural selection let's say it's about passing your variance your genetic variance onto the Next Generation so this we call it reproductive altruism where you forego altruism in order to help your ma the queen of the colony produce more offspring right that is lunacy in sort of simple darwinian thought and and Darwin felt that way I mean literally tossed and turned I'm thinking about these things and it wasn't until the 60s that we really got a good idea about how it works which is it turns out there are two ways I can pass my genetic variants my genes On to the Next Generation I can reproduce myself and have my own children fine or I can help my sister let's say have many children okay and because my sister is closely related to me I'm effectively producing more of my own genes through her so it's the indirect route which basically it's a sort of back of the envelope calculus um if she has that many children and I help her raise them that's arguably better than me having my own and that's what ants are doing it's again about they don't do the calculus they've evolved for the calculus that as a worker ant it's actually more profitable evolutionarily in terms of rep of my representation in the Next Generation to to produce more sisters more workers I.E to help Mom than it is for me to have my own offspring okay that wasn't until the 60s that we really figured that out this is a biggie speciation now this is probably not something you think about all the time but it's an incredibly important part of the evolutionary process you all know about natural selection natural selection is the thing where you've got zebras and here's the sad slow zebra at the rear of the herd and there's the lion genes removed from the population that's natural selection okay heartless Lots in Kansas stupid zebra um um that's part of it and so that's what that is is you know that's evolving ultimately faster zebras um but imagine a world where there was no speciation what is speciation speciation is where you have one species that somehow splits into two so if we had no if this process didn't happen the splitting process you have the origin of life 3.9 billion years ago he got some Wiggly Little molecules which are self-replicating Natural Selections go operate the the wiggly molecules that do the best job in terms of harvesting the resources and replicating themselves would do better than the other ones that's natural selection and it would get better and better and better and better and better and better an old Planet would eventually be overrun by a single probably rather multi-purpose microbe end of story right it's critical this process of splitting this speciation business Darwin didn't understand it we do now it's super simple we could do it we'll do an experiment with this crowd be patient I'm going to build a wall down the middle of the room here I'm going to have to with all due respect to the baptismal font or whatever that is there um so I'm going to put a wall here now we've got basically genetically identical population on either side okay okay um I'm going to build a wall and I'm going to provide both sides with everything they need okay there's going to be I think yogurt and breakfast cereal Wi-Fi okay up but and there's no communication between the two of you okay there are two sides I'm going to leave you here for half a million years or something now obviously it's going to get boring um it's a bit like Logan on a on a Thursday Thursday afternoon um um what's going to happen well genetic differences are going to arise between the two populations okay so this gentleman with the blue tie in the front a mutation occurs in him yes sorry Mr Mutant um now and maybe by chance that'll over the generations increase in frequency in this population it's not going to be in that population right because of the wall okay and that different mutation arises here and a different one here and a different one here and so on and so forth this is going to take a long time okay what does that mean that over time this population is slowly becoming more genetically distinct from this population okay now think of that process I described of development where you have a sperm and an egg and those two strings of genetic information remember this is just aggcc Etc okay they have to come together and collaborate to build the extraordinary complex thing that you are now we imagine the sperm and egg because we've waited half a million years and we've taken a lucky female descendant on this side and a lucky male descendant from this sign we've taken them to a motel room the sperm and egg genomes are quite different now because of that mutation process and that may be sufficiently different that they can no longer collaborate to produce the complex organism that they could they can do within population within population but not between populations that's speciation it's that simple Darwin didn't get it Darwin as we'll see was averse to talking about human evolution for all sorts of reasons it's a bit of a hot button topic um he thought it was too incendiary he virtually knew nothing about the fossil record um which is tragic actually heat was sort of defensive about the fossil record he felt that it was so gappy it didn't you know there were all sorts of problems with it actually it's just this glorious document supporting virtually everything he said but what I'm going to do now is I'm going to talk about humans because I'm going to leave that that's going to do finally because you can all relate to humans but I also want to talk about genomics so those are the two of these this plethora of things that I've selected but just to remind you what we're talking about now call me biased I'm a evolutionary biologist this is a this is biology's best idea well actually no I think this is the best idea full stop actually I think the bicycle comes close um no and but this is a weird thing to do in some ways landlocked as Kansas City but I think I think the weird wackiness of sea slugs best enshrined biological diversity I just think they're just ridiculous they're just amazing things no this super simple idea which a middle schooler can understand this is not rocket science explains where biological diversity comes from it explains why and how biological diversity is so perfectly tailored for its environment the hummingbird has the bill perfectly proportioned to probe to the base of the flower that's natural selection right so those are two biggies perhaps the biggest biggie is this simple idea descent descent descent from a common ancestor modification through natural selection occasional speciation event explains us if you're a philosopher you're interested in mind yeah and maybe you could say that sort of highest calling of a human being to really try to Grapple with our identities that mind is the product of brain that brain evolved on the plains of Africa it's an evolutionary process that gave us ultimately William Shakespeare now for a simple idea that's a pretty good threefa I have to say there's a great story Darwin was a sort of plodding well big beardy as you know um not if you were sitting next to him at dinner he wouldn't it wouldn't be sort of cut thrust and Parry he wouldn't be super Zippy he'd be nice but not zippy a person would be Zippy would be Thomas Henry Huxley he was famously so Darwin didn't do much of his own defending he left that to his sort of young his henchmen um and this guy Huxley was super sharp he was known as Darwin's Bulldog Huxley would you know if somebody criticized Darwin Huxley would go after him and eat him um but I love the Huxley read the origin of the species and had a sort of Homer Simpson moment um how extremely stupid not a thought of that I mean it's so bloody obvious um so that's my point we've got this elegant super simple not rocket sciencey idea which as I say 158 years has remained wonderfully sound I'm going to pull out two things to highlight about the excitement of what we're doing we collectively The evolutionary biology Community are doing today um and they're sort of rather Grand things uh I mean I've got you know another 30 minutes so let's do the underpinnings of biological diversity and understanding ourselves um biological diversity uh 15 years ago or so we had the Genome Project huge deal okay so this is this enormous technical accomplishment to get all this DNA information out of a human being okay um now what is extraordinary this is really remarkable is the technology that that original Meg I'm going to call a mega project spawned so this is the cost of sequencing a human genome okay and this was at the time that it was finished now it started off so this line is still going up here from when they started so is it much more expensive than 100 million dollars and by the way please note that this is a log scale okay now this is Moore's law more this is Gordon Moore Mr Intel there's this rule of thumb for the speed at which high tech computer technology increases which is basically it doubles every two years now that's pretty damn fast okay now it's a straight line because we're on a log plot but that that is the white heat of technology that line okay and for the first eight years or so of the 21st century DNA sequencing can attract it we were getting better at it but there was nothing spectacular then whoo whole bunch of really amazing new technologies sort of collectively known as Next Generation sequencing um hit about here such that today this is pretty much we're pretty much there the one thousand dollar genome okay which means by the way I don't know how much how much does an MRI cost okay which means this is rapidly going to be part of your medical record okay now but I don't care about that I'm not interested in medicine um that's your problem I'm interested in this because what this means is instead okay fine we've got the human genome sequence we can start exploring human medical problems and so that's obviously important and cool but from my point of view as an evolutionary biologist it means that we we can now do sequence genomes of lots of other species so this is the field of comparative genomics this is just to give you a flavor of it um this is a sequence of a particularly it doesn't matter what the gene is and this is actually it's not in the it's not the atgcs of um DNA this is actually the protein that comes from the Gene and so you've got 20 different amino acids make up the protein and these are this is actually or the one letter code for the different amino acids details completely unimportant what I want you to see is this is basically across mammals cows chimpanzees humans hamsters why hamsters get a look in um somebody had a pet clearly mouse rat now that's a lot of evolution the common ancestor of those things existed about 75 million years ago so that was 75 million years ago and then you've got the hamster going down there and you've also got other rodents of The Mouse and the rat but you've got humans and chimps going off over here um and we've got cows going off over here so it's it's not just 75 million years of evolution it's 75 plus 75 plus probably another 40. it's hundreds of millions of years of evolution and what's happened look at this block it's been kept exactly the same so how's that happen well plenty of mutations have occurred in that time on those different lineages that have changed these things what happens to those individuals it's like the sad chubby zebra that you so mocked okay that's natural selection thinning the herd so to speak but natural selection is stunningly precise and what's more and this is the message natural selection tends to keep things the same once something has arisen way back when in evolution if you like natural selection has figured out how to solve a biological problem what happens you keep it that way okay um and so look I find this stunning this thing this is a nematode worm this common ancestor between this young lady and this worm is on the order of more than half a billion years ago so that's a billion years of evolution because there's the common ancestor half a billion to humans half a billion to uh the worm and yet we're still about 50 this thing is incredibly simple it has 959 cells never 960 another 950 always 959 and yet we're still 50 uh proteins are 50 similar you can make this is even weirder um this is one of my favorite experiments in I work on fruit flies in fruit flies we have great names for our genes and they're sort of obvious names there was a mutation we found that caused fruit flies not to have eyes so we called it eyeless clever um the mammal people found a mutation that causes mice and all mammals in fact not to have eyes they called it Pax six I don't know what that's about anyway it turns out it turns out and this is amazing it's the same gene okay this is a gene early in development says build an eye here what you can do is you can take a fruit fly which has no working eyeless Gene so it's going to be blind it's going to have no eyes there's no instructions saying build an eye and you can take the gene out of the mouse which as I say is a billion years of evolution apart give or take stick that in the fruit fly and the fruit fly gets eyes okay now that's especially amazing this isn't a mouse eye but it's close enough um when you consider we're dealing with completely different eyes so this is the basic signal says build an eye here and it's conserved it's essentially identical between fruit flies humans and mice Okay so what does this mean it means that most of evolution is about keeping things the same okay which is a bit puzzling when you look around when you look at sea slugs right and you see all this diversity so how can we reckon this is this is a problem of the genomic age how can we reconcile all this conservation this natural selective mediated conservation with the biological diversity we see around us and this is perhaps best enshrined by an experiment we did this is artificial selection so it's a bit of a cheat but it's amazing about 12 000 years ago we took one of these babies a wolf and domesticated it and then all sorts of weird people over the years says I want a really big loopy wolf descendant I want something that looks like a you know you know an unfortunate baby um no I mean no I'm serious I mean look look what we've done and the these things are almost all basically almost genetically identical to each other they're all just recently derived from wolves right and yet they're crazy different so what this is telling us is there's this process whereby you can leverage small must be small genetic differences which have very significant if you like Downstream consequences in terms of the behavior anatomy and physiology of the organism we're dealing with so that's and this is the study is unfortunately named this is where development comes in there's this study of Evo Devo which sounds like a sort of sort of late 80s synthesizer band or something um but uh it turns out it's development which is a key player here I'm going to give you two ways in which development can do this tiny changes in a genome have massive Downstream consequences the first piece is the obvious One turns out development is a hierarchical switching process I think what I just told you about the eye so there is a gene that says build an eye here and then that recruits a whole bunch of other genes which actually do the construction if you like and that itself is a hierarchical process obviously you're going to lay out the outline it's just like building something right you're going to lay out the outline of the eye and then you're going to recruit more genes which actually fill in so to speak um so once you've got a hierarchical process if you tweak something high up in that Cascade okay that's going to have really significant consequences if you go right down at the bottom of the Cascade that's not going to probably change very much you might change the color of the eye but if we tweet something up here it's it's I or no I okay so it's that hierarchical switching process allows us to make small changes of major consequences this is one of the most famous well no it is the most famous fruit fly mutant in the world it's amazing this if you like me you've spent many years of your life staring fondly down a microscope at fruit fly faces this will this is I mean this is like you know your sister's baby picture for me there's its eyes there's its antennae and there's this is it's it's little it's it's labial lips these are it's it's kisser it's it's very that's feeding apparatus so that's a normal fruit fly face this is a an abnormal fruit fly phase this as the eyes has the mouth it doesn't have any antennae instead of antennae it has legs coming out here fully formed legs this is a single base pair mutation in DNA it's a trivial change but what has happened is you've confused the geography of the embryo so there should be a signal in the thorax in the middle part of the body that says build legs here there should be a signal at the front of the head that says build antennae here you just switch that just tiny change and you've got legs coming out of your head and again perfectly form legs so that the whole recruitment has worked it just is you know inconvenient and there are other ones by the way this is what a normal fruit fly looks like it's a dip Turin which means it has two Wings has these funny little things actually stabilizing organs called halters here this is a not so normal fly where instead instead of having this you've got a second set of wings now you don't have to be a genius to imagine how this could have been important in the evolution of insects right because Wing number is something that can change and we can change it in the lab rather simply so that's number one this hierarchical idea the second idea is um algorithmic now think about again let's go back to that sperm egg moment and you know that that's burmeg is going to divide 2 4 8 16 and it's going to do that awful lot because I say there's several tens of trillions of cells in each one of you okay uh and it turns out that there's sort of rules fate rules we call them which determine what these dividing cells are going to be and here's a this is this is a notional idea but I just want to give you the power of this kind of thinking so here is a set of rules which is if you the three if you've got a row in the parent row of three blacks you have a black in the middle and if you've got two blacks and a white you get a black and so on so forth if you've got three whites you'd put a white underneath okay so let's run this rule okay now that's kind of boring but you know you've you've produced structure from this very simple set of rules okay let's change these just ever so slightly it's going to be we're also going to have eight rules and these are super simple rules so here's a slightly different set of rules now let's run it whoa isn't that pretty um that's with a second set of simple rules third set so again slightly different what do we get now now we get something which is formally chaotic there's no pattern at all and it's not repeating okay so look I'm not going to go to too much to town on this the point is that given the fact you've got this iterative process you tweak those rules just a tiny little bit you've got all sorts of potential for generating all sorts of major Downstream difference so that very briefly is what I have to say on how we can reconcile this problem that that natural selection keeps genomes the same on average because they're preserving the things that work and yet you've got all this diversity when we look around the natural world let's move now to ourselves to human beings um as the energy in the room begins to Sag people regroup regretting that second Whiskey on soda um so here's the Origin of Species um 1859 and look all the famous debates about the Origin of Species were about one key issue is it really true that us wonderful humans are modified great apes this is what I mean this is this is a pretty pretty seismic idea created in the image of God or modified grade A that's a biggie now I'm sorry to say that Charles Darwin m a wimped out this is he was probably astute he realized he's playing with fire anyway remember this is heresy what he's doing in the first place um so he decides he decides even though it's the thing that everyone's most interested in he decides to sort of tiptoe past the issue this is the most he has to say about human evolution in the Origin of Species much light will be thrown on the origin of man and his history great Charles now um um I don't and this was as I say this is strategic on his body he 12 years later he wrote a big book The Descendant man about human evolution and by the way he was complete it's not like he was confused or anything um in fact I think the most underrated moment in the Darwin story is this one I mean we all think of Darwin in the Galapagos he's on the prow of the beagle and the winds ripping Rippling in his sideburns as the Beagle plunges forward he leaps into the surf and there are Finches hopping around with the different sized bells and he slow-mo Eureka I mean that's our sort of perception of him it was completely wrong by the way he didn't get the finches at all but um but this I think it's really amazing actually so because he's just got back from Voyage of the beagle he's still in a state of ferment he's he's sort of developing his ideas but he hasn't got any ideas yet um when for the and he's not seen any great apes by the way on his travels but for the first time in London there is a living great ape which is a juvenile uh orang Jenny and because he's a he's a gentleman scientist he actually can go and hang out in the cage with Jenny and you cannot have a close encounter with a great ape and Come Away with any idea other than the fact that there is extraordinary proximity whatever that is between us and them so I'm just going to show I think this is a beautiful movie clip this is a an awful movie um called creation and it was about Darwin's anxieties and so on but they did and they were just I think incredibly lucky when they filmed this episode so here's the Young Darwin and his Jenny [Music] thank you [Music] foreign [Music] children was creative [Music] oh come on [Music] thank you [Music] what you get the idea isn't that wonderful um uh Darwin was actually completely on board with uh human evolution and he actually understood something in a rather sophisticated where he understood that humans must have evolved in Africa as he recognized on anatomical grounds that guerrillas and chimpanzees our closest relatives are both in Africa so sort of by default we must come from Africa ourselves now I'm not going to so we and we now of course he had none of this we now have this amazing fossil record it's absolutely stunning what has happened in the about seven million years since our lineage split off from chimpanzees um and these are hard one fossils you know these generations of graduate students have spent their lives on their knees shuffling through dirt in really hot and obscure parts of North Africa looking for these specimens and several of them you know only one in 12 get one and that's that's the PHD mate um I'm not going to talk about these though they are fantastic I'm a geneticist so I want to talk about the genetic approaches we brought to bear to human evolution and you'll be familiar with many of the broad results but I'm not I'm going to skip over them so this is here's the common ancestor of us and chimpanzees there's two species of chimpanzees as you know um here are our ancestors and it's important to appreciate and that's where the fossils come in there's lots of bushy branching here um who do it's always a problem who do we use to be the canonical the ER the archetypal human being I'm tempted obviously use myself um but no this is this is a Harvard Alumni Association sponsored event so here is Drew Faust um president of my University I hope you're watching the live stream Dr Faust yes um now so it all happened in Africa uh over seven million years and then about 1.8 the first Out of Africa group was a species called Homo erectus that left about 1.8 million years ago moved into Europe and Asia so you've now now got hominins as they're called our relatives Out of Africa then there was a second Out of Africa event uh which uh gave about half a million years ago which gave rise to the Neanderthals they went to Europe and Western Asia okay what about us well this is our family tree passed into Africans and non-africans this is fortunately not on the test I'll give you the simple version this the simple version is actually really remarkable this famous study from 1987. um that one our species arose very recently in Africa one and two non-africans are just one branch from within the African family tree so this is the common ancestor of all humans and both branches are African then you've just got this group of Africans who headed out of Africa okay now that's the so-called Out of Africa idea you're all familiar with it but more interesting we've got modern humans leaving Africa 70 000 years ago these guys were still around okay so what happened well we as you know and again you've seen versions of this I'm sure it's an extraordinary story the uh diaspora of our species Moving Out of Africa and colonizing the world and that I mean as you know very late into the Americas maybe 17 000 years ago incredibly late but the most remarkable part of this story I think is this Madagascar Madagascar is right next door to where all the action is okay so you're and it's this fantastically fertile piece of Tropical Real Estate you would have thought it would have been sort of part of the action rather early on in the piece the first humans to get to Madagascar got there about 2 000 years ago and they came from Southeast Asia so the the um the original language group um in Madagascar is is Bahasa Malay basically um anyway there's that but what happened when our ancestors came out and met the folk already there the Neanderthals was it something like this probably not um but we definitely overlap with them and so it was this question did we kill him did we beat him up what happened to them okay and it's difficult to know right I mean this is the anatomical difference these guys just much heavier boned adapted to a northern climate and by the way bigger brains than us um swept back they were sort of pre-adapted for doing one of those downhill sledding events in the Winter Olympics um but Anatomy won't get you very far and I'm a geneticist what's exciting and what I'm going to spend the next five or ten minutes talking about the final five or ten minutes about talking about is ancient DNA we now have the technology I sound like the what was it called six Six Million Dollar Man we now have the technology to take DNA from a 30 000 year old Neanderthal bone and and analyze it just as we would your DNA okay um and this is really recent so it's it's super tricky um but this is 2010 we had one two studies of ancient DNA 2011 still not much 2012 just getting up there 2013 a few more 2000 up getting better 2015. woo so this is a major so this is the latest this is a major growth industry and we're just getting all this extraordinary information and it's all super super recent and the first thing and you already all know this I think stunning and this was from the original study 2010 we now know that everyone in this room who is not a pure African is part neanderthal okay so um and what it turns out that people in Europe are about as much Neanderthal as people in Asia as people in New Guinea or Australia okay so what does that suggest it suggests that what happened happened here sort of when our ancestors were first coming out and then so then you have if you like the injection of Neanderthal material and then it's spread around but the really cool thing is it's not only neanderthals it turns out that neanderthals had a close relative known as the denisovans from this cave the only thing we know about these things we know quite a lot about neanderthals but we know they were smart we know they had culture they did ritual burials and so on um the this is something we know we have a pinky bone and a tooth and it's clearly it's a species related to neanderthals but really quite different from neanderthals so we call those denisovans and what we have now is this absolutely reformed vision of human evolution so previously we've kind of thought of those seven million years as a sort of March and things brains are getting bigger and we're getting more bipedal and we're ever getting more human to sort of the drive to Homo sapiens right now it turns out that yes of course there's all sorts of interesting evolutionary things going on but then there's smutty acts in dark corners of the Middle East neanderthals and then some is having sex with a denisovan we are we're like villagers dogs curs mutts when there's something pure and pristine and beautiful about us so here are so this is the main line of human evolution in Africa then you have the group that went out these are the Neanderthals leaving Africa and becoming the Neanderthals but then and splitting off and producing the denisovans okay and then here's African moderns and the Out of Africa event which led to Modern Europeans Asians and oceanians and you've got all this interbreeding two percent of your genome is Neanderthal on average okay now God this is not a good slide to introduce at the late phase of an evening talk but genetics 101 you loved it I just want to remind you of a little bit of genetics that when you have chromosomes from mum and dad when you're making gametes when you're making sperm and eggs they exchange material okay so in other words the chromosome that I might Crump the chromosome 2 that I passed on to my daughter Megan okay is a mix of the chromosome 2 I received from I've receive one chromosome true from my mother one chromosome two from my father and then they've they've done this weird thing where they've swapped segments so Megan has a unique chromosome too which is a sort of hybrid of my parents chromosome too okay why am I telling you this this is really cool so let's travel back in time where we've got these are the chromoses well let's say this is chromosome two so and we've got two two copies of each this is chromosome from your mother and one from your father and this is the Neanderthal and he is a modern so we're just color coding it so we're going to cross we're going to do the cross this is genetics and so the first generation you've got a pure Neanderthal chromosome and a pure modern chromosome but now what's going to happen let's have them this individual breed with another modern okay so that's another pure blue one okay but we're going to have that recombination process occurring here okay now we're going to do that now we've got now that's what we've got okay don't take notes um this is going to keep going okay so we're going to have another cycle of this we're going to have another cross and now this the point is if we keep Crossing to the blue we're going to break up these pieces of red every generation right into ever smaller islands of neanderthal DNA in the genome okay um so actually we can look at this over several Generations here it is so this is the first hybrid child and there's a grandchild and the great grandchild and all I want you to get is as the generations Roll by oops sorry um getting over excited um as the generations Roll by so the islands of redness get smaller okay which is why if we look at this is I think 12 genomes of um oh sorry 15 non-africans looking at their entire genome so this is Australian B2 and black is clearly modern Homo sapiens sequence and then you see these tiny Islands yellow and blue are tiny islands of Neanderthal DNA so it's exactly what I described you you do this process for enough generations and you're going to break this up into tiny little islands and that's what your genome has it has lots of tiny little islands of Neanderthal DNA now this is the cool thing as paper where we found this is ancient DNA gain from a modern human who's 45 000 years old okay uh here's the materials fished out of a riverbank in Siberia somewhere um what I'm going to do is add that individual now remember this hybridization occurred maybe seventy thousand years ago when we first came out of Africa these people are all today so there's been lots of chances for those blocks to get made smaller and smaller and smaller let's see what our friend from 45 000 years ago has whoa say he does he's got a few small bits but he's got some big ones as well so the size of those blocks are an indirect indicator of how many generations have elapsed lots of generations here rather few Generations between the the moment of hybridization and taking this data okay so that's the pattern we have and we can actually from this we can date the hybridization from the from the size of these chunks of DNA that's what we have but what about your two percent what does it do is it important or is it irrelevant this is kind of cool this is something that's gone looked at a thousand and four I don't know why they did the extra four um they went so it could be everyone in this room the sequence of DNA and identify everyone's Neanderthal bits okay so what do we find so here's the Neanderthal genome we find if we look across all those thousand people there's a fair bit of the Neanderthal genome which is missing okay now that's probably natural selection that's not useful DNA okay so Natural Selections got rid of that now if we look at my genome okay so there's my two percent and let's take Mr blue tie here again mutant man um that's his genome okay so he's there's some overlap here but in terms of on Neanderthal DNA but he's got his own little bit in the NFL D and then I've got my own little Neanderthal DNA the cool thing is this stuff there's some missing and there's some witches at so unexpectedly high frequencies it's almost in everyone so what does that suggest I'd say this stuff has been eliminated by natural selection this stuff has been boosted by natural selection so what this hybridization has done it's allowed what I call genetic cherry picking now think about it neanderthals came out of Africa moved into Europe 500 000 years ago their Natural Selections done its job it's turned them from very dark-skinned into light-skinned you want to be fair-skinned in the North or you get you get vitamin related problems okay um it's over those years it's if those Neanderthals have evolved to cope with the diseases you have in the north that you don't have in the South and so on so that's a lot of natural selection okay what we get by breeding within Neanderthal we get a cassette of ready-made for Europe adaptations okay it's actually really cool so this again this is all really recent stuff um immune and pigmentation traits these are the things that our species has cherry-picked from the Neanderthals so we really are hybrids and I'll give you a final example because it's a beautiful example it's really well worked out Tibetans Tibetans are adapted genetically to life at super high altitude okay they just cope better than you do you're staggering around gasping and turning blue they just fine and it turns out you can do the genetic studies it turns out there's a particular Gene that is associated with that and tibans have a very different version of the gene than you do or even the populations hand Chinese in the vicinity so there's something peculiar and that sort of makes sense they're adapted to this this very unusual environment so you'd expect them to have unusual Gene the really amazing thing is that their unusual Gene and this is complicated I appreciate these are people each line is people so and this is a chunk of DNA sequence and what we've basically black is the difference what I want you to see is one that Tibetans as a whole are rather different from Chinese okay the really cool thing is and really quite different from Chinese the cool thing is the Tibetans are very similar to the denisovans so in other words Tibetans got their ability to cope with high altitude from denisovans okay again it's more of this fantastic complex admixture this this we're much we're curse we're mongrels so and Darwin this is the final paragraph of his book on human evolution I think he said it beautifully we must acknowledge as it seems to me that man with all his Noble qualities with sympathy which feels for the most of bass with benevolence which extends not only to other men but to the humblest living creature with his god-like intellect which is penetrated into the movements and Constitution of the solar system with all these exalted Powers man still bears in his bodily frame the indelible stamp of his lowly origin and I do think if he was sitting at the back and maybe is Darwin would be absolutely thrilled by these latest developments it's added Whole New Dimensions to his ideas these are things he couldn't even conceive of but they fit in exquisitely powerfully and beautifully into his simple not rocket science idea of 1859. thank you very much [Applause] all right we have time for a few questions raise your hands I'll come by with a microphone we want to get the audio on our live stream feed just hold it close to your mouth thank you question with the the Neanderthal genes do we have any understanding yet what those genes actually do what their function is uh you mean the ones that are high frequency in US told us about the one with the gazelle Tibetans is one the other two major sets are immune function genes okay and the idea here is in Africa you're dealing with a completely different set of diseases essentially than you are in Europe the Neanderthals have spent several hundred Generations adapting to those diseases we get their immune their evolved immune response the other one is skin color and other pigment related phenomena neanderthals probably had a more or less Irish complexion sort of reddish appearance we know that from the from DNA information um why it turns so neanderthal ancestors were black Africans Coming Out of Africa okay and black Africans in Africa had to be black in order to protect their skin from high sunlight intensities okay uh you don't want to and this actually the the famous cases of people very dark-skinned people moving to Northern Britain let's say and living in Manchester and getting having all sorts of Developmental problems because for example to to synthesize certain vitamins of vitamin D in particular you need a reasonable amount of sunlight and if you've got very dark skin and you're living in Manchester where the sun has never Shone yet um you're you're going to be you're at a severe disadvantage so so there's natural selection in favor of a loss of pigmentation and again in it's natural selection it's incredibly inefficient and slow so one individual is slightly paler so they do slightly better than the dark individual they have slightly more children and that so there's the better representation of that variant in the Next Generation and then a few more in the following generation and so on it takes time okay but that's what happened to the Neanderthals and it's what happened to us so our ancestors were black when they came out of Africa um and pretty damn rapidly 70 000 years so my and this isn't all worked out but my money's on that we got whole cassettes of fair-skinnedness and other related traits from the Neanderthals it's a super interesting question and definitely ongoing territory Professor Barry back here in the middle of the room a few years back uh National Geographic ran a series on the evolution of humans one of their claims was that Africans migrated Out of Africa and to the Orient developed speech and then went back to Africa and then shared that Gene do you have any uh evidence to support that or have you seen that I've not seen it it sounds with all due respect to National Geographic bogus um I mean it's one of the Striking things about uh human evolution is Africa is really the locus where things happen I mean obviously I've focused on these weird outlying events relating to neanderthals and so on um look there might have been interesting two-way traffic um but anyone who claims they can nail that speech happened here then is I would suggest overreaching so um no no Professor Barry over here on your right we have an online question from our live stream audience Braden wants to know do you believe that random mutation and natural selection provide enough evidence to explain the complexity and apparent organization of life uh they don't provide evidence uh is natural selection sufficient to account for what we see It's actually an interesting piece of History except the answer is yes um I'm an evolutionary biologist uh um but there's an interesting piece of History here um Darwin Advanced the idea of national selection 1859 uh and there are actually two components to the the theory one is what we'll call dissent with what Darwin called descent with modification which is this idea you have a common ancestor and then next generation is slightly different and the next generation is slightly different so it's a Divergence process and also means that everyone's related okay it's easy to see that we're related chimpanzees we're also related to other to cows let's say but just rather further back that's descent with modification the second piece was natural selection which is this incredible it is horribly crude process okay some zebras run slightly faster than others okay and they're the ones which and so they're fast running genes are going to be passed on to the next generation and there was pushback a bit again I would say to to the question so can that crude fumbling process where generation is being generated at random and then you've got this filter which is a lion's eating the slide is that really going to work and people began to doubt it because you look around you see all this Exquisite precise design in nature until and they came up with various other slightly sort of mystical ideas and so on until um basically the 20s 1920s um which was that was when finally Mendel's ideas a genetic theory and Darwin's ideas came together and it allowed the development of a mathematical treatment of natural selection so and that's the joy of math instead of depending upon your intuition God is complex I can't believe this fumbling process could do it what you can do is basically extrapolate over vast periods of time we call it integration right and so you can actually establish quite satisfactorily that even if you've only got tiny selective differentials even if the slow zebra is only running half a mile an hour faster than the other zebras that's enough over the vast periods of time that we have and we do 3.9 billion years is a lot of time that's enough to produce what we see around us yes sir Karen you comment upon the the lifespan of organisms and how how it gets determined as well as how the lifespan of an organism uh in one species it Compares with that of another that's a really interesting question so um why do some things live a really long time and other things flicker in and out um so one is and I think this is an interesting idea that aging is preventable okay and that's true in humans it's true in mice it's true in fruit flies in a sense it's a programmed process okay um essentially you start falling to pieces after a bit probably after you've reproduced and so on now why is that because Naturals you've already reproduced natural selection doesn't care about you very much now you're falling to pieces okay yeah so so so a bunch of mutations are kicking in and sort of taking you down basically now so in principle if we knew where those mutations were and could manipulate them we could prevent you from falling to pieces okay there's no there's no absolute reason I mean people would maybe disagree with me but there's no absolute reason that we have to decay so then the question is why do we Decay one and two and this is your same question why do we Decay at different rates why do we last 80 years and mice last three years okay all right the uh best explanation I know of this came from Superior Medawar and he talked about uh beer glasses something which is close to every englishman's heart now imagine you've got 100 beer glasses uh in a very smart Pub in the West End of London okay where everyone just has a delicate little drink thank you okay versus another cohort of glasses which is in a really rough part of town where you whether yes they're occasionally used for drinking from but they're largely weapons okay okay so think about the life expectant and this has nothing to do with the glass itself it's to do with its environment the bad neighborhood glasses have a very short life expectancy okay whereas the good neighborhood glasses have a long life expectancy okay now we live in different environments we do different things okay but that essentially transfers to uh the natural world if you leave if you live in a high risk environment it's in your interest to develop fast reproduce fast live fast Die Young okay if however you can control your environment or you're in a low risk environment then that pressure is off and you can have a longer lifespan okay but I think I do think it's a really interesting problem because I think I mean I don't think it's something we'll do in the next even in the foreseeable future but I think we can probably prevent aging Professor Barry back here uh on your left towards the back of the room what would you say would be the best response to the argument that various life forms have a lot of information and information only comes from an intelligent mind so maybe there's an intelligent designer um well that might be an intelligent designer you don't need one to account for the array of information we see in living organisms that's not to say that somebody hasn't injected DNA information into platypuses or something no um what I say to that is look at the history of life we have a pretty good model it's a difficult thing to really understand because we don't have fossils we don't have direct evidence but we we have a pretty good model of how life originated okay and that sorry it's random it's a bunch this is chemistry becoming biology it's a bunch of molecules that haven't get stuck together which happen by chance to have the ability to replicate themselves and once you've got that ability then you've got natural and then natural selection I've already said this kicks in right because if you've got a bunch of those molecules the ones which are best at garnering resources of the environment they're going to out-compete the other ones so natural selection takes over now natural selection is looking after that information remember that slide I had of the con conservation of protein sequences that's natural selection doing its business of maintaining that information so no I don't think there's anything about the and it is extraordinary the amount of information in you and in every other species but I don't think there's any need to invoke non-material causes to account for it all right um hang on one second there's a question back here you caught me off guard here I was sorry was I supposed to go on longer I was not prepared just about 10 seconds longer would have been great I'm sorry biology and life form start how far back do you go oh it's a really interesting question um uh it's very difficult to know um so we do geochemists have some really smart ways of detecting the presence of life even though we don't have fossils of very early microbes but there's still it's contested I mean there was a paper that came out two months ago which claimed to push back the origin of Life by a few million years um I I tend to stay about 3.5 maybe up to 3.9 billion years ago now so that and as I've already described that's the transition yes we had chemistry um and there's nothing magical about this all it is is all we are sorry people is some really fancy high-end chemistry and it started off super simple namely just a string a simple molecule that had the ability to replicate itself okay now interestingly uh if you talk to the chemist it turns out that given our models of how this might have happened it quite possibly happened not frequently but it's not that unusual in event so why then and it's quite clear if you look at all the similarities from the simplest bacteria to you to a platypus it's quite clear we do so many basic things in exactly the same way that we must all be descended from a single common ancestor but it's quite possible that way back then there were multiple experiments in life and it just so happened that the one that we are a current instantiation of was the one that did best that out competed the other ones right Professor Barry up here on your right and due to the time we have time for two more questions we'll take one up here and then we have another live stream question that we'll end with okay well just for the record I I want to mention that Darwin is always seen as his theories of natural selection and mutation but what gets pushed under the carpet and and I haven't heard from you maybe to restraints of time is that actually one of his quotes is God protect me from Lamarck's nonsense and actually part of his life he was agreeing with Lamarck that giraffes have along neck because they have to reach the leaves of the trees so just opposite of what he's famous for maybe you can so yeah this relates to poor old Darwin had this problem with not having Mendel so his intuition on genetics is actually a very reasonable intuition but turns out to be wrong he believed in something called which we've termed retrospectively blending inheritance now blending the inherits is is a tall person has children with a short person the children tend to be somewhere in the middle a very dark-skinned person has children with a very light-skinned person that children are somewhere in the middle so so often it works but if if you think about it it's a real problem imagine you've got a bell curve of zebra running speeds okay and let's just say that zebra is appearing more or less at random okay and that blending inheritance rules the roost now this is the fastest running zebra this end of the bell curve almost certainly that individual is going to breed with somebody over here right so their offspring is going to be in the middle here so we've just lost that extreme okay same even with the slows because that on average will breed with a faster one producing something in the middle and you can it's a simple mathematical model what will happen under blending inheritance is you lose the extremes of the distribution and everything just converges on the middle okay um Darwin hadn't thought this through and it was in 19 sorry 1867 uh so eight years after the publication the origin when a Scottish engineer with a wonderfully precise Turn of Mind fleaming Jenkin pointed this out and it's a real problem because think about what natural selection is if if genetics is always just pushing everything into the middle so all the zebras are now sort of medium speed when when we know natural selection it's supposed to be favoring the the fastest running ones but we've lost we don't have any faster running ones because they've sort of bred with the slower running ones okay so Darwin I won't say panic but he went into overdrive to come up with a theory of genetics that would save his theory and he came up with us with a lamarchian idea he called pengenesis where China and it's it's sort of Science Fiction slash fantasy almost he claimed that different bits would produce tiny little generals so the bits that were most useful so for the fastest running zebras their legs would produce lots of fast-running demules which would accumulate in the zebras gonads and those would get passed on so it really is inheritance of acquired characters as per Lamarck um and that's the tragedy that Darwin really should have read some German Professor Barry one more question and this comes from one of our live stream viewers this is from Christina if we were to find life forms out in the universe what qualities do you think would be universally shared oh that's that's that's a really uh oh yeah no they'd all have English accents and be interested in evolutionary biology um so it's quite interesting so there is this field of astrobiology which is a sort of offshoot of evolutionary biology and they're actually interest in the questions that the lady at the back raised which is the transition from chemistry to biology and and the question is this is there only only a finite number of ways in which you can make complex life so or are there lots of different ways if there's only one or a finite number of ways then maybe whatever's out there and there is stuff out there has to be just statistically there's plenty of real estate out there plenty of chemistry going on um but the question then is are these things going to be you know so alien for one of a better term or are they actually going to be because there's only a finite number of ways it's the laws of physics and chemistry have you know there's there's certain channels that you can go down so for example will it be a carbon based life form well it turns out probably Yes actually um just from the periodic table carbon has this marvelous flexibility you can do almost anything with it you can pull these weird bonds and base it's like it's like a it's like a Lego block basically so and the closest and I'm not a chemist so I'm this is what the chemists tell me the closest possibility would be silicon and so you could maybe have a silicon-based life form which and that has some of the same flexibility in terms of being able to create all sorts of different permutations but it's much bigger so it's a much it would be much more unwieldy and we do know that we got plenty of silicon here and that never took off here so so I think there would I think this is really down to chemistry there would be some coming out as I think it would be a carbon-based life form the Astro biologists make fairly effective arguments about the fact that it's water is a key solvent now you say why couldn't we say have an acetone based life system it's just a water is a really good solvent for all sorts of reasons and it's got a good range in terms of its its availability it's you know between zero and 100 degrees Centigrade it's it's available as liquid and so on um so two things carbon-based and water dependent beyond that I don't know and it's this great question actually um Stephen J Gould uh posed it um if we were to re so given that we've got our chemistry and all our constraints on this planet if we were to quote replay the type of life and this is always a difficult thing to talk to undergraduates these days I assist we just have these things called VHS tapes um but he says let's go back half a billion years and with what we had half a billion years ago would would we be sitting here this is so this is about sort of predetermination and predestiny and he and he was absolutely of the opinion no because there are all sorts of random interventions the biggest of which is the rock that fell out of the sky 65 million years ago and hit the dinosaurs on the head right because that was what gave mammals have been around for 100 million years or so scurrying around never getting bigger than this at the feet of the dinosaurs and it's only the elimination of the dinosaurs that allow mammalian Evolution to take off so that's this sort of serendipitous part of the process so carbon water rocks right and then all bets are off because there's so many contingencies that could account for things Professor Barry thank you thank you and thank you all for attending tonight's event you know this was the 15th annual Paul D Bartlett senior lecture so it's been 15 years already and one of the best well thank you and good night foreign

Channel: Linda Hall Library

Views: 38,901

Keywords: evolution, Darwin, science, engineering, technology, human evolution

Id: 0UXI-UCbC3E

Length: 75min 37sec (4537 seconds)

Published: Tue Apr 04 2023