Carl Zimmer | 2019 Allen Frontiers Symposium

it's my pleasure to introduce as our first keynote speaker Carl Zimmer he is a columnist for The New York Times and the author of 13 books about science he in his latest book she has her mother's laughs the powers perversions and the potential for entity when the National Academy of Sciences communication award and was selected by the New York Times Book Review as notable book of the year he has a professor adjunct at Yale University and today he'll be speaking on braided history reporting on human origins please well please join me in welcoming Carl ok that's great so so it's a pleasure to join you today and you know obviously the the out the Alan frontiers group works a lot supports a lot of research on biology kind of as biology as today as you know as it is in our bodies right now but of course that biology has a history has a very long history and I it's been a real privilege of mine to be able to report on that on that history for the New York Times it might it might seem like you know if you're at a newspaper and you're writing about things that happen like 50,000 years ago you wouldn't be very busy but actually it keeps me surprisingly busy and is quite challenging and and and but in a really satisfying way just to give you one example from April this is an article I wrote about an entirely new species a new species of Homo called Homo losin dentists and it was found by Armand salvo Tommy Harris from the University of the Philippines and he was working in a cave initially he was looking for traces of farming in the Philippines and then he thought well maybe I should dig a little deeper and so he dug a little deeper and he found lots of bones he found lots of bones of at least three individuals maybe about 50,000 years ago 50,000 years ago there were Homo sapiens humans like us in Asia but this was not human in the sense that it wasn't Homo sapiens it was a lot like us but it might have been only three feet tall maybe less and this was pretty remarkable to write about especially given that you know a couple years earlier I've been writing about another strange species from another island in in Southeast Asia this is called Homo floresiensis sometimes nicknamed The Hobbit just because again it's so small then this one lived between seven hundred and sixty thousand years ago not only are these small but their brains are small too they're you know roughly the size of a chimpanzees and over in Africa in South Africa there's been this recently described species called Homo Naledi maybe as recently as two hundred thirty six thousand years ago which in the scheme of things isn't that long ago and this is a reconstruction of it so we have all of the we have the at least three small strange species of human-like individuals that have all been found quite recently and and existed at a time when our species existed we we actually need kind of a new way of talking and writing about these kinds of finds because we're really locked into some old-fashioned ways of thinking about human evolution and you know my predecessors death in here at times a century ago were not immune from this way of thinking so this is an article where it's basically about research in the 20s and it wasn't clear exactly where human origins might have been Africa or Asia but you can just look at how they sort of set up how they visualize human evolution from ape to man the chain as it appears to the evolutionists and so you can see the sort of this gradation from lemur to monkey to chimpanzee to what was called eight men of Java now we call Homo erectus and Neanderthals to cro-magnon man so of course those fossils of humans from Europe being of course at the top of this chain and so people would would would think in this very linear way about what it meant to be human how we became human that there was this march of progress and that all we needed to do to to understand it was just to fill in a link in that chain and so once you got the link then it was simple then you understood it and people use this language so this is an article from about a decade later from the again from the times literally using language missing link seen in fossil of an ape so this was an Australopithecus species which was the most remarkable example at the time a species that had some ape-like characteristics and some human-like characteristics in one and one as one skeleton so again we this we're not we're not passed this way of thinking I mean you see it everywhere and certainly this iconic image removed off challenger from from the 60s I believe it's with us everywhere this is like an incredibly common image and we see it in all sorts of forms this is just one of many I could pick up and this is really how people think about it and you know if you're not if you're working with an editor who has this sort of mindset it can be very challenging to talk about different kinds of humans existing at the same time because they're like well where does it fit in in the March and you have to explain well it's not a March and even I think I would argue that a lot of scientists themselves try to simplify human evolution into some sort of linear March and one across a certain threshold where we're human and so we say like well what makes us uniquely human well we must have gone in some sort of direction and then we cross the line and then voila human and so you know you you can see here for example this is this is not from a cartoon or from a newspaper this is from a published paper and and it's showing human brain size increasing over time in this you know linear way of course if we look at the time scale at the bottom you realize that things are maybe not so simple and I'll point out how they're actually a lot less simple than that so what do we know we if you look at DNA it's is clear that the great apes are our closest relatives and that instead of thinking of us sort of moving along in a chain we need to think of Apes and the ancestors of humans branching apart at different points in time and so our ancestors branched from our closest living relatives chimpanzees and bonobos maybe six or seven million years ago so what happens in that in that branch after that branching that last branching well you would the most important information I would argue some of the most important information comes from fossils and you know while I was showing you in the early 1900s there was this thing called Java man and there was this thing called Strela pissah consensus Neanderthals and that was about it so really about three three kinds of fossils this is this is kind of what we're talking about now this is this is going over the past seven million years or so we've got a lot and a lot of these were were found after I started working as a science journalist so it's kind of amazing to be able to write articles where people are literally sticking new rectangles on this chart so Bernard wood who does this he this is actually like one of his latest iterations he keeps having to revise it because we keep finding these new things now one of the clear the clearest lessons of this is that everything below that blue line is from Africa so it is pretty clear that that our origins are very deep origins are in Africa even are not so deep origins are as well the oldest thing that looks like closer to humans than to Apes the oldest hominin appears to be something called sal anthropocentrism its skull and this is a reconstruction of it you might say like well I'm not really clear how that's not a chimpanzee but there are some pretty fundamental differences so for example the angle at the base of the skull is more like ours than like a chimpanzees which suggests that it was holding its head more upright similarly another hominin called aurora in from around the same time scientists have only found some fragments but some important ones like the leg bones and the angle of those femurs also suggest that it was upright so the there's these clues that that being upright was a key kind of transition from the other apes and then when we get by the time we get to about four or five million years ago there's a species called Ardipithecus and we have scientists have found much more of that and that clearly was able to walk upright what's interesting is you know it may have it also seems to have been very adept at climbing in trees so it was still kind of a hybrid of a you know ground walker tree climber several million years after our ancestors split off from other apes and still had a very small brain chimpanzee sized brain now you this this this er aint ancient history is incredibly fascinating and you know not surprisingly there are a lot more questions than answers because it's hard to find fossils from three four or five six million years ago but if we just focus in on the last million years you might think like well okay well that's all settled right I mean we we found everything we need to find there's everything you know people have found everything that could be found right and the fact is no and the irony is that this chart which I lifted from a paper that came out in 2016 is out of date because that species I told you about Homo lose and incest it's not there I came to light afterwards so here's a if you zoom in on the past million years this is a paper that came out just a month or two ago this is one way of interpreting all the different hominins the members and these are actually all Homo that existed in the last million years and there are a lot of them you see homo losin dentists in the corner there so just to orient you where these sort of pale blue bars then you got homo Naledi over here and this are light green Homo floresiensis is this dark blue Neanderthals the unit halls are this sort of light green and then there are these other people called the Denisovans who I'll talk about a little bit later but this is just a sampling of lots of different kinds of humans all sharing the planet at once not very long ago and and it's likely they were going to keep finding new humans given just how these were all found quite recently except for the Neanderthals obviously we're going to be finding more and you know there are they pose immediate challenges to our kind of old-fashioned ideas about about human evolution about that sort of march of progress now it is clear it's that our brains are much bigger than chimpanzees they're much bigger than cell anthropos that's hominin but is that because natural selection kept working on the human brain in some sort of steady relentless way and and just made it bigger and bigger and bigger and is you know what was the was the selective pressure the same for that whole period is it just a one-way street as this would suggest no actually if you if you really look at the brain sizes things get a lot more complicated their brains have wide range even within a single species and see if I can point here and then you have homo Naledi in Homo floresiensis over here recent homo species with brains that are just way way too small this should not be like this and these are not deformities these these were healthy individuals that just had brains not like ours and so you some researchers have argued you know we've got a couple choices either these the either they evolve from very deep branches and they just never got big or they descended from big brained ancestors and got really small really fast you know is it like if you put if you put someone on an island put a population of people on an island do their brains shrink these these individuals were still able to make stone tools they were still able to hunt you know it's not like they were in some sort of island institution or something these were totally capable individuals who lived in these places for tens hundreds of thousands of years so what happened we need to sort of rethink what could the human brain is capable of to to explain this Neanderthals in Neanderthals always have this this reputation you know as being stupid you know Neanderthal itself is kind of an insult um but but really they they they they compared quite well to our own ancestors from the same period of time you have to bear in mind the a natales coexisted with humans they had brains that were as big or bigger than humans these are from the left as a homo sapiens then the inner tall's and then a couple chimpanzee skulls on the other side the inner tall's lived across a spectacular range in all sorts of different environments it's not like they were just if you picture them on some Ice Age glacier that's that's not it they lived out in Siberia they lived in the Near East they lived in Spain they they caught dolphins they did all sorts of amazing things and they even seemed to have had some sort of sense of serve self maybe or being part of a group because scientists are finding things like ornaments so this is a shell that was actually painted with pigment that see there was in a place that where Neanderthals lived they appear to have made necklaces out of Eagle talons so imagine a Neanderthal you know all decked out with with jewelry maybe face painted with ochre one of the most intriguing things that's been found in recent years is in a cave in France there are these stalactites that have been broken off from the from the cave and then arranged in circles and this is at a time when they're only Neanderthals in Europe and and this is deep underground and you know obviously scientists are trying to figure out was this some sort of sacred space that where wooden Turtles worshipping here what was going on it's it's hard to know but but the fact remains that it was our you know so-called lowly Neanderthals who were making those things then we have Denisovans and again the this is a kind of human that I didn't know about until very far to my science writing career because nobody knew about them in a cave in Siberia scientists were finding bones pinky bones teeth of something that looked like it might be human might need Neanderthal it was too hard to tell but fortunately it had DNA in it and so number of researchers including David Reich who's here they analyzed these and found that it was distinct from the DNA from humans and from the in Turtles in other words it was separate branch which has been called Denisovans named after the Denisova cave so that was exciting to write about but it was always kind of weird that like for several years like the only place that anyone knew about Denisovans was from the Denisova cave and you know you you sort of figure it's something that's been around for tens or hundreds of thousands of years probably isn't just living in cape and so it was really kind of mind-blowing to have a chance earlier this year to write about scientists finding Denisovans thousands of miles away in tibet so in this spectacular location there is a cave right here which has actually been visited on regular occasions as you can see here it's it's it's not an isolated place this is people go here to pray and in tibet tibetan monk was just sort of you know in the middle of prayer and happened to notice a jaw on the cave floor and this went into a collection in a chinese university and really kind of got neglected for a while but now it turns out that this was also a Denisovan Denisovan 160,000 years ago living at very high elevation in tibet and so so again we don't know a lot about these Denisovans but they have to have been pretty amazing individuals to survive at that kind of altitude so then we got then we get to our species and you might think like okay well alright this is where things get simple right Homo sapiens you get Homo sapiens evolving and then that's it we're uniquely human how complicated could story get at this point well there have been some amazing discoveries this was in 2017 where scientists published what they argued was the oldest fossil of our species about 300,000 years old in Morocco and it is clearly very very important find and in it and it helps bolster this-this-this hypothesis that our species arose in africa and you can see that not just by looking at fossils but by looking at our own DNA so Africans have way more diversity in terms of their DNA than everybody outside of Africa and the read this the clearest explanation for that is that our species started in Africa maybe around 300,000 years ago stayed in Africa African living Africans have inherited a lot of the genetic diversity that built up over that time and non-africans all descend from a very small group of people who expanded Out of Africa with much less genetic diversity so these these different lines of evidence fit together and if you try to draw a family tree as it were this is the kind this is this is the kind of tree that you see and so all non Africans are over here is this tiny little branch coming off of the East African branch but what's what's interesting is that up here things don't sort of converge down to some neat little small group of people in fact it's getting hard to say like well ok Africa is a big place so where in Africa did did things start some people would say well we found this one in Morocco this fossil Morocco so there must be there North Africa that's where Homo sapiens started but the genetic evidence is not pointing that way clearly and actually some scientists have argued if you look at others fossils from around the same time in Africa that no one's quite known what to do with this is like florists Pat for example this is a skull found in a place called Flores bad no one's quite knowing what to call this for years uh and so some scientists are actually are you know like actually these are both distinct populations of humans that both that all fed into our species and so if you want to like visualize the way they're thinking about it this is how they used to to think about the origin of our species where you've got you know one little population producing living populations there are scientists who arguing we need to think very differently when you need to think about lots of populations that are linked to each other interbreeding genes are flowing between each other some hit dead ends others survived through time but if you were to say like well what's the ancestor of this you'd say like well okay well I guess there's this and this and you know it gets it gets complicated I think that's the point that that the thinking about evolution as a chain as a line and so on just even as a even that even as a tree the tree metaphor really starts to strain at this point another another way in which that tree metaphor really starts to strain is when we look at our own DNA and look at the the DNA we have inherited from extinct groups of humans like Neanderthals like Denisovans this has this was this is something that's been clear for I guess it's been about 10 years now that Neander non-africans have between forget what the numbers are now between 1 and 3 percent roughly Neanderthal DNA and there are people who have a lot of Denisovan DNA so this is a just adapted from a recent study where you can see that in different places you have different percentages so the orange is a Neanderthal DNA turns out that East Asians have the most Neanderthal DNA of living humans people in New Guinea Papua not of Denisovan DNA but in any case they're just billions of people walking around with the with is genetic heritage from people that we would think of as being extinct as being other kinds of humans they're here they're you I when I was working on my most recent book I was really fascinated by what how these kinds of discoveries affect how we think of ourselves and so as part of my explanation exploration I got my genome sequenced and and then I went to some scientists and I asked them to help me to sort of make sense of it and so Joshua a key at Princeton I asked him you know I I don't want to just know like what my percentage of Neanderthal DNA is I'm I'd be curious to see what Neanderthal genes I got and he's like okay and then you know a couple weeks later he and his grad student sent me a list that's the beginning of the list I've got I think like 700 Neanderthal genes which is pretty standard and it's very exciting but of course like you know if you start to say like oh Q s ox1 of and the Anfal version of that what does that mean either they have no idea what it means to have the Neanderthal version or they have no idea what that gene does . so so this is a I find this like a very exciting frontier if you will of what it means to us to our health to have Neanderthal genes to have Denisovan genes to have genes from other kinds of humans that we haven't even encountered yet and what what this speaks to again is that human evolution has been complicated and so that it's not a chain and it's not even really a tree I mean it's a tree you know plus it's a you have these these populations where there has been interred reading between the branches this is a very very simplified version of what the reality seems to be I could have added in a lot more arrows and giving you a headache but these are some of the main ones and so the reason that I have all those mysterious Neanderthal genes is because of that big blue arrow the reason that East Asians have and Southeast Asians have more Neanderthal DNA then say Europeans seems to be because they interbred with Neanderthals more there were more interbreeding events and so when we try to like put this all into a big picture what we see is is humans originating in Africa it's maybe interbreeding with with other kinds of humans in Africa that's a big question that remains to be sorted out and then expanding Out of Africa maybe once maybe twice maybe coming the south end of the Red Sea may be going through Sinai and then encountering in the inter tall's Denisovans others and there's interbreeding there's also extinction so there's no like distinct group of people that we would call Neanderthals around anymore there are no more hobbits there's just us and so that's another interesting question of how it was that this big expansion happened and then all of that diversity or showing you started to to go away but you know it still it is still with us and and it it it you know for those of you who for example study the brain it probably has a big impact not just on the human brain per se but on differences between humans because we inherit different Neanderthal genes and I wrote an article based on a paper that came out in Current Biology recently where the if you inherit certain the inter tall genes there are two of them and have been identified so far your brain has a slightly Neanderthal shape you can see here Neanderthals had sort of football like brains and sort of modern human brains are rounder and it appears that the reason that having a Neanderthal these Neanderthal genes changes your shape a little has to do with the way that particular regions of the brain are different and you know the cerebellum to put them in these are regions that have specialized functions so what does that mean I mean the thing is that like you can find like people who have these genes and the inner tall genes or don't like within a population the study was actually done in the Netherlands so it's not like you can say like oh all the Europeans over here have brains like this and all the Asians have brains like that it's way more complicated than that but we don't really know what it all means finally just what one last example and this is like the most I'd say the most charged one because is is about skin color skin color was one of the four primordial ways in which people would distinguish groups of people from each other I mean it was it was at the it was one of the foundations for the concept of race for racism so black people working the the argument was their skin was dark because of the curse of ham because and their because they it was just outward sign of their inferiority and therefore it was okay to enslave them there was plenty of writing during the Enlightenment making this kind of argument but what is but what is skin color and why is it that people have different colors so CEREC Tishkoff for the university of pennsylvania has been looking into this with with some colleagues and what's interesting to you know is that you know we have a very simplistic idea about skin color but the reality of skin color is pretty complicated that you have people with dark skin in lots of different places including the Bolivian Highlands and within Africa you know people will call Africans quote-unquote black but this huge range of skin color just within Africa so these folks are all not just within Africa they all live pretty close to each other in East Africa I should say the bottom three sorry the Botswana people learn in South Africa but part of this is because Africa covers a huge range in terms of from the equator outwards and so you're you're being exposed to different levels of sunlight and so Tishkoff and her colleagues took a look at the gene look for genes that they could associate with differences in skin color among Africans and found a whole just they found a bunch of new genes that hadn't been identified before and they were actually able to estimate when the mutations that cause differences in skin color arose and you can see they found a combination of gene of gene variants that lead to light skin and dark skin within Africa and that's a lot several of them as you can see here actually they arose before our species existed so so the history of skin biology is really complicated what seemed to be the simplest thing about human differences is actually remarkably complicated it has a deep history that we don't really understand we don't know actually exactly what the color of the first Homo sapiens was you know maybe there are very light-skinned Africans at the time and very dark-skinned ones or maybe there was a combination of these genes it's hard to know what's exciting about skin color is that when scientists get DNA out of ancient skeletons one of the many things that they can do is they can say they can try to infer what their skin color might be this is still a very rough art at this point because there may be genes that influence the skin color that we don't yet understand nevertheless at the Natural History Museum in London not too long ago they actually put up this bust of what's called cheddar man which is very famous skeleton in in Britain and you know they they they recently published their results on this they they're able to get DNA out of cheddar man and as far as they could tell it seems that it's skin was certainly not pale and it might have been either dark or very dark as you can imagine this made quite a stir and you know there were just a lot of people who did not want to believe that the people who lived on their Island once looked like that it was kind of a kind of an ugly scene but but that's where the science goes and the reason may that people in England don't look like cheddar man now is has more to do with human history and human movement then about evolution per se and DNA is actually showing us that even in just the past say ten thousand years there's been these incredible movements of people and mixing their genes together so in Africa you can't look at anybody in Africa today as being some sort of like timeless primitive representative of the origin of our species that is kind of a racist way of looking at it and and the the DNA shows that even these these these would have once called the Bushmen of the Kalahari people like the sand they have they have DNA coming in from out of Africa several thousand years ago so so even in Africa there's there's been been all this mixing and this is I mean to understand what is happening in Europe i've Cribs them some pictures from David Reich's book you have you have people coming out of Africa and then expanding into other other places and so by 40,000 years ago you've got people in Central Europe you've got these hunter-gatherers but these people are not closely related to living Europeans you have other expansions so you have say around thirty thirty thousand years ago you have an expansion coming from another part of Europe and then during the ice as the ice the glaciers are retreating in the Ice Age you have an expansion coming seems to be out of Spain and as these people move into areas they are either interbreeding or replacing the people who are there these are all hunter-gatherers but there's a huge complicated history even 14,000 years ago you have yet another expansion things really get dramatic when farming is invented and then you have people from Anatolia spreading through Europe coming into contact with hunter-gatherers sometimes pushing them out of the way sometimes just stopping where they can't really farm successfully but they do manage to get to England among and Spain among other places but then you have yet another expansion something it was really exciting to report on just a few years ago you have people from the Russian steppes showing up the relatives of what people call the yam Naya and they just come in and really make their mark in some places they completely take over in other places they they interbreed and it's those yum nya pastoralists and it's also the the farmers come from Anatolia who seemed to have lighter skin and as they move in and as their genes become more common the skin of Europeans in different places gets lighter so it's a replacement it's not so it's not just oh you're European therefore you're white David Reich and his colleagues have also done more recently some really remarkable work just in focused in Spain a relic the limited place but there's so much ancient DNA now that you can get this very fine-grained look and so this kind of you know very complicated diagram there the one reason I'm showing it to you is just to make the point it's complicated in one little place like Spain it's complicated you start seven thousand nine thousand nine thousand years ago you know with these hunter-gatherers I was telling you about farmers arrived the the people from the steppe arrived but then you get more people coming in you and all through history the the genetic profile of the people in Spain is changing so that the people today over here are not the people they're there because of this constant mixing and turbulence of history you can't just look at it as some sort of like simple kind of march of progress so you know just basically just to sum up I mean I think that you know what's been my challenge in reporting on on human evolution in human history has been that it's how do you get that complexity into into you know relatively short articles but the the message is clear whether you're looking on the scale of millions of years ago whether you're looking at the scale of the past couple hundred thousand years or even just the past few thousand years we've got a we got to get beyond this way of talking about human history yeah take that chain just we have to break it and replace it with something more interesting and and that's been my privilege to do as a journalist and I'm sure that I'll be doing a lot more of it in years to come so thank you very much for your time [Applause] thank you we have time for a few questions there are mics in the center of the aisles if you have some questions to ask please make your way to that mic hi that was fascinating what's the current thinking of the role that the emergence of language played on sorting all this out yeah the question is what about the emergence of language and starting all this out so language has been like one of the great towering challenges and understanding human evolution there's supposedly at the Academie Francaise in the nineteenth century they just said stop it we're not going to talk about it because it's just too complicated and pointless to discuss I it seemed I would say maybe about how long about 15 years ago it seemed like things where we were on our way to figuring that out and there was a gene called fox p2 which had you know if people had mutations to it it seemed like it affected their their ability to use grammar to speak and people said ah this is this is a language gene and then they compared it to other species and they found that there were some interesting molecular changes to it that seemed to be possessed by every human and so the thing was like aha like natural selection in the past say hundred thousand years changed this gene it helped us to give language boom we were able to do all things totally differently than the inter calls and others and that's why we won I've been dying a little bit but there was a there was that kind of an attitude there was a lot of excitement about fox p2 there was actually a paper that came out a few months ago where scientists says like hmm like we only seem to have been looking at fox p2 at a pretty limited number of people would it be be like more systematic about this what if he be global about this lo and behold it turns out that people have lots of the Fox b2 that kind of you would have thought would make them unable to speak because they have they have different mutations in it and so I would argue that I mean I literally had the Fox b2 story in a textbook I co-authored in the new edition I took it out because I don't it's that story we don't I don't think we understand that story well at all now I that's my sense of it I mean there may be some facts b2 researchers here we're going to lecture me please do but it's it's gotten a lot Messier and you know you can argue that yes language our ability to communicate that must have helped sure but we don't really you know maybe Neanderthals and Denisovans were able to communicate pretty well too I don't think we know and so I so there so I I would love for the B to be some great advances in language evolution to report on as a reporter but I'm not I'm not really seeing it right now in fact I think things that we thought were clear have gotten unclear the closer we look okay great talk thanks very much I'm I'm wondering whether in all the static analysis there's evidence for postzygotic isolation and substantive or incompatibility in other words you have all these populations moving amongst each other and and they obviously mate with each other and produce offspring but are there movements where they don't mate and produce offspring in other words in cadet that could be do because it could be because they don't want to make this or prezygotic isolation you know they just don't want to mate with each other and we've seen a lot of that but it could also be due to some incompatibility between these separate rather different species and I I don't there's two questions here one is would you expect there to be this kind of isolation and I mean it seems like humans can mate with anyone currently on the planet but is there any evidence for it in all these populations so we have this paradoxical situation where you have populations that acquire that become isolated from each other but then mix with each other from time to time and and so we're sort of stuck in this kind of in-between situation they're there you know I don't you know we're humans and the animals not just attracted to each other well I you know I guess we get into issues about what attraction is it's a little harder for humans and fruit flies to talk about that it's more complex I mean clearly like humans and Neanderthals when they make contact did not just sort of merge flow together and so in just sort of into one union but it's not like they were completely apart in fact there seem to be repeated contacts and but what is interesting is that you know the why is it that we have you know relatively little in the Anatol DNA there have been models that suggest that there was a sort of a you know that Nia inheriting Neanderthal genes did lower Fitness overall for modern human they might have been some Neanderthal genes that would be give you some advantages like maybe immunity to diseases in Asia maybe that's one idea that people have offered but for the most part it seems like they lowered Fitness and and so that so that they've been gradually going away although that's there's a lot of research on that and I may be forgetting a recent study or something evidence in the end biology for reasonably closely related species up which would be able to physic we rate but which of course are not viable and that's this post psychotic problems revival so the question is do you see examples of close mixing with no mixing I mean physical mixing but no mixing genetically and EC and cannot be attributed to some biological incompatibility and development or something it's it's kinda stress I just don't have a feel for why all this happens so readily except that it it does okay thank you very much Carl thank you [Applause]

Channel: Allen Institute

Views: 1,962

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Keywords: New York Times, Paul G. Allen Frontiers Group, human evolution, ancient dna

Id: 1-m3HkOJztc

Length: 47min 15sec (2835 seconds)

Published: Thu Oct 31 2019