Chris Stringer on Human Evolution, Recent Discoveries, and their Implications

can slowly start so uh let me welcome uh everyone here to our second talk of hillary term uh we are very pleased that so many of uh our members are joining us remotely and some of us uh in person as well uh our today's uh guest speaker is uh chris stringer who is or was let's say interested in human evolution since the since the primary school and uh he has excavated that site in britain and abroad directed the ancient human occupation of britain project from 2001 to 2013 and he has published over 250 scientific papers and his recent books uh include complete world of human evolution the origin of our species and britain one million years of human story uh so there are plenty of publications and scientific papers on on human evolutions and uh chris will be giving us updates on on human evolution from from his perspective and from the news research he has done today so i'm leaving this spiritual stage do you know chris okay thank you very much um yeah so human evolution some recent discoveries and their implications um and of course you know some basic groundwork that that everyone around today of course is is a member of this species we call ourselves homo sapiens wise humans may not be such a good name but that's the name we've got um and of course if we look around the world there's a lot of diversity people come in many different sizes shapes and colors but genetically we are all closely related and we belong to this one species and when we take away the superficial features and get down to the skeleton we also have shared features in our skeletons and on the right hand side there you can see a modern human skeleton from the exhibition at the natural history museum in london and when we look at that skeleton we can see a number of derived features that are special to our species so in the skeleton as a whole we've got a high narrow rib cage we've got a narrow less flared pelvis compared with earlier humans we've got smaller joint surfaces a lighter build to the skeleton generally the muscle markings are are not so strong as we find in earlier human species and that goes for the skull as well we have a number of differences there so we've got this high and rounded globular brain case the upper parietal region is expanded out the base of the skull is narrow we have distinct ear bone shapes compared with other humans we have a weak or non-existent brow ridge at the front of the brain case the face is flat transversely flat and retracted under the brain case we have relatively small front teeth and we have a chin on the lower jaw so these are all features we can look for in fossils to track back when homo sapiens originated but there was a lot of diversity in the past and this is you know my attempt to map that diversity so these bars in this diagram represent different lineages i would call most of them different species of human during the last one million years and we're over there on the top left green bar homo sapiens we've got the yellow ball the neanderthals and another lot but i'll be talking about the denisovans in the center there so there's all this diversity and even recently um there were a number of different humans around so even 70 000 years ago of course geologically like yesterday there were at least five kinds of humans around we had been evolving in africa homo sapiens the neanderthals have been evolving in europe and asia the denisovans over in east asia and down in ireland southeast asia we have these strange small-bodied species of human and small brain species of human um onflores homophoresiensis nicknamed the hobbit and on the in the philippines homo luzinensis a species only named in the last couple of years so even 70 000 years ago there was still all this diversity and homo erectus the the more ancient species might even still have been around as well uh that's not so well mapped so i'm going to talk about four things if there's time in the talk talk about the situation in africa and our origins there talk about neanderthals in europe and asia and our interactions with them talk about the denisovans um in east asia and then finally that big question which of course is very interesting for archaeologists too why are we the only humans on earth what happened to those those other species that were around until recently so let's look at the african story briefly and here's a simple representation of the evolution of the neanderthal and homo sapiens lineages so on the left there we've got the neanderthal lineage stretching for several hundred thousand years in europe and asia and we've got this fossil from the siemens in spain about 430 000 years old and showing what seemed to be clear early neanderthal features so the neanderthal lineage goes deep in time and in africa we can trace our own lineage back over a similar length of time we've got a homo sapiens fossil on the top right there from crow manual in in france but lower down there the jubilee hud1 fossil from morocco seems to be in early homo sapiens at around 300 000 years ago geneticists estimate that we had a common ancestor with the neanderthal lineage probably more than 500 000 years ago but who that ancestor was and where that ancestor lived i think now is is much less certain than i used to think i used to think the common ancestor was a species called homo heidelbergensis um and now i'm i'm not sure about that and i'm not sure what continent that common ancestor lived on it may have been in europe it may have been in asia it may have been in africa and because the african story seemed to be relatively simple until recently so here's a common representation of the evolution of homo sapiens in africa with this earlier species homo hyder begensis or rhodesian cis sometimes called represented here from the broken hill fossil also known as cabway estimated often at 500 000 years old giving rise to early forms of homo sapiens and giving rise then to later forms of homo sapiens so this was seen as a relatively gradual transition and possibly uh in fact probably for some people occurring in only one area of africa east africa was often the the favored area for this transition from hyder bergensis through to homo sapiens and we know that that uh representation of homo sapiens as we have suggested goes back quite deep so the jubilee hood fossils which some of them were found back in the 1960s um they've only recently been been dated properly and more material has been recovered from the site so we have these beautiful stone tools from the site we have luminescence dates and esr dates for the material of around 300 000 years and we've got more complete reconstructions of the jubilee material now so a composite reconstruction there of the jubilee huduan fossil with a jawbone added to it from relatively new discoveries and the ghibli hood fossil has got some modern human features in the teeth in the jaws in the middle of the face the shape but the brain case is still quite primitive uh it looks like it if it is a homo sapiens hasn't yet evolved that high rounded brain case that we find in later homo sapiens but that high-end rounded break is is there and we now know it was there in ethiopia more than two hundred thousand years ago so this fossil on the cubish one found by richard leaky's team back in 1967 in in southern ethiopia the cranial vault is high and rounded there's a small brown ridge there's a chin on the lower jaw it has upper parietal expansion and there's also a skeleton associated with it which does have modern humor features including in the pelvis so this fossil as it says is recently been dated by a major explosive eruption of the sharla volcano in the main ethiopian rift by dating the proximal deposits of this eruption we obtain a new minimum age for the homo fossils of about 233 thousand so this is a fossil which for me is is a a modern homo sapiens at least in the parts preserved and yet it's over 200 000 years old but when we look at the african fossil record as a whole for homo sapiens it's really quite diverse and there isn't a clear pattern of change through time if you line these fossils up in the best we can in a chronological sequence they don't form an ordered gradual sequence through from more primitive to more derived more modern looking some of the fossils show mixed features and even at one site such as alma kibbish we have two very different looking fossils which appear to be about the same age so there's no clear pattern of change through time and this has led me and others to develop the idea that there wasn't a a single gradual place where modern humans evolved it wasn't east africa um actually modern humans were evolving across the african continent so this is a pan-african origin and i've worked with other people such as elena sherry on this and ellen's quote there says that humans did not stem from a single ancestral population in one region of africa as is often claimed instead our african ancestors were diverse in former culture and scattered across the continent i wouldn't necessarily say the entire continent but various regions contributed to the evolution of what we call homo sapiens and what we call modern homo sapiens so the evolutionary pattern is as shown there on the bottom right there we've got lineages in different parts of africa at times going their own separate ways at other times when climate allowed it mixing with other populations and so we get a kind of mosaic evolution of homo sapiens and a coalescence of the modern homo sapiens pattern in the last 100 000 years so no single center of origin and not certainly a gradual change in one place a much more complex pattern than we used to think and it's even more complicated than that because this map here shows some of the early homo sapiens fossils in in black and grey but there are archaic humans around at the same time as we now know so this fossil from broken hill cabway this is a paper from 2020 um where we dated this fossil directly and as it says here the best age estimate is about 299 000 years the age estimate raises further questions about the mode of evolution of homo sapiens in africa and whether homicide of against his rhodesians was a direct ancestor of our species so that's both chronologically because of course you know we've now seen that the omo kibish1 fossil which looks much more modern is only about 70 000 years maybe younger than this fossil um and we also look at the morphology of these fossils so the broken hill fossil for me um has a face which is very unlike that of homo sapiens much less like homo sapiens than say the ghibli hood face so i think that this group that i've called highly beginner cysts or rodisiensis i think it shows derived features away from the modern human pattern in the face and for me that makes it much less likely that this group is the common ancestor for us and the neanderthals and that's also unlikely when several examples certainly are actually contemporary with homo sapiens rather than earlier so this model seems not to be accurate now as it says here the evidence suggests that the large and non-sapiens-like faces of bodo and broken hill 1 represent taxonomic diversity in the african middle pleistocene record which could exclude the large fossils as representative of an ancestral morph for homo sapiens and it's even more complicated than that because of course down in southern africa we have a a much more primitive species surviving until around three hundred thousand years ago this is hormone naledi uh only found in the last ten years or so um and as it says here a composite skeleton reveals homology's overall body plan his shoulders hips and torso heart back to earlier ancestors while its lower body shows more human like adaptations the skull and teeth show a mix of traits and that includes a brain capacity which is really only comparable with with some of the great apes of today chimpanzees and gorillas so this small brained species still surviving around 300 000 years ago so yes the the sapiens lineage seems to be evolving in in northern and uh northeastern africa uh we've got hindu against his or redesigns is still around about 300 000 years ago in zambia and down in southern africa something much more primitive still homo naledi and of course we have no idea when the heidelbergensis rudisiensis and the lady lineages actually disappeared and we can date them around three hundred thousand they may well have survived later than that and of course dna contributes to the story and one of the regrettable things is that because of the climate of africa we have uh only very poor dna preservation and the known dna from african fossils only at the moment goes back to about 15 000 years so whether we'll ever have fossils from those earlier forms those earlier species is is looking it looks unlikely at the moment but what the data do show is that modern humans outside of africa today genetically seem to trace their common ancestry back to a dispersal that happened about 60 000 years ago so this is from a paper i was on from earlier last year and as we say here this diagram shows in black here a number of fossils that have complete or partial or complete genomes which suggest that genetic ancestry is consistent with deriving from the major worldwide dispersal less than 60 000 years ago so that dispersal of course was going to bring these humans into the territories of the neanderthals and it's a bit more complicated than that so this dispersal 60 000 it looks like it wasn't the only one that homo sapiens the only excursion that homo sapiens made out of africa this diagram this map shows some possible earlier ones including to china and australia and we've got this incomplete fossil from greece from epidemic cave in the peloponnese and epidemic one as shown there at the bottom it's only the back of a skull but it looks like a homo sapiens fossil the back of the skull is high and rounded and it looks most like a fossil like skull 5 which is on the bottom right there and that fossil of school 5 is similar in the preserved parts to epidemic one so this morphology of epidemiology is very different from the neanderthals very different from heidelbergensis and yet this fossil is dated by uranium series to over 200 000 years old and what's interesting is that epidemic cave it looks like neanderthals occupied the cave after this date so we've got a situation where we seem to have a maybe a brief dispersal of homo sapiens into europe um and then that population disappears and is replaced by neanderthals and there's further complications from the far east so we've got sites in china which seem to show homo sapiens fossils at more than 80 000 years old we've got a couple of teeth from sumatra which seemed to be more than 65 000 years old and equally challenging the data the archaeological data from northern australia so major baby 2 this rock shelter has a long sequence with a series of luminescent states and at about 65 000 years ago there's a very rich layer rich in complex technology enriching pigments 65 000 years old assumed to be the work of homo sapiens and yet dating from 65 000 years ago which is of course before this putative 60 000 dispersal which gave rise to modern day genetic diversity outside of africa now of course not everyone accepts the dating there so here's a paper that critiques that dating and argues that the material in major baby is more likely about 45 000 years old so i think this is an open question obviously more dating will help resolve this more sites will help to resolve this whether major baby can't just be the only site in northern australia of this age there will be others to be to be found and dated if that story is correct but because it does lead to issues in explaining the data in matching the archaeological data the anthropological data and the genetic data so yes it looks like there could well have been earlier ways out of african more than a hundred thousand years ago including epididyma including that material in southeast asia and australia and then we have the main wave which geneticists map from present day diversity outside of africa which occurred around 60 000 years ago and we have to argue that that main wave over printed any surviving trace of those earlier dispersals of homo sapiens out of africa so whether those early dispersals were unsuccessful and disappeared completely or this wave at 60 000 was was so strong it swamped them if you like genetically and removed any trace of those earlier waves in terms of the genes of people outside of africa today so now let's look at the situation in uh europe and asia and the interactions with the the last neanderthals and of course it's worth i don't need to tell you people i'm sure that the neonatal image has greatly changed in the last particular last 20 years i think so the original neanderthal fines of course dating back to 1856 in the neander valley we now know that neanderthals covered a wide range geographically they weren't just european they were in western asia they were in uzbekistan and they were over in siberia at times i think they were probably in china at times and their image as it shows on the right hand side on the top right there we've got uh an image of the neonatals from the early 1900s where at that time there were no really primitive african morphologies we didn't have fossils of australopithecines for example uh back in the early 1900s and so people who believed in human evolution kind of pushed the neanderthals into this position of a sort of missing link that neanderthal they're depicted as very bestial bent knees hairy uh grasping big toes head hung forward and so on and then at the bottom right there we've got a contrasting image from our exhibition in london uh by the kenneth brothers showing this much more human representation of the neanderthals in fact the kenneth brothers told me that they had based this reconstruction the expression of it on a photograph they'd seen sean connery so here we are a very human representation of the neanderthals but they were distinct from us uh i think they were fully human but a different kind of human so we've got a neanderthal skeleton now compared with the modern human one so neanderthals have got a much bigger rib cage more voluminous wider deeper probably the lung capacity was 20 bigger than that in homo sapiens um a much wider uh and more flared pelvis probably the internal organs of the neanderthals were somewhat larger than our own um the joint surfaces are much larger on the on the bones the muscles muscle markings are much deeper and the differences are there when we come to the the skull as well so at the top there we've got a neanderthal from not pharisee um some primitive features there so the brain case is long and low as it is in earlier humans with a strong broward up front not much sign of a chin on the lower jaw large front teeth and then some really distinctive features in the neonatal skull such as that projecting mid face an enormous nose on on the middle of the face and the face is pulled forwards distinct earbud shapes and a little depression at the back of the skull called the superiniac fossa sony avatars can be recognized very well from there from their fossil record and as we've said modern humans having evolved in africa start to emerge from there particularly in the last 60 000 years and so these are some of the genomes that we can map that dispersal of homo sapiens into the territories of the neanderthals and so that brings up that always tricky and controversial question of interbreeding with the neanderthals it's something we've argued about for many years so on the bottom right there we've got a fossil from portugal the libido child from algarve and that's been argued to be a hybrid of a modern human and neanderthal we now know that fossil it's only about 26 000 years old unfortunately there's no dna from it but it seems very unlikely that it's any kind of hybrid uh it seems to be just a homo sapiens child from the gravity um and at the top left there we can see evidence from modern species of mammals that they can hybridize successfully so there's an example of the brown bear and polar bear hybridizing successfully in zoos and the offspring are fertile they're interfertile and the divergence time of the polar bear and brown bear is about comparable with the divergence time of us and neanderthals so i was certainly aware that closely related mammal species could often hybridize we know jacquards and wolves can many species of baboon can but my view until recently was well that happened a long time ago it was probably rare um and we're not going to find any evidence of it today uh but i'm because wrong and of course and that was shown clearly from 2010 onwards when um the first really good quality neanderthal genomes were reconstructed and as it says here close encounters of prehistoric kind the long-awaited sequence of the neanderthal genome suggests that modern humans in neanderthal was interbred tens of thousands of years ago perhaps in the middle east in fact we'd now say in a number of different regions of europe and asia as a result uh pretty well everyone living outside of africa has inherited a small but significant amount of dna from these extreme humans and many of us listen to this talk today we'll have around two percent neanderthal dna in our genomes from these ancient interbreeding events and we can map the interactions of the last neanderthals and these homo sapiens dispersing from africa here are some of the sites which show the evidence a number of these have been published recently and here's just one example from owasi in romania so this jawbone found many years ago now has a strong chin on the front and therefore looks like a homo sapiens but the teeth are large and have some unusual features and so it was hypothesized that it might be some kind of hybrid and sure enough when the genome was was analyzed from this fossil which is about 40 000 years old on a direct radiocarbon date it was found to have about nine percent uh neanderthal dna in the genome so much more than we find today and as it says here it's estimated that this individual's neonatal ancestor was introduced in the previous four to six generations so this is data from a time when as far as we know the neanderthals were heading for extinction physical extinction at least around 40 000 years ago and yet there was still interbreeding going on between homo sapiens and some of these late neanderthals and here's a paper that's worth a look if you want to really get an update on the genetic data and this is rather a complex diagram of some of the genetic data so on the left hand side there in yellow we've got the neanderthal and denisovan lineages diverging off quite early maybe 550 000 years ago from the homo sapiens lineages then on the right hand side we've got african lineages going through to the present day and then in the center there we've got a variety of genomes from europe including some of the ones i've talked about and what's interesting and as you can see there ust ishim oase and zlatikun some of these early lineages don't seem to have any modern descendants in the africa in the european genomes so some of these lineages seem to have actually died out but others as shown here contributed dna which we find today in europe and east asia and siberia and that neanderthal dna and estimated that it could have been as high as 10 percent in some of these uh early populations that were mixing with the neanderthals but it's soon selected away so there's a wasa on the left-hand side there close to 10 percent neanderthal dna but other early modern genomes are shown there at the bottom and these show a declining amount of neanderthal dna through time so selection is removing that neonatal dna pretty quickly and it soon gets down to the level of around two percent that we find outside of africa today so this talk of interbreeding in the antares brings up this always tricky question of species and harlem neonatals the same species as us and i've written a piece which you can find on the natural history museum website so as i say here in my view of neandertals and homo sapiens remain separate long enough to evolve such distinctive skull shapes pelvises and ear bones they can be regarded as different species interbreeding or not humans are great classifiers and we do like to keep things orderly but we should not be surprised when the natural world past and present does not match up to our neat and simple schemes so there's the biological species concept which says that species are defined as being reproductively isolated but that's only one of about 35 different species concepts that someone mapped recently and we know that the biological species concept doesn't work for species of bears species of cats species of dog many species of birds it's estimated that 20 of closely related bird species do a bit of hybridization so i think us and the neonatals it's not the exception we separated 600 000 years ago that was not long enough in our case to evolve complete reproductive isolation from the neanderthals and of course some of that dna is active in us today and here's a one nice uh one of many papers really that have been written about this activity of some of these bits of neanderthal dna genomes today so as you can see here type one balding menopause age sunburn susceptibility um false visceral by the capacity so lung power and so on bone density whether you're a morning or an evening night nighttime person uh your white blood cell count all of these seem to be influenced by the presence of particular bits of neanderthal dna so some of this is certainly active today and our immune systems seem to show activity linked with neanderthal dna and and that's not surprising probably because of course coming out of africa we had no natural immunities to the diseases outside of africa whereas the neanderthals had evolved natural immunities over hundreds of thousands of years so by interbreeding with them we got a quick fix to our immune systems and that was good news 40 or 50 000 years ago not such good news today when there are some autoimmune conditions which again seem to be linked to the presence of neanderthal dna what's also interesting is the bits of dna that did not change that we did not acquire from neanderthals so there are these so-called deserts in our genomes today where you don't find any neonatal and so experts are looking geneticists are looking at those deserts and looking at the genes in those deserts and as it says here genes which are important for the refinement of neural circuits including those relevant for speech and language are found in integration deserts we suggest that modifications of a complex network in cognition or learning took place in modern human evolution possibly related to other brain related vocal tract or neural changes and at the bottom there experimental mapping of what some of these genes which seem to be largely or totally unique to modern humans are doing so differentially active sequences are associated with divergent transcription factor binding motifs with genes enriched for vocal tract and brain anatomy and function this work provides insight into the regulatory function of variants that emerged along the modern human lineage and the recent evolution of human gene expression okay let's move on now to look briefly at the denisovans who were in east asia so of course denisova cave in southern siberia in the altar region um russian archaeologists have been digging this cave for more than 50 years and they had found some fragmentary human fossils and although the teeth were very large even homo erectus size it was very difficult to tell what kind of human they were but of course in the last 10 years or so those fossils have given up dna and we now know that there were there was another kind of human living in this cave over a period of probably and fifty thousand or two hundred thousand years that we could now call the denisons and the fragments that have given rise to this dna are shown in the top of this diagram um very fragmentary as you can see there's one big two-third dinosaur iv and there's also some cranial remains not published yet um and these some of them have really high quality genomes as good as you can get from bones today so remarkable preservation and what's also interesting is that the cave also has neanderthals in it so these fragmentary remains in the lower part of this diagram are actually neandertal fragments and they produce neanderthal dna and remarkably denisova 11 there is actually seemingly a first generation hybrid of a tunisian and a neanderthal so this is a girl who seems to have had a neanderthal mother and a denisovan father she's been called denny so remarkable evidence and if we go back to that previous diagram you can see on the bottom right there um the denissimum fossils are mapped i think in grey and the adata fossils are mapped in red so both these populations are there alternating in occupation and even at times probably coexisting in this cave over tens or hundreds of thousands of years and we don't just need fossils now to get this ancient dna so here's a paper which looks at obtaining nuclear and mitochondrial dna from k sediments in siberia and spain and so we now have the capability in both mitochondrial dna and nuclear dna from the cave sediments so if an ancient human has been in a cave and relieved themselves if a woman has given birth into a in a cave if a ninja individual has died and pretty well all their physical remains has disappeared but genetic material persists then dna may be recoverable from the sediments and that's what's happened at dennis 4k and again this remarkable preservation of the site due presumably to the cold conditions so as it says here so these these dots are all ancient dna samples taken from the cave sediments of dennis became so as it says it's 728 sediment samples 94 percent of them contain mammalian ancient dna and that includes things like woolly mirossaris and hyena and so on um 24 and so about nearly a quarter of them actually contain traces of hormone dna so from the k sediments now we have even more neodytals even more denisovans and in the top of the sequence from about 45 000 years onwards we have early homo sapiens so incredible data and this is of course extremely important for future work because it means that many cave sites even without fossils but with some archaeology showing ancient humans were there may have dna in the cave sediments and it's not just dna that we can look for so there's another area of work which is now developing and taking off called proteomics so of course as well as the dna which comes from the nucleus of the cell and from the mitochondria of the cell we actually have fossil proteins and these may have a longer preservation time than dna so there's a good possibility that we'll be able to recover fossil proteins from fossils um even though dna has not been recovered and that was the situation for this jaw bone from the tibetan plateau of china from balashia cable thought to be from by sheer cave this jawbone very robust very big teeth which have been likened to the denisovans no chin on the lower jaw dated over 150 000 years old by uranium series dating so dna recovery was not possible but they managed to recover a bit of fossil protein from it and that fossil protein mapped onto the denisovans closer than it mapped to the neanderthals and homo sapiens so this is a probable denison of fossil over 150 000 years old from the tibetan plateau of china and there are a number of other fossils in the far east and in india which could be denisovans this includes the namada fossil from india this jawbone from pengu off the coast of taiwan fossils like dali and zuchariao none of them have had their dna sequenced yet so we don't know whether they are tunisiveness but this is certainly something to be looked at and equally their proteins their fossil proteins could be investigated and this is true for this beautiful fossa which i was involved in studying and publishing last year uh the so-called dragon man find from harbin in northeastern china so this fossil very large brained archaic features in the cranial vault long and low with a great big brow ridge but the face looks much more like a homo sapiens face and there's only one tooth preserved in the upper jaw one tooth left but it's a massive molar very like the ones from denisova cave so again this could be a denisovan more than 150 000 years old as well in this case but until we have its dna or its proteins we can't be sure and what's interesting of course is that dinosaur dna isn't just found in siberia or the japan plateau of china because we find signs of interbreeding with penicillins down in the islands of southeast asia particularly and places like australia new guinea and the philippines so now the ancestors of modern australian aborigines for example modern philippine people not thought to have gone anywhere near siberia so the hypothesis is that this dispersal may 60 000 years ago modern humans from from africa went through western asia and there was mixing with neanderthals there then the populations moved from southern asia and down into southeast asia and it was down there that they interbred with a denisovan-like population which is why some of these individuals in australia getting in the philippines have up to four percent denisovan-like dna as well as about two percent of neanderthal dna and where did those southern municipans live that uh appear to have interbred with the ancestors of populations in new guinea and australia and the philippines well we think that homoluzanensis was in the philippines homo floresiensis was in flores homo erectus may still have been in java so my best bet bet and that of some the rest of us is that these southern denisons were living in places like sumatra borneo and sulawesi and indeed there are artifacts on sulawesi that are thought to be more than 150 000 years old may well have been made by tunisians but until we have fossils of course down there which we can match with the ones from dynasty cave it's going to be very difficult to map the presence of these southern denisons down there and possibly then this maps the range of both neanderthals and incidents so neanderthals had an east-west range largely whereas tunisians may well have had a much more of a north-south range ranging from the colder areas of eastern asia siberia and china down into the tropical and sub-tropical regions of southeast asia and on genetic data it appears that the denisons are somewhat more varied genetically than the neanderthals were so a lot more to learn about these genitalians including of course their extinction day because the physical extinction of the neanderthals we think we can map to around forty thousand years ago uh for the genesis we have no idea how long they survived and some geneticists think that they could still have been around in ireland southeast asia and thirty thousand years ago so that last big question why are we now the only humans on earth and what happened to the others so these different kind of humans are all around at 70 000 but by 30 000 years ago as far as we know those other species had physically disappeared of course genetically the neanderthals and tunisians did not disappear they live on some of their dna lives on us today so why well i grabbed these from uh from the popular literature and i'm sure you've got your own contributions to make to this debate so top left there homo sapiens were to blame for neanderthal extinction because they were better hunters and out-competed them for food a computer model shows uh bottom left there climate change likely ice the neanderthals out of existence two extremely cold dry periods correspond to the disappearance of the neanderthals because the problem there is if it was extremely cold for the neonatals it would also be extremely cold for early homo sapiens um top right there one of the most recent ideas the end of the neonatal is linked to a flip of the earth's magnetic poles the studies suggest an event 42 000 years ago combined with the fallen solar activity was potentially cataclysmic researchers say well again the problem there is you know this does seem to have been a significant event but of course it would have been significant for everything on the surface of the earth and not just the neanderthals so i think this this is an over this idea is overreached and we've written and published a reply to this paper critiquing some of the conclusions and the just over interpretation of the data um bottom right there homo sapiens developed a new ecological niche that separated it from other hominins a new studies argues that the greatest defining feature of our species is not symbolism or dramatic cognitive change but rather a unique ecological position as a global generalist specialist and in the center there and quite a nice idea humans are our evolutionary success to friendship cooperation was the key to our long-term survival so we may have had a lower level of aggression within our groups greater cooperation greater networking between different populations compared with these other humans my summary and my feeling at the moment i think our behavior was a big factor probably the biggest factor in our success maybe we networked and accumulated knowledge better learned to extract resources more intensively from the environment than those other humans did and above all fam ways of improving the survival of our children and probably older people as well as our numbers grew and we spread over wider perhaps we simply absorbed some of those other species out of existence so thank you for listening and i'd like to thank all the people who supported my research all my collaborators and all my sources of data and illustrations and there's some books you can uh read and those have been mentioned already and if anyone's on twitter you can find me on twitter with that handle so yeah i'll stop there thanks very much many thanks for this talk chris uh it was really exciting one um as always if uh anyone who is joining us with any questions you can write and write them down in the chat and i will uh read read out loud or you can just raise your hand and ask your question directly but yeah before that i i will give you some time to think about your questions and start with my own marks so chris uh going back uh to the start of your talk uh how widely would you say it's now accepted that pan pan-african uh origin theory or hypothesis you were well i think genetically there's no doubt that we have a primary african origin um and i think what's happened is that it's it's no longer a 100 percent reason african origin and if i was giving this talk 15 20 years ago i would have said yeah we're pretty well 100 recent african origin now you'd have to say it's more than a 90 recent african origin so it's not a complete recent african origin and this has led to a revival of this other idea of multi-regional evolution but i think what we've got is really modern humans coming out and mixing with those other species so i would call it out of africa and hybridization mostly out of africa that's fanti pablo's term for it now mostly out of africa i think that's a good term so we largely map our genetic uh and physical evolution back to african ancestors behaviorally that's obviously something for you archaeologists to think about um for me i think it's it's less clear but i would still say that most of our behavior probably maps back to africa as well in its origins and it remains to be seen how much we acquired behavior from these other species that we've been mixing with this is because one of the most interesting things um for the neanderthal modern human coexistence there were certainly genetic exchanges going on neanderthals were joining modern human groups so how much cultural exchange was going on in both directions and for the denisovans we know obviously far less about that but how much of that intermixture with the neanderthals with the tunisians was accompanied not only by gene flow but also by exchanges of culture information behavior all right thank you um gary is asking whether there are enough prominent fossils to make conclusions about early evolution yeah well i would say in some areas there certainly aren't enough so for africa i didn't get a chance to really pick up on one of those diagrams but our african fossil record i would say comes from from less than 10 of the african continent so there are huge empty areas where we have no fossil evidence for ancient humans even though we know they were there from stone tools the indian subcontinent and that vast area has only one significant ancient human fossil than a marder fossil so um for some areas we still lack a lot of data for europe the situation is is much better but even there we can have surprises as we've seen from the epidemic fossil so i think in places our data are pretty good the genetic data of course are building up all the time and the increase in genetic data is much faster than the growth of significant fossil data so yeah we build the scenarios we can i've changed my views about things such as the position of homo hydro bergensis as a common ancestor for us and the neanderthals and i would say i'm no longer sure who our common ancestor was it might be there in the fossil record already but not identified um so yeah we have to we have to work with what we've got something like homo naledi comes along provides us with a great surprise homo floresiensis that was a huge surprise back in 2004 so i think you know we build our model with with greater confidence but with continuing caution because yes we have to be aware there's still a lot we don't know uh about human evolution well i will give a bit of a follow-up question on what you've just mentioned and it's like recently there have been like many new human species being uh named or introduced based on sometimes only on very partial evidence i would say i don't know mandible or part of skull can this be a problem for or can it cause a problem in the future for for archaeology and for development in archaeology yes i mean certainly it is it is a problem with the proliferation of species how many of these are really good species and when we get more data will they be shown to be actually similar to other species so hormone lusinensis is is the case in point really where you've got quite fragmentary material and it does seem to be distinct it's distinct from horror floresiensis on the bits preserved but um when we have more material it might be that that will seem to be more similar to fluoresceins than it seems to be at the moment um for neanderthals we've got a pretty good fossil record now and the cemetery sauce material you've got probably 29 individuals in the pit of the bones at attacker from about 430 000 years ago over 6500 fossils so it's an it's a really good sample and so we have a good idea of that little window in time at least of the diversity and the anatomy of those people they seem to be morphologically neandertals and of course um they also seem to be genetically indian told so there's even dna from the siemens placing them on the neonatal lineage so yeah for some bits of the story you know i have reasonable confidence we're close to the truth but for other areas and certainly for the denisovans we're really only beginning to learn about them and that whole area of ireland south east asia who knows how many other species might still be lurking there waiting to be discovered great thank you um sharon is asking whether you think that the melting of permafrost is likely to reveal any surprises yes well there certainly might be a homo sapiens or two preserved up there in the permafrost um whether the neanderthals were ever up there i think that's much less likely i think probably for neanderthals there's more hope maybe of finding a neonatal in a peat bog so for example we've got preserved peat deposits from the last interglacial in europe and who knows maybe maybe a neanderthal fell in there once and we might one day find the body so um you know it's it's always you never say never there have been remarkable finds from permafrost and from of course uh melting glaciers in the alps for example we think of otzi um found in the uh in the alps so maybe we will have tissue preservation of the neanderthals or denisovans one day it will be wonderful because if we do but the dna itself is obviously very very helpful and more and more can be drawn out from that dna data as i was showing from some of those studies of the introgressed bits of dna and what they were doing probably in the additives compared with us so if we would have some of this dna preserved of other species which we don't have for now would it be possible to trace uh whether we have still some parts of the dna present in ourselves today or as it is possible with neanderthals or yes so i was on a paper which attempted to test in ireland southeast asia whether there was evidence of these other species in the dna so we've got denisovan dna represented at the level of about four percent in some of those populations so we all tested whether we tested whether there might be very small amounts of distinct archaic so-called archaic dna that might be coming from let's say floresiensis or luzenensis or homo erectus and we couldn't find any trace of it in the samples we had and with the resolution we had now that's not to say there couldn't be a little bit of it there and we weren't able to pick it up so it's possible there will be others and in africa there's certainly some data that africans too have introgression from archaic humans in sub-saharan africa so possibly this is from uh hyderabad against his rhodesians possibly even from homo naledi who knows um so there are traces of arcade dna there but because as i mentioned the african conditions we don't have um a genome of one of those ancient african humans to compare to really map where it's coming from so we don't have the equivalent of a neanderthal or a denisovan genome in africa that can tell us the source of this putative introgress dna but it looks like it is there and so african populations too may have a similar level of what can be called archaic dna not yet well mapped all right thank you um are there any other questions [Music] do you have just come in here and you can get on this video thank you so much for the talk um i just wanted to ask you your hypothesis about you know um behavioral reasons for us being the only species left present times is there would you suggest any ways to gain more clarity on what exactly this behavior might have been maybe something we can observe in the archaeological record what we can look out for when we're trying to understand why we were the only ones left yeah i think that's a very good question i mean i i don't have the answer to why we're the only ones left i think for the neanderthals and us we can map the disappearance of neonatals pretty well and of course the behavioral gap between us and the antis is narrowed down so it's very difficult to point to a single thing i mean representational art representing animals and figures for me i i don't see evidence for that in neanderthals we know now that uh early modern humans were apparently producing representational art over in borneo and sumatra as early as they were in europe so i think probably that kind of art was there in the common ancestor of those populations so it probably was in africa before 60 000 years ago and it came out with modern humans and spread with them um so that may indicate something about the minds of modern humans compared with neanderthals that kind of representational figurative heart but you know i'm not an archaeologist so i'm treading in dangerous territory here um and it may well be that it was an organizational thing for modern humans and so it may be that as we are able to map the sites of early modern humans and compare them with neonatals and tunisians in more detail we may find that it was indeed networking that larger group sizes uh allowing the greater storage of information and passing it on from one generation to the next it may well be the survival of older people that are not only going to be grandparenting which will help the survival of infants but it also means they've got a store of knowledge which covers a longer period of time and that knowledge store can be important in the bad times older people may remember survival strategies that worked uh in in the previous past and also something that we see for australian aborigines for example is the older people are the ones who store the kinship knowledge so they have in their heads this fantastic map of relationships of who's married who in the past and that can be important in building alliances with with other groups in tracing back to a common ancestor so i think even the survival of old older people may have been important in the success of modern humans if less were surviving in the advertised indianism that may also have held them back a bit and of course you know there could be some technology some people suggest that bows and arrows were were key to the success of modern humans and there's some evidence from africa that they appeared early but for me as you know looking at the record and you people would know this better than me i think the presence of uh bows and arrows is very difficult to map against the spread of of modern humans across europe and asia so yeah i'm i can't point you at anything specific but i think it's going to be a pattern in the end built up from really good site data and also really the best dating that's possible in these populations and something also didn't talk about is how the interbreeding happened that may also be a factor in the disappearance of these other populations and of course what we've got evidence of is neanderthals joining homo sapiens groups which is why we have neanderthal dna today what there isn't much evidence of in the late until so far is homo sapiens dna going into the neanderthals it may have been happening and we just haven't got it yet but it seems to be um much rarer in the late neonatals than in their reverse direction so of course if you're taking out prime age breeding individuals out of the neanderthal gene pool and incorporating them into the homo sapiens gene pool that's going to be bad news for the neanderthal jeep losing prime age individuals to these early modern human groups so that even even that interbreeding if it was mainly going one way could be part of the story of why these other groups eventually faded away yeah thanks so much um we have another question from steve uh what do you predict to be the most exciting development with regards to our understanding in human evolution over the next 10 years or so yeah that's a good question i think that the sediment dna is going to be really important because um you know there are many parts of europe and asia where we don't have a good fossil record but there are cave sediments with stone tools so if the preservation conditions are right we will be at a map now the presence of neanderthals denisovans and homo sapiens in these sites from dna evidence and we may even find you know other other humans like the denisons that were there too so i think the sediment dna is going to revolutionize the way sites are dug archaeologically in this time period if there's dna preservation then collecting for dna samples should be part of the excavation strategy from the very beginning now of any new site that is going to be excavated and the good thing is that even in africa in high altitude sites in deep cave sites there might even be sediment dna preservation there where you haven't got fossils so i think that's a huge breakthrough and will be very important on the genetic side yeah i think that studies that are going on of the intragress dna what comes across into modern humans and what doesn't come across into non-humans um that can be that will be important in really pinning down what bits of dna are unique or largely unique to the homo sapiens lineage and which are unique to the neanderthal and tunisian lineage and then looking at at least to some extent what the function of those bits of dna is and possibly what differences there were between the population so for example a high altitude gene present in people in tibet now can be linked with the tunisians now it may not have been a high altitude gene in the geneticism it may have been there for high energy for for um you know fast running or something like that but things like that are going to be important to mapping the specific functions of some of these bits of dna that are different between the populations all right thank you um it seems that there are no more questions so thank you very much chris for this talk and for your time we really appreciate that we could have you as a as our guest speaker uh we will be looking out for this new research paper that has to come out next week and in a couple of weeks yeah of course uh we wish you a good luck with any uh future research you will be doing and yeah hopefully many of us will join us in two weeks for our next talk and we will see each other then i should check out the program for your talks i guess i can find those on a website somewhere uh yeah i can send you the our term card and that would be great i'd like to see who else is talking thank you cheers thank you very much

Channel: Oxford Archaeological Society

Views: 58,515

Keywords:

Id: bySp0XRr2O0

Length: 59min 14sec (3554 seconds)

Published: Thu Mar 09 2023