The Infinite Monkey Cage - The Human Story: How We Got Here and Why We Survived.

Episode Date: February 6, 2017

The Human Story: how we got here and why we survived. Brian Cox and Robin Ince are joined by comedian Ross Noble, Professor Danielle Schreve and Professor Chris Stringer as they look at the tricky job of piecing together the history of modern humans and how we came to be here. They look back to the earliest known human ancestors and the fossils and tools that have allowed us to paint the picture of our journey out of Africa, to become the last surviving human species on the planet. They ask why we have gone from more than 5 or 6 species of humans some 200,000 years ago, to just 1 today. They also look at how discoveries made in just the last 5 years have completely transformed our understanding of human history and what new DNA technology has revealed about our ancient past. They also reveal what surprising tropical animal remains have been found buried deep under Trafalgar Square.Producer: Alexandra Feachem.

In our new podcast, Nature Answers, rural stories from a changing planet, we are traveling with you to Uganda and Ghana to meet the people on the front lines of climate change. We will share stories of how they are thriving using lessons learned from nature. And good news, it is working. Learn more by listening to Nature Answers wherever you get your podcasts. This is the BBC. Hello, I'm Robin Ince. And I'm Brian Cox. And in today's Monkey Cage, we ask Brian and a Neanderthal up a tree. K-I-S-S-I-N-G.

Which is a praise-y of the subject, actually. We don't. In the last decade, our understanding of who we are and where we came from has been transformed by fossil discoveries and, perhaps more importantly, DNA research. Today, we tell the story of how humans evolved from a common ancestor we share with chimpanzees 8 million years ago in the East African Rift Valley, and why we are the only human species alive today.

Or to put it another way, why is Robin Ince not a bonobo in a cardigan? I'll tell you why, cos I haven't got the energy. I don't know if you've ever seen any bonobo footage. Anyway, so... Some of this will only make the podcast. I really don't want that image, actually. It's too late. That's not how the mind works.

And by not wanting it, it's going to stay there for even longer. In fact, this is going to be looking at the way that the understanding of our family tree has changed and the things that are on that family tree. It's actually a little bit like one of those moments on Time Team where they think they've found the remnants of a new small human species, only to realise that it's just Tony Robinson

having a nap at the back of a cave. Today's panel includes one scientist who we got hold of by actually having to ring up their cave, and at least one guest who is going to be extremely excited when he discovers that there really are hobbits. Which guest could it be? And the panel is... I'm Chris Stringer, and I'm a research leader in human origins

at the Natural History Museum in London. And, yeah, one of the surprising things about human evolution that, you know, has come up lately is that our brains have actually got smaller in the last 20,000 years. Actually, maybe with human behaviour, that's not so surprising. Hello, my name's Danielle Shreve. I'm a professor of quaternary science and researcher into ice age mammals at Royal Holloway University of London. And the most surprising thing for me about human evolution is that unlike modern humans, Neanderthals did not appear to be particularly artistic.

Hello, I'm Ross Noble, and I clearly have no qualifications. And my most surprising thing... I think the most surprising thing about human evolution is that if you're in a lift and you yawn, everyone else does. Yet if you fart... LAUGHTER And this is our panel. everyone else does. Yet if you fart... LAUGHTER And this is our panel.

APPLAUSE Well done, Ross. So quickly from the shrinking of the human brain to you lowering the tone ten minutes earlier the last time you were on. Yeah, you're welcome. Chris, we'll start with you, definitely, rather than Ross. Now, when I was a child, back in the 70s, I had one of those books, I think it was

called something like Tell Me Why, or the How and Why book of prehistoric life, and it would have this image, which was Australopithecus followed by Homo erectus, followed by Neanderthal, followed by Homo sapiens. If that was just basically it, one turned into the other and then the other turned into the other,

how right or wrong was that? Yeah, it was wrong. We know that. It was wrong. So, yes, what we know now is that instead of being like a tree trunk leading up to us at the top, it's actually really a radiating tree, a bush-like thing, with loads of different species coexisting. We're the only survivor of all those experiments in human evolution that went on over a period of maybe seven million years. So how would the

illustration change for you? So if we take Australopithecus, can we still say, if we look at that as the starting point of the journey towards the modern human, what are we now seeing in that illustration? Yeah, so for the period, I mean, we think we shared a common ancestor with chimpanzees maybe around 7 million years ago. For the next four, let's say the next 3 million years, it's really sketchy what actually the evidence is. We've got fragmentary fossils from Africa,

a thing called Sahelanthropus, a thing called Ororin, a thing called Ardipithecus. You're regretting asking me now, aren't you? And these are very fragmentary. A lot of people think they're on the human line, but it's really not clear that they are. And then about four million years ago, we've got the evidence of this creature, Australopithecus.

And there are a number of different species of that creature. We're not sure which of them, if any of them, are our ancestors. So again, you've got this radiating pattern of different species coexisting. Then we get to 2 million years. Yes, Homo erectus puts in an appearance around that time, but alongside it are some other early Homo erectus puts in an appearance around that time, but alongside it are some other early Homo species. So, again, you've got that radiation, even of the very first humans. Then we come down to us and Neanderthals,

and instead of it being Neanderthals evolving into us, they're alongside us. They're evolving in Europe and Asia. We're evolving in Africa. And our ancestry probably goes back to a common ancestor maybe 600,000 years ago. Danielle, if you find a fossil, certainly the earliest times, as you said,

fragmentary fossil evidence. So how do you... You find this thing, a very small object, a fossil. How do you go about characterising that, saying what it is and dating it? One of the more unsavoury parts of my job is actually going and collecting modern skeletons to get comparative skeletal material,

to actually be able to identify these things. Because luckily for the periods that Chris and I are interested in, a lot of the species that we look at are either still living today or their close relatives are. So if we find a tiny fragment, you're absolutely right that it's very rare for us to find complete skeletons. It's only in very occasional cases, like the mummies in the permafrost in Siberia, for example.

More often than not, we find teeth, we find bones, we find fragments of those, and we have to go spend a lot of time trying to identify it to species and then undertake whatever kinds of analyses from basic measurements we might look for example if it's a tooth at the very very fine patterns of dental micro wear on the surface so that we can try to reconstruct diets if it's of suitable preservation suitable age we might be able to do dating directly on it we might look at ancient d. There's lots of new techniques that we can use now, but at the very fundamental level, it's basic vertebrate

paleontology, so identifying, comparing, classifying. Can I ask you, Chris, how much can you define, and how much has the definition changed? Because you work in human origins, the definition of human. Currently, what is that? Yeah, that has changed a lot. So, for example, when I was a student, there was this term, man the toolmaker. We'd say human the toolmaker now. But the idea was that humans were defined by that ability to make tools. We now know that lots of other animals make tools and use tools,

including chimpanzees. Not only that, the evidence of archaeology shows that stone tool making now goes back more than three million years. So it actually goes back a long way before we find creatures that we can call homo. So it goes back beyond our genus homo. So human now, if we look at the anatomy, yes, we can talk about a relatively large brain. We can talk about a good adaptation to walking upright on two legs. We can talk about hands that are obviously good at manipulating the environment. We've lost that climbing and hanging in the trees capacity that some of the earlier hominins have got. And also, of of course there's all the behavioral evidence the complexity of our behavior that we find with the genus homo

getting eventually to us and neanderthals with really complex behavior can you just give us a quick definition of the the terminology there so genus genus yes so that's basically a you know it's it's a group of species or it may even be a single species, but that group shares common characteristics. So we can think of the cat genus, so things like panther, lions, and so on, closely related. Two species of chimpanzee, the common chimpanzee, Pantroglodytes, and the bonobo, paniscus. So those two are distinct species within the genus pan, within the genus homo. We think now there are probably at least eight species, maybe more.

So an incredible diversity of humans, which going back to that textbook of years ago, there were only a few species recognised. Now we know there are many, many species, as we define them, at least from the fossils as species. And our genus emerges around 2 million years ago or so. Yes, so we think about 2 million years ago

we've definitely got three kinds of humans around 2 million years ago. There's some evidence they may go back beyond 2 million. Ross, obviously, yeah, I felt this was the time to bring you in. I didn't mean to laugh in your face. No, but I knew that you were thinking, how are they going to bring me into this?

Yeah, yeah, yeah. So was I. Let's see how this works out, shall we? Exactly. Well, I heard the words dating skeletons before and I went, there's got to be a joke in there somewhere. But I kept quiet, you know. A lot of what this is originally based on is these, especially in Victoria, collectors, people who are... Now, you are, I know, someone who has always been a collector,

predominantly of tat, I think. I know that you used to have the biggest collection in the United Kingdoms of Billy Big Mouth Bass singing fish. I did, yes. I changed my words. Yeah, all right, you laugh. You laugh, right? Yeah, you see, that's the sort of ignorant attitude that people like me, right, all right, you laugh. You laugh, right. Yeah, you see, that's the sort of ignorant attitude that people like me, right, people say, right, why would you want to have, say, you know,

buy 5,000 Big Mouth Billy Bats just because they're in a warehouse and you can get them incredibly cheaply? Well, it actually relates to the subject because what I'm going to do is I'm going to get all those Big Mouth Billy Bats, I'm going to get a shipping container, andybats, I'm going to get a shipping container, and when I die, I'm going to go in there

with some unusual goats, and, like, they're bred specially, you know, goats, like, odd ones, and then... Goats? Goats. Yeah, yeah, goats. I thought you said goods, but actual goats. Antigoods, fancy goods, if you like. They're going to... Fancier goods than the billybigmouthbats? Very much so. They're going to... Fancier goods than the Billy Big Mouth Basses.

Very much so. They're going to put my body in there and I'm going to be concreted in and I'm going to be buried to mess with your colleagues in the future. That's the plan. Why are you going in with goats? Because they'll find the bones

and they'll find my bones and they'll go, hang on, why has he got a load of mechanical fish and a goat? It's got to be confusing. You can't just be, you know, it has to be an unusual concept. I would think, Danielle, surely you, for example, as a professor...

Sorry, can I just say, though, I don't think this will confuse them because I think when someone finds a skeleton surrounded by Billy Big Mouth Bass with two goats in it, they'll go, oh, this must be the skeleton of Ross Noble. We've read about him. Sorry, but I'll let you... You wouldn't think there was a goat-human hybrid organism there,

would you, because you saw this... That's most unlikely, but actually Ross has perhaps unwittingly hit on one of the very essences... LAUGHTER has perhaps unwittingly hit on one of the very essences... LAUGHTER APPLAUSE Sometimes it takes an idiot to get to the real point. You've hit the nail on the head. And this is to do with grave goods. So, actually, one of the things that we can see with Neanderthals is that seemingly, while they may have buried their dead,

they probably just dug a bit of a hole in the side of a cave, put the body in, and that's it. It's only with modern humans, really, that we start to see modern humans being buried with things, whether it's Billy Bass, whether it happens to be goats, and there are occasions where people have been found buried with goats, early signs of domestication.

So, yeah, you know, it started a long time ago. But I'll be mounted riding the goat. Right, so when do you see that? What sort of time period does that come in, then? Really, you're looking at the very end of the last ice age for sort of domestication, if we're on the goats. But certainly... So to speak.

So to speak. So, yes, but it's behaviour, behaviour burying. But certainly... So to speak. So to speak. Yes, but it's behaviour burying. So, I mean, even with modern humans going back, you know, 100,000, 120,000 years in the Near East, we can see that modern humans seem to be buried with, for example, their arm crooked deliberately around, say, a deer antler or some other kind of... Something else that's been deliberately put in there.

So, yeah. Is that telling us there's ritual involved or something about the level of sophistication in the society? It's telling us there's been a change, for sure, because we don't see that kind of behaviour with Neanderthals. And, of course, yes, there's been a lot made of it in terms of potential ritual, potential thought of some kind of afterlife, that kind of thing.

So were they buried or was it literally just wherever they fell? No, those have been deliberately buried, haven't they? Yes, yes. So 35,000 years ago, there were four people buried in a site in Russia and the two children there were buried head to head and their graves are full of things made out of mammoth ivory, things that would have taken months to produce, even spear shafts made out of mammoth ivory, things that would have taken months to produce, even spear shafts made out of mammoth tusks. Now, mammoth tusks are curved,

so someone had actually probably steamed a mammoth tusk 35,000 years ago, steamed it till it was straight, then they carved it down into a two-metre-long spear, and then those spears were put in the graves of those kids. So those kids were special kids. They couldn't have earned that status in their lifetime, so they were important children, and they were buried with these really extremely valuable objects.

And do we have no evidence that Neanderthals had any kind of sophistication in that regard? I thought there was some possible evidence they did some... Yeah, so there was a claim that in Iraq, Neanderthals were buried with flowers on the burial. We now think those flower heads got down there because gerbils burrowed down and took the flower heads down. That is a beautiful image, isn't it?

In 20,000 years' time, someone in your position would be going, we now believe that the Billy Big Mouth bass were actually just brought down there by gerbils. Yeah, yeah, yeah. Dano, can we ask you a little bit about... Going back to the fossils, how... Well, first of all, what is the likelihood

of a living thing being fossilised? I mean, this is one... Often we hear about different problems with a fossil record, and then you hear people trying to explain, well, not everything fossilises. So what is the possibility of, say, larger mammals fossilising? And what are the conditions required? It's a very good question because, of course, we're not wading shoulder high in the remains of Ice Age mammals now.

Something has obviously happened to those animals since they were around living on the landscape. And eventually, potentially, turn into fossils. So, yes, ideally, you need for the animal to be buried fairly quickly after death, so preferably not scavenged, not lying out on the landscape where the bones weather, for example, and become broken, not trampled on by other animals. So in short, there are lots of things that can happen to bones. I mean, obviously, some are going to be more durable than others. So, generally speaking, the bigger you are, the more robust you might be, the better potential you have to fossilise.

But equally, teeth are really good, because, obviously, they're covered in enamel, hardest substance in the body, so they tend to be very durable, and they preserve in lots of different environments. And that's good, because teeth are identifiable to species. So that's handy for us to be able to identify these things in the first place. But yes, a lot of things can happen to an animal from the point of its death. It's actually relatively unusual for it to make it as a fossil.

So if we go back two million years or so to the Rift Valley, so we have Australopithecus around, and then there's a change, the speciation, the homo genus appears. So what do we know about why that happens? Well, we're not really sure why it happened. We think it's linked with obviously the environmental change. So East Africa was drying up and it looks like resources were getting more scattered and our ancestors started to cover more distance on the land. And that probably drove some changes in the skeleton to make us longer distance walkers and even runners. So there's an idea that a lot of the Homo erectus anatomy is for running and jogging long

distances to cover the landscape, to get to your prey, to get to a carcass, to scavenge it. So it could be that that made some of the changes. And also, of course, the arrival of meat eating really did make a difference because meat eating certainly gives you a much more concentrated source of food. It gives you extra energy. You can start to run a bigger brain, because our brains use about 20% of our body energy. So having something like meat gives you that chance to evolve a bigger brain,

and that seems to have come in a bit before two million years, and then you start to see an increase in brain size. You start to see the genus Homo. There's been been maybe more than that but two in particular major discoveries um in this century haven't they in terms of the change of human two different uh humans that we weren't necessarily uh expecting so i wonder if you can explain a little bit about what was the journey to discovery and if you could explain in fact what they were. Yeah, yeah. So, yes, in the last 100,000 years,

we knew that there was us and the Neanderthals, possibly Homo erectus might have been surviving, but that was really all we knew about for sure. And then on the island of Flores in Indonesia, you know, beyond Java, sort of towards Australia, an isolated island, as far as we knew, only modern humans had ever got to. They found a skeleton in 2003, I think it was,

of a tiny human on that island, a primitive human with a brain about the size of a chimpanzee's brain that was still there in the last 60,000 years. So it looks like evolution ran this experiment maybe for a million years or more on that island of a strange, isolated lineage of a primitive human surviving right into the time of modern humans. So this was Homo floresiensis, which, because it was only a metre tall as an adult, became nicknamed the Hobbit.

So that's where we get hobbits coming into it. And indeed, the skeleton... I just say for the listeners, the gesture was towards Ross. And the skeleton shows they had big, flat feet. But we can't tell if they were hairy feet. No, I remember that. I do remember that when it was in the PR. I did get very excited. I was very close to spending a lot of money on a private jet, actually.

Not to look at the actual... Just to turn up as a wizard. What are you doing on my island? Is there... Actually, using nicknames like that, is it sometimes dangerous? Because most people do know that particular species as the Hobbit. I think also it wasn't far off the release dates of some of the Lord of the Rings films, which comes in handy as well. And yes, indeed, the Tolkien estate did take exception

to the use of the name and did send some letters to try and get... You're kidding! No, they did. They were angry at history. Could you not have just shown the research and gone, I think they did it first? I'm afraid nature is suing the jailhouse.

So it was around, on an island, one of these, I suppose you find these giant crabs and things on islands, just because it's a unique, separate ecosystem. Yeah, the idea is that this might be an example of island dwarfing. So medium to large mammals on small islands because of the lack

of resources. Evolution drives them to develop a smaller body size because they use less resources. And indeed the hobbit could be a dwarfed homo erectus. That's one view. Danielle, I'm sure, will give lots of examples of elephants that shrink down to the size of dogs, I think, in some cases. Oh, imagine that, just running into your couch.

Yeah, when he says shrink down, it doesn't mean they actually have an ability to shrink. Oh, well, this is ridiculous. Really, though, are elephants the size of dogs? They are the size of dogs. So on islands in the Mediterranean, you get the standard straight-tusked elephant, which was the large elephant that was around in Europe, in Britain,

during warm stages in the past. And, yes, it shrinks down. The largest males are just about a metre high at the shoulder. And how long are we talking for that to happen? Over what period of time? That's quite a difficult question because of the dating, but we know that, for example, on Jersey, we can see red deer dwarfing

to around, say, about 60% of normal body size, and that happens in maybe 6,000 or 7,000 years. You see, when people say, would you want to be immortal, that's why. Because I'd just, you know, I'd set up my elephant park. Just don't let anyone near them. I'd just sit there and wait. I'd have my little elephant dog.

I'd start my own show when there was one man and his elephant. That's what I'd have. And I'd have tiny sheep that were the size of gerbils. Come by, come by. Ah! And that's how you'd use your immortality. Yeah. Surely.

Yeah. Well, all right, it's up to you to suggest a better version. You'd just be sat there looking at the moon, just waiting. Just waiting. What's it going to do? Well, I'm entertaining people with the mini elephant trial. No, because most people are saying, you know, I'd use my time to acquire all the vast sweep of human knowledge

accumulated over the generations. No, I'd get an elephant and I'd sit there and I'd wait. I'd just wait. And it speeds up, because, of course, the smaller they get, the faster their turnover is. So, actually, you know, it accelerates as they go along. I don't want to go too fast. Well, you can do it with a hippo, too.

They'd be like ants crawling around. Fleas, like tiny elephant fleas. Ooh, there's another one. But would you not use the time when you were waiting to read the works of Aristotle? Right, I've got a very short life now. Am I using the time productively now? No, no, I'm not.

So you're just literally waiting... This morning, I spent, I would say, 45 minutes trying to get a sock into the basket from the other side of the room. You know? If our ancestors had been like Ross, would we have got out of Africa? It's a good question. It's a very good question. Of course you would. You'd be finding all these species of been like, Ross, would we have got out of Africa? It's a good question. It's a very good question.

Of course you would. You'd be fighting all these species of, like, this warrior race with long hair mounted on their tiny elephant socks. They would have got further, because I would have, you know, they would have harnessed the tiny elephants to take miniature cars. Oh, no, use a big elephant, you get there quicker. I've not thought that through. I have an inkling that whoever it was who led those people

managed to lure them by going I've heard if we go in that direction there's smaller elephants. So it's like just using a system, isn't it? Yeah, exactly. But the trouble is though, that might be a full-sized elephant, but in the distance. But that's why you'd keep on travelling, wouldn't you? As long as you keep the elephant at the right distance, you're fine.

He's miles away. Oh, no, he's there. Is that what happened? No. There you go, there you go. But it does raise, remarkably, again, Ross's... Why did you make it a segue where there might not be one? We're talking about... We've said it over and over again, out of Africa, out of Africa, out of Africa. And you speak of Africa in general,

but it tends to be the case that people talk of the Rift Valley in particular as being a special place. Is that just because that's where we find the evidence at the moment? Well, yeah, it's where the evidence is best preserved, of course. And Daniel has mentioned caves and how important they are they act as traps so in south africa you've got loads of caves that have collected fossils including australopithecus fossils in east africa it's it's where the rifting is opening up the continent and you've got these sedimentary basins lakes and rivers and so on and they accumulate sediments and they accumulate fossils so. So they're excellent, but when you look at

where all the key finds have come from, yes, they're in East Africa and South Africa, but that's only about 5% of the African continent. So it's where the stuff's best preserved, but the whole of the rest of Africa, we know from stone tool evidence, had humans over it for most of the last 2 million years, and we've got virtually no fossils

from all the rest of that area. So we've got a huge amount to learn, and this discovery of H last two million years, and we've got virtually no fossils from all the rest of that area. So we've got a huge amount to learn, and this discovery of Homo naledi, which is, I don't know whether that was on the agenda to talk about, but this thing in South Africa that turned up a couple of years ago, deep in a cave they find nearly 2,000 fossils of a new species of a creature with a small brain about the size of the hobbit's brain in South Africa.

What are these bones doing deep in a cave? No-one knows how they got there. The idea is that these creatures were actually taking their dead deep into a dark cave and leaving them there. Seems unlikely to me, but that's the main hypothesis. Could they have been dragged in by gerbils? That's it, yeah. Or little elephants, if there are any around, maybe.

Pushing them, pushing them down there. Maybe, maybe. So is that the Denisovans? No, that's Homo Naledi. So Denisovans are another cave in Siberia. So that was the other thing I know we were going to talk about in the last 10 years or so, that yes, the Denisovans were completely unknown to science until 2010, and that was when some fossils, some fragmentary fossils, including a tiny little bit of a finger bone in this cave in Siberia, they actually got DNA out of these Siberian human fossils and found it was a new kind of human. So that little bit of finger bone had DNA preservation

as good as they could get from one of our bones today. So how much does that change, Danielle, in terms of now that it is possible, in terms of DNA research, how much does that change the importance of fossils? Or is this just all adding to the ammunition? It's all adding to it. And I think, obviously, there will be controversies. So, for example, amounts of interbreeding that we would never have detected, but the fossils will always be important.

I would say that as a paleontologist, but the thing is there are other things that you cannot get out of DNA, so you can't get, for example behaviour out of DNA. When you find, for instance, a single fossil say you just find one fossil, now how much can that, or what are the possibilities, what is the best example

of being able to see one example and go, right, now this is what we can extrapolate from this. Well, we can take the Hobbit as an example, I suppose, because that was... I mean, there are some other bits and pieces, but essentially one skeleton. And it was so challenging to science that some people said,

this is a freak, it's a pathological freak, it's a diseased modern human with something like microcephaly. It's got a tiny brain because it's a diseased modern human with something like microcephaly. It's got a tiny brain because it's a diseased modern human, and that's why it's so small. So it was so challenging, that's what people preferred to argue. And we now know that there are other remains that show it's for real. Not only that, there are ancestral fossils now,

fragmentary bits and pieces from 700,000 years ago on Flores, that shows us that little population was already there nearly a million years ago. So yes, it started with Monskeleton and when they found it, they thought actually they had the remains of a child at first because it was so small, but then they looked at the jawbones and saw that the wisdom teeth were erupted.

So it was an adult. So it was very challenging. When we talk about the evolution of intelligence, let's say, so this transition from our common ancestor with the chimpanzee through to a civilisation today, how much of that, our understanding of how intelligence evolved from our ancestors, is that related just to skull size and brain size

or is it related to the tools that you find and the rituals that you see that were performed at the time? What's the weight of evidence? Well, yeah, you have to build that picture up from the evidence you've got, and unfortunately we are missing most of the behaviour of these ancient humans. Stone tools, of course, survive very well, so that's the main evidence of behaviour. And when we get to the Neanderthals and us,

yes, you can start to see the burials as well and more complex behaviour. But before that, we just have to judge, yes, the brains are getting bigger. It looks like behaviour, the way they're processing carcasses, they're able to get dangerous animals, so they must be increasing their intelligence to be able to acquire food. I mean, at Boxgrove half a million years ago, they not only were getting food from horse and deer, but even rhinos, rhinoceroses, which are really big, dangerous animals. And yet there are four butchered rhinos at Boxgrove. So they were capable enough to get those in an open, dangerous landscape

with lions, hyenas, wolves around. You say rhinos there, so this is in northern Europe at, what, 150,000 years ago or so? It was completely normal for us to have rhinos and elephants in every warm stage in the past, and were it not for a sequence of events, very rapid climatic oscillations, probably combined with a bit of human persecution in there as well,

we would expect to have rhinos and elephants in our forests in Britain today. And hippopotamus, is that right? So hippos were everywhere across Britain during the last interglacial, so the last warm stage before the present day, about 125,000 years ago. And they were everywhere from Trafalgar Square, so there's a very famous site in Trafalgar Square in the middle of London,

where hippo remains were found in the 1950s when the foundations were being put down into former River Thames gravels, and you can find them all the way up to North Wales, North Yorkshire, and in fact Stockton-on-Tees is the most northerly record of a hippo fossil. Sorry, sorry, you've just said... Sorry, hang on, hang on. You've just said you can find hippos in Stockton and I'm not supposed to make a joke about the nightclubs there. That's unacceptable. Unbelievable.

Whereabouts in Trafalgar Square? Is there a plaque? There's got to be a plaque. Well, what about the plinth, the fourth plinth? Why isn't there a hippo on that plinth? Instead of a plinth, why don't you have a glass ditch? That you can look into and see a hippo on that plinth? What, instead of a plinth, why don't you have a glass ditch? Well... That you can look into. That you can look into.

And see the hippo remains. Well, there were lions as well. At least the lions are there, but that's a coincidence. That was his lions, yeah. I'm not a scientist. So there was hippos. There was hippos and there was lions. There was lions.

Also, like, Trafalgar Square was just littered with... I thought this was, like, one amazing find. It's just littered with all kinds of safari-i. Shut up. It makes an important point that I think a lot of the animals that we tend to think of as, say,

African animals, they were much more widespread in the past. We had spotted hyenas here, we had lions here. The big predators in particular, they're not fussed really whether they eat a reindeer or a fallow deer. It doesn't really matter as long as there's adequate food sources. Well, that would ruin Christmas for the kids, though, wouldn't it?

Not if you've got them a nice small elephant wrapped up. So what do we know about this? We had this great diversity of hominin species at some point around what? In the last 100 000 even 100 000 yeah so so the question has to be why now do we only only have one yeah that is one of the big unanswered questions and obviously have you got the answers to any of these questions

i want to set myself up as an expert. Well, that's the question. We don't really know. Nobody does. I've got to keep myself in a job. I don't want to solve all the problems. He gave you gerbils. How many more do you want? He does sound actually really, really intelligent. When you go, well, we don't really know.

It's a very intelligent response. I'm going to start doing that all... Oh, no, I already do that. It's on the clear. Sorry, I'm going to start doing that all... Oh, no, I already do that. It's on the clue. Sorry, go on. I think these other... So we evolved in Africa and we came out of Africa from about 100,000 years ago, modern humans started to emerge into these other areas

where these other humans were living. And within 60,000 years, all those other humans had gone physically extinct. Not genetically extinct, we might get onto that with the DNA, but physically they'd all gone by about 40,000 years ago as far as we know. So is it a coincidence? I don't think it's a coincidence. I think modern humans were involved in those processes, but was it an intentional extinction? Did modern humans go hunting the Neanderthals and the hobbits and the Denisovans to kill them off? I doubt it. I

think it was probably that modern humans increased their numbers. They moved into those environments. They were hunting the same animals, collecting the same plants, wanting to live in the best cave sites. And so there was economic competition, if you like. We know genetically what we've got, the data for Denisovans and Neanderthals, is that they were not highly varied genetically. They were actually relatively small in number, not genetically very diverse. So they already, in a sense, were threatened by their low diversity in numbers.

The arrival of modern humans might have, along with climate change, which was also happening, that maybe was enough to tip them over the edge. So it wasn't just modern humans that led to that extinction. A combination of factors, but modern humans were part of the reason, I think, why they went extinct. And maybe that's what's happened to all the other large mammals

that were around. You know, why don't we have rhinos and elephants and things in Europe now? Well, the fact humans are here is probably a big part of that story, isn't it, of the answer why we don't have them. I would say for sure. I mean, we lack the smoking gun in so many ways.

I mean, you know, the occasions where you find, for example, a mammoth keeled over with a spear tip embedded in its ribs. You could count them on the fingers of one hand. But the background of climate change, it was so rapid, so abrupt. It tipped a lot of the big prey species, so things like woolly rhinos and then later things like mammoths. It eventually tipped them over the edge,

because, I mean, just as you find today, when populations become fragmented, a loss of genetic diversity, human hunting, you don't have to have that much extra to actually drive these things to extinction. So it probably is a combination of the two and neanderthals seem to have gone the same way that that their prey did eventually although as you suggested um genetically speaking uh we interbred with them with with all of them that we only know with the neanderthals well with the nissavans too so this is again something we've only really learned

in the last ten years for sure. I mean, people have argued about it for a long time. My view used to be, well, you know, there maybe was a little bit of interbreeding 40,000, 50,000 years ago, but we're never going to find it today because it would have been insignificant. But that was wrong. It is there today, and so we on this panel

have got around 2% Neanderthal DNA in us. You can decide, audience, which... Where you think that distribution, plus or minus 2%, is actually distributed, but it's around 2%, on average, Neanderthal DNA in people outside of Africa. And then when you look at Australia and New Guinea, they've got 4% of their DNA from a source like related to the Denisovans. Now we think the ancestors of Australian Aborigines and New Guineans never went anywhere near

Denisovan cave in Siberia. So that probably means the Denisovans were ranging over a lot of Asia, probably down into Southeast Asia. When modern humans were migrating out of Africa towards Australia and New Guinea, they met some Denisovans, there was some interbreeding down there, they picked up their DNA. We came out of Africa into the Middle East and probably 50,000 years ago, we started mixing on some scale with the Neanderthals and we picked up their DNA.

You've had the test done, haven't you, for Neanderthal? Didn't you have it done for one of your shows? No, no, I just... Not just for leisure, really. LAUGHTER There were those cheap DNA sequencing things you can do. I think it was about 2%. Who do you think you are? It's a very limited show, isn't it?

And it goes back to the Victorian workhouse. Well, I was colossal... We've never knew the Neanderthals enough, have we? I was start crying. He was killed when a mammoth stood on him. I think we realised from the show that Ross is probably someone who would like to be found eventually in thousands of years' time. What is the best way he can increase the chance of being fossilised?

Of being scientifically important. I'd like to say that it would be a painless disposal in the permafrost, but actually, if you want to get good DNA out of Ross in several thousand years to come... Ooh, cheeky! Let's wait till the show's over first. Sorry, I couldn't resist. Go on. He needs to have his bones stripped of flesh first.

Oh! Yeah. So, yes, it's true that... I mean, we're finding sites now where, for example... And this is undoubtedly something that Chris can elaborate on, but where, for example, Neanderthals have essentially butchered and cannibalised their own, and the DNA out of that is superior. Yeah, that's true.

Yes, it seems that cannibalism seems to help the preservation of DNA. That's a nightmare because my wife's a vegetarian. Where's your buried? Well, if you've got less flesh on you, then when you're defrosting out, as that permafrost melts at some

time in the future, again, if you're down to your bare bones, you might be surviving. Your DNA might survive better than if you've got decaying flesh around you. I think we're working it cross-purposes. I think you're thinking of being cryogenic frozen so you can be brought back to life again at some point. No, no, no. Because then it would be a bad

idea to just preserve your skeleton. You really want the whole frozen head. It's the Jurassic Park. They just need a bit of DNA and they can, woof, off you go. So, we always ask the audience a question as well and today we asked them, what trait would you most like to see humans evolve next?

So, the first one is the ability to look like Brian Cox so I can be Mum's favourite son. Oh, John! It's under Pinocchio. Noses that grow longer when you lie so politicians finally start telling the truth. To only get athlete's foot if you are actually an athlete. Here's a great...

Mr Spock ears to receive Wi-Fi. Breathing underwater to enable me to sing when swimming. Well done, Maggie. The ability to think of witty answers to quiz questions. Eternal youth, Brian, seems to know something we don't. But you do know that isn't the original Brian. He gets changed every year. It's like Seat Freedom Roy.

The ability to shrink and inflate your breasts when required, i.e. shrinking for running away and inflating when required. LAUGHTER I like somebody who at the last minute went, i.e. shrinking for running away and inflating when required. I like somebody who at the last minute went, I think just when required will do, actually. The ability to give any new particles that are discovered a sensible name, and that's from Boaty Mac Boatface. Brian exists. There is no need to evolve further.

What a stupid answer. Do a phone number on it. So thank you very much to our panel, Ross Noble, Daniel Shreve and Chris Stringer. Next week is the final episode of this series where we discuss making the invisible visible and we're having difficulty finding a panel for that. So anyway, thank you very much for listening.

Goodbye. Thank you. Turn down ice again. This is the BBC. Turned out nice again. This is the BBC. In our new podcast, Nature Answers, rural stories from a changing planet, we are travelling with you to Uganda and Ghana to meet the people on the front lines of climate change. We will share stories of how they are thriving using lessons learned from nature.

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