0:00:17 > 0:00:20We like to think that humans are special.
0:00:20 > 0:00:22And we are.
0:00:22 > 0:00:24But we're not one of a kind.
0:00:29 > 0:00:35The past 30 to 40,000 years in human history are really unique
0:00:35 > 0:00:38in that we are alone on the planet.
0:00:38 > 0:00:40Earlier, there were always
0:00:40 > 0:00:43different forms of humans around that we met,
0:00:43 > 0:00:44and would mix with each other.
0:00:44 > 0:00:48We now know that there were at least four other distinct types of human
0:00:48 > 0:00:52on the planet at the same time as us.
0:00:52 > 0:00:55Maybe there were even others that we don't know about yet.
0:00:56 > 0:01:01And all of them, except us, are now lost in time.
0:01:01 > 0:01:05Studying human origins at this time is very, very exciting,
0:01:05 > 0:01:07because the story keeps changing.
0:01:07 > 0:01:09We are really writing it now.
0:01:11 > 0:01:15More and more, we've found that they were getting feathers
0:01:15 > 0:01:17for ornamentation, to wear them in some way.
0:01:17 > 0:01:21And we now know that we, homo sapiens,
0:01:21 > 0:01:24made contact with these other humans.
0:01:24 > 0:01:27When we got the first result that suggested that there had been
0:01:27 > 0:01:30interbreeding, we were very sceptical, all of us.
0:01:30 > 0:01:34Traditional palaeoanthropology, based on fossils,
0:01:34 > 0:01:37is being transformed by genetics.
0:01:37 > 0:01:41And right at the vanguard in the hunt for these lost tribes
0:01:41 > 0:01:46are scientists digging into modern and ancient DNA.
0:01:46 > 0:01:49Over the next few years, we'll be able to convincingly show
0:01:49 > 0:01:52that there are multiple forms of human
0:01:52 > 0:01:54that we have no fossil data for,
0:01:54 > 0:01:58and the only evidence of their existence is in our DNA.
0:01:58 > 0:02:02Who were all these other ancient humans?
0:02:02 > 0:02:04What did they look like?
0:02:04 > 0:02:05And where did they all go?
0:02:07 > 0:02:10The answers to these questions strike deep into the core
0:02:10 > 0:02:12of who we think we are
0:02:12 > 0:02:16and reveal that at least parts of these ancient lost tribes
0:02:16 > 0:02:18are still alive today.
0:02:34 > 0:02:39Evolution explains the diversity of life on Earth.
0:02:39 > 0:02:43But for us, the species who worked it out,
0:02:43 > 0:02:45it holds a special message.
0:02:45 > 0:02:48We are descended from ancient apes.
0:02:48 > 0:02:53And I've been fascinated by this image for as long as I can remember.
0:02:53 > 0:02:56It's such an iconic image of human evolution,
0:02:56 > 0:02:59starting off with this knuckle-walking ancient ape
0:02:59 > 0:03:02and then this ape who is standing a bit more upright.
0:03:02 > 0:03:04And then we have the Neanderthal,
0:03:04 > 0:03:08still a bit stooped, and then finally, Cro-Magnon man
0:03:08 > 0:03:10with his spear here,
0:03:10 > 0:03:14and he's well on his way to being a truly modern human.
0:03:14 > 0:03:17But this isn't the real picture of human evolution.
0:03:21 > 0:03:24Piecing together who our ancestors actually were
0:03:24 > 0:03:27has been an extraordinary scientific adventure.
0:03:29 > 0:03:33A dramatic story of mystery and revelation.
0:03:35 > 0:03:41What we need is a new image to replace that old iconic one.
0:03:41 > 0:03:44So, we can start off with a lineage,
0:03:44 > 0:03:46which is just one line
0:03:46 > 0:03:51that eventually ends up around 200,000 years ago
0:03:51 > 0:03:55being us, being modern humans.
0:03:55 > 0:03:59Anatomically and genetically, we have arrived as a species.
0:04:01 > 0:04:06So did we evolve from Neanderthals, or are they, as some suspected,
0:04:06 > 0:04:10a completely separate and distinct human lineage?
0:04:17 > 0:04:19It's dawn.
0:04:19 > 0:04:22A small hunting party of Neanderthals
0:04:22 > 0:04:24are silently stalking their prey.
0:04:26 > 0:04:29They are at home in the seemingly endless forest.
0:04:30 > 0:04:33But they will, in time,
0:04:33 > 0:04:34disappear from the Earth.
0:04:54 > 0:04:58Neanderthals were the archetypal cave dwellers...
0:05:02 > 0:05:05..thick set, short and muscular,
0:05:05 > 0:05:09with a characteristically heavy brow ridge.
0:05:09 > 0:05:12They were thought to be much less intelligent than us.
0:05:19 > 0:05:22Many people still think of the Neanderthal as
0:05:22 > 0:05:25a simple-minded, thuggish people.
0:05:25 > 0:05:28But recent, quite often unexpected discoveries,
0:05:28 > 0:05:31are forcing us to confront that perception.
0:05:43 > 0:05:47Archaeologist Clive Finlayson and his team are convinced that this
0:05:47 > 0:05:51simplistic impression of Neanderthals is wrong.
0:05:54 > 0:05:58We've been working in these caves in Gibraltar now for over 25 years.
0:05:58 > 0:06:00We have dates in these caves now with Neanderthals
0:06:00 > 0:06:03as recently as 32,000 years ago.
0:06:03 > 0:06:05That would make this the last site where Neanderthals lived.
0:06:07 > 0:06:12This, the last known refuge of a lost tribe of Neanderthals,
0:06:12 > 0:06:16has produced thousands of bones and artefacts.
0:06:16 > 0:06:20It presents us with almost a total picture of Neanderthal life
0:06:20 > 0:06:22in this part of the world.
0:06:22 > 0:06:24Families were living here,
0:06:24 > 0:06:27sleeping here and going out to hunt and forage from here.
0:06:27 > 0:06:31In my view, the stereotype of the ape-like Neanderthal
0:06:31 > 0:06:34I think is changing. People are realising, even anatomically, that
0:06:34 > 0:06:38there may be physical differences between our ancestors and them,
0:06:38 > 0:06:42but they're not as huge as we thought, once upon a time.
0:06:42 > 0:06:45What is really changing our view is the cultural evidence,
0:06:45 > 0:06:50the evidence of the abilities that we thought only we had
0:06:50 > 0:06:53and caused our expansion across the globe.
0:06:53 > 0:06:54And we're beginning to realise that
0:06:54 > 0:06:56Neanderthals were not that different.
0:06:59 > 0:07:03In the past, experts suggested that Neanderthals were incapable of
0:07:03 > 0:07:07planning, of thinking two or three steps ahead.
0:07:08 > 0:07:11That's not true at all. These people knew their environment very well,
0:07:11 > 0:07:13they knew what they had here and they exploited it very well.
0:07:13 > 0:07:16And that's probably the key to their success and their survival
0:07:16 > 0:07:17for such a long time.
0:07:19 > 0:07:21The Neanderthals were not only
0:07:21 > 0:07:24an immensely successful European species,
0:07:24 > 0:07:28but we're starting to realise that they were cultured in a way
0:07:28 > 0:07:33that we thought was the sole preserve of modern humans.
0:07:33 > 0:07:36The clues are hidden amongst the many bird bones
0:07:36 > 0:07:38buried in these caves.
0:07:40 > 0:07:44More and more we've found that the evidence is in the form of cut marks
0:07:44 > 0:07:47on the bones and what we realised was that a lot of the marks were on
0:07:47 > 0:07:50the wing bones of these birds.
0:07:50 > 0:07:53Using stone tools and dead birds found on the shoreline,
0:07:53 > 0:07:56Clive's team have been exploring what the Neanderthals might
0:07:56 > 0:07:58have been doing.
0:07:58 > 0:08:02If you dissect the wing bone of a vulture or an eagle,
0:08:02 > 0:08:04what you find is a bone and a tendon
0:08:04 > 0:08:07and the feathers attached to the skin. There's no meat,
0:08:07 > 0:08:10because you have to be lightweight to be able to soar.
0:08:10 > 0:08:13So if you're cutting these wing bones in the birds of prey,
0:08:13 > 0:08:17it has to be something to do with feathers and certainly has nothing
0:08:17 > 0:08:18to do with meat or food.
0:08:21 > 0:08:24In parallel, we realise that a lot of the species of bird of prey being
0:08:24 > 0:08:27brought in were birds of prey with dark feathers.
0:08:27 > 0:08:30And we showed that there seemed to be a discrimination
0:08:30 > 0:08:31in terms of colour.
0:08:31 > 0:08:34Neanderthals preferred black, for some reason.
0:08:36 > 0:08:39The conclusion that we came to after a lot of analysis is that
0:08:39 > 0:08:41they were getting the feathers for ornamentation,
0:08:41 > 0:08:43to wear them in some way.
0:08:45 > 0:08:48Many cultures across the globe, historically and today,
0:08:48 > 0:08:52use bird feathers. North American Indians, for example.
0:08:52 > 0:08:55Because of this close relationship that they had with birds,
0:08:55 > 0:08:58we decided to call them the Bird People of Europe.
0:09:10 > 0:09:11Deeper in these caves,
0:09:11 > 0:09:15the team have found evidence suggesting that these Bird People
0:09:15 > 0:09:18had the capacity for abstract thought.
0:09:18 > 0:09:23Something else which was believed to be exclusive to modern humans.
0:09:23 > 0:09:26We have found this incredible engraving on the rock,
0:09:26 > 0:09:27made by Neanderthals.
0:09:27 > 0:09:30And it is the only one that is known today anywhere.
0:09:33 > 0:09:37It took us two years of intensive study and we came to the conclusion
0:09:37 > 0:09:40that it took them at least two hours to do,
0:09:40 > 0:09:43because we replicated the whole procedure, so it wasn't something...
0:09:43 > 0:09:46It wasn't a doodle - they'd actually thought about it.
0:09:46 > 0:09:49And it wasn't marks done for butchery, for example,
0:09:49 > 0:09:51if you're cutting through skin.
0:09:51 > 0:09:55We tried to replicate that with skin and the lines go all over the place.
0:09:55 > 0:09:58This was something that wasn't functional,
0:09:58 > 0:10:00it was sending a message to somebody, and it was done
0:10:00 > 0:10:03very, very deliberately, and it took a long time.
0:10:03 > 0:10:06This is not mere survival.
0:10:06 > 0:10:08This looks like art.
0:10:08 > 0:10:11It's the next step, if you like.
0:10:11 > 0:10:14The smoking gun, in terms of Neanderthal behaviour.
0:10:15 > 0:10:18So, contrary to the popular perception of them,
0:10:18 > 0:10:22we are now realising that Neanderthals exhibited many aspects
0:10:22 > 0:10:25of what we call modern human behaviour.
0:10:28 > 0:10:31And they are much closer to us in other ways, too.
0:10:33 > 0:10:35They are cousins of ours.
0:10:35 > 0:10:38We've known that from an anatomical point of view, looking at the bones,
0:10:38 > 0:10:42but now we know it from genetics as well.
0:10:42 > 0:10:46What we know about them is that they branch from a common ancestor,
0:10:46 > 0:10:48500,000 to 700,000 years ago,
0:10:48 > 0:10:50and here they are,
0:10:50 > 0:10:54almost surviving to the present day, but not quite.
0:10:55 > 0:10:59Genetically, Neanderthals were a species distinct from
0:10:59 > 0:11:03the modern humans who originated in Africa
0:11:03 > 0:11:06and who, much later on, would emerge from that continent
0:11:06 > 0:11:09and venture into the Neanderthal's home territory.
0:11:13 > 0:11:15As the climate changes,
0:11:15 > 0:11:19modern humans are spreading from other parts of the globe
0:11:19 > 0:11:21into what will eventually become known as Europe.
0:11:25 > 0:11:29Tall and lean bodied, modern humans also skilled hunters.
0:11:35 > 0:11:37But they've got to compete for resources...
0:11:40 > 0:11:42..with the local Neanderthals.
0:11:49 > 0:11:53I find it really interesting to imagine what might have happened
0:11:53 > 0:11:56if these two groups of people had come into contact with each other.
0:11:56 > 0:12:01The incoming modern humans and the indigenous Neanderthals.
0:12:01 > 0:12:04How different did they seem to each other?
0:12:04 > 0:12:08Would they have reacted with friendliness and curiosity?
0:12:08 > 0:12:13Or would it have inevitably been violent and hostile?
0:12:17 > 0:12:21We're faced with an interesting challenge.
0:12:21 > 0:12:24If we look at the archaeological record,
0:12:24 > 0:12:27at what Neanderthals did and made,
0:12:27 > 0:12:30and then we look at what modern humans made,
0:12:30 > 0:12:32can we see any suggestion that
0:12:32 > 0:12:35there was not only contact between the two groups,
0:12:35 > 0:12:38but a fruitful exchange of ideas?
0:12:47 > 0:12:50Based at the Natural History Museum in London,
0:12:50 > 0:12:54anthropologist Chris Stringer has been investigating ancient humans
0:12:54 > 0:12:57for over 30 years.
0:12:57 > 0:13:02In particular, the similarities and differences between modern humans
0:13:02 > 0:13:03and Neanderthals.
0:13:05 > 0:13:08Neanderthals are very evolved humans.
0:13:08 > 0:13:10In their own way, as evolved as us, overall.
0:13:10 > 0:13:12They walked upright as well as we do
0:13:12 > 0:13:14and their brains were as large as ours.
0:13:14 > 0:13:18We now know that Neanderthals shared much of their behaviour with us.
0:13:18 > 0:13:19They buried their dead,
0:13:19 > 0:13:23they were very capable at their stone toolmaking.
0:13:23 > 0:13:26This is a typical Neanderthal hand axe.
0:13:27 > 0:13:30- It is a beautiful one, isn't it? - Yeah.
0:13:30 > 0:13:31Beautifully shaped.
0:13:31 > 0:13:33It was top-quality flint.
0:13:33 > 0:13:35And they had a knack of finding that, you know?
0:13:35 > 0:13:38Yes. So this is a 60,000-year-old one?
0:13:38 > 0:13:40Wonderful, isn't it? Beautiful.
0:13:40 > 0:13:43Neanderthals and modern humans were both expert craftsmen
0:13:43 > 0:13:44in their own ways,
0:13:44 > 0:13:49carefully preparing their flint and able to strike off a usable
0:13:49 > 0:13:52flake or blade with a single strike.
0:13:52 > 0:13:55I'll try in between the two and see.
0:13:55 > 0:13:59- There we are. All that cutting edge down there.- Fantastic. Look at that.
0:13:59 > 0:14:02This is buffalo hide, and that's gone straight through.
0:14:02 > 0:14:04- Sharp as a razor.- Yeah, yeah.
0:14:04 > 0:14:05Wonderful.
0:14:09 > 0:14:12There are a number of Neanderthal sites across Europe,
0:14:12 > 0:14:14where the technology, to some experts,
0:14:14 > 0:14:19looks suspiciously similar to that found at modern human sites.
0:14:19 > 0:14:23It's tempting to ask whether they each developed the techniques
0:14:23 > 0:14:28independently, or whether this represents an exchange of ideas.
0:14:30 > 0:14:34There is a view that that perhaps reflects contact between the groups,
0:14:34 > 0:14:37that Neanderthals were picking up aspects of behaviour and they are
0:14:37 > 0:14:40reflected in these changes that they are making.
0:14:40 > 0:14:43They are making tools which we might think typical of modern humans,
0:14:43 > 0:14:48they are using, to a much greater extent, bone or ivory.
0:14:48 > 0:14:51As well as tools, there are other cultural artefacts which go
0:14:51 > 0:14:54far beyond what's been found at other Neanderthal sites.
0:14:55 > 0:14:59These sites contain evidence of jewellery, for example,
0:14:59 > 0:15:01pierced animal teeth. So, the Neanderthals,
0:15:01 > 0:15:03they are making body adornments
0:15:03 > 0:15:06which normally would be thought of as modern human features.
0:15:06 > 0:15:09'Now, with much better dating techniques,
0:15:09 > 0:15:12'we are able to use radiocarbon to show that
0:15:12 > 0:15:17'the Neanderthal cultures do go on to perhaps 39,000 years ago,
0:15:17 > 0:15:19'maybe a bit younger in places.
0:15:19 > 0:15:21'And a modern human arrival certainly'
0:15:21 > 0:15:24arrives before 40,000 years ago, in Europe.
0:15:24 > 0:15:27So there is an overlap and potentially,
0:15:27 > 0:15:29when these groups came together,
0:15:29 > 0:15:32we did pick up some things from Neanderthals that were an
0:15:32 > 0:15:35advantage to us, about living and surviving
0:15:35 > 0:15:37in those colder environments in Europe and Asia.
0:15:40 > 0:15:45So the archaeological evidence hints at an exchange of ideas
0:15:45 > 0:15:47between Neanderthals and modern humans.
0:15:52 > 0:15:53But eight years ago,
0:15:53 > 0:15:58a fossil fragment from a cave in southern Siberia was about to drop
0:15:58 > 0:16:00what can only be described as a bombshell
0:16:00 > 0:16:03into the world of paleoanthropology.
0:16:03 > 0:16:07Because it suggested that Neanderthals and modern humans
0:16:07 > 0:16:09had neighbours.
0:16:09 > 0:16:14Another tribe of humans living right on their doorstep.
0:16:19 > 0:16:21Deep in the Altai Mountains,
0:16:21 > 0:16:26near to where Kazakhstan will one day meet Mongolia,
0:16:26 > 0:16:27winter is coming.
0:16:29 > 0:16:33But this mountain-dwelling tribe is at home in their environment.
0:16:38 > 0:16:40Their cave is on a migration route...
0:16:42 > 0:16:46..which offers herds easy passage through the mountains
0:16:46 > 0:16:48to the warmer grasslands further south.
0:16:59 > 0:17:03Surprisingly, the eventual discovery of this tribe
0:17:03 > 0:17:09would actually be made 3,500 miles away, in Leipzig, Germany.
0:17:09 > 0:17:13Svante Paabo is a geneticist from the Max Planck Institute
0:17:13 > 0:17:17and he specialises in archaic DNA.
0:17:17 > 0:17:21He and his team are collaborating with Russian archaeologists
0:17:21 > 0:17:24who are excavating the remote mountain cave.
0:17:26 > 0:17:28So, in 2008,
0:17:28 > 0:17:32our colleagues found a lot of different bones.
0:17:32 > 0:17:34And among those bones,
0:17:34 > 0:17:36they found a tiny little piece,
0:17:36 > 0:17:40a little fragment of the last phalanx of a little finger.
0:17:40 > 0:17:42Just a piece of it.
0:17:42 > 0:17:46It was obviously from a child, because it was very, very small.
0:17:46 > 0:17:48And it's a bit unclear how old it is.
0:17:48 > 0:17:53It's at least in the order of 50,000 years, probably older.
0:17:53 > 0:17:58And they sent this, along with some other bones, to us in Leipzig.
0:18:03 > 0:18:07They sent it to Svante in the hope that he and his team
0:18:07 > 0:18:11could extract some DNA and perhaps determine whether the bone was
0:18:11 > 0:18:14Neanderthal or Homo sapiens.
0:18:22 > 0:18:25What we do when we get the bone to sample
0:18:25 > 0:18:28is to remove the surface and little area,
0:18:28 > 0:18:30drill the hole with a dentistry drill,
0:18:30 > 0:18:32so we get powder out.
0:18:42 > 0:18:45From that, we then isolate the DNA.
0:18:45 > 0:18:49We purify it away from all of the other components of the bones at
0:18:49 > 0:18:52this end, the minerals are there, the proteins, the fats.
0:18:55 > 0:18:57And you then have it in a form
0:18:57 > 0:18:59that you can feed into sequencing machines.
0:19:01 > 0:19:06The problem when you study ancient DNA is that first of all,
0:19:06 > 0:19:09there's very little there, in the remains.
0:19:09 > 0:19:14The vast majority of the DNA is not indigenous to the bone,
0:19:14 > 0:19:18but comes from bacteria and fungi that have colonised the bone
0:19:18 > 0:19:20over tens of thousands of years
0:19:20 > 0:19:23when it was deposited in the cave.
0:19:23 > 0:19:27And perhaps the biggest problem is the risk of contamination from
0:19:27 > 0:19:32present-day human DNA, from ourselves in the laboratory,
0:19:32 > 0:19:34in a room like this, where people move around.
0:19:34 > 0:19:39A large part of the dust in the air is actually skin fragments
0:19:39 > 0:19:43and a single such dust particle can contain a lot more DNA
0:19:43 > 0:19:46than we have in our sample of the bone.
0:19:49 > 0:19:53DNA is very fragile and it doesn't preserve easily.
0:19:55 > 0:20:00But amazingly, despite lying for thousands of years in a cave,
0:20:00 > 0:20:04the DNA in that tiny bone had hardly degraded at all.
0:20:05 > 0:20:10This little part of the little finger was so well-preserved,
0:20:10 > 0:20:13we were able to sequence, actually, the entire genome to a very high
0:20:13 > 0:20:16quality, as high a quality as you would sequence
0:20:16 > 0:20:19your or my genome today.
0:20:19 > 0:20:21It's an astonishing achievement
0:20:21 > 0:20:25to get a complete genome from a 50,000-year-old bone.
0:20:27 > 0:20:31But the biggest shock came when they tried to identify
0:20:31 > 0:20:33what species of human it was.
0:20:37 > 0:20:41We were very surprised to find that it was not a Neanderthal.
0:20:41 > 0:20:44It was very, very distant from other Neanderthal genomes
0:20:44 > 0:20:45we had looked at.
0:20:47 > 0:20:51So we immediately realised this was something very special.
0:20:51 > 0:20:54It was not a Neanderthal, it was not a modern human,
0:20:54 > 0:20:56it was something new.
0:20:56 > 0:21:00We had found a new form of extinct human.
0:21:04 > 0:21:07This was completely unexpected.
0:21:07 > 0:21:10A human that was related to all of us,
0:21:10 > 0:21:12but genetically distinct.
0:21:13 > 0:21:16Another group of cousins.
0:21:21 > 0:21:25So we had a lot of discussions among ourselves and our Russian colleagues
0:21:25 > 0:21:28what we'd call this group of humans.
0:21:28 > 0:21:30And after a lot of back and forth,
0:21:30 > 0:21:32we agreed to call them the Denisovans.
0:21:32 > 0:21:35Just like Neanderthals are called Neanderthals
0:21:35 > 0:21:36after the Neander Valley,
0:21:36 > 0:21:40where the first remains of Neanderthals were found,
0:21:40 > 0:21:44Denisovans are called after the first place where they were found.
0:21:47 > 0:21:50We know very little of Denisovans, it's very frustrating.
0:21:52 > 0:21:54We do know that they lived in this cave and that they lived
0:21:54 > 0:21:56intermittently with Neanderthals there.
0:21:56 > 0:21:59There seem to have been Neanderthals there early,
0:21:59 > 0:22:01there were then later Denisovans
0:22:01 > 0:22:04and later again, Neanderthals.
0:22:04 > 0:22:07And it's, to me, a really amazing place in the world,
0:22:07 > 0:22:09because it's the only place we know
0:22:09 > 0:22:12that at least three different forms of humans have lived.
0:22:13 > 0:22:18We can tell that Denisovans were more closely related to Neanderthals
0:22:18 > 0:22:19than to us.
0:22:20 > 0:22:23Whereas the ancestors of Neanderthals and modern humans
0:22:23 > 0:22:26split around 600,000 years ago,
0:22:26 > 0:22:30Denisovans split from a common ancestor with Neanderthals,
0:22:30 > 0:22:32about 400,000 years ago.
0:22:34 > 0:22:38And really, we only know about this species from their genetics.
0:22:38 > 0:22:41We don't know much about their anatomy at all,
0:22:41 > 0:22:43the fossil record is so fragmentary.
0:22:44 > 0:22:49Further excavations in the cave have uncovered two Denisovan teeth
0:22:49 > 0:22:53and so far, that is all the physical evidence we have
0:22:53 > 0:22:57of this new lost tribe of mountain-dwelling humans.
0:22:58 > 0:23:01The burning question that remains, though,
0:23:01 > 0:23:05is did Denisovans ever meet our own wandering ancestors?
0:23:11 > 0:23:15It is well accepted that our species, Homo sapiens,
0:23:15 > 0:23:18originated in Africa.
0:23:18 > 0:23:24But just how and when our ancestors left Africa to colonise the globe
0:23:24 > 0:23:27has been a matter of considerable debate.
0:23:27 > 0:23:30And each new piece of genetic and fossil evidence
0:23:30 > 0:23:32changes our understanding.
0:23:32 > 0:23:38Some very recent finds have really pushed the boundaries of how far
0:23:38 > 0:23:43and how early modern humans strayed from their African homeland.
0:23:44 > 0:23:47And the earlier we left Africa,
0:23:47 > 0:23:51the more chance we had of overlapping in time
0:23:51 > 0:23:55and in the same parts of the world with our other human cousins.
0:24:01 > 0:24:02To understand the story of
0:24:02 > 0:24:04what really happened to us,
0:24:04 > 0:24:08we really need to take into account the whole map. And China
0:24:08 > 0:24:12is a very, very important part of this puzzle.
0:24:14 > 0:24:18Archaeologist Maria Martinon-Torres, from University College London,
0:24:18 > 0:24:22has teamed up with colleagues from the Chinese Academy of Sciences
0:24:22 > 0:24:26to study a treasure trove of human teeth found in a cave
0:24:26 > 0:24:29in Daoxian province in south-east China.
0:24:30 > 0:24:33Some people might think that all teeth look the same,
0:24:33 > 0:24:34but they do not.
0:24:34 > 0:24:37Teeth are like little landscapes in miniature.
0:24:39 > 0:24:43These teeth are clearly modern human, Homo sapiens,
0:24:43 > 0:24:48rather than from an archaic hominin, like a Denisovan or a Neanderthal.
0:24:48 > 0:24:53Homo sapiens have very simple teeth and they are really very slender.
0:24:53 > 0:24:56The roots are very thin, they are really narrow towards the tip.
0:24:56 > 0:25:00However, if you look at the roots of an archaic hominin,
0:25:00 > 0:25:03they have really stout and robust roots,
0:25:03 > 0:25:06like columns that really diverge and open very strongly.
0:25:06 > 0:25:09So it's really a big difference.
0:25:10 > 0:25:14The teeth had been perfectly preserved in the limestone cave
0:25:14 > 0:25:17underneath a layer of calcite.
0:25:18 > 0:25:23The Daoxian teeth were found in the calcite layer, like a gravestone,
0:25:23 > 0:25:27that is really like sealing all the layer where the fossils were found.
0:25:27 > 0:25:32We dated the stalagmites that really grow on top of that layer
0:25:32 > 0:25:35and the stalagmites have been dated 80,000 years ago.
0:25:39 > 0:25:43Meaning that everything that is accumulated below has to be at least
0:25:43 > 0:25:4580,000 years ago.
0:25:47 > 0:25:52This new evidence and dramatically overturns previous theories
0:25:52 > 0:25:54about human movement around the world.
0:25:57 > 0:26:03It shows us just how well-travelled these early modern humans were.
0:26:03 > 0:26:06The Daoxian teeth are very important,
0:26:06 > 0:26:12because they represent the earliest and soundest evidence we have
0:26:12 > 0:26:15of our own species, Homo sapiens, being outside Africa.
0:26:15 > 0:26:19And they were outside Africa much earlier than expected.
0:26:22 > 0:26:26So in order for Homo sapiens to reach China so long ago,
0:26:26 > 0:26:31we must have left Africa around 100,000 years ago, possibly earlier.
0:26:31 > 0:26:35That means modern humans must have spent thousands of years roaming the
0:26:35 > 0:26:40planet and sharing it with the other two human tribes.
0:26:44 > 0:26:48And this is very exciting for a scientist, with the Daoxian teeth,
0:26:48 > 0:26:51we have a lot of new questions, like
0:26:51 > 0:26:54did the hominins we found in Daoxian ever meet Neanderthals?
0:26:54 > 0:26:57Did they ever meet these mysterious Denisovans?
0:26:57 > 0:27:01So there are a lot of new questions we have to understand about
0:27:01 > 0:27:04who we were about 100,000 years ago.
0:27:06 > 0:27:09The answers to some of these questions will no doubt be found
0:27:09 > 0:27:11somewhere in Asia,
0:27:11 > 0:27:16a vast continent sure to contain many anthropological surprises.
0:27:24 > 0:27:27In fact, the South East Asian islands have already thrown up one
0:27:27 > 0:27:31of the most startling and controversial the discoveries
0:27:31 > 0:27:33of recent years in paleoanthropology.
0:27:33 > 0:27:40Evidence of a lost tribe that is human, but almost unrecognisably so.
0:27:44 > 0:27:48Living on an island isolated from the rest of the world...
0:27:50 > 0:27:52..is a group of miniature humans.
0:27:54 > 0:27:58Adults are only one metre or 3ft tall.
0:28:01 > 0:28:03Living off dwarf elephants
0:28:03 > 0:28:08and using technology as advanced as other human groups around the world.
0:28:21 > 0:28:25Anthropologists Laura Shackelford and Fabrice Demeter
0:28:25 > 0:28:28study human fossils across south-east Asia,
0:28:28 > 0:28:32but they hadn't anticipated that in 2003,
0:28:32 > 0:28:37a group from Australia would discover a hobbit-sized human
0:28:37 > 0:28:40in a cave on the island of Flores in Indonesia.
0:28:42 > 0:28:45When the fossils were discovered on Flores, it was a very exciting find,
0:28:45 > 0:28:48because no-one knew quite what they were.
0:28:48 > 0:28:50When Flores came out to the public,
0:28:50 > 0:28:53it was a big shock for the scientific community.
0:28:53 > 0:28:56This was a species that looked nothing like anything
0:28:56 > 0:28:58that had been discovered before.
0:28:58 > 0:29:01Because it has very specific features.
0:29:01 > 0:29:05Particularly its short stature, only about 3ft tall.
0:29:05 > 0:29:08And what was even more interesting about the species
0:29:08 > 0:29:10was that they had a very small brain,
0:29:10 > 0:29:13a brain that was about the size of a chimpanzee's brain.
0:29:13 > 0:29:17So this was a new species that no-one really knew what to do with.
0:29:18 > 0:29:21Initially, there was scepticism.
0:29:21 > 0:29:25Fears that this was just a single deformed modern human.
0:29:26 > 0:29:30But now, with accurate dating and several individuals uncovered,
0:29:30 > 0:29:34it's accepted that these were a distinct species of human.
0:29:40 > 0:29:42They've been named Homo floresiensis,
0:29:42 > 0:29:44after the island they were found on.
0:29:46 > 0:29:50But more popularly, they are known as the hobbits.
0:29:50 > 0:29:53I don't think it is nice to say something like this about a human,
0:29:53 > 0:29:55but they are weird.
0:29:55 > 0:30:00You know, and they are weird in their aspect, in their age,
0:30:00 > 0:30:02in their location, in their history.
0:30:05 > 0:30:09The riddle of the unusual size of Homo floresiensis
0:30:09 > 0:30:13could actually be answered because of the island they lived on.
0:30:15 > 0:30:19100,000 years ago, the sea level was very, very low.
0:30:22 > 0:30:26So these islands were connected to the continent.
0:30:30 > 0:30:35But Flores was always an isolated island.
0:30:35 > 0:30:37Recently-discovered fossils show
0:30:37 > 0:30:40that the ancestors of the hobbit-sized humans
0:30:40 > 0:30:44were already small 700,000 years ago.
0:30:45 > 0:30:49It does seem that the island itself may have been to blame.
0:30:49 > 0:30:53Since they've always been isolated, then they were probably subject to
0:30:53 > 0:30:55a phenomenon that is called island dwarfism.
0:30:55 > 0:30:58And this is a phenomenon where
0:30:58 > 0:31:03when a species of any sort, not just human, but animals as well,
0:31:03 > 0:31:05when they are isolated on an island,
0:31:05 > 0:31:09then often, the species will be reduced in size.
0:31:09 > 0:31:13And this may be because there are fewer resources on an island,
0:31:13 > 0:31:16so the species may get smaller to conserve resources.
0:31:19 > 0:31:23The discovery of the hobbit-sized humans has raised many more
0:31:23 > 0:31:26questions about human origins than it has answered.
0:31:31 > 0:31:34Homo floresiensis is such a puzzle.
0:31:34 > 0:31:36It was a startling discovery,
0:31:36 > 0:31:39and we are still struggling to make sense of it.
0:31:39 > 0:31:44These tiny people seem to have evolved from ancestors who go back,
0:31:44 > 0:31:49way back in the family tree of humans to perhaps
0:31:49 > 0:31:522 million or maybe even 3 million years ago.
0:31:52 > 0:31:56What is really fascinating about this is that in contrast to today,
0:31:56 > 0:32:00where we are the only human species on the planet,
0:32:00 > 0:32:06you don't have to go back that far to find all of these others.
0:32:06 > 0:32:08The diminutive Homo floresiensis,
0:32:08 > 0:32:10the surprisingly cultured Neanderthals,
0:32:10 > 0:32:13the enigmatic Denisovans,
0:32:13 > 0:32:18all living alongside modern humans 100,000 years ago.
0:32:18 > 0:32:22But 30,000 years ago, we were still there...
0:32:24 > 0:32:27..and all these others had gone extinct.
0:32:33 > 0:32:39The past 30,000 to 40,000 years in human history are really unique
0:32:39 > 0:32:43in that there are no other closely-related forms around.
0:32:43 > 0:32:44We are alone on the planet.
0:32:52 > 0:32:55So why did Homo sapiens survive
0:32:55 > 0:32:59when all those other human tribes died out?
0:32:59 > 0:33:02The Neanderthals were, as far as we know,
0:33:02 > 0:33:05the last of our cousins to disappear.
0:33:05 > 0:33:07And the latest research suggests
0:33:07 > 0:33:09there are many reasons for their demise,
0:33:09 > 0:33:13but perhaps the most inescapable was the fluctuating climate.
0:33:16 > 0:33:19Repeatedly, the Neanderthal populations were hit
0:33:19 > 0:33:22by very rapid climate changes. They could never stabilise and
0:33:22 > 0:33:24grow their numbers for any length of time.
0:33:24 > 0:33:28Every time they expanded in the better conditions, suddenly,
0:33:28 > 0:33:30a tremendous drop in temperature very rapidly,
0:33:30 > 0:33:33and a lot of those populations died out.
0:33:34 > 0:33:37Between each period of relative warmth,
0:33:37 > 0:33:41which can last for thousands of years, the cold would come back,
0:33:41 > 0:33:45sometimes engulfing Europe within a matter of a fewer decades.
0:33:45 > 0:33:50And the Northern Neanderthal groups would have been wiped out again.
0:33:50 > 0:33:52For me, it is a matter of luck.
0:33:52 > 0:33:56Had modern humans and Neanderthals been in that place at a time when
0:33:56 > 0:33:59instead of the climate getting colder and drier,
0:33:59 > 0:34:01it got warmer and wetter,
0:34:01 > 0:34:03then we might well be Neanderthals today
0:34:03 > 0:34:06discussing why the others went extinct.
0:34:08 > 0:34:12I think the Neanderthals were already an endangered species,
0:34:12 > 0:34:14before modern humans came out of Africa
0:34:14 > 0:34:16and started overlapping with them.
0:34:16 > 0:34:18Then I think even by a small amount,
0:34:18 > 0:34:22modern humans were more effective at hunting and gathering
0:34:22 > 0:34:25and I think the Neanderthals just got displaced
0:34:25 > 0:34:28by that growing success of modern humans.
0:34:28 > 0:34:32The lesson that the Neanderthals tell us is that you can be an
0:34:32 > 0:34:35intelligent, large-brained hominid and still go extinct.
0:34:39 > 0:34:43The changing climate would have affected human populations across
0:34:43 > 0:34:49the globe and evidence of the impact of that is written into ancient DNA.
0:34:56 > 0:35:01Janet Kelso, a colleague of Svante Paabo at the Max Planck Institute,
0:35:01 > 0:35:03has been studying the history of humans
0:35:03 > 0:35:05through comparative genetics.
0:35:09 > 0:35:12In terms of diversity, in the Neanderthal population,
0:35:12 > 0:35:14it was much lower than what we see in present-day populations.
0:35:14 > 0:35:17So if you look around this train carriage,
0:35:17 > 0:35:20there's more diversity in this train carriage, perhaps,
0:35:20 > 0:35:23than there was in the population of Neanderthals that we know about.
0:35:23 > 0:35:26We think that that's probably because they were living
0:35:26 > 0:35:28in rather small populations.
0:35:33 > 0:35:37When they got the first really high-quality Neanderthal genome,
0:35:37 > 0:35:41one surprise was where the two versions of the genome
0:35:41 > 0:35:45that this individual had inherited from its mother and its father
0:35:45 > 0:35:47had no differences between them.
0:35:47 > 0:35:51And this obviously suggests that the mother and father of these
0:35:51 > 0:35:54individuals were closely related.
0:35:54 > 0:35:57You're on the level of half-siblings,
0:35:57 > 0:35:59or double first cousins.
0:35:59 > 0:36:03We don't know if this is typical of Neanderthal societies at that time,
0:36:03 > 0:36:06or if it's something special that happened in this cave
0:36:06 > 0:36:08at this point in time.
0:36:10 > 0:36:14What's certain is that low genetic diversity
0:36:14 > 0:36:16is not good for a population.
0:36:17 > 0:36:20It is known that populations that are more integrated,
0:36:20 > 0:36:21that have less diversity,
0:36:21 > 0:36:25have less ability to respond to, say, a new pathogen
0:36:25 > 0:36:27or a changing environment.
0:36:27 > 0:36:30So this diversity kind of provides a buffer for the environment,
0:36:30 > 0:36:33and if the Neanderthals were less diverse, it's quite possible
0:36:33 > 0:36:35that may have contributed to why they died out.
0:36:44 > 0:36:45But it turns out that
0:36:45 > 0:36:49Neanderthals may not have died out completely after all.
0:36:49 > 0:36:52Genetic research can tell us a great deal about who we are and where
0:36:52 > 0:36:57we come from and it is completely reshaping our idea
0:36:57 > 0:36:59of what it is to be a modern human.
0:37:05 > 0:37:08While our Homo sapien's ancestors
0:37:08 > 0:37:11were sharing the planet with the various lost tribes,
0:37:11 > 0:37:13there was, of course, the chance
0:37:13 > 0:37:16that they might have interbred with them.
0:37:18 > 0:37:20This meant that there was a possibility,
0:37:20 > 0:37:22however unlikely it seems,
0:37:22 > 0:37:26that there might be a remnant of some archaic DNA
0:37:26 > 0:37:30hanging around in the genomes of present-day humans.
0:37:30 > 0:37:33So the geneticists in Leipzig went digging for it.
0:37:36 > 0:37:39What we wanted to look at was whether there was interbreeding from
0:37:39 > 0:37:41Neanderthals into modern humans.
0:37:41 > 0:37:45And our expectation was that there was none.
0:37:45 > 0:37:48And when we got the first result that suggested that there had been
0:37:48 > 0:37:51interbreeding, we were very sceptical, all of us.
0:37:52 > 0:37:57Comparing modern human DNA to the detailed Neanderthal genome
0:37:57 > 0:38:01seemed to suggest some sharing of genes.
0:38:01 > 0:38:03We all kind of spent a lot of time looking at the data,
0:38:03 > 0:38:06trying to figure out how this could be an error.
0:38:07 > 0:38:09But the evidence was there.
0:38:09 > 0:38:13Certain modern human genomes from different parts of the world
0:38:13 > 0:38:17contained sections that matched the Neanderthal DNA.
0:38:20 > 0:38:23So what we're looking at here is a region of chromosome 4.
0:38:23 > 0:38:27At the top, we have two Neanderthals,
0:38:27 > 0:38:30and then we have a Denisovan,
0:38:30 > 0:38:32and here we have Asian individuals,
0:38:32 > 0:38:34European individuals,
0:38:34 > 0:38:36South American individuals,
0:38:36 > 0:38:39Papuans, Australians and then a group of Africans.
0:38:39 > 0:38:42And if you look down, you can see that in most positions,
0:38:42 > 0:38:43everyone is very similar,
0:38:43 > 0:38:45and that's because we are very closely related, right?
0:38:45 > 0:38:49Modern humans and Neanderthals are not that different from one another,
0:38:49 > 0:38:50which makes it really hard to
0:38:50 > 0:38:53work out where are the interesting differences.
0:38:53 > 0:38:55And so what we do is, instead, we mask out,
0:38:55 > 0:38:59we remove all the sites where everyone is the same.
0:39:00 > 0:39:02And we only look at the sites where individuals differ
0:39:02 > 0:39:04from the referenced genome.
0:39:04 > 0:39:08And so what you see here now is the Neanderthals and the Denisovan
0:39:08 > 0:39:12carry a difference from the modern human reference at this position
0:39:12 > 0:39:14and here and there and there.
0:39:14 > 0:39:18And some of those differences are shared by a number of populations,
0:39:18 > 0:39:20including the African individuals.
0:39:20 > 0:39:24And some of those differences are shared just by a few individuals,
0:39:24 > 0:39:28so here, and there, and there.
0:39:35 > 0:39:38The genomes of certain individuals contained evidence
0:39:38 > 0:39:42that our wandering ancestors bred with Neanderthal tribes
0:39:42 > 0:39:45and had offspring who survived,
0:39:45 > 0:39:48passing on their genes down the generations.
0:39:50 > 0:39:54And it wasn't just evident in a couple of individuals.
0:39:56 > 0:40:00When we went through the genomes of Africans
0:40:00 > 0:40:02and of Europeans and Asians,
0:40:02 > 0:40:06and counted how many DNA bases in each of the genomes matched the
0:40:06 > 0:40:07Neanderthal genome,
0:40:07 > 0:40:11we saw very consistently that all the groups outside of Africa
0:40:11 > 0:40:15shared more Neanderthal DNA than the groups inside of Africa.
0:40:19 > 0:40:24People with African heritage don't generally have Neanderthal DNA.
0:40:24 > 0:40:26But virtually everyone else does.
0:40:26 > 0:40:28Including me.
0:40:31 > 0:40:37Well, I've had my own genome analysed and I am 2.7% Neanderthal.
0:40:37 > 0:40:41And what is interesting is that my bit of Neanderthal DNA will be
0:40:41 > 0:40:45different to the bit of Neanderthal DNA in another person's genome.
0:40:48 > 0:40:51All people whose roots are outside Africa
0:40:51 > 0:40:54carry a bit of Neanderthal DNA.
0:40:54 > 0:40:58On average, each person carries somewhere between 1% and 2%.
0:40:58 > 0:41:01If we now look at these different pieces,
0:41:01 > 0:41:04that different people carry today,
0:41:04 > 0:41:07how much of the Neanderthal genome is still running around today
0:41:07 > 0:41:10on two legs in different individuals?
0:41:10 > 0:41:12How much do we get if we add it up?
0:41:12 > 0:41:15And the jury is still a bit out on that.
0:41:15 > 0:41:19But in the order of at least half of the Neanderthal genome
0:41:19 > 0:41:21still exists today in people.
0:41:23 > 0:41:27And that number just keeps rising, the more people they analyse.
0:41:31 > 0:41:33It's incredible to think that
0:41:33 > 0:41:38around about half the Neanderthal genome is still alive and well
0:41:38 > 0:41:41in us today. And going back just ten years ago,
0:41:41 > 0:41:46we had no idea that any of us had Neanderthal DNA.
0:41:46 > 0:41:51Now we know that practically everybody of predominantly
0:41:51 > 0:41:56non-African heritage has Neanderthal DNA in their genome.
0:41:58 > 0:42:01We interpreted that to mean that the mixture from the Neanderthals into
0:42:01 > 0:42:05the ancestors of those individuals had to have been very early.
0:42:05 > 0:42:07At the point very close to when they exited Africa,
0:42:07 > 0:42:09perhaps somewhere in the Middle East,
0:42:09 > 0:42:11when they were still a single population.
0:42:11 > 0:42:13And then as they spread out,
0:42:13 > 0:42:16they carry with them that Neanderthal DNA to wherever they go.
0:42:22 > 0:42:27And Denisovans also left their mark in the DNA of living people.
0:42:27 > 0:42:29Some more than others.
0:42:31 > 0:42:35So if your origins are in Papua New Guinea or aboriginal Australians,
0:42:35 > 0:42:41for example, they have in the order of 5% of their DNA from Denisovans,
0:42:41 > 0:42:45so three or four times more than they have,
0:42:45 > 0:42:48or people in Europe would have, from Neanderthals.
0:42:49 > 0:42:55Traces of Denisovan DNA can also be found in populations across Asia,
0:42:55 > 0:42:58in India, the Himalayas and China,
0:42:58 > 0:43:02and it's estimated that there could be as much as 60-80%
0:43:02 > 0:43:05of the Denisovan genome still in existence,
0:43:05 > 0:43:09spread around the world's populations.
0:43:09 > 0:43:13So, clearly, the wandering tribes of early modern humans
0:43:13 > 0:43:17readily mixed with our human cousins.
0:43:17 > 0:43:18Where they come into contact,
0:43:18 > 0:43:21they are doing some interbreeding where they overlap.
0:43:21 > 0:43:24And it could have included things like adopting babies,
0:43:24 > 0:43:27finding orphaned Neanderthals, Denisovan babies,
0:43:27 > 0:43:30taking them into the group and then bringing them up in your group.
0:43:30 > 0:43:33So that could have been part of it, too.
0:43:33 > 0:43:35At other times, it might have been raiding groups
0:43:35 > 0:43:38and stealing women, because a group lacked females.
0:43:38 > 0:43:40They would actually go and steal some.
0:43:40 > 0:43:43And this happens today in chimpanzee groups
0:43:43 > 0:43:45and it happens today in some hunter-gatherer groups,
0:43:45 > 0:43:48so I'm sure that was happening as well.
0:43:48 > 0:43:50So I think we've got a whole range of possibilities
0:43:50 > 0:43:53of how these matings actually happened.
0:43:57 > 0:44:03We have realised that these groups of humans are not totally extinct,
0:44:03 > 0:44:06if you like. They live on a little bit in people today.
0:44:08 > 0:44:12The most fascinating and surprising secrets
0:44:12 > 0:44:15of our long-lost past are finally being uncovered.
0:44:18 > 0:44:22The idea of modern humans crushing all other species
0:44:22 > 0:44:26in a brief and dramatic conquest of the globe
0:44:26 > 0:44:30has to give way to a process of assimilation
0:44:30 > 0:44:32that has truly shaped who we are today.
0:44:39 > 0:44:41But that's not the end of the story.
0:44:41 > 0:44:44As genetic techniques get better
0:44:44 > 0:44:48and as we delve deeper into our DNA,
0:44:48 > 0:44:51a new secret has recently been revealed.
0:45:00 > 0:45:04On the grasslands of present-day Africa,
0:45:04 > 0:45:08hidden deep in the genomes of certain people,
0:45:08 > 0:45:12are the remnants of a fifth human population,
0:45:12 > 0:45:17a lost tribe of whom all other traces have disappeared.
0:45:25 > 0:45:30The plains of central Africa are a harsh and unforgiving environment.
0:45:32 > 0:45:37And yet, an isolated hominim tribe doggedly clings to survival,
0:45:37 > 0:45:39leaving no trace in the landscape.
0:45:45 > 0:45:50This tribe was actually discovered 9,000 miles away in Seattle,
0:45:50 > 0:45:52on the West Coast of America.
0:45:54 > 0:45:58Geneticist Joshua Akey has been analysing the genes
0:45:58 > 0:46:01of certain modern African populations
0:46:01 > 0:46:05and he's uncovered sections of DNA that can't be found
0:46:05 > 0:46:07in other modern humans.
0:46:09 > 0:46:11We were able to identify sequences
0:46:11 > 0:46:13that we're confident are archaic in origin,
0:46:13 > 0:46:17but when we try to match them to the Neanderthal or the Denisovan
0:46:17 > 0:46:19genomes, they didn't match at all.
0:46:19 > 0:46:22So this is clearly from an unknown group of humans
0:46:22 > 0:46:26that existed in Africa. We don't have any fossil data for them,
0:46:26 > 0:46:30we don't know anything about them, except for the trace amount of DNA
0:46:30 > 0:46:34that they've left in the present-day individuals from Africa.
0:46:34 > 0:46:36So, think about the human family tree.
0:46:36 > 0:46:41We know that Neanderthals and Denisovans split off
0:46:41 > 0:46:46from modern humans around 700,000 years ago.
0:46:46 > 0:46:50And this archaic sequence split off from modern humans
0:46:50 > 0:46:54probably 700,000 to 800,000 years ago.
0:46:54 > 0:46:59And there's gene flow from this mystery group of archaic individuals
0:46:59 > 0:47:03from Africa into the ancestors of present-day Africans,
0:47:03 > 0:47:0550,000 to 80,000 years ago.
0:47:09 > 0:47:11So they were survivors,
0:47:11 > 0:47:14and we don't know much else about them.
0:47:14 > 0:47:19Except that their fossil remains may be out there in Africa somewhere,
0:47:19 > 0:47:20waiting to be discovered.
0:47:22 > 0:47:26And what's fascinating to me is that we can make these inferences
0:47:26 > 0:47:31not by discovering fossils or ancient DNA extracted from a fossil,
0:47:31 > 0:47:35but simply by looking at the DNA sequence variation that is present
0:47:35 > 0:47:37in modern African individuals.
0:47:37 > 0:47:41And it provides this amazing window into human history and allows us to
0:47:41 > 0:47:44find these missing twigs of the human family tree.
0:47:51 > 0:47:56DNA evidence of genetic mixture between different forms of human
0:47:56 > 0:48:00might also help solve the mystery of certain fossils
0:48:00 > 0:48:03that don't fit neatly into our standard categories.
0:48:05 > 0:48:08This skull, for instance, has a mixture of characteristics.
0:48:08 > 0:48:12Some of which look over 100,000 years old,
0:48:12 > 0:48:14others only 14,000 years old.
0:48:16 > 0:48:19So, how do you explain that? Well, theoretically at least,
0:48:19 > 0:48:21we can put forward the idea that
0:48:21 > 0:48:23maybe something like Homo heidelbergensis
0:48:23 > 0:48:27or a very primitive form of Homo sapiens survived for much
0:48:27 > 0:48:29longer in central West Africa,
0:48:29 > 0:48:33then interbred with the later forms of Homo sapiens.
0:48:33 > 0:48:37And here we've got a fossil that reflects that interbreeding.
0:48:38 > 0:48:43The possibility of ancient interbreeding with the lost tribes
0:48:43 > 0:48:46is causing experts to re-evaluate many other fossils, too.
0:48:48 > 0:48:52You know, there was a lot of exchange of interactions between
0:48:52 > 0:48:53these different groups,
0:48:53 > 0:48:57so we really have to look with new eyes to the old fossil records.
0:48:57 > 0:49:02There are many of these fossil samples that don't fit the story,
0:49:02 > 0:49:05because indeed, the story was built without them.
0:49:11 > 0:49:15Could fossil evidence of ancient interbreeding
0:49:15 > 0:49:17have been staring us in the face?
0:49:24 > 0:49:29There are many fossils being found that I don't quite know
0:49:29 > 0:49:32what they are. I think there will be surprises coming there.
0:49:34 > 0:49:37Those could be further evidence of this interbreeding,
0:49:37 > 0:49:39not just Neanderthals and Denisovans,
0:49:39 > 0:49:42other examples of interbreeding, too.
0:49:45 > 0:49:47And the new species don't stop here.
0:49:47 > 0:49:52Experts are now much more open to the idea that there probably are
0:49:52 > 0:49:56other archaic human tribes yet to be properly identified.
0:49:58 > 0:50:01I think as we look in more geographically diverse individuals,
0:50:01 > 0:50:04that there's a real potential that we'll discover
0:50:04 > 0:50:07other branches of the human family tree.
0:50:09 > 0:50:12We still have a lot to discover and to understand,
0:50:12 > 0:50:15so whether it is new groups or new species,
0:50:15 > 0:50:19or whether we have to start recognising those that were
0:50:19 > 0:50:22the result of an interchange between different hominid groups,
0:50:22 > 0:50:24I don't know.
0:50:24 > 0:50:27But it's going to be something much more complicated than we thought.
0:50:31 > 0:50:34So, when modern humans spread out from Africa,
0:50:34 > 0:50:38they encountered a very different world to the one we know today.
0:50:41 > 0:50:43The picture that is emerging
0:50:43 > 0:50:45from fossils,
0:50:45 > 0:50:47from scraps of ancient DNA
0:50:47 > 0:50:50and from modern DNA
0:50:50 > 0:50:53is a world of overlapping human groups.
0:50:55 > 0:50:59It's now known that there were Neanderthals living in Europe,
0:50:59 > 0:51:02the Middle East, and even nudging into Asia.
0:51:05 > 0:51:08Denisovans in western Asia, but in all likelihood,
0:51:08 > 0:51:11they lived right across Asia and South East Asia.
0:51:13 > 0:51:16Floresian hobbits, minding their own business,
0:51:16 > 0:51:19cut off on a remote island in Indonesia.
0:51:23 > 0:51:26As yet nameless archaic Africans, the survivors.
0:51:28 > 0:51:30And us.
0:51:30 > 0:51:31Modern humans.
0:51:31 > 0:51:33Homo sapiens.
0:51:34 > 0:51:36The ultimate wanderers.
0:51:36 > 0:51:38Originally from Africa,
0:51:38 > 0:51:42but then restlessly, repeatedly exploring the globe.
0:51:42 > 0:51:45And it turns out that our story is not so much about
0:51:45 > 0:51:49where we came from, but who we slept with on the way.
0:51:53 > 0:51:57The recent revelations emerging largely from a genetic research
0:51:57 > 0:52:00are helping us to update our family tree.
0:52:01 > 0:52:03So we know that there is at least...
0:52:05 > 0:52:09..one other African archaic population, perhaps even species...
0:52:11 > 0:52:15..going back about 800,000 years ago, to the branch point there.
0:52:15 > 0:52:19And we've got DNA from that coming into modern humans.
0:52:19 > 0:52:23And, of course, that wasn't the first glimpse that we've had
0:52:23 > 0:52:26of genes coming in from other species.
0:52:26 > 0:52:31The first indication we had was that there was some Neanderthal genes
0:52:31 > 0:52:33coming this way into modern humans.
0:52:33 > 0:52:37Now we've got evidence that there are modern human genes,
0:52:37 > 0:52:40not surprisingly, going back in the opposite direction.
0:52:40 > 0:52:44We've also got genes coming in from the Denisovans.
0:52:45 > 0:52:50And there are other archaics coming into Denisovans
0:52:50 > 0:52:53and also into Neanderthals at some point, too.
0:52:53 > 0:52:58I think it's been quite difficult to come to this
0:52:58 > 0:53:01concept of the family tree of humanity.
0:53:01 > 0:53:06We seem to have been so wedded to that idea of a linear progression.
0:53:06 > 0:53:09And what we can see now is that it is a family tree, but not just that.
0:53:09 > 0:53:12It's a tangled web of connections as well.
0:53:16 > 0:53:19Our DNA is a mosaic.
0:53:19 > 0:53:23It contains traces of these other species.
0:53:24 > 0:53:29We contain echoes of the lost tribes of humanity within us.
0:53:30 > 0:53:34So I suppose you could say we are genetic mongrels.
0:53:45 > 0:53:48But there's one final twist in our story.
0:53:49 > 0:53:53A secret that each of us carries inside.
0:53:54 > 0:54:00The archaic DNA within our modern genomes is not defunct.
0:54:00 > 0:54:04It continues to have a profound effects on our lives today.
0:54:06 > 0:54:12In Seattle, Josh Akey is taking advantage of modern data techniques
0:54:12 > 0:54:14to look at our health.
0:54:14 > 0:54:18There's been amazing technological innovations that have happened over
0:54:18 > 0:54:21the last decade. Computing power to be able to crunch all the numbers,
0:54:21 > 0:54:24that allows us to access genomic data on a scale that wasn't
0:54:24 > 0:54:27really even imaginable a few years ago.
0:54:28 > 0:54:33Josh has analysed the genetic data and detailed health records
0:54:33 > 0:54:36of 28,000 people.
0:54:36 > 0:54:3828,000 people fill half of this stadium.
0:54:41 > 0:54:45The idea was to track down the parts of their genomes that were inherited
0:54:45 > 0:54:47from their Neanderthal ancestors and ask
0:54:47 > 0:54:51what is the spectrum of traits or diseases that the remaining
0:54:51 > 0:54:56Neanderthal variation influences in present-day individuals?
0:54:56 > 0:55:00We are still figuring out the full spectrum of consequences,
0:55:00 > 0:55:03but we do know we've picked up some Neanderthal genes
0:55:03 > 0:55:06that were important components of the immune system that provided
0:55:06 > 0:55:09our ancestors a benefit to survive and reproduce
0:55:09 > 0:55:12as they encountered pathogens that they hadn't seen before.
0:55:14 > 0:55:18Increased genetic diversity related to our immune system could have been
0:55:18 > 0:55:22a major advantage gained unwittingly through interbreeding.
0:55:24 > 0:55:28There are certain places in our genome where we are actually more
0:55:28 > 0:55:31Neanderthal-like than we are modern human.
0:55:31 > 0:55:36And the frequency of the Neanderthal copy of the gene is 70 or 80%.
0:55:38 > 0:55:40And those mountain-dwelling Denisovans
0:55:40 > 0:55:42have also left their legacy.
0:55:44 > 0:55:48Researchers have found a highly unusual gene variant found only in
0:55:48 > 0:55:52Tibetans and a very few Han Chinese individuals.
0:55:54 > 0:55:57But it is present in the Denisovan genome.
0:55:58 > 0:56:02Denisovans contributed a version of the EPAS1 gene,
0:56:02 > 0:56:05or EPAS1, to Tibetans
0:56:05 > 0:56:08that allows them to exist and survive and thrive
0:56:08 > 0:56:11at high altitudes.
0:56:11 > 0:56:15So it's sort of interesting to think that we would perhaps
0:56:15 > 0:56:19not have such big populations in the high plateau in Tibet today
0:56:19 > 0:56:22if it wasn't for this contribution from Denisovans.
0:56:23 > 0:56:25But it wasn't all good news.
0:56:26 > 0:56:31New research suggests that our ancestors' fertility was negatively
0:56:31 > 0:56:35affected by having too much Neanderthal or Denisovan DNA.
0:56:37 > 0:56:41It seems that the merging of genomes that ultimately helped us to adapt
0:56:41 > 0:56:43and proliferate was a tainted gift.
0:56:45 > 0:56:47It appears that there was a trade off.
0:56:47 > 0:56:49In present-day individuals,
0:56:49 > 0:56:53many of those Neanderthal variants that were, at one time, protective
0:56:53 > 0:56:56seem to also predispose to various autoimmune diseases.
0:56:56 > 0:56:59In general, Neanderthal ancestry
0:56:59 > 0:57:04explains about 2% of the disease risk to a wide number of traits.
0:57:10 > 0:57:12As an anatomist,
0:57:12 > 0:57:16I'm naturally much more comfortable with bones than with molecules.
0:57:16 > 0:57:21But I find it remarkable how much DNA is now telling us
0:57:21 > 0:57:24about our human origins.
0:57:24 > 0:57:27I find it utterly extraordinary that we are now able to extract
0:57:27 > 0:57:32DNA from bones that are not just tens of thousands of years old,
0:57:32 > 0:57:35but hundreds of thousands of years old.
0:57:36 > 0:57:41What we're currently working on is making the techniques we use
0:57:41 > 0:57:44even more sensitive, so that we could go even further back in time.
0:57:44 > 0:57:48I think these techniques will be like carbon dating or something like
0:57:48 > 0:57:51that, which revolutionised archaeology and became
0:57:51 > 0:57:54a standard tool in the tool box of archaeology.
0:57:56 > 0:58:00So, in the future, we can expect genetics to shed even more light
0:58:00 > 0:58:03on who we are and where we came from.
0:58:08 > 0:58:09Over the next few years,
0:58:09 > 0:58:13we will be able to convincingly show that there's multiple forms
0:58:13 > 0:58:15of humans that we didn't know about before,
0:58:15 > 0:58:18that we have no fossil data for
0:58:18 > 0:58:21and the only evidence of their existence is in our DNA.
0:58:23 > 0:58:26The last 20 years, particularly the last ten years,
0:58:26 > 0:58:28has been a really exciting.
0:58:28 > 0:58:30There is so much going on.
0:58:30 > 0:58:32You don't know what's round the corner.
0:58:32 > 0:58:35I've learnt in the last few years to expect the unexpected.
0:58:35 > 0:58:36And I'm sure that will go on.