The Lost Tribes of Humanity Horizon


The Lost Tribes of Humanity

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We like to think that humans are special.

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And we are.

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But we're not one of a kind.

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The past 30 to 40,000 years in human history are really unique

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in that we are alone on the planet.

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Earlier, there were always

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different forms of humans around that we met,

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and would mix with each other.

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We now know that there were at least four other distinct types of human

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on the planet at the same time as us.

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Maybe there were even others that we don't know about yet.

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And all of them, except us, are now lost in time.

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Studying human origins at this time is very, very exciting,

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because the story keeps changing.

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We are really writing it now.

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More and more, we've found that they were getting feathers

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for ornamentation, to wear them in some way.

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And we now know that we, homo sapiens,

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made contact with these other humans.

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When we got the first result that suggested that there had been

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interbreeding, we were very sceptical, all of us.

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Traditional palaeoanthropology, based on fossils,

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is being transformed by genetics.

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And right at the vanguard in the hunt for these lost tribes

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are scientists digging into modern and ancient DNA.

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Over the next few years, we'll be able to convincingly show

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that there are multiple forms of human

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that we have no fossil data for,

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and the only evidence of their existence is in our DNA.

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Who were all these other ancient humans?

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What did they look like?

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And where did they all go?

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The answers to these questions strike deep into the core

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of who we think we are

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and reveal that at least parts of these ancient lost tribes

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are still alive today.

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Evolution explains the diversity of life on Earth.

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But for us, the species who worked it out,

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it holds a special message.

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We are descended from ancient apes.

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And I've been fascinated by this image for as long as I can remember.

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It's such an iconic image of human evolution,

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starting off with this knuckle-walking ancient ape

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and then this ape who is standing a bit more upright.

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And then we have the Neanderthal,

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still a bit stooped, and then finally, Cro-Magnon man

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with his spear here,

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and he's well on his way to being a truly modern human.

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But this isn't the real picture of human evolution.

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Piecing together who our ancestors actually were

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has been an extraordinary scientific adventure.

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A dramatic story of mystery and revelation.

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What we need is a new image to replace that old iconic one.

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So, we can start off with a lineage,

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which is just one line

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that eventually ends up around 200,000 years ago

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being us, being modern humans.

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Anatomically and genetically, we have arrived as a species.

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So did we evolve from Neanderthals, or are they, as some suspected,

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a completely separate and distinct human lineage?

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It's dawn.

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A small hunting party of Neanderthals

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are silently stalking their prey.

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They are at home in the seemingly endless forest.

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But they will, in time,

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disappear from the Earth.

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Neanderthals were the archetypal cave dwellers...

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..thick set, short and muscular,

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with a characteristically heavy brow ridge.

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They were thought to be much less intelligent than us.

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Many people still think of the Neanderthal as

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a simple-minded, thuggish people.

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But recent, quite often unexpected discoveries,

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are forcing us to confront that perception.

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Archaeologist Clive Finlayson and his team are convinced that this

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simplistic impression of Neanderthals is wrong.

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We've been working in these caves in Gibraltar now for over 25 years.

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We have dates in these caves now with Neanderthals

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as recently as 32,000 years ago.

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That would make this the last site where Neanderthals lived.

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This, the last known refuge of a lost tribe of Neanderthals,

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has produced thousands of bones and artefacts.

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It presents us with almost a total picture of Neanderthal life

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in this part of the world.

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Families were living here,

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sleeping here and going out to hunt and forage from here.

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In my view, the stereotype of the ape-like Neanderthal

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I think is changing. People are realising, even anatomically, that

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there may be physical differences between our ancestors and them,

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but they're not as huge as we thought, once upon a time.

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What is really changing our view is the cultural evidence,

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the evidence of the abilities that we thought only we had

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and caused our expansion across the globe.

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And we're beginning to realise that

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Neanderthals were not that different.

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In the past, experts suggested that Neanderthals were incapable of

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planning, of thinking two or three steps ahead.

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That's not true at all. These people knew their environment very well,

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they knew what they had here and they exploited it very well.

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And that's probably the key to their success and their survival

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for such a long time.

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The Neanderthals were not only

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an immensely successful European species,

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but we're starting to realise that they were cultured in a way

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that we thought was the sole preserve of modern humans.

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The clues are hidden amongst the many bird bones

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buried in these caves.

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More and more we've found that the evidence is in the form of cut marks

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on the bones and what we realised was that a lot of the marks were on

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the wing bones of these birds.

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Using stone tools and dead birds found on the shoreline,

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Clive's team have been exploring what the Neanderthals might

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have been doing.

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If you dissect the wing bone of a vulture or an eagle,

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what you find is a bone and a tendon

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and the feathers attached to the skin. There's no meat,

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because you have to be lightweight to be able to soar.

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So if you're cutting these wing bones in the birds of prey,

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it has to be something to do with feathers and certainly has nothing

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to do with meat or food.

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In parallel, we realise that a lot of the species of bird of prey being

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brought in were birds of prey with dark feathers.

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And we showed that there seemed to be a discrimination

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in terms of colour.

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Neanderthals preferred black, for some reason.

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The conclusion that we came to after a lot of analysis is that

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they were getting the feathers for ornamentation,

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to wear them in some way.

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Many cultures across the globe, historically and today,

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use bird feathers. North American Indians, for example.

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Because of this close relationship that they had with birds,

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we decided to call them the Bird People of Europe.

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Deeper in these caves,

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the team have found evidence suggesting that these Bird People

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had the capacity for abstract thought.

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Something else which was believed to be exclusive to modern humans.

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We have found this incredible engraving on the rock,

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made by Neanderthals.

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And it is the only one that is known today anywhere.

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It took us two years of intensive study and we came to the conclusion

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that it took them at least two hours to do,

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because we replicated the whole procedure, so it wasn't something...

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It wasn't a doodle - they'd actually thought about it.

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And it wasn't marks done for butchery, for example,

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if you're cutting through skin.

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We tried to replicate that with skin and the lines go all over the place.

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This was something that wasn't functional,

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it was sending a message to somebody, and it was done

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very, very deliberately, and it took a long time.

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This is not mere survival.

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This looks like art.

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It's the next step, if you like.

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The smoking gun, in terms of Neanderthal behaviour.

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So, contrary to the popular perception of them,

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we are now realising that Neanderthals exhibited many aspects

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of what we call modern human behaviour.

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And they are much closer to us in other ways, too.

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They are cousins of ours.

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We've known that from an anatomical point of view, looking at the bones,

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but now we know it from genetics as well.

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What we know about them is that they branch from a common ancestor,

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500,000 to 700,000 years ago,

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and here they are,

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almost surviving to the present day, but not quite.

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Genetically, Neanderthals were a species distinct from

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the modern humans who originated in Africa

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and who, much later on, would emerge from that continent

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and venture into the Neanderthal's home territory.

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As the climate changes,

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modern humans are spreading from other parts of the globe

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into what will eventually become known as Europe.

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Tall and lean bodied, modern humans also skilled hunters.

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But they've got to compete for resources...

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..with the local Neanderthals.

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I find it really interesting to imagine what might have happened

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if these two groups of people had come into contact with each other.

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The incoming modern humans and the indigenous Neanderthals.

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How different did they seem to each other?

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Would they have reacted with friendliness and curiosity?

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Or would it have inevitably been violent and hostile?

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We're faced with an interesting challenge.

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If we look at the archaeological record,

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at what Neanderthals did and made,

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and then we look at what modern humans made,

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can we see any suggestion that

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there was not only contact between the two groups,

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but a fruitful exchange of ideas?

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Based at the Natural History Museum in London,

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anthropologist Chris Stringer has been investigating ancient humans

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for over 30 years.

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In particular, the similarities and differences between modern humans

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and Neanderthals.

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Neanderthals are very evolved humans.

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In their own way, as evolved as us, overall.

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They walked upright as well as we do

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and their brains were as large as ours.

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We now know that Neanderthals shared much of their behaviour with us.

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They buried their dead,

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they were very capable at their stone toolmaking.

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This is a typical Neanderthal hand axe.

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-It is a beautiful one, isn't it?

-Yeah.

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Beautifully shaped.

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It was top-quality flint.

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And they had a knack of finding that, you know?

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Yes. So this is a 60,000-year-old one?

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Wonderful, isn't it? Beautiful.

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Neanderthals and modern humans were both expert craftsmen

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in their own ways,

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carefully preparing their flint and able to strike off a usable

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flake or blade with a single strike.

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I'll try in between the two and see.

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-There we are. All that cutting edge down there.

-Fantastic. Look at that.

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This is buffalo hide, and that's gone straight through.

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-Sharp as a razor.

-Yeah, yeah.

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Wonderful.

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There are a number of Neanderthal sites across Europe,

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where the technology, to some experts,

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looks suspiciously similar to that found at modern human sites.

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It's tempting to ask whether they each developed the techniques

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independently, or whether this represents an exchange of ideas.

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There is a view that that perhaps reflects contact between the groups,

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that Neanderthals were picking up aspects of behaviour and they are

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reflected in these changes that they are making.

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They are making tools which we might think typical of modern humans,

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they are using, to a much greater extent, bone or ivory.

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As well as tools, there are other cultural artefacts which go

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far beyond what's been found at other Neanderthal sites.

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These sites contain evidence of jewellery, for example,

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pierced animal teeth. So, the Neanderthals,

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they are making body adornments

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which normally would be thought of as modern human features.

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'Now, with much better dating techniques,

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'we are able to use radiocarbon to show that

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'the Neanderthal cultures do go on to perhaps 39,000 years ago,

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'maybe a bit younger in places.

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'And a modern human arrival certainly'

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arrives before 40,000 years ago, in Europe.

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So there is an overlap and potentially,

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when these groups came together,

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we did pick up some things from Neanderthals that were an

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advantage to us, about living and surviving

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in those colder environments in Europe and Asia.

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So the archaeological evidence hints at an exchange of ideas

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between Neanderthals and modern humans.

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But eight years ago,

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a fossil fragment from a cave in southern Siberia was about to drop

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what can only be described as a bombshell

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into the world of paleoanthropology.

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Because it suggested that Neanderthals and modern humans

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had neighbours.

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Another tribe of humans living right on their doorstep.

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Deep in the Altai Mountains,

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near to where Kazakhstan will one day meet Mongolia,

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winter is coming.

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But this mountain-dwelling tribe is at home in their environment.

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Their cave is on a migration route...

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..which offers herds easy passage through the mountains

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to the warmer grasslands further south.

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Surprisingly, the eventual discovery of this tribe

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would actually be made 3,500 miles away, in Leipzig, Germany.

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Svante Paabo is a geneticist from the Max Planck Institute

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and he specialises in archaic DNA.

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He and his team are collaborating with Russian archaeologists

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who are excavating the remote mountain cave.

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So, in 2008,

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our colleagues found a lot of different bones.

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And among those bones,

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they found a tiny little piece,

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a little fragment of the last phalanx of a little finger.

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Just a piece of it.

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It was obviously from a child, because it was very, very small.

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And it's a bit unclear how old it is.

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It's at least in the order of 50,000 years, probably older.

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And they sent this, along with some other bones, to us in Leipzig.

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They sent it to Svante in the hope that he and his team

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could extract some DNA and perhaps determine whether the bone was

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Neanderthal or Homo sapiens.

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What we do when we get the bone to sample

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is to remove the surface and little area,

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drill the hole with a dentistry drill,

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so we get powder out.

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From that, we then isolate the DNA.

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We purify it away from all of the other components of the bones at

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this end, the minerals are there, the proteins, the fats.

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And you then have it in a form

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that you can feed into sequencing machines.

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The problem when you study ancient DNA is that first of all,

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there's very little there, in the remains.

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The vast majority of the DNA is not indigenous to the bone,

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but comes from bacteria and fungi that have colonised the bone

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over tens of thousands of years

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when it was deposited in the cave.

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And perhaps the biggest problem is the risk of contamination from

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present-day human DNA, from ourselves in the laboratory,

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in a room like this, where people move around.

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A large part of the dust in the air is actually skin fragments

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and a single such dust particle can contain a lot more DNA

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than we have in our sample of the bone.

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DNA is very fragile and it doesn't preserve easily.

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But amazingly, despite lying for thousands of years in a cave,

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the DNA in that tiny bone had hardly degraded at all.

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This little part of the little finger was so well-preserved,

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we were able to sequence, actually, the entire genome to a very high

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quality, as high a quality as you would sequence

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your or my genome today.

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It's an astonishing achievement

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to get a complete genome from a 50,000-year-old bone.

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But the biggest shock came when they tried to identify

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what species of human it was.

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We were very surprised to find that it was not a Neanderthal.

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It was very, very distant from other Neanderthal genomes

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we had looked at.

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So we immediately realised this was something very special.

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It was not a Neanderthal, it was not a modern human,

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it was something new.

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We had found a new form of extinct human.

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This was completely unexpected.

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A human that was related to all of us,

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but genetically distinct.

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Another group of cousins.

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So we had a lot of discussions among ourselves and our Russian colleagues

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what we'd call this group of humans.

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And after a lot of back and forth,

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we agreed to call them the Denisovans.

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Just like Neanderthals are called Neanderthals

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after the Neander Valley,

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where the first remains of Neanderthals were found,

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Denisovans are called after the first place where they were found.

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We know very little of Denisovans, it's very frustrating.

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We do know that they lived in this cave and that they lived

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intermittently with Neanderthals there.

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There seem to have been Neanderthals there early,

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there were then later Denisovans

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and later again, Neanderthals.

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And it's, to me, a really amazing place in the world,

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because it's the only place we know

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that at least three different forms of humans have lived.

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We can tell that Denisovans were more closely related to Neanderthals

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than to us.

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Whereas the ancestors of Neanderthals and modern humans

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split around 600,000 years ago,

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Denisovans split from a common ancestor with Neanderthals,

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about 400,000 years ago.

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And really, we only know about this species from their genetics.

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We don't know much about their anatomy at all,

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the fossil record is so fragmentary.

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Further excavations in the cave have uncovered two Denisovan teeth

0:22:440:22:49

and so far, that is all the physical evidence we have

0:22:490:22:53

of this new lost tribe of mountain-dwelling humans.

0:22:530:22:57

The burning question that remains, though,

0:22:580:23:01

is did Denisovans ever meet our own wandering ancestors?

0:23:010:23:05

It is well accepted that our species, Homo sapiens,

0:23:110:23:15

originated in Africa.

0:23:150:23:18

But just how and when our ancestors left Africa to colonise the globe

0:23:180:23:24

has been a matter of considerable debate.

0:23:240:23:27

And each new piece of genetic and fossil evidence

0:23:270:23:30

changes our understanding.

0:23:300:23:32

Some very recent finds have really pushed the boundaries of how far

0:23:320:23:38

and how early modern humans strayed from their African homeland.

0:23:380:23:43

And the earlier we left Africa,

0:23:440:23:47

the more chance we had of overlapping in time

0:23:470:23:51

and in the same parts of the world with our other human cousins.

0:23:510:23:55

To understand the story of

0:24:010:24:02

what really happened to us,

0:24:020:24:04

we really need to take into account the whole map. And China

0:24:040:24:08

is a very, very important part of this puzzle.

0:24:080:24:12

Archaeologist Maria Martinon-Torres, from University College London,

0:24:140:24:18

has teamed up with colleagues from the Chinese Academy of Sciences

0:24:180:24:22

to study a treasure trove of human teeth found in a cave

0:24:220:24:26

in Daoxian province in south-east China.

0:24:260:24:29

Some people might think that all teeth look the same,

0:24:300:24:33

but they do not.

0:24:330:24:34

Teeth are like little landscapes in miniature.

0:24:340:24:37

These teeth are clearly modern human, Homo sapiens,

0:24:390:24:43

rather than from an archaic hominin, like a Denisovan or a Neanderthal.

0:24:430:24:48

Homo sapiens have very simple teeth and they are really very slender.

0:24:480:24:53

The roots are very thin, they are really narrow towards the tip.

0:24:530:24:56

However, if you look at the roots of an archaic hominin,

0:24:560:25:00

they have really stout and robust roots,

0:25:000:25:03

like columns that really diverge and open very strongly.

0:25:030:25:06

So it's really a big difference.

0:25:060:25:09

The teeth had been perfectly preserved in the limestone cave

0:25:100:25:14

underneath a layer of calcite.

0:25:140:25:17

The Daoxian teeth were found in the calcite layer, like a gravestone,

0:25:180:25:23

that is really like sealing all the layer where the fossils were found.

0:25:230:25:27

We dated the stalagmites that really grow on top of that layer

0:25:270:25:32

and the stalagmites have been dated 80,000 years ago.

0:25:320:25:35

Meaning that everything that is accumulated below has to be at least

0:25:390:25:43

80,000 years ago.

0:25:430:25:45

This new evidence and dramatically overturns previous theories

0:25:470:25:52

about human movement around the world.

0:25:520:25:54

It shows us just how well-travelled these early modern humans were.

0:25:570:26:03

The Daoxian teeth are very important,

0:26:030:26:06

because they represent the earliest and soundest evidence we have

0:26:060:26:12

of our own species, Homo sapiens, being outside Africa.

0:26:120:26:15

And they were outside Africa much earlier than expected.

0:26:150:26:19

So in order for Homo sapiens to reach China so long ago,

0:26:220:26:26

we must have left Africa around 100,000 years ago, possibly earlier.

0:26:260:26:31

That means modern humans must have spent thousands of years roaming the

0:26:310:26:35

planet and sharing it with the other two human tribes.

0:26:350:26:40

And this is very exciting for a scientist, with the Daoxian teeth,

0:26:440:26:48

we have a lot of new questions, like

0:26:480:26:51

did the hominins we found in Daoxian ever meet Neanderthals?

0:26:510:26:54

Did they ever meet these mysterious Denisovans?

0:26:540:26:57

So there are a lot of new questions we have to understand about

0:26:570:27:01

who we were about 100,000 years ago.

0:27:010:27:04

The answers to some of these questions will no doubt be found

0:27:060:27:09

somewhere in Asia,

0:27:090:27:11

a vast continent sure to contain many anthropological surprises.

0:27:110:27:16

In fact, the South East Asian islands have already thrown up one

0:27:240:27:27

of the most startling and controversial the discoveries

0:27:270:27:31

of recent years in paleoanthropology.

0:27:310:27:33

Evidence of a lost tribe that is human, but almost unrecognisably so.

0:27:330:27:40

Living on an island isolated from the rest of the world...

0:27:440:27:48

..is a group of miniature humans.

0:27:500:27:52

Adults are only one metre or 3ft tall.

0:27:540:27:58

Living off dwarf elephants

0:28:010:28:03

and using technology as advanced as other human groups around the world.

0:28:030:28:08

Anthropologists Laura Shackelford and Fabrice Demeter

0:28:210:28:25

study human fossils across south-east Asia,

0:28:250:28:28

but they hadn't anticipated that in 2003,

0:28:280:28:32

a group from Australia would discover a hobbit-sized human

0:28:320:28:37

in a cave on the island of Flores in Indonesia.

0:28:370:28:40

When the fossils were discovered on Flores, it was a very exciting find,

0:28:420:28:45

because no-one knew quite what they were.

0:28:450:28:48

When Flores came out to the public,

0:28:480:28:50

it was a big shock for the scientific community.

0:28:500:28:53

This was a species that looked nothing like anything

0:28:530:28:56

that had been discovered before.

0:28:560:28:58

Because it has very specific features.

0:28:580:29:01

Particularly its short stature, only about 3ft tall.

0:29:010:29:05

And what was even more interesting about the species

0:29:050:29:08

was that they had a very small brain,

0:29:080:29:10

a brain that was about the size of a chimpanzee's brain.

0:29:100:29:13

So this was a new species that no-one really knew what to do with.

0:29:130:29:17

Initially, there was scepticism.

0:29:180:29:21

Fears that this was just a single deformed modern human.

0:29:210:29:25

But now, with accurate dating and several individuals uncovered,

0:29:260:29:30

it's accepted that these were a distinct species of human.

0:29:300:29:34

They've been named Homo floresiensis,

0:29:400:29:42

after the island they were found on.

0:29:420:29:44

But more popularly, they are known as the hobbits.

0:29:460:29:50

I don't think it is nice to say something like this about a human,

0:29:500:29:53

but they are weird.

0:29:530:29:55

You know, and they are weird in their aspect, in their age,

0:29:550:30:00

in their location, in their history.

0:30:000:30:02

The riddle of the unusual size of Homo floresiensis

0:30:050:30:09

could actually be answered because of the island they lived on.

0:30:090:30:13

100,000 years ago, the sea level was very, very low.

0:30:150:30:19

So these islands were connected to the continent.

0:30:220:30:26

But Flores was always an isolated island.

0:30:300:30:35

Recently-discovered fossils show

0:30:350:30:37

that the ancestors of the hobbit-sized humans

0:30:370:30:40

were already small 700,000 years ago.

0:30:400:30:44

It does seem that the island itself may have been to blame.

0:30:450:30:49

Since they've always been isolated, then they were probably subject to

0:30:490:30:53

a phenomenon that is called island dwarfism.

0:30:530:30:55

And this is a phenomenon where

0:30:550:30:58

when a species of any sort, not just human, but animals as well,

0:30:580:31:03

when they are isolated on an island,

0:31:030:31:05

then often, the species will be reduced in size.

0:31:050:31:09

And this may be because there are fewer resources on an island,

0:31:090:31:13

so the species may get smaller to conserve resources.

0:31:130:31:16

The discovery of the hobbit-sized humans has raised many more

0:31:190:31:23

questions about human origins than it has answered.

0:31:230:31:26

Homo floresiensis is such a puzzle.

0:31:310:31:34

It was a startling discovery,

0:31:340:31:36

and we are still struggling to make sense of it.

0:31:360:31:39

These tiny people seem to have evolved from ancestors who go back,

0:31:390:31:44

way back in the family tree of humans to perhaps

0:31:440:31:49

2 million or maybe even 3 million years ago.

0:31:490:31:52

What is really fascinating about this is that in contrast to today,

0:31:520:31:56

where we are the only human species on the planet,

0:31:560:32:00

you don't have to go back that far to find all of these others.

0:32:000:32:06

The diminutive Homo floresiensis,

0:32:060:32:08

the surprisingly cultured Neanderthals,

0:32:080:32:10

the enigmatic Denisovans,

0:32:100:32:13

all living alongside modern humans 100,000 years ago.

0:32:130:32:18

But 30,000 years ago, we were still there...

0:32:180:32:22

..and all these others had gone extinct.

0:32:240:32:27

The past 30,000 to 40,000 years in human history are really unique

0:32:330:32:39

in that there are no other closely-related forms around.

0:32:390:32:43

We are alone on the planet.

0:32:430:32:44

So why did Homo sapiens survive

0:32:520:32:55

when all those other human tribes died out?

0:32:550:32:59

The Neanderthals were, as far as we know,

0:32:590:33:02

the last of our cousins to disappear.

0:33:020:33:05

And the latest research suggests

0:33:050:33:07

there are many reasons for their demise,

0:33:070:33:09

but perhaps the most inescapable was the fluctuating climate.

0:33:090:33:13

Repeatedly, the Neanderthal populations were hit

0:33:160:33:19

by very rapid climate changes. They could never stabilise and

0:33:190:33:22

grow their numbers for any length of time.

0:33:220:33:24

Every time they expanded in the better conditions, suddenly,

0:33:240:33:28

a tremendous drop in temperature very rapidly,

0:33:280:33:30

and a lot of those populations died out.

0:33:300:33:33

Between each period of relative warmth,

0:33:340:33:37

which can last for thousands of years, the cold would come back,

0:33:370:33:41

sometimes engulfing Europe within a matter of a fewer decades.

0:33:410:33:45

And the Northern Neanderthal groups would have been wiped out again.

0:33:450:33:50

For me, it is a matter of luck.

0:33:500:33:52

Had modern humans and Neanderthals been in that place at a time when

0:33:520:33:56

instead of the climate getting colder and drier,

0:33:560:33:59

it got warmer and wetter,

0:33:590:34:01

then we might well be Neanderthals today

0:34:010:34:03

discussing why the others went extinct.

0:34:030:34:06

I think the Neanderthals were already an endangered species,

0:34:080:34:12

before modern humans came out of Africa

0:34:120:34:14

and started overlapping with them.

0:34:140:34:16

Then I think even by a small amount,

0:34:160:34:18

modern humans were more effective at hunting and gathering

0:34:180:34:22

and I think the Neanderthals just got displaced

0:34:220:34:25

by that growing success of modern humans.

0:34:250:34:28

The lesson that the Neanderthals tell us is that you can be an

0:34:280:34:32

intelligent, large-brained hominid and still go extinct.

0:34:320:34:35

The changing climate would have affected human populations across

0:34:390:34:43

the globe and evidence of the impact of that is written into ancient DNA.

0:34:430:34:49

Janet Kelso, a colleague of Svante Paabo at the Max Planck Institute,

0:34:560:35:01

has been studying the history of humans

0:35:010:35:03

through comparative genetics.

0:35:030:35:05

In terms of diversity, in the Neanderthal population,

0:35:090:35:12

it was much lower than what we see in present-day populations.

0:35:120:35:14

So if you look around this train carriage,

0:35:140:35:17

there's more diversity in this train carriage, perhaps,

0:35:170:35:20

than there was in the population of Neanderthals that we know about.

0:35:200:35:23

We think that that's probably because they were living

0:35:230:35:26

in rather small populations.

0:35:260:35:28

When they got the first really high-quality Neanderthal genome,

0:35:330:35:37

one surprise was where the two versions of the genome

0:35:370:35:41

that this individual had inherited from its mother and its father

0:35:410:35:45

had no differences between them.

0:35:450:35:47

And this obviously suggests that the mother and father of these

0:35:470:35:51

individuals were closely related.

0:35:510:35:54

You're on the level of half-siblings,

0:35:540:35:57

or double first cousins.

0:35:570:35:59

We don't know if this is typical of Neanderthal societies at that time,

0:35:590:36:03

or if it's something special that happened in this cave

0:36:030:36:06

at this point in time.

0:36:060:36:08

What's certain is that low genetic diversity

0:36:100:36:14

is not good for a population.

0:36:140:36:16

It is known that populations that are more integrated,

0:36:170:36:20

that have less diversity,

0:36:200:36:21

have less ability to respond to, say, a new pathogen

0:36:210:36:25

or a changing environment.

0:36:250:36:27

So this diversity kind of provides a buffer for the environment,

0:36:270:36:30

and if the Neanderthals were less diverse, it's quite possible

0:36:300:36:33

that may have contributed to why they died out.

0:36:330:36:35

But it turns out that

0:36:440:36:45

Neanderthals may not have died out completely after all.

0:36:450:36:49

Genetic research can tell us a great deal about who we are and where

0:36:490:36:52

we come from and it is completely reshaping our idea

0:36:520:36:57

of what it is to be a modern human.

0:36:570:36:59

While our Homo sapien's ancestors

0:37:050:37:08

were sharing the planet with the various lost tribes,

0:37:080:37:11

there was, of course, the chance

0:37:110:37:13

that they might have interbred with them.

0:37:130:37:16

This meant that there was a possibility,

0:37:180:37:20

however unlikely it seems,

0:37:200:37:22

that there might be a remnant of some archaic DNA

0:37:220:37:26

hanging around in the genomes of present-day humans.

0:37:260:37:30

So the geneticists in Leipzig went digging for it.

0:37:300:37:33

What we wanted to look at was whether there was interbreeding from

0:37:360:37:39

Neanderthals into modern humans.

0:37:390:37:41

And our expectation was that there was none.

0:37:410:37:45

And when we got the first result that suggested that there had been

0:37:450:37:48

interbreeding, we were very sceptical, all of us.

0:37:480:37:51

Comparing modern human DNA to the detailed Neanderthal genome

0:37:520:37:57

seemed to suggest some sharing of genes.

0:37:570:38:01

We all kind of spent a lot of time looking at the data,

0:38:010:38:03

trying to figure out how this could be an error.

0:38:030:38:06

But the evidence was there.

0:38:070:38:09

Certain modern human genomes from different parts of the world

0:38:090:38:13

contained sections that matched the Neanderthal DNA.

0:38:130:38:17

So what we're looking at here is a region of chromosome 4.

0:38:200:38:23

At the top, we have two Neanderthals,

0:38:230:38:27

and then we have a Denisovan,

0:38:270:38:30

and here we have Asian individuals,

0:38:300:38:32

European individuals,

0:38:320:38:34

South American individuals,

0:38:340:38:36

Papuans, Australians and then a group of Africans.

0:38:360:38:39

And if you look down, you can see that in most positions,

0:38:390:38:42

everyone is very similar,

0:38:420:38:43

and that's because we are very closely related, right?

0:38:430:38:45

Modern humans and Neanderthals are not that different from one another,

0:38:450:38:49

which makes it really hard to

0:38:490:38:50

work out where are the interesting differences.

0:38:500:38:53

And so what we do is, instead, we mask out,

0:38:530:38:55

we remove all the sites where everyone is the same.

0:38:550:38:59

And we only look at the sites where individuals differ

0:39:000:39:02

from the referenced genome.

0:39:020:39:04

And so what you see here now is the Neanderthals and the Denisovan

0:39:040:39:08

carry a difference from the modern human reference at this position

0:39:080:39:12

and here and there and there.

0:39:120:39:14

And some of those differences are shared by a number of populations,

0:39:140:39:18

including the African individuals.

0:39:180:39:20

And some of those differences are shared just by a few individuals,

0:39:200:39:24

so here, and there, and there.

0:39:240:39:28

The genomes of certain individuals contained evidence

0:39:350:39:38

that our wandering ancestors bred with Neanderthal tribes

0:39:380:39:42

and had offspring who survived,

0:39:420:39:45

passing on their genes down the generations.

0:39:450:39:48

And it wasn't just evident in a couple of individuals.

0:39:500:39:54

When we went through the genomes of Africans

0:39:560:40:00

and of Europeans and Asians,

0:40:000:40:02

and counted how many DNA bases in each of the genomes matched the

0:40:020:40:06

Neanderthal genome,

0:40:060:40:07

we saw very consistently that all the groups outside of Africa

0:40:070:40:11

shared more Neanderthal DNA than the groups inside of Africa.

0:40:110:40:15

People with African heritage don't generally have Neanderthal DNA.

0:40:190:40:24

But virtually everyone else does.

0:40:240:40:26

Including me.

0:40:260:40:28

Well, I've had my own genome analysed and I am 2.7% Neanderthal.

0:40:310:40:37

And what is interesting is that my bit of Neanderthal DNA will be

0:40:370:40:41

different to the bit of Neanderthal DNA in another person's genome.

0:40:410:40:45

All people whose roots are outside Africa

0:40:480:40:51

carry a bit of Neanderthal DNA.

0:40:510:40:54

On average, each person carries somewhere between 1% and 2%.

0:40:540:40:58

If we now look at these different pieces,

0:40:580:41:01

that different people carry today,

0:41:010:41:04

how much of the Neanderthal genome is still running around today

0:41:040:41:07

on two legs in different individuals?

0:41:070:41:10

How much do we get if we add it up?

0:41:100:41:12

And the jury is still a bit out on that.

0:41:120:41:15

But in the order of at least half of the Neanderthal genome

0:41:150:41:19

still exists today in people.

0:41:190:41:21

And that number just keeps rising, the more people they analyse.

0:41:230:41:27

It's incredible to think that

0:41:310:41:33

around about half the Neanderthal genome is still alive and well

0:41:330:41:38

in us today. And going back just ten years ago,

0:41:380:41:41

we had no idea that any of us had Neanderthal DNA.

0:41:410:41:46

Now we know that practically everybody of predominantly

0:41:460:41:51

non-African heritage has Neanderthal DNA in their genome.

0:41:510:41:56

We interpreted that to mean that the mixture from the Neanderthals into

0:41:580:42:01

the ancestors of those individuals had to have been very early.

0:42:010:42:05

At the point very close to when they exited Africa,

0:42:050:42:07

perhaps somewhere in the Middle East,

0:42:070:42:09

when they were still a single population.

0:42:090:42:11

And then as they spread out,

0:42:110:42:13

they carry with them that Neanderthal DNA to wherever they go.

0:42:130:42:16

And Denisovans also left their mark in the DNA of living people.

0:42:220:42:27

Some more than others.

0:42:270:42:29

So if your origins are in Papua New Guinea or aboriginal Australians,

0:42:310:42:35

for example, they have in the order of 5% of their DNA from Denisovans,

0:42:350:42:41

so three or four times more than they have,

0:42:410:42:45

or people in Europe would have, from Neanderthals.

0:42:450:42:48

Traces of Denisovan DNA can also be found in populations across Asia,

0:42:490:42:55

in India, the Himalayas and China,

0:42:550:42:58

and it's estimated that there could be as much as 60-80%

0:42:580:43:02

of the Denisovan genome still in existence,

0:43:020:43:05

spread around the world's populations.

0:43:050:43:09

So, clearly, the wandering tribes of early modern humans

0:43:090:43:13

readily mixed with our human cousins.

0:43:130:43:17

Where they come into contact,

0:43:170:43:18

they are doing some interbreeding where they overlap.

0:43:180:43:21

And it could have included things like adopting babies,

0:43:210:43:24

finding orphaned Neanderthals, Denisovan babies,

0:43:240:43:27

taking them into the group and then bringing them up in your group.

0:43:270:43:30

So that could have been part of it, too.

0:43:300:43:33

At other times, it might have been raiding groups

0:43:330:43:35

and stealing women, because a group lacked females.

0:43:350:43:38

They would actually go and steal some.

0:43:380:43:40

And this happens today in chimpanzee groups

0:43:400:43:43

and it happens today in some hunter-gatherer groups,

0:43:430:43:45

so I'm sure that was happening as well.

0:43:450:43:48

So I think we've got a whole range of possibilities

0:43:480:43:50

of how these matings actually happened.

0:43:500:43:53

We have realised that these groups of humans are not totally extinct,

0:43:570:44:03

if you like. They live on a little bit in people today.

0:44:030:44:06

The most fascinating and surprising secrets

0:44:080:44:12

of our long-lost past are finally being uncovered.

0:44:120:44:15

The idea of modern humans crushing all other species

0:44:180:44:22

in a brief and dramatic conquest of the globe

0:44:220:44:26

has to give way to a process of assimilation

0:44:260:44:30

that has truly shaped who we are today.

0:44:300:44:32

But that's not the end of the story.

0:44:390:44:41

As genetic techniques get better

0:44:410:44:44

and as we delve deeper into our DNA,

0:44:440:44:48

a new secret has recently been revealed.

0:44:480:44:51

On the grasslands of present-day Africa,

0:45:000:45:04

hidden deep in the genomes of certain people,

0:45:040:45:08

are the remnants of a fifth human population,

0:45:080:45:12

a lost tribe of whom all other traces have disappeared.

0:45:120:45:17

The plains of central Africa are a harsh and unforgiving environment.

0:45:250:45:30

And yet, an isolated hominim tribe doggedly clings to survival,

0:45:320:45:37

leaving no trace in the landscape.

0:45:370:45:39

This tribe was actually discovered 9,000 miles away in Seattle,

0:45:450:45:50

on the West Coast of America.

0:45:500:45:52

Geneticist Joshua Akey has been analysing the genes

0:45:540:45:58

of certain modern African populations

0:45:580:46:01

and he's uncovered sections of DNA that can't be found

0:46:010:46:05

in other modern humans.

0:46:050:46:07

We were able to identify sequences

0:46:090:46:11

that we're confident are archaic in origin,

0:46:110:46:13

but when we try to match them to the Neanderthal or the Denisovan

0:46:130:46:17

genomes, they didn't match at all.

0:46:170:46:19

So this is clearly from an unknown group of humans

0:46:190:46:22

that existed in Africa. We don't have any fossil data for them,

0:46:220:46:26

we don't know anything about them, except for the trace amount of DNA

0:46:260:46:30

that they've left in the present-day individuals from Africa.

0:46:300:46:34

So, think about the human family tree.

0:46:340:46:36

We know that Neanderthals and Denisovans split off

0:46:360:46:41

from modern humans around 700,000 years ago.

0:46:410:46:46

And this archaic sequence split off from modern humans

0:46:460:46:50

probably 700,000 to 800,000 years ago.

0:46:500:46:54

And there's gene flow from this mystery group of archaic individuals

0:46:540:46:59

from Africa into the ancestors of present-day Africans,

0:46:590:47:03

50,000 to 80,000 years ago.

0:47:030:47:05

So they were survivors,

0:47:090:47:11

and we don't know much else about them.

0:47:110:47:14

Except that their fossil remains may be out there in Africa somewhere,

0:47:140:47:19

waiting to be discovered.

0:47:190:47:20

And what's fascinating to me is that we can make these inferences

0:47:220:47:26

not by discovering fossils or ancient DNA extracted from a fossil,

0:47:260:47:31

but simply by looking at the DNA sequence variation that is present

0:47:310:47:35

in modern African individuals.

0:47:350:47:37

And it provides this amazing window into human history and allows us to

0:47:370:47:41

find these missing twigs of the human family tree.

0:47:410:47:44

DNA evidence of genetic mixture between different forms of human

0:47:510:47:56

might also help solve the mystery of certain fossils

0:47:560:48:00

that don't fit neatly into our standard categories.

0:48:000:48:03

This skull, for instance, has a mixture of characteristics.

0:48:050:48:08

Some of which look over 100,000 years old,

0:48:080:48:12

others only 14,000 years old.

0:48:120:48:14

So, how do you explain that? Well, theoretically at least,

0:48:160:48:19

we can put forward the idea that

0:48:190:48:21

maybe something like Homo heidelbergensis

0:48:210:48:23

or a very primitive form of Homo sapiens survived for much

0:48:230:48:27

longer in central West Africa,

0:48:270:48:29

then interbred with the later forms of Homo sapiens.

0:48:290:48:33

And here we've got a fossil that reflects that interbreeding.

0:48:330:48:37

The possibility of ancient interbreeding with the lost tribes

0:48:380:48:43

is causing experts to re-evaluate many other fossils, too.

0:48:430:48:46

You know, there was a lot of exchange of interactions between

0:48:480:48:52

these different groups,

0:48:520:48:53

so we really have to look with new eyes to the old fossil records.

0:48:530:48:57

There are many of these fossil samples that don't fit the story,

0:48:570:49:02

because indeed, the story was built without them.

0:49:020:49:05

Could fossil evidence of ancient interbreeding

0:49:110:49:15

have been staring us in the face?

0:49:150:49:17

There are many fossils being found that I don't quite know

0:49:240:49:29

what they are. I think there will be surprises coming there.

0:49:290:49:32

Those could be further evidence of this interbreeding,

0:49:340:49:37

not just Neanderthals and Denisovans,

0:49:370:49:39

other examples of interbreeding, too.

0:49:390:49:42

And the new species don't stop here.

0:49:450:49:47

Experts are now much more open to the idea that there probably are

0:49:470:49:52

other archaic human tribes yet to be properly identified.

0:49:520:49:56

I think as we look in more geographically diverse individuals,

0:49:580:50:01

that there's a real potential that we'll discover

0:50:010:50:04

other branches of the human family tree.

0:50:040:50:07

We still have a lot to discover and to understand,

0:50:090:50:12

so whether it is new groups or new species,

0:50:120:50:15

or whether we have to start recognising those that were

0:50:150:50:19

the result of an interchange between different hominid groups,

0:50:190:50:22

I don't know.

0:50:220:50:24

But it's going to be something much more complicated than we thought.

0:50:240:50:27

So, when modern humans spread out from Africa,

0:50:310:50:34

they encountered a very different world to the one we know today.

0:50:340:50:38

The picture that is emerging

0:50:410:50:43

from fossils,

0:50:430:50:45

from scraps of ancient DNA

0:50:450:50:47

and from modern DNA

0:50:470:50:50

is a world of overlapping human groups.

0:50:500:50:53

It's now known that there were Neanderthals living in Europe,

0:50:550:50:59

the Middle East, and even nudging into Asia.

0:50:590:51:02

Denisovans in western Asia, but in all likelihood,

0:51:050:51:08

they lived right across Asia and South East Asia.

0:51:080:51:11

Floresian hobbits, minding their own business,

0:51:130:51:16

cut off on a remote island in Indonesia.

0:51:160:51:19

As yet nameless archaic Africans, the survivors.

0:51:230:51:26

And us.

0:51:280:51:30

Modern humans.

0:51:300:51:31

Homo sapiens.

0:51:310:51:33

The ultimate wanderers.

0:51:340:51:36

Originally from Africa,

0:51:360:51:38

but then restlessly, repeatedly exploring the globe.

0:51:380:51:42

And it turns out that our story is not so much about

0:51:420:51:45

where we came from, but who we slept with on the way.

0:51:450:51:49

The recent revelations emerging largely from a genetic research

0:51:530:51:57

are helping us to update our family tree.

0:51:570:52:00

So we know that there is at least...

0:52:010:52:03

..one other African archaic population, perhaps even species...

0:52:050:52:09

..going back about 800,000 years ago, to the branch point there.

0:52:110:52:15

And we've got DNA from that coming into modern humans.

0:52:150:52:19

And, of course, that wasn't the first glimpse that we've had

0:52:190:52:23

of genes coming in from other species.

0:52:230:52:26

The first indication we had was that there was some Neanderthal genes

0:52:260:52:31

coming this way into modern humans.

0:52:310:52:33

Now we've got evidence that there are modern human genes,

0:52:330:52:37

not surprisingly, going back in the opposite direction.

0:52:370:52:40

We've also got genes coming in from the Denisovans.

0:52:400:52:44

And there are other archaics coming into Denisovans

0:52:450:52:50

and also into Neanderthals at some point, too.

0:52:500:52:53

I think it's been quite difficult to come to this

0:52:530:52:58

concept of the family tree of humanity.

0:52:580:53:01

We seem to have been so wedded to that idea of a linear progression.

0:53:010:53:06

And what we can see now is that it is a family tree, but not just that.

0:53:060:53:09

It's a tangled web of connections as well.

0:53:090:53:12

Our DNA is a mosaic.

0:53:160:53:19

It contains traces of these other species.

0:53:190:53:23

We contain echoes of the lost tribes of humanity within us.

0:53:240:53:29

So I suppose you could say we are genetic mongrels.

0:53:300:53:34

But there's one final twist in our story.

0:53:450:53:48

A secret that each of us carries inside.

0:53:490:53:53

The archaic DNA within our modern genomes is not defunct.

0:53:540:54:00

It continues to have a profound effects on our lives today.

0:54:000:54:04

In Seattle, Josh Akey is taking advantage of modern data techniques

0:54:060:54:12

to look at our health.

0:54:120:54:14

There's been amazing technological innovations that have happened over

0:54:140:54:18

the last decade. Computing power to be able to crunch all the numbers,

0:54:180:54:21

that allows us to access genomic data on a scale that wasn't

0:54:210:54:24

really even imaginable a few years ago.

0:54:240:54:27

Josh has analysed the genetic data and detailed health records

0:54:280:54:33

of 28,000 people.

0:54:330:54:36

28,000 people fill half of this stadium.

0:54:360:54:38

The idea was to track down the parts of their genomes that were inherited

0:54:410:54:45

from their Neanderthal ancestors and ask

0:54:450:54:47

what is the spectrum of traits or diseases that the remaining

0:54:470:54:51

Neanderthal variation influences in present-day individuals?

0:54:510:54:56

We are still figuring out the full spectrum of consequences,

0:54:560:55:00

but we do know we've picked up some Neanderthal genes

0:55:000:55:03

that were important components of the immune system that provided

0:55:030:55:06

our ancestors a benefit to survive and reproduce

0:55:060:55:09

as they encountered pathogens that they hadn't seen before.

0:55:090:55:12

Increased genetic diversity related to our immune system could have been

0:55:140:55:18

a major advantage gained unwittingly through interbreeding.

0:55:180:55:22

There are certain places in our genome where we are actually more

0:55:240:55:28

Neanderthal-like than we are modern human.

0:55:280:55:31

And the frequency of the Neanderthal copy of the gene is 70 or 80%.

0:55:310:55:36

And those mountain-dwelling Denisovans

0:55:380:55:40

have also left their legacy.

0:55:400:55:42

Researchers have found a highly unusual gene variant found only in

0:55:440:55:48

Tibetans and a very few Han Chinese individuals.

0:55:480:55:52

But it is present in the Denisovan genome.

0:55:540:55:57

Denisovans contributed a version of the EPAS1 gene,

0:55:580:56:02

or EPAS1, to Tibetans

0:56:020:56:05

that allows them to exist and survive and thrive

0:56:050:56:08

at high altitudes.

0:56:080:56:11

So it's sort of interesting to think that we would perhaps

0:56:110:56:15

not have such big populations in the high plateau in Tibet today

0:56:150:56:19

if it wasn't for this contribution from Denisovans.

0:56:190:56:22

But it wasn't all good news.

0:56:230:56:25

New research suggests that our ancestors' fertility was negatively

0:56:260:56:31

affected by having too much Neanderthal or Denisovan DNA.

0:56:310:56:35

It seems that the merging of genomes that ultimately helped us to adapt

0:56:370:56:41

and proliferate was a tainted gift.

0:56:410:56:43

It appears that there was a trade off.

0:56:450:56:47

In present-day individuals,

0:56:470:56:49

many of those Neanderthal variants that were, at one time, protective

0:56:490:56:53

seem to also predispose to various autoimmune diseases.

0:56:530:56:56

In general, Neanderthal ancestry

0:56:560:56:59

explains about 2% of the disease risk to a wide number of traits.

0:56:590:57:04

As an anatomist,

0:57:100:57:12

I'm naturally much more comfortable with bones than with molecules.

0:57:120:57:16

But I find it remarkable how much DNA is now telling us

0:57:160:57:21

about our human origins.

0:57:210:57:24

I find it utterly extraordinary that we are now able to extract

0:57:240:57:27

DNA from bones that are not just tens of thousands of years old,

0:57:270:57:32

but hundreds of thousands of years old.

0:57:320:57:35

What we're currently working on is making the techniques we use

0:57:360:57:41

even more sensitive, so that we could go even further back in time.

0:57:410:57:44

I think these techniques will be like carbon dating or something like

0:57:440:57:48

that, which revolutionised archaeology and became

0:57:480:57:51

a standard tool in the tool box of archaeology.

0:57:510:57:54

So, in the future, we can expect genetics to shed even more light

0:57:560:58:00

on who we are and where we came from.

0:58:000:58:03

Over the next few years,

0:58:080:58:09

we will be able to convincingly show that there's multiple forms

0:58:090:58:13

of humans that we didn't know about before,

0:58:130:58:15

that we have no fossil data for

0:58:150:58:18

and the only evidence of their existence is in our DNA.

0:58:180:58:21

The last 20 years, particularly the last ten years,

0:58:230:58:26

has been a really exciting.

0:58:260:58:28

There is so much going on.

0:58:280:58:30

You don't know what's round the corner.

0:58:300:58:32

I've learnt in the last few years to expect the unexpected.

0:58:320:58:35

And I'm sure that will go on.

0:58:350:58:36

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