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Documentary, PBS First Peoples 2015-06-3of5 in Asia
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00:01Today, there are four billion people living in Asia.
00:06All of them, members of the same species.
00:10Homo sapiens. Us.
00:14But it wasn't always this way.
00:17When we left Africa and entered Asia,
00:21it was already inhabited by different species of human.
00:25They were veterans in this land. We were the rookies.
00:34But what happened next?
00:37Is it possible we mated with these ancient humans and picked up their genes?
00:44When we analyzed the DNA from this, this was a new form of extinct humans.
00:50Even though they went extinct 30,000 years ago,
00:53their DNA lives on in each of us.
00:57We have inside of us the genes of these ancient people influencing us today.
01:03But how have their genes helped us colonize the planet?
01:08This is the story of our ancestors.
01:21As they spread to every continent of the world.
01:25What was the secret to their success?
01:28Their story is our story.
01:34First Peoples was made possible in part by a generous grant from the Anne Ray Charitable Trust,
01:52the Corporation for Public Broadcasting,
01:54and by contributions to your PBS station from viewers like you.
02:00Southeast Asia, 63,000 years ago.
02:11A band of hunter-gatherers on the lookout for food.
02:18A band of hunter-gatherers on the lookout for food.
02:28They're newcomers here, migrants from Africa, at the edge of the known world.
02:34People in the tropics tend not to live in caves.
02:52There are too many poisonous predators.
02:54They use them as a shelter to escape the rain.
03:06But for one young woman, this cave will be her final resting place.
03:19Her remains have recently been discovered.
03:21They may be the oldest modern human remains found anywhere in Asia.
03:38Laos is one of the most isolated countries in Southeast Asia.
03:46Until recently, cut off from the Western world.
03:49But two Western archaeologists have been working here since 2007.
04:03Laura Shackelford from Chicago and Fabrice Demeter from France.
04:10They came to Laos on a hunch.
04:12That prehistoric people may have lived in these hills.
04:23The north of Laos is riddled with caves.
04:27During the Vietnam War, they were used as shelter against the bombs.
04:31But no one has properly explored them until now.
04:42With thousands of caves to choose from, Demeter and Shackelford started excavating here, at this cleft in the mountainside.
04:51Tam Pa Ling.
04:55Tam Pa Ling.
05:10Assisted by a small army of Lao workers, they began digging through tons of clay.
05:12Do you think that they can finish this level today?
05:13Maybe not today, tomorrow morning, I guess.
05:14It should be okay.
05:15I wanted to show you something.
05:16The white line.
05:17Oh, the white line.
05:18Yes.
05:19And that's it?
05:20Here?
05:21Yes, the same one.
05:22morning, I guess. Should be okay. I wanted to show you something. The white... Oh, the white line.
05:29The white line, yes. Yes. And that's it. Here? That's the same way. Even with a dig this size,
05:36they weren't confident of finding anything. There are very few fossils here in Asia,
05:43in large part because this is a wet tropical environment. Things don't fossilize well here
05:50for that reason. But in 2008, they discovered some fragments of charcoal.
05:57Evidence, perhaps, of a prehistoric campfire.
06:06Spurred on by what they found, they carried on digging.
06:12We opened up the same pit. We enlarged it just a little bit.
06:15And it was in that first pit that we found our first fossils.
06:23Embedded in the sediment were fragments of a human skull.
06:32Here are the human remains that we discovered.
06:34The front part here corresponds to the top of the skull.
06:40Afterwards, we found a complete upper jaw.
06:43When I had two pieces in my hands, I knew straight away that it was a modern human.
06:48I was very excited.
06:52A CT scan reveals the size and shape of the skull.
06:56The size and shape of the skull is clearly that of a young woman.
07:01But what's remarkable is its age.
07:06Previously, the most ancient modern human found in this part of the world was 40,000 years old.
07:13But this skull was much older.
07:15At 63,000 years old, this is the oldest fossil in East or Southeast Asia.
07:25And it really puts the age of modern humans in this part of the world back by at least 20,000 years.
07:33The woman from Tampaling is now the oldest, definitively modern human found anywhere in Asia.
07:50Her people left Africa and migrated 4,000 miles eastward, following game, looking for new sources of food.
08:11But their presence in Southeast Asia, so early, radically alters the prevailing theory of human migration.
08:20Conventional wisdom says modern humans migrated out of Africa and into Asia about 60,000 years ago.
08:36But the woman from Tampaling was living on the other side of the continent, in the hills of Laos, 63,000 years ago.
08:46People must have left Africa earlier than previously thought.
08:50Archaeologist Jeff Rose is trying to piece together the route taken by the first people out of Africa.
09:11He's looking for evidence where the journey began on the Arabian Peninsula.
09:20Up until just a couple of years ago, most archaeologists thought the great human expansion out of Africa occurred along this coastline.
09:34People called it coasting out of Africa, coastal migration, coastal express.
09:46The idea was they had become seafarers.
09:49They had somehow developed aquatic subsistence.
09:52They could fish.
09:54They could collect shellfish along the coast.
09:56And that then led to this colossal expansion into Asia and the rest of the world.
10:03That's the theory.
10:05But is it really true?
10:06If an African culture came to this place, they're going to leave evidence of that culture behind in their stone tool technology.
10:16And we should be able to see this.
10:18So it's testable.
10:19In 2010, Jeff Rose got funding to excavate in Oman and find that evidence.
10:33Anything on the shore itself would have been washed away long ago.
10:38But in the hills behind the shore, he expected to find some sign of prehistoric human life.
10:45Now, this mountain range here rises up pretty steeply from the coast.
10:51It is full of caves.
10:52It's like Swiss cheese.
10:54We just thought it's a foregone conclusion.
10:56It's just a matter of time.
10:57Not if we find anything, but when we find anything.
11:00We dug a test pit over there.
11:02We dug one there.
11:03We dug one there.
11:04We dug one on the slope leading up to the cave.
11:06In each case, we went down really deep as far as we could go.
11:10And in all that time, we found nothing.
11:12We never found a single artifact.
11:17I remember just sitting there and saying, that's it.
11:19Forget it.
11:20Forget the coast.
11:21We need to go somewhere else.
11:22We need a completely different strategy.
11:24The project was failing.
11:31So Jeff Rose headed inland.
11:37Over a hundred miles from the coast, in the middle of the desert, he came across a dried-up riverbed.
11:44This is the Wadi Gadoon, one of the biggest ancient river valleys in all of Arabia, perhaps.
11:54It's probably half a mile to the other side.
11:58It's dry now, but a hundred thousand years ago, this thing was full of water.
12:03All of Arabia was green, for that matter.
12:05It was covered in savannas and lakes.
12:07And you have this vast network of river valleys that run through this plateau.
12:13He began to explore the hilltops above the ancient riverbed.
12:19And here, he found a field of flaked rocks.
12:23So, like, this is the stuff I've been looking for all those years along the coast.
12:32This is called chert, or flint.
12:35And it's the raw material that was essential to make the stone tools throughout prehistory.
12:39And the site like this is literally covered in a carpet of this material.
12:44Prehistoric toolmakers would come to a site like this.
12:47They would bang away, make their stone tools, leave the refuse behind, and then go off down into the valleys.
12:52Where the water was.
12:54So, this is a prehistoric workshop.
12:58It was unmistakable.
13:01People had passed through here.
13:03And hung around long enough to make thousands of tools.
13:09But who and when?
13:14The stones told him all he needed to know.
13:18That is gorgeous.
13:19Yes, that is a classic Nubian point.
13:23This is the tool that was made by the first people that left Africa.
13:28Nubian points came from a part of Africa, now in modern-day Egypt.
13:32They were made about 100,000 years ago.
13:38If the same tools can be found in Oman, it suggests people were on the Arabian Peninsula at the same time.
13:49100,000 years ago.
13:50We're not looking at something that looks like it may have a similarity to an African technology.
13:59We're looking at the identical African technology.
14:02If Africans were in Arabia 100,000 years ago, then people were migrating into Asia much earlier than archaeologists thought.
14:17But what drove them on into the unknown, perhaps it was the climate.
14:32Today, Northern Africa and Arabia are hot and dry.
14:36Northern Africa and Arabia are hot and dry.
14:39But 100,000 years ago, this region was very different.
14:45The deserts bloomed.
14:50The landscape was green.
14:52The world was in a wet phase.
14:55The climate here is cyclical.
14:58So you have this monsoon system that's circulating through the Indian Ocean.
15:02And then every once in a while, it intensifies, it strengthens, and it pushes into the interior of Arabia.
15:09Rivers like this, that were once dry, were flowing again.
15:12And so it was almost like the highways were open, and they just filled them up.
15:15It wasn't the beaches that lured people into Arabia, but the rivers, filled by monsoon waters.
15:32What we realized was that people weren't interested in the coastline.
15:37They weren't these fishermen who had adapted to new technology and were moving along this new ecosystem.
15:42They were the same people as they were in Africa, and they were opportunistic.
15:47These river valleys would have been paradise, because not only is it the exact landscape that they already knew,
15:52it was also unoccupied, so there was nobody to compete with.
16:01Some of the qualities that we can see in these people, which we really haven't seen before in prehistory, is they're curious.
16:08There was no overpopulation, so they weren't forced out of Africa.
16:14But they would wake up every day on one side of the Red Sea, and they'd look across.
16:19And at some point, somebody couldn't stand it anymore and had to go scratch that itch.
16:25I think it was this curiosity that was driving them.
16:28And I think that's what we are.
16:30That's the defining aspect of our species, is we want to know what's on the other side.
16:35They would have followed a network of rivers, natural corridors through the continent.
17:05Some of the longest rivers in the world are in Asia.
17:18A constant source of fresh water and food.
17:22Still today, over 90% of the world's population lives within 10 miles of a river.
17:36The Mekong River flows 2,000 miles through Southeast Asia.
17:49It's known locally as the Mother of Water.
17:52It could have led the First Peoples to the hills of Laos, and eventually on to Thampa Ling.
18:01If people entered Asia 100,000 years ago, they would have had more time to migrate across the continent.
18:14They had to move only 2 miles every generation to reach here, 63,000 years ago.
18:22Archaeologists know so little about these people, because they find so few artifacts in Southeast Asia.
18:40The problem is, there's barely any flint to make tools or spear points.
18:46But there is something else, bamboo.
19:03It's dawn in Bansa, a village in northern Laos.
19:07The work of the day begins, and bamboo is everywhere.
19:20It's strong enough to build houses, but supple enough to bend at will, and tender enough to eat.
19:30Bamboo is a supergrass that grows up to three feet a day.
19:39It can withstand more weight than concrete.
19:42And when dry, it's stronger than steel.
19:47In a land without flint, it would have been a multi-purpose solution for the First Peoples.
19:53If you're traveling, then stone tools aren't necessarily something that you want to travel with.
20:02Organic materials like bamboo are easy to use, to discard, and then to make again wherever you move to.
20:10It's certainly something that people 60,000 years ago could easily have used.
20:17But bamboo is also highly absorbent.
20:20Once it gets wet, it softens and rots away, leaving nothing for archaeologists to find.
20:32That makes the trail of the first Asians hard to follow.
20:37So much of the evidence has disappeared.
20:40The next hint of that trail turns up 300 miles further east, in southern China, among the limestone outcrops of Guangxi province.
20:59Chang Zujian is one of China's most experienced geologists.
21:08He realized this was a landscape that would have attracted prehistoric humans.
21:13That over there is Mulan Mountain.
21:21It's a typical limestone formation.
21:24And as you can see, it has lots of peaks and lots of caves.
21:28They're quite treacherous.
21:31But they're natural dwellings.
21:34And for the ancient people, they provided a perfect habitat.
21:37In 2007, Professor Jin worked his way up Mulan Mountain to this cave, Jirindong.
21:54Local farmers had found animal fossils at the entrance,
21:59animals that may have been butchered by early humans.
22:03So Professor Jin decided to explore the interior of the cave.
22:15After 18 months of excavations, his team made a discovery.
22:27A human jawbone.
22:30A mandible.
22:33This is where we found the bone.
22:38Above it, you can see where the first layer is.
22:41And then down here, there's another layer.
22:45And it was right there in the middle of the two layers
22:49that we found the Jirindong jawbone.
22:51When he dated the surrounding layers, he discovered the mandible was 102,000 years old.
23:03It was older than the skull at Tampa Ling.
23:08It was older even than the tools in Oman.
23:12If the dates are right, people must have left Africa and entered Asia even earlier than the evidence suggests,
23:24reaching China at least 102,000 years ago.
23:29But there is an alternative explanation.
23:37Perhaps the mandible is not from a modern human.
23:42Perhaps it's from a different species.
23:45Everyone alive today, all 7 billion of us, are members of the same species.
23:58The human family tree starts more than 2 million years ago.
24:03Before that time, we were more ape than human.
24:07Ever since, there have been innumerable branches, twigs, and shoots.
24:12Giving rise to different species.
24:13Anthropologists classify all those that came before us as our own species.
24:14The human family tree starts more than 2 million years ago.
24:19Before that time, we were more ape than human.
24:25Ever since, there have been innumerable branches, twigs, and shoots.
24:31Giving rise to different species.
24:37Anthropologists classify all those that came before us
24:41as archaic humans.
24:44The most successful of these species was Homo erectus.
24:51Despite having a brain only two-thirds the size of ours,
24:56Homo erectus spread out from Africa 1.5 million years before modern humans.
25:05They, not us, were the first inhabitants of Asia.
25:11Maybe that's why the mandible from Jirindong is so ancient.
25:18It might not be Homo sapiens.
25:21Is it Homo erectus?
25:24Homo erectus is an expert on the differences between the two human species.
25:37The mandible is a defining feature.
25:40In particular, the size and angle of the chin.
25:44In Homo sapiens, it juts forward ahead of the teeth.
25:51But in Homo erectus, it slopes backward.
25:54This is the mandible of Homo erectus.
26:00In general, it's very robust.
26:02And also, the most important is that
26:06the angles of the chin
26:09usually less than 70 degrees.
26:12From ancient time to the modern,
26:17the angles just increase.
26:20To the modern humans, usually lack that,
26:23the 90 degrees or even more than that, like 100 degrees.
26:27What about the mandible from Jirindong?
26:38Is it erectus or sapiens?
26:41By analyzing it in a CT scanner,
26:45it's possible to measure the angle of the chin,
26:48also the thickness of the bones,
26:51and the size of the teeth cavities.
26:53On all these scores,
27:00the mandible seems to be
27:01between sapiens and erectus.
27:05A mix of both species.
27:15It has long been thought
27:17Homo erectus went extinct
27:19before we turned up in Asia.
27:23But what if that's not true?
27:26What if they were still around?
27:30And the two species met each other?
27:33Would we have had enough in common
27:48to interact
27:50and interbreed?
27:57Perhaps that's why the mandible
27:59looks like a mix of two species.
28:01It's the result
28:05of interbreeding.
28:12So far,
28:13no other evidence of such encounters
28:15has been found in southern China.
28:18But it's an intriguing idea
28:20that modern humans arrived
28:22and mated with other
28:24archaic types of human.
28:25If it happened here,
28:30where else might it have happened?
28:32Who else was living in Asia
28:34when modern humans arrived?
28:36For the first Asians
28:47that headed north,
28:49this was a natural corridor
28:50across the wilderness of Siberia.
28:53And here,
28:58in the Altai Mountains,
29:01archaeologists have found a cave
29:03like no other,
29:06Denisova.
29:08You have this large opening
29:09and it's visible from quite a distance
29:11as soon as you get into that part of the valley.
29:14It was inhabited in,
29:16I think, the 18th century
29:17by a hermit
29:18called the Denis,
29:20the Holy Denis.
29:21And the cave is named after him.
29:23So it's Denis' cave,
29:24Denisova cave.
29:27Denisova was once a home
29:30to the rock stars of prehistory.
29:35The Neanderthals.
29:37Our closest cousins,
29:40the Neanderthals,
29:40the Neanderthals are a separate species
29:42that evolved in Ice Age Europe
29:46but expanded northeast
29:48as far as Siberia.
29:54Since the 1970s,
29:56archaeologists have unearthed
29:58thousands of artifacts
30:00made by Neanderthals.
30:03But they also find artifacts
30:05made by modern humans.
30:08There are few caves in the world
30:11where there's evidence
30:12that two types of human
30:14lived in the same place,
30:17albeit at different times.
30:20But very few bones
30:22have ever been excavated here.
30:25So in 2008,
30:27archaeologists intensified their search.
30:31I joined a Russian team
30:33that was excavating the cave
30:34since a long time
30:35and my role was mostly studying
30:37the human remains.
30:39The team very carefully
30:40and gradually removes
30:41the sediments that are in the cave
30:43to recover even the smallest remains.
30:46A lot of work is actually
30:47looking at all the little bone pieces
30:49and trying to figure out
30:49is there something human in there?
30:52And sometimes you actually
30:53do find human remains.
30:56Within a layer of sediment
30:58that was 41,000 years old,
31:02Russian archaeologists
31:03uncovered a tiny fragment of bone
31:06from a human finger.
31:08We have enlarged 3D print
31:13of the finger bone.
31:15It's five times as large
31:16as the original.
31:17It's part of the,
31:18probably of the little finger.
31:21This finger would still be growing.
31:23It's a child that's still developing.
31:25Maybe a five, five,
31:27seven-year-old kid,
31:28something around that age.
31:31The original size is this here.
31:34It's a tiny little piece
31:35as you can see.
31:37It's probably the least
31:38spectacular fossil
31:39that exists anywhere.
31:40A tiny fragment
31:41of a finger bone of a child.
31:44Who was this child
31:46in the Siberian hills
31:4841,000 years ago?
31:52Modern human
31:53or Neanderthal?
31:54There's only one way to tell.
32:01DNA.
32:08The finger bone was sent
32:10to the Max Planck Institute
32:12to Swedish geneticist
32:15Svante Pabo,
32:18a pioneer in the field
32:19of ancient DNA.
32:25When his team
32:26found some DNA
32:27still preserved in the bone,
32:30they set about analyzing it.
32:32As DNA ages,
32:41it breaks down
32:42into billions of tiny fragments
32:44that are mixed up
32:46and contaminated
32:47with the DNA of insects,
32:50bacteria,
32:51and fungi.
32:53The challenge
32:54for a geneticist
32:56is to identify
32:57the human fragments,
32:59isolate them,
33:00and reassemble them all
33:02in the correct order.
33:06A decade ago,
33:07it would have been impossible.
33:10But super-fast sequencing machines
33:12have made the impossible
33:14merely improbable.
33:18The whole last 30 years
33:21in molecular genetics
33:22is a history of revolutions
33:24driven by technology.
33:27The big step
33:29was really the ability
33:30to sequence
33:31millions of DNA molecules
33:33quite rapidly
33:34and inexpensively,
33:35and that changed
33:36the whole ballgame.
33:38In 2010,
33:41Pabo's team
33:41created an international storm.
33:45They sequenced
33:46the genome
33:47of a Neanderthal.
33:50It was the first time
33:52anyone had managed
33:53to read the genetic code
33:55of an extinct human.
33:57They used the same techniques
34:01on the Siberian finger bone.
34:04But its sequence
34:06was not what they imagined.
34:10When we analyzed
34:11the DNA from this,
34:12we expected it to be
34:13either a Neanderthal
34:15or a modern human
34:15that would have been there.
34:17We were very surprised
34:18to find that it was
34:19actually something else.
34:21This was a new form
34:23of extinct human.
34:24From the single finger bone
34:28of a child,
34:30they had uncovered
34:31a new branch
34:32of the human family tree.
34:36We had a big debate
34:37about what we would
34:38call these individuals.
34:40And we came up
34:41with the name
34:42Denisovans
34:42after the Denisovac cave
34:44where they had been
34:44first found.
34:45This was the first time
34:48that we identified
34:49a new form
34:50of extinct human
34:51just from a genome sequence.
34:54And hardly any information
34:56at all
34:57from bones
34:58or stone tools
34:59just from a genome sequence.
35:03It sounds like science fiction.
35:07From nowhere,
35:08a new population,
35:10the Denisovans,
35:12enter the human story.
35:13As modern humans
35:21pushed through Asia,
35:23they must have moved
35:24into Denisovan territory.
35:30What happened next?
35:38According to the genetics,
35:40the two peoples
35:41interbred.
35:43When geneticists looked
35:50at that Denisovac genome
35:51and they lined it up
35:53next to modern human genomes,
35:54they found that
35:55there were modern people
35:56who have pieces
35:57of this Denisovac genome
35:59inside of them.
36:00This is so incredible
36:01that this ancient population
36:03is still there
36:03inside of us.
36:04This is not the first evidence
36:12of interbreeding
36:12between modern
36:14and archaic humans.
36:16When the team
36:17at the Max Planck Institute
36:18sequenced the Neanderthal genome,
36:22they found the same
36:23sort of overlap.
36:25They concluded
36:26that modern humans
36:28interbred with Neanderthals
36:2955,000 years ago
36:32and carried some of their genes
36:36with them
36:36into Asia.
36:38We used to think
36:41of modern humans
36:42entering Asia
36:43and entering somewhere
36:45that was relatively,
36:46you know,
36:47sparsely inhabited,
36:48if at all.
36:51We now know
36:53that there were multiple populations
36:54of these archaic humans.
36:58Denisovans,
36:58Neanderthals,
37:00maybe some late surviving
37:03Homo erectus populations.
37:05And when modern humans show up,
37:08they're the new kids
37:09on the block
37:09in a place where
37:11there's already
37:12lots of different people
37:13that are pretty successful there.
37:18There must have been
37:19interbreeding
37:20and the people
37:21who were the products
37:22of that interbreeding
37:23went on to colonize
37:24much of East
37:25and Southeast Asia.
37:28There are 4 billion people
37:31in Asia today.
37:33All of them
37:33have genes
37:34inherited from
37:35archaic humans.
37:38Between 1 and 3%
37:41of their DNA
37:41comes from Neanderthals
37:43and in some people
37:45up to 5% more
37:47from Denisovans.
37:50Asia,
37:51the great melting pot
37:53of human diversity.
37:58What sort of genes
38:18might have passed
38:19from archaic
38:19to modern humans?
38:22What effect
38:23did they have on us?
38:25the clues
38:30are to be found
38:31on the Tibetan Plateau.
38:41It's early morning
38:42in the Himalayas
38:43and farmers
38:44are letting out
38:45their yaks
38:46for the day.
38:49It's a familiar routine.
38:51They leave the village
38:52and look for pasture
38:53up the mountainside.
39:06This is 13,000 feet
39:08above sea level.
39:12There's 40% less oxygen
39:14than at the coast.
39:17But Tibetans
39:19seem untroubled
39:20working at this altitude.
39:21their bodies
39:25have adapted
39:26to life
39:27on top of the world.
39:34Rasmus Nielsen
39:35believes the key
39:36to their survival
39:37is a lack
39:38of hemoglobin,
39:40the protein
39:41that carries oxygen
39:43in red blood cells.
39:45You might expect
39:46that if you're
39:47at high altitude
39:48you need more hemoglobin,
39:49but in fact
39:50Tibetans
39:50they actually produce
39:51less hemoglobin.
39:53That might sound backwards.
39:55Why would they produce
39:55less hemoglobin?
39:57But that's because
39:58that having too much
39:59hemoglobin in your blood
40:00can actually be detrimental.
40:01Because if you have
40:02too many red blood cells
40:03then your blood
40:04becomes too thick.
40:09We don't really know
40:11exactly how the Tibetans
40:12are functioning
40:13with less red blood cells
40:15in their blood.
40:15We think it's because
40:18they're better
40:18at producing energy
40:19in their muscles
40:20without using oxygen.
40:24One of the genes
40:26that controls
40:26the level of hemoglobin
40:28is EPAS1.
40:32Everyone has a copy
40:33of this gene
40:34located on chromosome 2.
40:37But Tibetans
40:39have a special variant
40:39that restricts
40:42their level of hemoglobin
40:43and allows them
40:46to work
40:47in the high pastures
40:48without ill effects.
40:53But where does
40:54this variant come from?
40:56How did it enter
40:57the Tibetan gene pool?
41:01Could it be
41:02the result
41:02of interbreeding?
41:06What we saw
41:07was that
41:08the DNA sequence
41:10that the Tibetans
41:11had really didn't
41:12match any other sequences
41:13in any other humans.
41:16But then we looked
41:17at this other species
41:19the Denisovans.
41:22So I was surprised
41:23what we found
41:24was that there was
41:25almost a complete match
41:26between the DNA
41:28and the Tibetans
41:29and the Denisovans
41:30sequence.
41:31We could show
41:31that the Tibetans
41:32sequence
41:33had come
41:33from this archaic
41:35species
41:35the Denisovans
41:36into the Tibetans.
41:39We don't know
41:40very much
41:40about Denisovans
41:41but it's possible
41:43that they were
41:44also high altitude
41:44adapted.
41:46By interbreeding
41:47with them
41:47modern humans
41:48picked up this gene
41:49that then also
41:50allowed them
41:51to be adapted
41:52to the high altitude
41:53environment.
41:57The same gene
41:59is still regulating
42:00the hemoglobin
42:01of Tibetans today.
42:02It's as if they've
42:06hitched a genetic ride
42:07on the back
42:08of the Denisovans.
42:13Mixture with
42:14these archaic humans
42:15was a tremendous
42:16shortcut for natural
42:17selection.
42:19The thing is that
42:20if you have a trait
42:21that you're trying
42:22to get that's
42:23useful for you
42:23you're waiting
42:24for the right
42:25mutations to happen.
42:26you could be waiting
42:30for thousands
42:31of generations
42:31but archaic humans
42:33have hundreds
42:34of thousands
42:35of years
42:35of adaptation
42:36already.
42:37Everything that's
42:38useful from this
42:39population
42:40has a huge potential
42:41of being picked up
42:42into modern humans
42:43with a little bit
42:44of interbreeding.
42:45EPAS1 is the first
42:49gene scientists
42:50know of
42:51that's clearly
42:52passed from one
42:53type of human
42:54into another
42:55through interbreeding.
42:58But it's likely
42:59to be just the tip
43:01of the iceberg.
43:04Many other genes
43:05have probably taken
43:06the same route
43:07and had a profound
43:10impact on us
43:11modern humans.
43:15The skin
43:16is the largest organ
43:18in the human body.
43:20It weighs up
43:21to eight pounds.
43:23It's packed
43:24with sweat glands
43:25blood vessels
43:26and nerve endings
43:27but it's only
43:28a tenth of an inch
43:29thick.
43:31It's all that exists
43:32between us
43:33and the outside world.
43:37These guys
43:39are providing
43:40a good example
43:40of showing
43:41why the human skin
43:42is so important.
43:44They're able
43:45to withstand
43:46the impact
43:47because of
43:47the special properties
43:48and toughness
43:49of skin
43:49and much
43:51of that toughness
43:51is governed
43:52by a protein
43:53called keratin
43:54which is a very
43:55tough, fibrous
43:56structural protein
43:57that provides
43:58the skin
43:59with things
43:59like elasticity
44:00and strength.
44:07According to
44:08the latest research
44:09genes that control
44:11the production
44:11of keratin
44:12were inherited
44:13from archaic humans
44:15not Denisovans
44:17this time
44:18but Neanderthals.
44:22There was something
44:24beneficial
44:24about Neanderthal skin
44:26biology
44:27and the way
44:27they processed keratin
44:29that was passed on
44:30by interbreeding
44:31and has stayed with us
44:34ever since.
44:35It could be related
44:37to skin pigmentation
44:39it could be related
44:40to wound healing
44:42but we know
44:44that inheriting
44:46the Neanderthal version
44:47of these genes
44:48provided an advantage
44:50to our ancestors.
44:53We're only just
44:55beginning to understand
44:56about how humans
44:58and Neanderthals
44:59and other archaic humans
45:01interacted
45:02and what those
45:03consequences were.
45:05Genetics
45:08is rewriting
45:09the human story.
45:13Evidence
45:14about who met whom
45:16where and when
45:18shows up
45:19in today's DNA
45:20more clearly
45:22than in any fossil.
45:26And that evidence
45:27suggests our cousins
45:28were more important
45:29to us
45:30than we ever realized.
45:32in any individual
45:36about one and a half percent
45:38of our genome
45:39came from
45:40Neanderthal ancestors
45:41but my one and a half percent
45:43might be different
45:44than your one and a half percent.
45:49If you take all
45:50of the different
45:51one and a half percents
45:52and you added them
45:53all together
45:54you'd come up
45:55with about 20 or 30 percent
45:56of the Neanderthal genome.
45:57which is quite remarkable
46:00because even though
46:02Neanderthals
46:02went extinct
46:0330,000 years ago
46:04their DNA lives on
46:06in each of us.
46:07just how influential
46:17were the genes
46:18we inherited
46:19from our evolutionary cousins
46:21they may make the difference
46:25between life and death.
46:27Every day
46:35our bodies
46:36are under attack
46:37from microbes
46:39seeking new hosts
46:42to invade
46:43and infect.
46:49But when microbes attack
46:51our body
46:52counterattacks
46:53thanks to our immune system
46:58which enlists an army
47:00of white blood cells
47:01known as
47:02natural killers.
47:17John Trousdale
47:18is a pathologist
47:19and an expert
47:21in the mechanics
47:22of human immunity.
47:27These are killer cells.
47:29Now killer cells
47:30work by
47:31killing any cells
47:33infected with
47:33a virus or a microbe
47:35so we need these cells
47:36in order to
47:37take out
47:38any infected cells
47:40in our bodies.
47:41In order to do that though
47:42these killer cells
47:43need a special network
47:45of genes
47:46and these genes
47:47are called HLA genes
47:48they're kind of
47:49an early warning system.
47:52HLA genes
47:55or human leukocyte antigens
47:57have long been regarded
47:59as key
48:00in the battle
48:01against disease
48:02but scientists
48:05have recently noticed
48:06geographical patterning
48:08to these genes.
48:09modern day Asians
48:13have clusters of them
48:14that don't exist
48:16among Africans
48:17it's as if their ancestors
48:22picked them up
48:23from a source
48:24already living in Asia.
48:25some of those genes
48:28look very different
48:29to modern human genes
48:32it looks as though
48:34they've been acquired
48:35from different species
48:36it seems increasingly likely
48:40that some types of HLA
48:42were inherited
48:43from Neanderthals
48:45or Denisovans.
48:48let's imagine
48:49these dice
48:50represent different HLAs
48:52and in a population
48:54like the African population
48:56each number represents
48:58a different HLA
48:59and actually provides
49:00a different kind of
49:01level of immunity
49:02and the more variety
49:04in the population
49:04the harder it is
49:05for a virus
49:06to get a hold
49:06on that population
49:07but as small numbers
49:09of people move out
49:10of Africa
49:11they've got much
49:12less variety
49:13so in other words
49:15they're more vulnerable
49:15to infection.
49:17So how does this population
49:19now acquire
49:20some more variety?
49:22Well it can wait
49:24for a mutation
49:25to come along
49:25but of course mutation
49:26in the normal course
49:27of evolution
49:28is very slow.
49:30However
49:30if they actually mate
49:31with another population
49:32let's say Neanderthals
49:34or Denisovans
49:35they can gain more variety
49:37so they might get
49:39a five here
49:40or a six here
49:41an additional variety
49:42that weren't missing.
49:44In addition to that
49:45they can actually also
49:46acquire some
49:48really novel HLA genes
49:49that maybe weren't
49:50even present
49:51in the African population
49:52and they provided
49:54resistance
49:55to particular infections
49:57that were prevalent
49:58in those environments.
50:00So it's a kind
50:01of evolutionary shortcut
50:02in other words
50:03these genes
50:04have been borrowed
50:05from other populations
50:06and incorporated
50:07into the population
50:08to provide that variety
50:09that they were missing.
50:13Billions of us today
50:14are better
50:15at fighting off disease
50:17because of archaic humans.
50:21We acquired
50:22their immunity.
50:24genes that were in their cells
50:30are now integral
50:32to our biology.
50:35Some people say
50:37that maybe
50:37one to three percent
50:38of our genes
50:39have come from Neanderthals
50:40so what's the big deal?
50:42I mean
50:42one to three percent
50:43isn't very much.
50:45However
50:46if you look at HLA genes
50:47it appears that
50:48these have actually
50:49provided a major advantage
50:51and in some populations
50:53it's estimated
50:54up to 90 percent
50:55of the genes
50:56have come from
50:57Neanderthals
50:57or Denisovans.
51:00So it may be
51:01that the immunity
51:01through HLA
51:02is one of the most
51:04important gifts
51:04we've had
51:05from these
51:06ancient populations.
51:14It's the end
51:15of the day
51:16on the Tibetan plateau.
51:17Farmers are bringing
51:21their yaks
51:22home for milking.
51:27These are hybrid animals
51:29that have been crossed
51:31with domestic cattle
51:32to become
51:33more resilient
51:34and more productive.
51:43Although the farmers
51:44don't realize it
51:45they are also hybrids.
51:47crossed with
51:49Denisovans,
51:50Neanderthals
51:51and perhaps
51:52Homo erectus.
51:58As with the yaks
52:00hybridization
52:01seems to have
52:02made them stronger
52:03tougher
52:04and healthier.
52:14People today
52:16are still living
52:17with the legacy
52:18of what happened
52:19in the ancient
52:20forests of Asia.
52:25When modern humans
52:26moved into Asia
52:27they had some
52:28of the tools
52:29they needed to make it
52:30but not all of them.
52:32they mixed with populations
52:42that had been there
52:42for hundreds of thousands
52:44of years
52:44and they began
52:46to pick up
52:47some of the adaptations
52:48that enabled them
52:49to survive
52:50in that new place.
52:53We have inside of us
52:55the genes
52:56of these ancient people
52:57influencing us today.
52:59we're only beginning
53:01to learn
53:02how much we owe
53:03to them.
53:05These encounters
53:06that happened
53:06tens of thousands
53:08of years ago.
53:09the impact
53:21of interbreeding
53:21goes way
53:22beyond Asia.
53:25The same people
53:27who expanded
53:27into Siberia
53:29would go on
53:30and colonize
53:32North America.
53:33others
53:42further south
53:43would take
53:44the greatest journey
53:45of all
53:46across the sea
53:47into Australia
53:49the world's
53:51most isolated continent.
53:52where ever they went
54:05they took with them
54:07the genes
54:08of ancient species.
54:13Hybrid humans
54:14first peoples.
54:22On the next
54:27First Peoples
54:28we venture
54:29to Australia.
54:31Australia was
54:31a tremendously
54:32challenging environment.
54:34Humans had to use
54:35all of their adaptability
54:36to make it there.
54:41Australia provided
54:42another challenge
54:43that they couldn't
54:45adapt their way out of.
54:47It's tremendously
54:47isolated.
54:49They were really
54:49in it by themselves.
54:50Next time
54:53on First Peoples.
54:57First Peoples
54:58was made possible
54:59in part by
54:59a generous grant
55:00from the Anne Ray
55:01Charitable Trust
55:02the Corporation
55:03for Public Broadcasting
55:04and by contributions
55:06to your PBS station
55:07from viewers like you.
55:16First Peoples
55:17is available on DVD.
55:19To order
55:20visit ShopPBS.org
55:22or call
55:221-800-PLAY-PBS.
55:24a new
55:3123-300-PLAY-PBS
55:32the.
55:33The Center
55:34is available on DVD.
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