The Incredible Human Journey (2009) s01e04 Episode Script

Australia

ROBERTS: They say this is where it all began.
That we are all children of Africa.
But if so, why do we look so different? And how on earth could a handful of African families become a whole world full of people? I'm Alice Roberts, medical doctor and anthropologist.
I'm fascinated by what bones, stones and even our bodies can reveal about the distant past.
I'm going in search of the traces left by our African ancestors and their journeys to populate the world.
This time, the most intriguing puzzle of all That's beautiful.
how on earth did people make the long and dangerous journey to Australia, before they even reached Europe? I'm really worried we're gonna get swept in by these breakers.
Come with me in the footsteps of our ancestors on the most epic adventure ever undertaken.
No one knows how humans first reached Australia.
WOMAN ON RADIO: Forty-one degrees in Mildura today and 4 1 in Swan Hill.
ROBERTS: So I'm starting where the journey could have ended, in a remote wilderness 800 kilometres from Sydney.
This landscape is just so parched and barren-looking.
And it's mid-morning, and it's already over 40 degrees out there.
Baking.
And as soon as you step outside the car, you get mobbed by hundreds of flies.
Not very pleasant.
It's hard to imagine why our ancestors would have wanted to make this their home.
If that's really what happened.
There's so little evidence.
But just recently, something was found near here.
one of the few people who knows its whereabouts is Warren Clark.
-We'll just walk up the ridge a bit.
-Up here? Yeah.
ROBERTS: The discovery was made by a young Aboriginal Australian.
ROBERTS: So major that as soon as it was revealed the site was buried again, to protect it.
It's still secret today? ROBERTS: But I've come here on a special day.
Because for the first time since the site was reburied, local Aboriginal people and archaeologists are gathering once more to check on their discovery.
over 500 human footprints.
ROBERTS: This is the heel here.
And you can see the way that the foot sort of lifts up here, that's where the arch of the foot would be.
And then the big toe is just there.
So this is a right foot.
It's amazing to see something which is so ephemeral, sort of normally here today, gone tomorrow.
This is looking like a pretty big footprint.
-Yeah, he's well fed.
-(LAUGHING) Yeah.
ROBERTS: It's incredibly hard, this layer, isn't it? Feels really stony.
-Is it a type of clay? -MAN: It's just like our pottery.
And it must feel pretty personal as well, 'cause, you know, this is I mean, this is your own heritage, isn't it? One of the oldest cultures in the world.
So it's very special and unique.
ROBERTS: But who do the footprints belong to? Tanya Charles was here when they were found.
TANYA: Other people that was with us, they were saying, ''They belong to the farmers that were here.
'' And we're like, ''No, they're ours.
'' (LAUGHS) You fellas wear shoes.
We don't.
We didn't back then.
We just knew in our hearts, we knew that they were ours.
ROBERTS: Scientists and Aboriginal trackers have interpreted the prints of men, women and children walking and running around the edges of what was once an ancient lake.
The most bizarre track seems to have belonged to a one-legged man.
Like, we sort of knew that he only had one foot, but we didn't want to believe it.
ROBERTS: Yeah.
'Cause, you know, one-footed men way back in them times is like, ''Oh, scary.
'' And he was chasing a kangaroo, and on his first throw he actually missed the kangaroo.
ROBERTS: (LAUGHING) Right.
Yeah.
On his second throw, he got him and dropped him down to one knee.
ROBERTS: How long ago did these people live? With a new technique called luminescence dating, scientists could measure the tiniest glow when grains of sand from the footprints were analysed.
And from this, they could calculate how long the footprints had lain buried.
The results were stunning.
The footprints were around 20,000 years old.
There's something really intimate about this, because it's just a moment in somebody's life, when they walked across this landscape.
And it just looks like it could be a footprint made yesterday.
And yet it's about 20,000 years old.
So is this when people first reached Australia, long after we colonised Europe and Asia? It would certainly make sense, given how far away Australia is.
But I've been told that there is other evidence around here that could turn this idea upside down.
What I'm looking for are the remains of an extinct beast, the giant kangaroo.
It's just about midday here and it's very hot.
All right, what's that? That is a stick.
I spotted that in the distance and thought, ''Oh, right, could that be a giant kangaroo?'' It's not, it's a stick.
Lots of little bits.
So this thing I've picked up is one of the long foot bones of a modern kangaroo.
Oh, look.
Right, so we've got two bits to it.
And if I put those together like that, that is the toe bone of an ancient giant kangaroo.
Now, if we look at that end, you can see that basically it's the same bone as this one, but this one belongs to a much chunkier animal.
They're actually similar length, if you imagine sort of the end on that as well.
But you can just see how much chunkier that is.
And you can imagine how much heavier that animal would have been.
Giant kangaroos could grow up to 2.
5 metres tall.
But they seem to have become extinct shortly after 50,000 years ago.
Could this possibly have been due to a new predator arriving on the scene? If so, it would mean that we humans arrived here much earlier than 20,000 years ago.
And there is something - or rather someone - who could support such an early arrival.
Mungo Man.
This is the skull of Mungo Man.
And these bones are the most ancient human remains that have ever been found in Australia.
And they are incredibly old.
The most conservative estimates put them at 40,000 years old, and some people say they might be up to 60,000 years old.
Now, that's quite extraordinary, because it would mean that modern humans were in Australia before they reached Europe.
Which seems highly unlikely.
Not only is Australia so much further from Africa than Europe is, there's an ocean to cross.
So unlikely does the journey seem that some scientists have poured doubt on it.
Instead, they suggest that Australians somehow evolved locally.
And it really is a mystery.
The problem is that there is very little physical evidence to show that this route from Africa all the way to Australia was ever taken.
It's one of the biggest puzzles of our human journey.
There's only one way to solve this mystery, and that's to go back to the beginning of the trail.
To Africa.
Previously, I saw evidence suggesting that most of us descend from a tiny group of people who left the continent around 70,000 years ago.
one theory is that those families crossed the Red Sea, and then pushed east, hugging the shoreline.
Then they would have probably trekked along the Indian coast.
So that's the first place to look for evidence of this journey towards Australia.
(CHANTING IN LOCAL LANGUAGE) It would be absolutely fantastic to have a trail of stone tools and human fossils all the way along the coast of India.
Sadly, there just isn't.
Along thousands of miles of coastline, nothing.
But maybe I'm looking in the wrong place.
I've heard that some new evidence has been unearthed in a very remote part of India.
(TYRE BLOWS) one which is proving tricky to get to.
Might hitch a ride on one of these tuk-tuks instead.
There is some real evidence turning up right now at an archaeological site a very long way from the coast.
It's called Jwalapuram, and it's right in the heart of southern India.
From here, it's a beautiful fertile valley, but just under the surface is a thick layer of white ash.
Today, it is mined by poor families from the village of Jwalapuram, who sell the ash to chemical companies.
But the ash itself has an incredible story to tell.
(VOLCANO RUMBLING) It starts thousands of years ago, when Mount Toba on Sumatra erupted.
A supervolcano.
The most devastating eruption in human experience.
The ash cloud was blown over 2,000 kilometres northwest, reaching as far as India.
Just imagine what it would've been like, a lush landscape suddenly transformed.
Clouds of ash in the air, choking plant and animal life.
It would have been an environmental disaster.
So what can Toba tell us? Well, we have a precise date.
Toba erupted 74,000 years ago.
The question for us is, had modern humans reached India by the time it happened? Until recently, the answer was no, but a new discovery could change that.
Indian archaeologists have joined forces with Mike Petraglia from Cambridge University.
-MIKE: It does look like a blade.
-Yes, sir.
But most importantly, there's retouch all along here.
Yeah, retouch.
Yes.
And it looks like an end scraper.
ROBERTS: And Mike is making some surprising claims from what they found deep in the ash.
So this is the Toba super-eruption, the deposit that we have representing the ash fall.
ROBERTS: That's a huge amount of ash.
Yeah, it's about 2 metres' worth of ash.
And the bottom part is what we call the primary ash.
So this is still ash down here, this grey stuff.
Yeah.
You see there's very sharp contact.
The beginning of the ash starts here and it goes up, all the way up to 2 metres.
And what's so striking is that we have so many spectacular artefacts coming out.
ROBERTS: That's like a little spearhead.
MIKE: Yes, that's exactly what it is.
We think it's actually the tip to a spear.
-Yeah.
-And what's so interesting about this particular piece is the tip is broken, and so we know the spear was launched and it broke in use.
Now, what's important about this particular piece is it occurs in deposits below the ash at 78,000 years ago.
So you know the date of it? We know very precisely the date of it.
It's in between 78,000 and 74,000 years ago.
That's a very, very early date, Mike.
Yes, and the importance of that date is that these spear points are also found in North Africa, anywhere between 90 and 60,000 years ago.
So our point fits exactly with that age range.
ROBERTS: Mike believes this is good evidence that our ancestors were here.
(RUMBLING) But could they have survived this, a supervolcano? Well, along with that one stone point the team have found many other types of tool.
We have continuity of the tools, found both below the ash and above the ash.
So we have literally hundreds of artefacts that look rather similar.
Right.
Does that mean that the human population that was here below the ash survived the Toba super-eruption? MIKE: Yes, that's our argument, that whoever was here survived the Toba super-eruption.
Even though this was a major event, it had an effect on those populations, but those populations survived through the volcanic event.
ROBERTS: But were these tools really left by our species? There are plenty of scientists who won't be persuaded until the team find more evidence, such as human bones.
But I must say, I'm personally quite convinced by the evidence here.
So Jwalapuram at 78,000 years is my first milestone on the route eastwards out of Africa.
So where did they go next? At last, a hint that our early ancestors may have come this way.
Perhaps some of those families who survived Toba began to slowly spread across the continent.
So it's not really a journey in the conventional sense, because although I'm certainly covering a lot of ground here trying to recapture the movements that these early humans made across the landscape, really what we're talking about is population expansion.
Pressure of numbers and competition for resources.
And the natural thing to do is for people to spread out across the landscape.
And you can just imagine family groups sort of splitting off and just moving away in all directions, and the genetic tree gradually growing and spreading out as well.
But behind that wave of colonisation pushing eastwards, some families would have stayed where they were and put down roots.
And maybe it's the people that stayed put who could provide the next clue.
The countries around the Indian ocean are dotted with remote tribes who look very different to everyone else.
Could they shed any light on the first colonisers? To investigate, I'm on my way to Malaysia.
What an amazing city.
The cosmopolitan capital, Kuala Lumpur.
But a few hours away there's a completely different world and a small group of people hanging on to a traditional life.
Could they be a relic of that first migration east from Africa? The Semang tribes are believed to be the most ancient people in Malaysia.
And they do look different from other Malaysians.
Now, this is a selection of typical Malaysian faces.
And you can see these people are quite light-skinned, quite East Asian-looking in their appearance.
And this is a Semang man.
And the Semang are completely different-looking.
They live in Malaysia, but they don't look like the rest of the population at all.
They're much darker-skinned.
Some people have even gone as far as to say that they look African in appearance.
And I just wonder whether their appearance is telling us something about their ancient ancestry.
The rainforest is disappearing around them and many now work on rubber plantations and logging camps.
But they are still proud of their hunter-gatherer traditions.
(TWIG SNAPS) I'm really noisy.
They're so stealthy.
And I'm stepping on twigs and things.
Excellent.
I'm gonna have a go as well.
(BLOWING) Okay! (LAUGHING) ROBERTS: And the girls also offer to pass their hunting skills on to me.
Oh, it's just brilliant.
They're all just wedged under this rock, desperately scrambling underneath it, trying to get those fish.
(LAUGHING) He's tiny! They're actually underwater now, just feeling around under stones and grabbing these fish.
And the whole thing is just great fun.
You know, they're schoolgirls having a laugh, finding a bit of food along the way.
And it's very sad that it's a way of life that isn't going to be possible for much longer, I don't think.
But the most revealing clue isn't the Semang's way of life or their appearance.
It's invisible to the naked eye, hidden inside them.
Amazingly, through their DNA it might be possible to trace that first great journey through Malaysia.
Genetics expert Stephen oppenheimer has flown in from oxford.
His work is helping revolutionise the story of our human journey.
STEPHEN: I guess it's something like a detective story, where you've got a very specific trail, which you can measure, just like traditional trackers, where they'll follow a trail which nobody else could see.
ROBERTS: Combining genes and geography, Stephen has mapped out a route from Africa, across the Red Sea and around the edge of the Indian ocean.
By looking at the DNA of the Semang, Stephen hopes to find evidence of that early migration towards Australia.
STEPHEN: The new genetics is extraordinarily powerful for looking at ancient migrations, because not only can you trace very specific migrations, but you can actually attempt to date them as well.
(DRUMS BEATING) (SINGING IN LOCAL LANGUAGE) ROBERTS: Stephen has been looking for unique genetic markers that will tell him when the ancestors of the Semang first arrived here.
What about dates? Because they certainly think they've been here forever.
-They think they're very ancient.
-I agree with them.
-You do? -Yes.
So they've been here 60,000 years? The ancestors have been here STEPHEN: At least 60,000.
I suspect it was much, much more.
I mean, that's amazing, 'cause if their uniqueness goes back that far, and, you know, if we can say that they have probably been here in this sort of area for 60,000 years, that means they were very close to the wave of colonisation, doesn't it? They were part of it.
They were in the vanguard.
-Yeah.
-They were just a colony dropped along the way as the vanguard advanced down towards New Guinea and Australia.
ROBERTS: It's incredibly frustrating that the first family groups pushing through these new lands left so little for us to find.
But genetics has come to the rescue.
Stephen's research tells us that the ancestors of the Semang were probably amongst the first modern humans to come through here.
And not only that, the genetics suggests that that vanguard moved surprisingly rapidly, getting all the way from Africa to Malaysia in the space of just a few thousand years.
There are other tribes thought to have ancient roots as well.
Together they are like distant echoes of that first migration, a journey that began in Africa, continued through India and round the coast to Malaysia.
But did they carry on? After the Malay Peninsula, the land runs out, breaking into a mass of islands.
But using a computer program which models past climate, it's possible to go back in time and see what the map looked like thousands of years ago.
And if we run the climate computer back through time - we're racing through tens of thousands of years here - we can see that those islands are starting to join up.
And in fact a lot of the islands that make up modern-day Malaysia and Indonesia are all joining together to become part of the continent.
They could have got all the way here to Borneo without getting their feet wet.
So much may be lost under the sea.
But there is something.
During the Second World War, Englishman Major Tom Harrison parachuted into Borneo on a special-forces mission.
He encouraged local tribes to use the ancient practice of headhunting against the Japanese.
After the war, Harrison, a keen archaeologist, stayed on and began investigating the legendary Niah cave.
Oh, I've seen pictures of the great cave at Niah, but nothing really prepares you for the sheer scale of it.
Harrison launched a major excavation.
He had a hunch that these caves would have made the perfect home for early humans.
This part of the excavation was known as ''Hell Trench''.
And stepping down into it, it's easy to see why, because it's suddenly very hot and humid.
But all the hard work and the discomfort paid off, because the archaeologists found something that was quite phenomenal.
It's a human skull.
It was in many pieces when it was first found, which have been carefully fitted back together like a jigsaw.
And this is the top of the skull.
It's unmistakably a modern human, it has a high, domed forehead.
The skull has been dated to nearly 40,000 years old, the oldest confirmed remains of our species in Southeast Asia.
But Niah cave also offers us a clue as to how these people survived in the challenging environment of the rainforest.
(BIRDS SCREECHING) As you move just a little bit deeper into the cave, it becomes significantly cooler and more pleasant.
And it just feels like an ideal place for those hunter-gatherers to have set up their camps.
And then they could have gone off roaming into the forest.
The archaeological evidence shows that they were bringing back a huge range of different foods to eat, from monkeys and pigs and lizards, to shellfish, yams and sago palm.
Compared with other species, we're incredibly adaptable.
To survive, we humans will eat just about anything.
And as if to make exactly that point, in another corner of the cave something really unusual is going on.
I've arrived at harvesting time for the ingredient used in the Chinese delicacy bird's nest soup.
It's made from the nests of rare swiftlets, and today these men are attempting a death-defying feat to gather them.
Well, this is human ingenuity, isn't it? A sweet little tiny swiftlet's nest.
It has just been built out from the wall of the cave.
Made of saliva.
It feels a bit like resin or something.
It's very odd.
I can't believe that anybody would want to make soup out of it.
The ability to survive in the rainforest would have helped people spread through these islands.
But discoveries on Flores suggest there may have been another challenge for the first modern humans in this part of the world.
The Indonesian jungle is full of life.
There are animals in there of every shape and size, some of them more friendly than others.
(GROWLING) Every year more species are discovered, and the jungle still has secrets to reveal.
It seems that however much we think we know about the other creatures we share the planet with, there are always new surprises.
Today on Flores, local people still tell stories of strange human-like creatures, the cave-dwelling Ebu Gogo.
So I'd really, really like to know more about the story of Ebu Gogo.
(SPEAKING LOCAL LANGUAGE) MAN: According to our ancestors, there were Ebu Gogo in our land, in our village, a long time ago.
Around the 1 5th century.
Are they humans? I mean, are they like us? MAN: They had two distinctive characteristics - they were like monkeys, but also like humans.
Their physical features were short, hefty, with long hair on the head and chest, and the females' breasts were big and long.
If they wanted to walk, they usually threw their long breasts over their shoulders.
But nobody's seen one for a couple of hundred years? MAN: They really did exist, and they were destroyed by our ancestors about seven generations ago.
(SPEAKING LOCAL LANGUAGE) MAN: There were two reasons for their elimination.
Firstly, because they stole food, and secondly, because they kidnapped our children.
ROBERTS: This sounds like the sort of spooky myths you might hear anywhere.
But believe it or not, this story may actually have some truth to it.
Archaeologists were excavating in this cave on the island, looking for signs of the earliest modern humans, when they made a startling discovery.
At first they thought they'd found the skeleton of a child.
But when they cleaned up the bones, they realised it was actually a tiny adult.
A small-bodied, small-brained creature, a type of human that nobody had ever seen before.
It quickly became known as ''The Hobbit''.
So this is the skeleton of this minute woman that the archaeologists found in the cave of Liang Bua on the island of Flores.
And she is just absolutely tiny.
When she was standing at her full height, she would have reached to about a metre tall.
She seems like an odd combination.
Some bits look like us, but in miniature, other parts look like more ancient human species.
People still are unsure about exactly who she is.
Most people believe that she is, indeed, a different species.
So it really does make us rethink what we think about ourselves and what we think about the whole human family as well.
Could The Hobbit have affected our ancestors'journey? Dating of the bones shows they were here around the time of the migration of our ancestors through Indonesia.
So would they have encountered this race, this population of very tiny people? And what would have happened if they did? I don't know what they would have thought about Homo sapiens.
If they really were the vicious Ebu Gogo, our ancestors might have been best advised to avoid Flores.
But to reach Australia, those early pioneers would have had to face the greatest challenge of all, one that was there even 60,000 years ago.
The deep seas around Australia.
I've arrived in Lombok, one of a string of Indonesian islands, stepping stones to Australia.
Nobody's ever found evidence of a boat from this long ago, but Austrian Robert Bednarik has been trying to work out what sort of sea craft our ancestors might have had.
He's been building prehistoric rafts for over a decade.
His philosophy is simple.
.
his rafts can be built with the tools and materials that would have been available to early humans.
But not all of them have been successful.
That is the most primitive model we've built so far.
This one is the most primitive? Great.
But it's also the most Hopefully, the most effective.
ROBERTS: I hope so, because I'm going to go on it.
Robert has used something that would have been available to the first Indonesians, just as it is today - bamboo.
We know they were clever, so As clever as us.
So if we look around and go, ''Well, bamboo looks great'' - I mean, that's a fantastic material to use - then undoubtedly, you know, they'd have been onto that as well.
We're going to attempt to cross a stretch of open sea to the next island.
It's nothing like the distance to Australia, but an excellent test of the principle.
The raft is very basic.
No sail, no shade.
And nothing to stop the water getting through.
Are we really going to sea on this? Do they think we're mad, going out on this raft? Ask him, go on, now, ask him.
(SPEAKING LOCAL LANGUAGE) Yeah, no problem.
-No problem? -No problem.
-So I'm in safe hands, then? -He say it depend on the weather.
Might there be a storm tomorrow? (SPEAKING LOCAL LANGUAGE) MAN: We cannot say ''no'' and we cannot say ''yes''.
For me, I worry about the sun.
-If hot sun? -Yeah.
(SPEAKING LOCAL LANGUAGE) He worry about the wind.
And he worry of the current coming and we cannot get there.
Okay.
What do they think of the rafts compared to their normal boats? No, they happen like when the boat is -Yeah.
-Yeah.
Losing everything, machine, everything.
-I think -You think we're gonna tip over? -What? -Could it capsize? Yeah.
ROBERTS: The message is clear.
No matter how well prepared we are, the elements will determine our fate.
Which is why the fishermen won't even contemplate this voyage without the help of the local mystic.
We all have to be blessed as protection against the spirit of the sea.
(SHOUTING IN LOCAL LANGUAGE) Just launching the raft is hard enough.
It is incredibly heavy.
It's really heavy, and it was quite an effort to actually get it into the water, but we did it.
And we're now making really good speed.
ROBERTS: Are we headed in the right direction? MAN: I hope so.
ROBERTS: Yeah.
MAN: I hope.
ROBERTS: on a paddle-powered raft, we are totally at the mercy of currents, just as our ancestors would have been.
We think the current should start pulling us north, then as we get halfway across, turn south.
So we won't be able to head straight across.
And if we get it wrong, we'll end up in the Indian ocean.
So what does Robert's decidedly non-Stone Age GPS tell us? -So we're heading north, Robert? -It's excellent.
So we might make it in five hours if we No, no, no, we're probably being pulled by the current now.
Right.
So you think that We're offshore, we're getting this northern current.
So you think the good speed that we're doing is actually the current? Some of the speed is the current, yes.
Okay? I don't believe that we are actually doing this.
(LAUGHS) Does anyone know any good paddling songs? (MAN SINGING IN LOCAL LANGUAGE) What's going on with the seat? It makes me wonder how those early sea crossings happened.
Perhaps families were out fishing and got carried off by rogue currents, and arrived in Australia by chance.
That's better.
or maybe desperation pushed some to look for a new island to live on, but I doubt it was planned.
Australia was far beyond the horizon.
So are the currents going to change direction now? -We don't know.
-We don't know.
Adds an element of excitement.
Makes it difficult to head for somewhere in particular, though.
At the halfway stage, it all seems rather easy.
The plan is working perfectly.
But over towards Sumbawa, trouble is looming.
ROBERTS: I suddenly feel very small in a very big sea.
our destination is an inviting, sandy beach.
But just a few hundred metres from safety, we're suddenly trapped in a rip current, pulling us back out to sea.
(ALL SHOUTING INDISTINCTLY) The current just keeps on dragging us from side to side, and we're headed for this There's a beach right up ahead with some big breakers.
I don't speak Indonesian, but they're saying to me we're gonna do that.
And the beach we've been aiming for is looking more and more distant.
The current just swept us round this headland.
We were level with that headland and heading for the beach.
And now we're gonna have to go and try to go round the other side of the headland.
I don't know.
There's massive breakers there.
It's starting to look a bit nasty.
We've been paddling since daybreak, and now it's starting to get dark.
But as far as the eye can see, there's a line of breakers over a coral reef, stopping us from landing.
The crew is concerned that there is a continuous coral reef here, and to get through those breakers we are likely to hit that.
I'm really worried that we're gonna get swept in by these breakers.
We're getting very close.
MAN ON RADIO: Are you getting too close to the rocks? Copy that.
We're getting too close to the rocks.
We're getting too close to the breakers.
We're going to carry on due south, so straight in the direction we're going.
At last, there's a gap in the reef.
We proved it was possible to cross open sea on a bamboo raft, with no sail or engine.
But it was a frightening experience.
Could our ancestors really have made it to Australia? Today, that's a crossing of nearly 500 kilometres.
Well, I've found a clue that makes me think they could have done it, and even hints at when.
Running the climate-change sequence for this part of the world, I'm particularly interested in what's going on between 60 and 80,000 years ago, because that's the time period at which we think the first Australian colonisers would have been en route.
And there seems to be a remarkable window of opportunity.
At about 65,000 years ago, the sea level drops about 1 00 metres below its present-day levels.
And the distance between Timor and the northern coast of Australia is reduced to 1 53 kilometres.
65,000 years ago.
Could this really have been the chance to cross the sea to Australia? It would make a nice end to that faint trail of evidence that I followed all the way through India and Malaysia, but it is only a suggestion.
Can I find any real evidence that this is what happened? I'm heading through the swamps of the Northern Territories, because it's here in the north that I hope to find clues to the earliest Australians.
I am slightly nervous, Gabby, 'cause there are crocodiles around, aren't there? -Do you think we're safe in this boat? -Yeah, we're pretty safe.
Pretty safe? (LAUGHING) This is the point at which Gabby and an entire BBC film crew put themselves into my hands.
Very slowly.
Getting around in the wet season isn't easy.
There's a fish there.
But at last, this is what I've been looking for.
When you're looking for clues this ancient, they are few and far between.
But this area of Australia is actually rich in a different kind of evidence of early humans.
Evidence of art.
And this is how the archaeologists know.
Well, this is ochre.
And this is ochre in its natural state.
These pebbles form out of the rocks here.
But what the archaeologists have found in a couple of rock shelters here in the Northern Territories, is ochre that has been ground down and used as a pigment.
And they've dated the pigments, and some go back almost to 60,000 years ago.
That's not long after sea levels were at their lowest.
People really might have reached Australia by 60,000 years ago.
Those same pigments are still being used today by Aboriginal Australian artists in recording the stories of their people.
And I'm really keen to meet some of these artists, to find out more about what their art means to them.
I've heard of remote sacred sites where I might find images of their creation story.
Artists Garry Djorlom and Wilfred Nawirridj agree to take me on a trip into the bush.
As we make our journey, they're constantly on the lookout for anything they can use.
What are you looking for, Wilfred? ROBERTS: Oh, yeah! Yeah.
Instant brush.
It's very strange, because I'm sort of looking round and just seeing plants everywhere and you're seeing food.
Bush passion fruit, apparently.
That is like a tiny little passion fruit.
Delicious.
Garry and Wilfred's families have become settled, but they still go off to look for food in the bush just as their ancestors did.
Oh, that's beautiful.
Is it still a special place for you? ROBERTS: Yeah.
Oh, they lived here? A long time ago? So grandfathers many generations back? Yeah.
From here I can see a beautiful view.
But for Garry's ancestors this was a place to survey the land, pick out distant game and plan their meals.
ROBERTS: Eventually, at the entrance to a rock shelter, we come across our first piece of ancient art.
Oh, that's beautiful.
There's so many images, all sort of on top of each other and jostling for room.
ROBERTS: Yeah, yeah.
Right.
So this all represents the sort of animals that you can eat.
Yeah.
But what they've really brought me here to see is further up the hill, deep within these rocks.
It's like a maze.
(CHATTERING INDISTINCTLY) (SPEAKING LOCAL LANGUAGE) Okay.
ROBERTS: Oh, wow! What a strange picture.
What is it? ROBERTS: Right.
So all those little bags hanging from her, they've all got babies in them? And where did she come from? ROBERTS: This is remarkable.
Traditionally, Aboriginal Australians believe they were formed by creative beings who also made their land.
But here on the northern coast they believe their creation mother came from across the sea.
A strange echo of a story told by fossils, stones and genes.
However unlikely it seemed, discoveries have convinced me that these Aboriginal Australians, just like me, are descendants of that small group who left Africa.
And that they really could have reached Australia by around 60,000 years ago.
What seemed an unlikely journey may actually have been one of our first.
So I've come to the end of this particular journey.
And the people I've met along the way have helped me to understand more about the essential human characteristics that we all share - ingenuity, resourcefulness and adaptability.
And for me, the Aboriginal Australians in particular seem to have held on to something I think so many of us feel we've lost in the 21 st century, a really intense physical and spiritual connection with their landscape and environment.
So it's been a journey about retracing that migration from Africa to Australia, but it's also been about what it really means to be human.