This is the story of how we are different
to every other creature that's ever walked the earth...
...and the key to its telling lies with your family.
That's my mother when she was four. That's one generation ago.
Look at the sulky face.
She sulks like I do - she'd just run away from home.
And there's my grandfather wearing his major's uniform.
This would have been about 1916, the time of the First World War.
Then over the page, we've got my grandmother
with her mother Julia, my great-grandmother.
That's three generations ago.
But supposing we could go back not just one generation,
or two generations, or even three generations,
but three hundred generations...
...or three thousand...
...to an ancestor who shared the world with the Neanderthals?
Jump back sixty thousand generations
and we'd meet one of the first people to ever set foot outside Africa.
A hundred thousand generations,
and meeting the relatives would be even more intimidating
than you could ever have imagined!
And that's just what we are going to do - travel through time
to meet the creatures who have become us,
to see how their lives have led to the amazing reality of ours.
Our dead ancestors have left us a key to unlock the past.
With their fossil bones and relics as a guide...
...scientists can build up a picture
of what it would be like to travel back in time.
If all the apeman fossils in the world were collected together,
I could probably fit the whole lot in the back of this car.
Yet each little fragment tells a tale about the world of which it was once a part.
These tiny pieces hold secrets not only to how our ancestors died...
...but to how they lived...
...from our closest cousins, the Neanderthals,
to the first fierce Europeans...
...from our ancestors with the wit to survive in the jungles of Asia...
...to the first true families who worked together in sun-baked Africa.
We're journeying back in time,
revealing the secret ingredients that make you and me unique,
and meeting the first creatures to have them -
the earliest toolmakers,
the heavyweight contenders who shaped our past...
...right back to see for ourselves how you and I came to be.
The first clear place our fossil guide takes us is here.
We've travelled three and a half million years into our past,
as science sees it,
to meet a creature who began the journey from ancient apes to us,
in Africa... in this tree.
This is your distant relative from 300,000 generations ago -
Australopithecus afarensis. They're nesting for the night.
This one has a special role in the story of you and me.
We'll call her Lucy. She's special to someone else as well -
her infant, born a few days ago.
Lucy's troop is engaged in a turf war -
a potentially violent territorial dispute.
In the morning, it will change their lives forever.
For afarensis, like apes of any time,
filling up with water is an important mission of the morning.
But there is something that sets these creatures apart from other apes -
the first step on the journey to us.
They can stand and walk on two legs.
This is the troop's most senior male.
He's also the father of Lucy's infant.
He is 25 years old and in his prime.
He could live as long as fifty years.
That's ancylotherium, a cousin of the rhino.
In this prehistoric world,
it's the leader's strength that holds the troop together.
But if you think standing on two legs
makes our ancestors king of the jungle, then you're wrong.
Aside from walking upright,
there's nothing very remarkable about these creatures at all.
They are as subject to the laws of nature as everything else.
Yet Lucy and her kind are the ancestors of you and me.
To discover exactly what makes them so special,
we must watch them rather more closely.
Lucy is twenty-two.
She's mother not only to her new infant,
but to several others in the troop, including this adolescent female...
...who also makes a handy babysitter.
(WHOOPING CRY)
The sound is an unsettling one. It's afarensis - but a rival troop.
Several times, Lucy's troop's territory has been invaded
in a battle for its rich pickings.
Losing their leader presents another problem -
two males are contenders for the throne.
He is the quiet man of the troop, dependable and solid...
...whilst he is brash and impulsive.
Now they're driven to work together.
A patrol party must be organized -
and the males will rouse themselves into a frenzy of display to form one.
An afarensis troop has a territory much like a modern chimp's -
perhaps ten square miles, bounded by rivers and mountains.
Though the adults know their way around well,
a crossroads is a flashpoint for the leadership battle to begin.
The first skirmishes are noisy displays.
(GRUNTING)
The eventual winner will gain respect,
and privileged access to the troop's females.
Meanwhile, the rival troop is surprisingly close by.
These reed beds form the overlap
between the neighbouring afarensis territories.
Normally, neither troop comes here, as it isn't good for fruits and food...
...but these intruder males are on the trail of something different...
...Lucy. Probably while foraging nearby, she's disturbed them.
An isolated afarensis is always vulnerable.
The intruder males will seek them out
and attack them to warn off their troop.
At just over a metre tall,
a female like Lucy is an easy target.
If they found her now, they'd almost certainly kill her.
It's a lucky escape.
With the trail cold, the intruder males move on.
The river marks their southernmost borders with Lucy's troop's land.
It also makes a handy refreshment stop.
And not only for the intruders.
By pure chance, the patrol party from Lucy's troop have also stopped by
for a drink.
As with rival apes of any time, the encounter provokes a face-off.
(AGGRESSIVE GRUNTING AND SCREECHING)
With the water between them, actual bloodshed is unlikely.
Instead, displays of noise and power are the order of the day...
...which is lucky for Lucy's males, as the intruders have arrived in numbers.
If they were to meet on different ground,
one might see a pretty uneven fight.
The more you watch these creatures, the more like apes they seem,
so why, in the one crucial aspect, are they so very unlike apes?
What on earth could have happened to make an ape stand upright
and walk on two legs?
Well, what happened is...
...the world changed.
Come with me and travel even further back in time,
before even afarensis was around...
four, five, six million years ago, and further still.
We're still in Africa, but it's eight million years ago...
...and home to the tree-living ancestor of Lucy and her kind.
We've never found any fossil evidence of these mysterious apes,
yet we know a few vital things about them.
We know that, like the apes in modern times,
they use their hands as well as their feet to help them get around.
We know that because it's the only way to get around in their dense forest home.
And how do we know this forest is their home?
Because this forest is everywhere!
Eight million years ago,
Africa is covered in thick forest almost from edge to edge,
and it's the forest and what happens to it
that holds the secret to why an ancient tree-swinging ape
was transformed into a two-footed afarensis.
The shift from creatures who move around on four limbs
to those that walk about on two
is so dramatic that it can only be achieved
by an equally dramatic change in the world around them.
And that change is being driven from thousands of miles away,
deep beneath the sea.
Here, the ocean floor is expanding.
At about the speed that fingernails grow,
the earth itself is on the move.
It's changing the face of the planet.
A vast chunk of the earth's crust has been pushed to the north.
One day, we'll know it as India.
Deep underground, as it collides with Asia,
it creates a twisted mass of rock.
Five miles high and three thousand miles long: The Himalayas.
The mountains are having an extraordinary effect on the weather.
They've prompted some of the heaviest storms ever seen -
the monsoons.
The rains strip the air of moisture,
so that the air currents that reach Africa
are not wet but dry.
Rainforests retreat and a new world is created.
Over millions of years, a landscape of scattered trees takes shape.
And something else has changed the scenery.
A vast chasm,
the great Rift Valley, has ripped down one side of Africa.
Everything from beetles to apes
has had to keep pace with this incredible change.
Our tree-swinging ancestors have evolved and transformed.
Forced to spend more time on the ground,
they've become the upright walking afarensis we've met, like Lucy.
But why use only two feet to get around on the ground?
It's easy to think that being upright brings obvious advantages.
Lucy can stand taller and see further...
...but that also means everything else can see her.
It's a black eagle,
an expert aerial hunter. An adult afarensis is too big to take on...
...but where there are adults, there are infants.
Two legs have, in fact, made Lucy neither quicker nor safer.
So what is the advantage to afarensis
of walking upright in this new world?
The truth is, walking on two legs
became a defining feature of my life and yours
for the most surprising of reasons.
Ultimately, it's all about sex.
The males have returned from their patrol.
They must have tired of their face-off with the intruders.
With security looked after, it's an opportunity for the troop
to get about the serious business of grooming and building relationships.
With Lucy's regular mate gone, she attracts immediate attention.
It's one of the leadership contenders - the quiet one.
In the natural world,
sex and raising babies is the key to a species surviving...
...so that anything that gives you extra energy to do it better
is like gold dust...
...and extra energy is what walking upright has given afarensis.
In this mix of trees and grass, walking on two legs is more efficient than walking on four.
The energy saved by changing from a four-legged way of life is tiny.
The total number of calories saved by afarensis in a year
is probably no more than that found in a packet of chocolate biscuits.
But even such a tiny amount makes a difference.
Lucy is able to recover that bit quicker after giving birth.
It could mean, in a lifetime, she could raise just one more baby.
And one more baby might be the difference
between survival of the species and extinction.
The rival troop are on the move again, this time from the west,
and once again,
patrolling takes priority.
But not all the males are going to investigate.
It's the brash would-be leader. He, too, has his eye on Lucy.
All the attention is not simply to do with sex.
To become the dominant male, he needs the support of the troop...
...and any chance to be alone with a high-ranking female like Lucy
is not to be squandered.
But his advances catch Lucy unawares,
and his position between Lucy and her baby adds to her alarm.
Suddenly, the situation is out of control.
It's become a fight for leadership.
(SHRIEKS AND GRUNTS)
The fight takes an unexpected twist.
The brash contender grabs Lucy's infant.
Whatever he hopes to achieve, the stakes are raised dangerously.
It's the rival troop. They've come right into Lucy's troop's territory.
With the new enemy surrounding them, the infant is instantly forgotten...
...except, of course, by Lucy.
It's Lucy.
An ape, not particularly clever, not particularly quick,
with only a small advantage in energy use,
who lived and died without ceremony here in the African bush.
It's not much of an epitaph,
but Lucy has begun the journey to you and me.
Her hands were in life little more than climbing tools,
but in generations to come, they'll find a million uses.
They'll search out food for a growing brain
and one day make tools to change the world around them.
And, freed from the task of helping her move,
the muscles of her chest will help her descendants to speak.
Dee!
A-wah.
Her adaptation, standing on two feet,
opens doors for the future.
She is, indeed, just an ape, but an ape with potential.
Knowing that her story will end in us,
is there anything else we can see in these creatures
that we will one day inherit?
Perhaps.
Is it something like love
which keeps this baby clinging to its dead mother's fur?
(SHRIEKING)
Is it the beginnings of what we know as grief
that you can hear in the troop's strange calls?
Certainly, there's some behaviour we'd like to think of as human.
It's Lucy's elder daughter.
She's come for the baby.
If she adopts it within the troop, there's a chance it might survive.
These creatures have taken the first step on our human journey.
In a few hours' time, it'll rain.
The waters will rise and will claim her body...
...and in just over three million years, she'll be found.
In 1974, scientists will dig up her fossilized bones,
and will call her after the song playing on their radio at the time -
"Lucy in the Sky with Diamonds", by The Beatles...
...and Lucy and her kind will set the world alight,
not because of what they are now,
but for what they will make possible.