(GRUNTS SOFTLY)
Some animals can show emotion.
These unique creatures are reacting to the death of one of their group
with what can only be described as grief.
It is the eldest female, who has eventually lost her fight with malaria.
Beside her body, her three-year-old orphan.
His mother was the most important thing in his life, and without her,
survival in a difficult world will become almost impossible.
This is the northern end of the Great African Rift valley -
a staggering landscape created by fractures in the continent.
This is the cradle of evolution for mankind.
The world has been transformed in the last few million years by one small plant.
Where once there was forest, there are now vast tracts of grassland.
And with grass have come new species of grazing mammals.
At first glance, you might think you were in the 21st century,
but there are important differences.
The big cats are actually of the sabre tooth variety,
although these ones only have small sabres.
And creatures like Deinotherium might look like elephants,
but they are three times the size,
with tusks that curve downwards for stripping bark off trees.
But on the edge of the forest live the most remarkable animals of all.
A type of ape has evolved
that clearly shows the first signs of becoming more human.
What makes them closer to us than other apes is not their brains,
which are only one third of the size.
It's not their skin, which is hairy.
It's something they do that other apes just don't.
Something that will one day lead them to be described as a ''missing link''.
These apes walk upright.
These are Australopithecus.
Go back 200,000 generations, and your relatives would look something like this.
They live in groups with complex social structures
and are also very political animals.
This is Grey, the eldest of the group.
He is 30 years old and the top male,
but only for as long as the females want him to be.
Females are two thirds the size of males,
but Grey needs their support if he wants to stay in charge.
Unfortunately, he's no longer getting it.
(GRUNTS AND SHRIEKS)
With the death of the lead female,
this noisy individual called Babble has replaced her,
and she is no fan of Grey.
Bottom of the heap is the orphaned male called Blue.
At three years old, his social skills are as yet undeveloped.
With the death of his mother, he is becoming an outsider.
But in truth, the whole group has problems.
Last year there were 12 of them.
As a result of malaria, they now number just eight.
This has led to tension within the hierarchy.
A younger, larger male called Hercules is starting to challenge Grey.
These fights are less violent than other primates.
Baboons, for example, have large canines and bite each other.
Australopithecus have small canines and their fights are mostly show.
Grey has managed to put Hercules in his place - for now at least.
One reason that our origins are here in Africa
is that it's an ideal habitat for an upright ape -
a patchwork of forest and savannah.
Unlike many of the creatures here,
the Australopithecus are comfortable in both the trees and the open spaces.
They share the waterhole with Ancylotherium -
an ancient type of animal that was once widespread
but is now only left in Africa.
Fortunately, these herbivores are fairly harmless neighbours...
which is more than you can say for Deinotherium.
These are the biggest animals in the Australopithecus world.
They are as tall as giraffes but weigh 14 times as much.
Even young Deinotherium are worth avoiding.
In the weeks that follow, the males continue their squabbling.
Blue, meanwhile, sits apart. He still has no idea how to integrate.
But this is no time for the group to be divided.
(SHRIEKS AND GRUNTS)
These males are from a larger neighbouring group.
They are challenging Grey for this territory.
Grey responds, but his group is now too few in number
to fend off so many full-grown males.
As the group flees, Blue is in danger of getting left behind.
With no one to look after him, he can only struggle to catch up.
Without the group he won't survive.
Blue HAS kept up,
but for his group, things have gone from bad to worse.
They have been pushed out of a territory they have held for many seasons.
Establishing themselves in a new area won't be easy.
Walking on two legs is an efficient way to travel
and gives the Australopithecus a higher viewpoint than other apes.
This means predators are easier to spot.
Out here in the open, they must be especially vigilant.
The group also needs to stick together - eight pairs of eyes are better than one.
It is four days since they left the forest.
They've been pushed north into less familiar terrain.
Tired from travelling, they notice the Deinotherium too late.
This male is coming into musth.
His body is pumped full of testosterone ready for mating.
Unfortunately, this makes him extremely aggressive.
In the chaos, a youngster has become separated from the group,
and now there is 14 tonnes of angry Deinotherium between him and his mother.
(SHRIEKS)
The youngster is Babble's.
His desperate calls to her are making her blind to danger.
Babble tries to reach the youngster, but she is soon running for her life instead.
Babble distracts the Deinotherium,
but the youngster does the worst thing possible - he continues to call out.
(SHRIEKS)
They very nearly lost another member of the group.
A few days later they have moved on
to a place that appears to have everything they need -
trees to hide in, water to drink and more fruit than they can eat.
And there don't appear to be any other Australopithecus around.
They only have to share the fruit with the Ancylotherium...
and they CAN be scared off if you know how.
(GRUNTS)
Hercules has learnt to use noise to appear more dangerous than he really is.
The group soon start to settle into their new surroundings.
For the first time in a few days, the youngest members of the group are playing.
But some things haven't changed. Blue is still on the edge of things.
Even though the other juveniles are younger than Blue, they ignore him.
With darkness round the corner, it's time to prepare for evening.
Australopithecus sleep in the trees because it is safer,
and make a new nest every night by folding down a bed of branches.
Primates were once all nocturnal creatures, but not any more.
Some have evolved great colour vision,
allowing them to pick out succulent leaves and fruit,
but this came at the expense of their night vision, which is poor compared to most animals'.
So for these apes and, in the future, humans, the night is a time to sleep.
Sadly, the Australopithecus will soon find
that this place is not the paradise it first appears.
(SNARLING)
Blackeye has stolen an egg from an ostrich nest.
Being able to carry things while on the move is another advantage of walking on two legs.
Before she can break into the egg...
Grey steals it from her.
Dinofelis is a killer of Australopithecus.
These cats don't have the speed to bring down fast-running herbivores,
so specialise in slower prey that they can kill easily and eat quickly.
Later members of the human family will rise up the food chain to become top predators,
but in this era, our relatives are prey.
After the attack, the group are quiet and subdued.
Blackeye's death has left a hole.
They spend a lot of their time grooming
to make new social bonds and strengthen old ones.
It's their equivalent of talking.
At last, Blue seems to be interacting with the group
and is learning to play the social game.
He is grooming Grey.
The group's numbers have now at least been boosted
by the arrival of a young female.
While males stay within the same group their whole lives,
female Australopithecus move to a new group when they are old enough to mate.
This prevents inbreeding.
It is a difficult transition for her.
It will take her some time to be accepted by the females.
The males, though, show more immediate interest -
she is a new possibility for mating.
Normally, only the dominant male gets access to the females,
but Hercules looks like he is about to try his luck.
Unlike just about every other mammal on the planet,
Australopithecus mate face to face.
Walking upright has changed the orientation of the pelvis
and, as a result, of the female's sexual organs, too.
Grey has just noticed and isn't having any of it.
Blue's one attempt at making friends has been scuppered.
When there is no fruit in season, the group's diet becomes more down to earth
as they dig for roots and tubers.
Australopithecus are masters of the varied diet.
They have a number of adaptations for feeding themselves -
hands that have become nimble and dexterous,
since they are no longer used for walking on.
Thick enamel on their teeth to help them cope with tough or dirty food.
And ingenuity - Australopithecus can use basic tools like sticks to dig.
They are not born with this ability.
They must learn it by imitating their elders...
and, in Blue's case, his lessons were far from over when his mother died.
He is having to learn fast because no one else is going to feed him.
There is another very important element of their diet...
meat.
Out on the savannah, carrion is quick to attract scavengers.
Often, the Australopithecus are among them.
But they have to be fast to beat the vultures.
In no time at all, they are all over the zebra carcass.
(SHRIEKS AND GRUNTS)
Once again, Hercules tries out his scare tactics...
to great effect.
There is no clearer display of the group's hierarchy than the order they get food.
Grey is used to getting the first bite,
but he finds Hercules is already getting stuck in.
It is nothing short of a coup.
Hercules returns to the carcass as top male.
At first the group are unsure how to react to the change of leadership.
Grey, meanwhile, nurses his pride in the background.
Meat is only a small part of the Australopithecus diet,
but it will become more important in the future for more humanlike apes.
An increase in meat eating will go hand in hand with an increase in brain size.
Meat contains nutrients vital for big brains.
Intelligent apes will develop special tools to get meat
until eventually they'll make weapons
and won't be scavengers, but predators.
Hercules's takeover has an immediate positive effect.
There is less internal conflict than there was before.
But the group's biggest problem hasn't gone away.
It is only a matter of time before the Dinofelis comes back.
Blue is in dire trouble.
Unable to get to the tree in time, he is an obvious target for the cat.
But suddenly the Australopithecus do something extraordinary.
The whole group spontaneously unites
and tries to turn the tables on the hunter.
For Blue, this is an important moment.
Not only has he survived a deadly situation,
something more profound has happened.
He may be the lowest-ranking member of this group,
but he is now at least valued enough to spur them into action. It's a start.
Apes have a long road to travel yet.
Outwardly they are almost human,
but their brains are no bigger than a chimpanzee's.
It will be at least another two million years
before any ape has a decent conversation.
Next time, the lost continent of South America,
a world of strange, exotic giants and a legendary killer -
Smilodon, the largest of all the sabre toothed cats.