Lucy Prehistoric Autopsy

Hello, and welcome back to Prehistoric Autopsy.

Here, at Glasgow University, we've been piecing together the bodies

of some of our most iconic ancient relatives.

Tonight the spotlight is on one of the most famous.

She's called Lucy and she lived over three million years ago.

For months we've been painstakingly rebuilding her skeleton.

Once again, we've consulted international experts

and used the latest research...

That's amazing, we've got a very, very different pattern

-in the way the forces are spreading throughout the bones.

-Yeah, yeah.

Here is an individual still growing its brain

and still learning from their parents.

..and we find out if our primate relatives hold any clues

as to how Lucy might have communicated.

-There's one here who is going...

-HE TUTS

-This is the lip smacking behaviour.

-Friendly?

-Yes.

We're going to find out just how important she was

on the evolutionary road to becoming human.

So, let's go inside and get started.

So far we've met a Neanderthal, La Ferrassie One,

and a member of the species Homo erectus, Nariokotome Boy.

Tonight, we're going to use these few bones, here,

to build one of our early bipedal ancestors.

In other words, someone who routinely walked upright.

So, how far have we come? Well, it's been quite a journey.

We started here in 2012 with us, Homo sapiens,

the ONLY species of human on the planet.

But you don't have to go back very far

to find we were sharing the planet with other species,

including a Neanderthal like La Ferrassie One.

We found out that they were good hunters,

probably had language and, although they eventually died out,

some of their DNA lives on in many of us.

Then we travelled further back, 1.5 million years ago,

to meet Homo erectus.

He's one of the first humans to look a lot like us.

He was a good runner with long legs,

he used tools and he could probably control fire.

Tonight we are going even further back

and to do that we are going to have to shrink the scale down

because the bit we are interested in is round about here,

3.2 million years ago,

and we're going to meet a female Australopithecus afarensis called Lucy.

But why did our ancestors leave the trees

and what did they trade for the ability to walk on two legs?

To try to get some answers we've got our lab up there, on the balcony,

where we'll be examining how these ancestors walked.

And over here is our experimental area

where we will be putting our ancestor's teeth to the test.

Paleoartist Viktor Deak and our team of model makers

have drawn on all this research to help them reconstruct Lucy.

There's very little of her skeleton to go on

and the team have spent weeks carefully rebuilding it, bone by bone.

Along the way we have gained an extraordinary insight

into how she walked, what she ate and even how she gave birth.

Lucy's species lived in Eastern Africa

between three and four million years ago.

When her skeleton was discovered it transformed our view of human evolution

and the man who discovered her is Professor Don Johanson.

He was working out in East Africa in 1973

when he came across a fossilised bone that eventually led him

to the skeleton of one of our early bipedal ancestors.

I caught up with him at Oakland Zoo, in California.

PRIMATE HOOTING

-What I saw was that...

-I mean, that's not much to go on!

..sticking out of the ground and I didn't think much of it.

I looked at it and I tapped it with my sneaker

and out fell this bone

but then I walked a couple of feet further and I looked down,

and found this bone, which is the bottom end of your thigh bone.

And when I put them together, like that, and looked at it,

I could see the characteristic angle of the shaft

-that comes with being a biped, walking upright.

-In a straight line?

In a chimpanzee it would be in a straight line,

in a baboon it would be a straight line,

but in a human it's at an angle.

'This single knee joint had enormous implications.'

All other primates,

in fact, all other mammals on the planet, walk on four legs

and we walk on only two legs.

So, to be able to find a bone that was,

that testified to the fact that these creatures,

these early humans at 3.4 million, was walking upright,

justified its placement on the human family tree,

rather than the ape family tree.

One year later, in 1974, Don returned

and made an even more remarkable find.

And a little glint of bone,

tiny little fragment of bone, caught my eye

and then I saw a shard of skull and a chunk of mandible,

and I looked up the slope and I could see other bones eroding out

and I thought, "My God, this is part of a skeleton!"

He'd found the most complete skeleton

of one of our early ancestors.

It was an extraordinary moment because at that point,

in terms of the search for human origins,

anything older than four million years,

you could put those remains in the palm of your hand.

There was a single tooth, a fragment of jaw,

a bit of arm but nothing else. This was really the childhood dream.

This is the dream I had as a kid.

Going to Africa, finding a skeleton, finding more than just a bone.

Don gave the skeleton a name.

Lucy, why did you call her that?

Well, I've always been a great fan of The Beatles

and I had a Beatles tape playing in my little tape recorder,

and Lucy In The Sky With Diamonds was playing,

and my girlfriend on the expedition said,

"Well, if you think it's a female, why don't you call her Lucy?"

And that's how she got her name.

Well, what a discovery.

Tonight, to help us turn those few bones that Don found

into a life-size reconstruction of Lucy

we're joined by Professor Carol Ward from the University of Missouri.

And Carol knows Don and Lucy really well, don't you?

I do, we've all worked together for many years!

So, tell us a little bit about her.

She is the smallest Australopithecus afarensis that we have.

She is minute.

How about her age? Any idea on her age?

Well, we can tell that even though she is small, she was fully adult.

When you look at the bones and the teeth, you can see signs of age,

for example, she has her wisdom teeth in.

So that is about a modern human 20-year-old, or so.

But on the long bones,

we can see that her growth plates would have been completely fused up.

No sign of a growth plate.

So she wouldn't have gotten any taller.

That happens when we get to be at the end of our teenage years.

-So, she is a young adult?

-She is a young adult.

Her teeth weren't too worn down so we know she wasn't very old.

-Maybe 20 years old or so.

-Yeah.

It is really interesting comparing her with that chimp.

It is really small. Because if you compare that

to that upper arm bone of the chimpanzee,

it is smaller, isn't it?

Yes. She is tiny, really tiny. But we know that she stood upright.

So, how tall would she have been?

About the size of a three-and-a-half-year-old child.

-So, very, very small. Smaller than that chimp if it stood up.

-Yes.

She is very, very tiny.

We are comparing her to a chimpanzee

and there is a good reason for that.

We know that we share 98.8% of our DNA with a chimpanzee.

Yes, we are both modern animals. Chimpanzees aren't our ancestors,

but it is still useful to make these comparisons.

We share a common ancestor with chimps.

Around five to seven million years ago we split.

The ancestors of chimpanzees took one evolutionary path

and our ancestors took another.

Around the time of the split much of Africa was covered in dense forest.

Our closest living relatives

are still well adapted to this environment.

When I visited Kibale Forest in Uganda,

I tried following one of them.

It looks as though they are moving quite slowly

but I can assure you they're not!

This is a fairly fast pace to be moving through the jungle.

'So, if getting around on all fours is so efficient

'why did our ancestors begin to walk upright?'

The answer could lie in the way that the world's climate was changing.

Around three to four million years ago in Eastern Africa,

where Lucy's species lived,

the thick jungle was gradually being replaced by open savanna.

And it was this changing environment

that may have contributed to Lucy's species

spending more and more time on the ground, walking on two legs.

So, what did she look like?

Well, these bones are really wonderful.

They are an incredibly accurate cast of Lucy's skeleton

and they are the starting point for our reconstruction.

Viktor is our paleoartist.

Viktor, there is really not that much to go on with Lucy.

We have 40% of her skeleton

but there are lots of missing bits as far as you are concerned.

So how are you filling it all in?

What I am doing is,

because Lucy is similar to humans in some respect, I am using

a modern human skeleton to help me infer some of the missing pieces.

I have mirror-imaged certain bones to fill in the gaps.

Wow! Fantastic. This is just a virtual skeleton

but a team in America have filled in some of the missing parts

using other fossils and making a physical model of the skeleton

which we are going to use

as the basis for our own reconstruction of Lucy.

We had a copy of it delivered to our model-makers' workshop

and I went down to help them put it together.

Jez Gibson Harris is in charge of the team.

Cast in plaster, these bones are an exact copy of the originals,

which are kept under lock and key in Ethiopia.

So the brown parts are casts of the original fossils.

So they have been painted

so that we know that that's what the original fossil was.

And then the white parts are the reconstruction.

But that will have been based on other fossils.

-Isn't it amazing how narrow her jaw is?

-It is very small.

-But the teeth are huge.

-Yes.

All we have to do now is assemble it.

It is quite nerve-racking

having got this amazingly accurate cast, to then start drilling into it!

Everything is hanging off the skull and the spine.

I just want to check something else,

which was the angle that these would fit onto the apron.

This is a very close-fitting joint.

It is a question of getting that anterior edge,

the front edge here, matching up.

-OK.

-So it kind of feels right. It locks in.

'But with important pieces like the rib cage, hands, and feet missing,

'there are still a lot of questions to answer.'

Ancient skeletons are often found without hands and feet

because they are small bones and the first to disappear.

But luckily there are other ways that we can find out

how our ancestors walked.

-And George, you are finding out, up on the balcony.

-Absolutely.

I am up here in the lab

with Professor Robin Crompton of the University of Liverpool.

Robin, you are one of the world's experts

on the bipedalism of afarensis.

What have we got here?

What we can see in front of us is a small section

of a series of footprint trails from the Laetoli area in Tanzania.

And you can see one small trail representing a young individual.

And next to it, a larger trail which we think represents two adults,

with the second adult treading in the footsteps of the first.

-So it's a family group?

-It's a family group.

And rather nicely, they may have been holding hands.

How do we know that these footprints

were made by Australopithecus afarensis?

To the best of our knowledge there is only one species present at Laetoli

at 3.65 million years ago, and that is indeed Australopithecus afarensis.

How did it form?

There was a nearby volcano called Sadiman

which occasionally erupted and produced volcanic ash.

The layers appear to be about 20 centimetres deep.

And they get wet, the moisture seeps through the ash layer,

and becomes cemented and rigid,

so that the footprints can form clearly above it.

And extra ash from the volcano falls on top, and seals this in time?

Exactly.

-How would my footprint compare to these?

-Let's have a look.

I thought you might say that, actually!

What I'd like you to do is go to the end of this trackway here,

and, I'm afraid, take your shoes and socks off.

What we have got is a little short section of sand.

To get you used to the feel of sand under your feet

before you tread in the ash layer,

which is the closest mimic we can produce for the Laetoli deposits.

That is what you are after?

A nice, even short stride, with, if possible, both feet in the ash layer.

Right. I am going to walk as if ambling along a volcanic ash bed.

There we are. Fantastic. Right, well, you have got two there.

You've got a left and a right.

-What happens now?

-OK, let's scan them.

And we put the rather Heath Robinson arrangement on top.

I like that, it's good.

Laser scanner.

And we should be set up.

And here we go.

This is really hi-tech stuff.

That helps you make a completely accurate 3D image of my footprint?

Absolutely.

-And here's the image.

-There it is!

Now we do some analysis using other software to bring up the image.

I hope that's me in the middle.

That is indeed you in the middle, with a lovely high arch

-demonstrating you're undoubtedly a human.

-And that is afarensis?

That is afarensis.

What you're seeing here is the deeper the red,

the higher the pressure. You can see in particular,

and most importantly, a large, deeper impression

under the heel which is absolutely diagnostic of upright walking.

Excellent.

And here we have a bonobo, or pygmy chimpanzee.

Look at the difference.

Afarensis and me, our big toe is much in line, parallel...

We've closely adapted, or brought into the other toes.

They are giving push-off force to the ground

and there's very little of that in the bonobo.

The Laetoli footprints show that Lucy, and her kind,

had traded their opposable big toe for an arched foot like ours

and were walking upright over three million years ago.

And that's not all, there were other footprints,

some from hyenas and even Deinotherium.

Ancestors of the modern elephant, they were around four metres tall

and weighed up to 18 tonnes.

For little Lucy, and her kind, this would have been a dangerous place to walk around in,

but walk they did.

Well, it's not just our feet that were changing,

not just our ancestors' feet that were changing,

it was other bits of their anatomy as well.

And we should have some animations coming up.

Now, this is a human walking along,

and we can see that we walk with a nice, straight leg.

And one of the key bits of anatomy is up here,

these are the abductor muscles on the outside of your hip joint,

and they stop your hips swinging from side to side as you're walking.

-Robin, that's a chimp over your end, isn't it?

-Yep.

Completely different gait,

so that's very bent, very bent hip, bent knee.

Really, what you can see in the chimpanzee is

the strong flexure of the knee,

bringing all the force of the body down behind the knee

and in front of the foot.

Now this is continually flexing the knee joint

and this is what makes that sort of walking so inefficient.

-That looks very inefficient...

-It does, yeah.

..with this rotating hip. It's very hard to do.

One of the reasons is if you stand in this sort of posture,

gravity's continuing to flex your knee

and your muscles at the front of your thigh work harder and harder

to stop you bending more and more and it becomes very tiring.

It's very tiring and your knees start to shake.

So it's much more efficient to actually straighten your legs.

-It's more efficient to stand that way and walk this way.

-Absolutely.

-And so who's this in the middle, then?

-That's Lucy.

So this is how Lucy would have walked?

I would say a little bit more straight-legged than that too.

-Even more straight-legged?

-More straight-legged than that.

There's a slight swing of the hips, isn't there.

There's basically a broader hip than we would have had.

I think we need to emphasise that chimpanzees

are NOT our ancestors and we're using them as a comparison.

It seems that what we've got here in Australopithecus afarensis

is something which is almost halfway between a very chimpanzee-like

way of walking and a modern human way of walking.

Well, looking at the anatomy of Lucy's feet,

knees and pelvis, it suggests she's spending lots of time

walking on the ground.

But some new research has been looking at another bit of her anatomy - her hands.

And this may shed some light on how much she was using THEM for climbing.

Even though I'm a human and well adapted to walking on the ground,

I'm still a primate and I can climb pretty well.

This is quite unapelike this first bit...

climbing up a ladder.

There's no doubt that our ancient ancestors spent a lot more time in the trees than we do.

So when did they decide to trade life in the trees

for life on the ground?

Now, I'm really excited by some new research which is looking

not just at the shape of bones but looking right inside them

at their detailed architecture and it has the potential

to give us a new insight as to when our ancestors came out of the trees.

It seems the way that we use our hands,

in climbing a tree or gripping a tool

may be recorded within our wrist bones.

I've come to Powell Cotton Museum in Kent, where I did work for my PhD.

It's home to one of the most important primate study centres in the world.

'I'm meeting paleoanthropologist Professor Gabriele Macho.

'She's been studying the wrist bones of modern chimpanzees and humans

'and comparing them with wrist bones from Lucy's species,

'Australopithecus afarensis.'

Gabriele, specifically which bones have you been looking at?

We have been looking at the capitate,

which is the biggest bone of the wrist,

and it's sitting right in the middle here

and it's along the main load transfer from the middle finger

-to the upper arm.

-Right.

'Gabriele has been putting capitate bones into a CT scanner

'to reveal the internal structure of trabecular bone.'

In a little bone like this you get a very complex arrangement

of trabecular bone.

And it's no coincidence that it is also called the spongy bone.

-It looks like a sponge.

-Of course, it's completely hard.

It's amazing when you look at these little tiny bones

and the complexity of the structure on the inside,

-all this scaffolding inside them.

-Absolutely!

'Having made CT scans of capitate bones,

'Gabriele applied the same computer modelling

'that aircraft manufacturers use to analyse stress on aircraft wings.

'This showed where the spongy bone had been reinforced

'to cope with the forces applied to them.'

The difference between the two bones is quite striking.

In the chimpanzee you see the red loads travel towards the left side

-and this is the side where you have your little finger.

-Right, OK.

And in the modern humans, see it quite nicely,

it is travelling towards the thumb side.

'So chimps show evidence of reinforcement

'on the little finger side of this bone

'because that is where the loading is greatest when they climb trees.

'But in humans, who use their thumbs far more,

'the loading is on the thumb side of the bone.'

That's amazing, so applying these virtual loads we've got a very different pattern

-in the way the forces are spreading throughout the bone.

-Yeah.

This technique could reveal how much time ancient species

spent in the trees.

Next Gabriele looked at capitates from Austraolopithicus afarensis,

the same species as Lucy.

She also analysed capitates from another slightly older species,

Australopithecus anamensis.

So looking at this anamensis capitate,

this does look like it's loading on this side, on the little finger side,

-just like the chimpanzee.

-That's correct.

And in afarensis the loads start to travel towards the thumb's side.

What does that mean in terms of what these species

would have been doing with their hands?

Anamensis probably climbed the tree,

either for shelter, for protection, sleep, or for feeding purposes.

By 3.5 million years, when you come to Australopithecus afarensis,

they were mainly using the terrestrial habitat.

So what do you think about this wrist bone, then?

Because that's what we were looking at in the film,

was this little tiny capitate bone,

and the differences between the capitate bone,

which comes from just there in the hand, in afarensis and anamensis.

What we may be seeing is a process of evolutionary change.

Not all animals change all body parts at the same rate and time in evolution.

Do you think we can still say that Lucy's kind

was spending less time in the trees,

or do you think it's difficult to argue that

based on just what we've got in the fossils?

I think that would be a tough thing to argue right now,

what we need is more fossils.

It's really interesting, isn't it?

We always need more fossils!

The cry is always, "more fossils"!

What I find fascinating is, is the way we are talking about this mosaic model of evolution.

It's not like things all arrive in a package.

Bits of the body are changing at different times

and species are adapting bits of themselves to changing environments over time.

Exactly, and that's partly how we know they're different species.

They're using the environments in different ways, in different parts of the world.

Well, there's one bit of Lucy's anatomy that could tell us

so much more if only we had it - her hands.

Unfortunately, we've only got a few of her finger bones.

'So the challenge for our model makers was how to recreate

'this key part of Lucy's anatomy for our reconstruction.

'I went down to their workshop to find out how they were getting on.

'They'd been to America to scan a replica Australopithecus afarensis hand.'

-Are you Matt?

-I am. Nice to meet you, Alice.

-Nice to meet you too.

-So, this is Lucy's hand.

-This is it!

'With this data, designer Matt is able to build a physical model

'using a process called stereolithography.'

So this is a very technologically advanced photocopier?

Yes, well, sort of.

It's already looking like a hand, it looks fantastic.

'Four hours and several cups of tea later, the hand is complete.'

That looks really odd. It looks kind of slimy.

Well, that's the support material you see in there.

-That's the stuff you've got to peel away to reveal the model bones inside.

-Right, OK.

-But the actual print of the bones is inside there?

-That's right.

'All that remains now is to carefully remove the bones from the printer

'and clean off the support material.'

Right, so hands in here, into the rubber gloves.

Wow! Oh, my God!

-Nothing's coming off.

-Go a little bit closer.

It should almost act like a blade.

Ah, this is so satisfying. Look at that.

That's lovely, so you can really start to see the detail now.

That little hand, that's lovely.

'With both hands finished, we finally have all the elements

'we need to complete our Lucy skeleton.'

And here is our finished reconstructed skeleton.

It's wonderful.

It's fantastic to see her standing up. It's great.

-It's lovely.

-And she's really tiny.

I think when you put all the bones together like this

you suddenly realise how small she really is.

What always impresses me is how you can reconstruct this

from just a tiny handful of bones.

And she's got a quite nice straight leg there,

-so I think Robin would be happy with that.

-Very happy.

-She's knock-kneed, her knees are right under her centre of gravity.

-That's lovely.

The way the femurs are sloping in towards the knees here.

And the beautiful curvatures in her spine,

which is something that only humans have, you never see in apes.

So why did our ancient ancestors choose to walk upright?

The forests were retreating and out on the savanna

they were easy prey.

Walking meant they could travel further to find food

and it freed up their hands.

Walking on two legs clearly has advantages

but it comes at a price

and it's one we're still paying today.

Well, over here we have Professor Karen Rosenberg,

from the University Of Delaware.

She's been studying this part of Lucy's anatomy very carefully.

So this is a modern human pelvis,

and it's a completely different shape from the chimpanzee.

It's completely different because of the way that we walk.

As bipeds we've had to modify our pelvis completely

in order to walk on two legs, which a chimpanzee doesn't do.

I mean, this is like a blade.

-In fact, we do call this the iliac blade, don't we?

-Exactly.

And in us it's formed a kind of basin shape.

-It's a completely different shape.

-Completely different.

And the birth canal is completely different as well.

In humans, the birth canal, which is here, is wide at the top,

and then long at the mid-plane in the middle,

and then approximately round at the outlet.

And chimpanzees are long in all dimensions,

-so it's quite a different shape.

-So do chimpanzees have any problems giving birth?

Apparently not, apparently they have a pretty easy time.

The baby's head is much smaller than the birth canal

and it seems to go through in a pretty straightforward way

without a lot of difficulty.

So, do you think that the changes to the human pelvis,

that have come about because of this adaptation to walking on two legs,

-have had a knock-on effect for childbirth?

-Huge effect for childbirth.

And not just the modifications for locomotion,

but it's because we give birth to babies with large brains.

Yeah, that's a bad bit of design, isn't it?

-A very bad design.

-OK.

So, babies with big brains would have come along a bit later,

after Lucy's kind, but over here

we've got a reconstructed Lucy's pelvis. I think it's very useful

to see the pelvis in the round with the sacrum at the back as well.

Now, first of all, it's very, very tiny,

but I think if I put it in the middle there,

I think that looks more like a modern human pelvis

than it does like a chimpanzee.

-It's looks nothing like a chimpanzee pelvis.

-Absolutely.

The modifications that happened because we walk on two legs

had taken place obviously by the time of Lucy,

and so the pelvis looks much more similar to a modern human.

But it doesn't look exactly like a modern human.

And that's because the birth canal didn't have to give birth

to a large-brained baby.

So do you think Lucy would have still been able

-to give birth relatively easily, then?

-Relatively easily,

but differently than in a chimpanzee.

How have you been able to work that out and how differently?

Well, quite differently.

If we look at the way that modern humans give birth.

So this is a newborn baby, by the way.

This is a model of a newborn baby.

In modern humans, the fit between the baby's head

and the baby's shoulders and the birth canal is quite tight,

as lots of people know from personal experience.

Yes, I know it from personal experience!

The baby's head typically enters the birth canal facing to the side,

-like this.

-Yeah.

-But then it usually gets stuck.

So it usually turns, rotates, 90 degrees,

and emerges like this...

..so the back of the baby's head

is facing to the front of the mother's body.

So the mother can't easily reach down and clear

the baby's breathing passage, or move the umbilical cord if it's around the neck.

Those are things that, in other animals,

the mother can do for herself,

but it's more difficult for humans to do.

Humans are typically, almost always, born with another person helping.

So with Lucy's pelvis, then, why do you think it would have been

difficult to get a baby out through Lucy's pelvis?

Because her babies would have had much smaller heads than ours.

Yes, but Lucy's pelvis and Lucy's birth canal in particular

is different from both modern humans and a chimpanzee.

It's like a modern human in that it's wide from side to side,

but then, it has that shape all the way through.

-So her baby wouldn't have twisted around in the same way?

-Exactly.

And not only didn't need to turn and twist,

it probably couldn't turn and twist.

This is really interesting.

It means that in order to stand and walk upright on two legs,

Lucy was paying a price.

She was paying a price in that it made childbirth more difficult.

Absolutely.

This is all about babies fitting through birth canals.

There are things on the outside of the pelvis as well,

and that's what I want to have a look at next,

so let's go over and see Viktor,

who should be putting the muscles on the outside of Lucy's skeleton.

That's lovely, Viktor.

Yeah, I mean, she's a strong little female.

And we're really kind of getting

an idea of her proportions there as well.

She's got quite short legs and long arms,

especially compared to Nariokotome Boy.

Right, absolutely. Her skeleton shows a lot of virgosities.

It means that she had strong muscles in certain parts -

-forearms, shoulders.

-And you're reflecting that.

So she is quite well-muscled, isn't she?

She's really starting to take shape.

Imagine her walking along on that volcanic ash

-in Laetoli and making those footprints.

-I know.

When you're reconstructing this,

you're not just thinking about the muscles and skin

and all that, but their lives and what affected them.

-She's really starting to take shape. That's great, Viktor.

-Thank you.

Down in the model-making workshop,

the team use Viktor's digital prototype

as a starting point for the final reconstruction.

Following his advice, sculptor Reza began to put flesh on the bones.

She's looking great so far.

My biggest suggestion might be

to tone down the thickness of the calves,

cos you get this from a lot of running,

and while Lucy definitely had the ability to run,

-her calves may not have been as developed.

-Right.

However, her thighs would probably still stand to be developed,

because either climbing and walking, they're going to be strong.

The gluteus looks good. It's flat and broad,

really following what the anatomy of the pelvis is showing,

so you've done a really great job at capturing that.

It's painstaking work, and Reza's job now

is to build Lucy from the bottom up before the next stage

in the model-making process can begin.

Well, we've discussed her pelvis and childbirth, but until recently,

there was very little information about afarensis children.

But all that changed six years ago

when a dramatic new discovery was announced.

Found buried beneath the sandstone of Ethiopia's Dikika region

were the remains of a fossilised child.

From the same species as Lucy,

this child was just three years old when she died,

but lived 3.3 million years ago.

It's a discovery that's given us

more information about how Lucy's species moved.

But more importantly,

it's cast light on a fundamental aspect of being human - childhood.

To meet the man who freed this child from her sandstone tomb,

I've come to the California Academy of Sciences in San Francisco.

Paleoanthropologist Professor Zeray Alemseged is still

researching his once-in-a-lifetime discovery.

Known as Dikika Baby, these exact casts of her tiny bones

hold clues to the origins of one of our oldest ancestors.

What makes this find so special?

This find is simply unprecedented because it has a face.

When you have a face like this, you are basically looking at a child

that lived 3.3 million years ago.

You can actually look straight into her eyes.

She looks at you too.

But when this child was found, she looked nothing like this.

Her entire remains were completely encased in sandstone.

When found, only this cheekbone was sticking out of the sandstone.

That is amazing.

It took Zeray years of painstaking work

to remove the sandstone rock with a dentist's drill -

one grain at a time.

This represents three years of work.

Three years of work removing sandstone grains,

a grain at a time?

A grain at a time, and there is no short cut.

You can now see the skull,

you can see the jaw...

And you can see the spinal column at the back...

..folded round there.

..which was almost invisible here.

Zeray cast copies of the bones at every stage of the process,

and it took him a total of eight years' labour

before the final result was revealed.

What a reward!

I mean, what an incredible...

An amazing reward.

'This skeleton is a far more complete record than Lucy's bones.

'It's over 60% complete.

'Among her bones are Dikika Baby's two scapulae,

'and they have their own evolutionary story.'

Tell me about the shoulder blade. What does it particularly reveal?

This shoulder joint is critical in exploring

the type of movement that this creature was involved in.

'This is the socket that the arm sits in.

'In humans it faces sideways.'

In Dikika,

we know that it was oriented upwardly,

like what you see in apes.

Which means it could hang very easily?

It could raise its arms, yes.

But even more important evidence was revealed

when Zeray examined the skull.

Three-year-old Dikika Baby's skull was the same size

as a three-year-old chimp's skull.

But unlike a chimp, Dikika's brain hadn't finished growing.

And this is crucial for our evolution as a species.

Here is an individual from the dawn of humanity, 3.3 million years ago,

still growing its brain and still learning from the parents -

the mother, the father, the brother.

Because their brain is very immature at birth.

And this is, I think, the earliest known evidence

for the emergence of childhood,

which is a unique thing characterising homo sapiens today.

Quite incredible.

I have to confess, it was really quite emotional

looking into that child's face from that far back in time.

And so much painstaking work going into exposing that fossil as well.

Such a tiny, delicate fossil that gives us so much information.

So the gist of this is that Dikika Baby's brain

is so small that actually she was still a child,

or this was still a child,

that there was still some growing to do,

whereas if she grew at the same rate as chimpanzees,

then we would have expected that baby to have an adult-size brain.

Or at least slightly larger, exactly.

This is an Australopithecus afarensis adult,

and a chimp adult.

And the brain is bigger, isn't it, by about 20% in afarensis?

Very slightly larger.

It overlaps with chimps, but it's just a little bit bigger.

And it's really interesting, then, to know that from Dikika Baby,

that not only is the brain getting bigger in afarensis,

but it's taking longer to grow as well.

We may be beginning to see a very slight change

towards a longer childhood.

But it's only very slight.

OK, so even if it is only slight, what are the implications of that?

Well, the reason we have long childhoods is that it takes

a long time to learn to be a grown-up.

Kids take a long time to learn from their parents,

and that's what the long childhood is about.

If we're beginning to see that in early hominids,

that may be the start of becoming human in a way.

And it's very interesting that we may begin to see

little tiny hints of that in Australopithecus.

Unfortunately, there's so much about our ancestors

that doesn't fossilise, like learning and language.

But there is another important line of evidence that we can turn to,

and that is looking at living primates.

I've been to find out about a new research project

in its infancy that's looking into just that.

Language is a key part of what it means to be human.

So how did our ancestors communicate with each other

before they could speak like we do today?

It may be possible to find some clues

by looking at the way primates communicate.

Supervising a study doing just that

is evolutionary psychologist Dr Bridget Waller

from the University of Portsmouth.

So you look at all the living primates nowadays,

they are all using very similar facial expressions -

so we can be very confident if you try and reconstruct

the behaviour of extinct hominid species

that they would have used very similar-looking facial expressions -

things that look a bit like smiling, look a bit like laughing.

Some things are a little more confusing, like frowning,

but lots of them would look very, very similar.

It's an intriguing idea, and in Hampshire,

a new research project is putting this theory to the test.

Marwell Wildlife Park is home to the world's first centre

specialising in the study of this remarkable creature -

the rare Sulawesi crested macaque.

Here, Bridget's colleague Jerome Micheletta

is six months into a long-term research project

working with the macaques.

What exactly are you trying to find out about them?

What I'm interested in is their communicative ability in general,

so that includes vocalisation, facial expressions and gestures.

And I'm interested in how they combine all these things

to communicate in their daily social life.

Ultimately, Jerome wants to quantify the range of facial expressions

that these macaques use.

There's one here who is going...

SMACKS LIPS

-The lip smacking behaviour.

-Friendly.

-Yes.

He's designed an experiment to measure the macaques' abilities

to communicate non-verbally.

Here is how the experiment works.

On this touch screen here, which the macaques have access to,

appears a picture of a macaque.

If they want to play the game,

they touch the screen three times.

Two other pictures appear.

One exactly matches the first,

the second one isn't the same at all.

If they press the image that matches the first one...

-MACHINE BLEEPS

-..they get a bing and they get a treat.

If they choose the wrong image...

QUIET BEEP

..they get a "bloop" sound and they don't get any reward,

and they have to wait longer for the screen to restart.

So far, they're not doing too badly.

So, he's got the majority correct.

I think so, yeah.

MACHINE BLEEPS

On average, how successful are they?

At the moment, they are around 70% of success.

That's impressive, but this is only the first phase of the research.

The next step is to get the macaques to match facial expressions

and eventually for Jerome to be able to work out

what those expressions mean.

A recent study of rhesus monkeys showed

they distinguish up to a dozen different expressions.

Jerome thinks macaques might recognise even more.

So how important could facial expressions have been

to Lucy's species three million years ago?

Lucy would have lived in a certain group structure.

She would have been in a group with lots of females,

possibly one or more males,

and so that tells us that they would have needed to communicate

in order to live in such a structure.

They would have needed to use their faces,

would have needed to use non-verbal behaviour

in order to solidify the communication

and the social interactions

that they would have had with each other.

By looking at the behaviour of modern-day primates,

new research like this is beginning to shed light

on how language might have evolved.

Perhaps Lucy communicated with her group just like these macaques.

So, if you can't talk, it's all about how you look.

It is interesting, isn't it,

that there are all these complex facial expressions

that primates are using very generally

to communicate with each other.

Primates are such social animals,

and that's where we got it all from too.

We use everything we can to communicate with one another.

And it even looks as though chimpanzees smile.

I think the latest research shows that the bared teeth grin

of chimpanzees is actually equivalent to human smiling.

They do. They smile, they effectively laugh,

they communicate with looks and gestures all the time.

There's so much more than making sounds to communication.

Non-visual communication is really prevalent among primates.

We've discovered a lot about Lucy's species.

We know they had been walking on two legs for some time.

This was probably as a result of the changing climate

and the need to adapt to different environments.

The price they paid was a more difficult childbirth.

But it's not just about walking upright.

In terms of survival, the ability

to eat a variety of foods is a big evolutionary advantage.

And thanks to a new scientific technique,

we may be able to say what Lucy and her species were eating.

This is Dr Paul Constantino,

and he's a biological anthropologist from Marshall University in the US.

Paul, what can you tell about Lucy by just looking at her teeth?

There are a few different techniques that researchers have developed over the years,

but one that my colleagues and I have developed lately

is extracting information about diet and bite force from chips in teeth.

What does this machine do and how can it help us understand what's happening with teeth wear?

I'm going to crank down on this handle here

and what that's going to do, you can see a human molar tooth

loaded there, and just above it is an indenter.

-You can also see that on this image over here.

-That's a hard object.

-Exactly.

-It's going to bear down on the tooth.

-Exactly.

It's simulating a large, hard object.

We've loaded it near the cusp of the tooth, near the edge,

so that it will create a chip.

-OK.

-Shall we have a go?

-Absolutely, yeah.

-We should put on our safety glasses just in case.

-Is it that hazardous?

Every once in a while, a chip will fly across the room.

-99% of the time, it just drops to the side.

-OK. Right.

So here you go, applying the force.

First I have to tell the computer to acquire the data and start reading.

Now we can see that graph.

And there it goes, that's going to be a small chip, but you can see,

here's where the force was being loaded onto the tooth.

-And then it dropped.

-Then it drops off because a chip has pulled away

from the side of the tooth and...

So we should be able to see a small fragment.

Yes, I just have to unload it a bit.

That's quite a large fragment of tooth!

Actually, it is quite a large fragment.

That's sheared off the whole of that edge there.

It was loaded so close to the edge of the tooth

that it took a big portion off without that much force, actually.

That would be something that might happen

if you'd chewed down a really hard object.

-Like an olive stone or something.

-Exactly.

We chip our teeth all the time, actually.

It turns out hominins did as well.

Here's a maxilla of Australopithecus afarensis, Lucy's species,

and you can see at least three different chips in these teeth.

-This one is quite enormous.

-That's a huge one there.

-That's a massive great chunk.

-It is.

And what can this research actually tell us

about what afarensis and her kind were eating?

The interesting thing about this research is that

we've been able to, through several of these experiments,

plot the force that's required to create a chip

versus the size of the chip itself.

What we've learned is that it's a nice linear relationship.

So what this means is that we can look at chips in the teeth

of Australopithecus afarensis in this instance

and just measure that chip and get an estimate of the bite force

the animal was using when it created that chip.

And that shows that they were actually able to access

a wide range of foodstuffs, soft and hard.

In afarensis' case, they were probably able to access things

that chimpanzees, for instance, or ancestors of chimpanzees, weren't.

So, if you were able to access a wide range of foods, harder foods,

that other things perhaps can't, that makes you much more adaptable and able to survive.

Animals that can generate a lot of bite force generally don't

specialise just on harder, tough foods, but they expand

the breadth of their diets so they still eat the same food as everybody else,

but now they can access some certain hard nuts and seeds

which can be quite nutritious, or even things like underground storage organs like tubers,

which may not be super nutritious, but they can get you through tough times when other food is scarce.

That is very interesting.

But there's something even more intriguing about her diet.

Was she using tools to access those kinds of food?

Chimps use twigs as tools to dig out termites,

but their fingers lack the precision grip of humans.

But was Lucy gripping and using tools more like us?

It's controversial, but animal bones unearthed in Ethiopia,

in the same region as Dikika Baby was found, may hold a clue.

Back at the California Academy of Sciences,

Professor Alemseged showed me the evidence.

So, what have we got here?

This is a bone from an animal

that lived over 3.4 million years ago.

And comes from a site which is only 200 metres away from where the Dikika child was found.

What makes it so special?

What's special is marks that were induced

when early hominins were wielding stone tools,

removing meat off the bone

and maybe pounding on the bones to access the bone marrow.

Therefore this is the earliest evidence for tool use.

'This looks convincing, but what's the scientific evidence?'

What we did is we mapped the chemical composition of the bone,

in the marks and out of the marks.

And when we did that, the part that is not marked

was very rich in calcium and phosphorus,

-which is what you expect for bones.

-Yeah.

Whereas when we mapped in the marks themselves,

we found a small crystal, a rock fragment, that must have been

dislodged from the tool that was wielded to induce these marks.

And the way we know that is that the chemical composition of that rock

was very similar to what you encounter in igneous rocks.

And of course if you were attempting to use a tool to cut off meat,

you would not use a soft rock,

you would pick the hardest rock around, an igneous rock...

There's evidence of that rock right in the cut.

That's it.

It's as if the hominins were kind enough to leave evidence to tell us,

"By the way, we were using this tool.

-"If you can't recognise us, here's the evidence."

-I'm convinced.

-Thank you.

He was really passionate about it and the marks seem

so exactly parallel and the bits of rock inside.

-I was sort of convinced of that.

-I'm a bit more sceptical.

How about you, Carol?

Whether it's convincing evidence or not, I think it's fairly good.

The fact that these guys were using and making tools

shouldn't really surprise us too much because after all,

chimpanzees use and make tools today, even orang-utans use them for all kinds of purposes.

We probably shouldn't be too surprised if Lucy and her relatives were using tools, too.

Why are you sceptical? Why... Because, you know.

I'm sceptical because other researchers have looked at that evidence

and they've said, come on, actually, this bone was lying in ground which had lots of stones within it

and actually, those marks could have been caused by trampling.

So, OK, yeah, they're effectively the mark of a stone on a bone,

but that could have got there by a trampling where that stone

has effectively been driven into the bone.

But the section of the cuts is like that,

as if you've dragged something across the bone.

Yeah. I think it's up for debate at the moment.

Some people believe it and some people think you could see the same thing from trampling.

But I think Carol's hit the nail on the head.

Chimpanzees make and use tools so why on earth wouldn't

we expect Australopithecus afarensis to have been doing the same thing?

I think, as we'll see more and more people going into the field and finding evidence of using tools,

if they're really using them, we're going to find more evidence of it.

With only a couple of bones to go on, these marks need to be

treated with caution, but it's an intriguing discovery.

Now, our reconstruction of Lucy is nearly finished.

The finer details have to be honed with a mixture of deduction and intuition.

Let's catch up with Viktor. How are you doing?

Yeah, I would love to show her to you right now, but I've got to hold off for a minute.

You are showing me her back.

Well, you know, what you're seeing here may look different than many

Australopithecus afarensis you've seen, but what's great about working in this nature

is that it gives you the ability to test out different looks,

different hair and different skin colour, before you commit.

So the science gives you the kind of range of possibilities

-that then as an artist you can choose where you're sitting within that.

-Precisely.

There's all these decisions at the end,

-like choosing what her eyes are going to be like.

-Sure.

We can talk about it before we go to the final thing to make that decision.

We can all be in agreement before a hair is punched.

-I just want her to look at me. She's looking fantastic.

-She will, thank you.

So our reconstruction is almost complete

and now that the muscles are finished,

the model-making team can focus on the next stage in the process.

It's in the bag.

Viktor has flown over with Lucy's head,

which he made at his workshop in New York.

There are some important decisions to be made

that will have a big impact on how she will look when she's finished.

It's interesting thinking about afarensis and eyes.

They are apes, they are bipedal apes,

but what's interesting is when you look at chimpanzee eyes,

the sclera, the whites of the eyes, aren't that pronounced.

They can be earlier on.

The colouration in the iris tends to sort of bleed out over time.

When you look at certain gorillas, mountain gorillas,

they have very human-looking eyes.

So I think any route you take is going to be fine.

However, one is going to give you

a slightly more human appearance to her face

and this one's going to give her

a slightly more ape-ish look to her face.

With the final decisions made,

the model-makers can put the finishing touches to Lucy

before revealing her to us for the first time.

So we're coming to the end of our incredible time here.

We began with just us, Homo sapiens,

and then we started with fragments of skeletons

and pieced together the bodies of three of our most iconic ancestors

in extraordinary anatomical detail.

First we met a Neanderthal, La Ferrassie 1, from 70,000 years ago.

Each night we've travelled further and further back,

deep into our evolutionary past.

At 1.5 million years ago, we met Nariokotome Boy

from the species Homo erectus, one of the earliest humans.

And now we've arrived back 3.2 million years ago

to meet Lucy, from the species Australopithecus afarensis.

-Viktor, please can we unveil her?

-Guys, everybody.

-I'm so excited.

I thought you would never ask!

-Come and have a look.

-It's time. I'm feeling a bit emotional.

-Me too.

-I bet you are.

-I can't wait to see what she looks like.

-Everybody ready?

-Yeah.

-Right.

One...two...three.

-Wow!

-She's so little.

-She's so sweet!

-That's amazing.

-Isn't she lovely?

-She really is.

-Look at this little person from three million years ago.

-Incredible.

-Those hands are just wonderful.

Really beautiful.

She could have held a stone flake,

she could have made stone tools, possibly.

Even though the hands are bigger than ours are, perhaps,

they're shaped so human-like and so in proportion that it's really astonishing.

And she's only just entering adulthood,

but presumably she could have already had children.

Just about now, yeah. About the time she died, absolutely.

Robin, the feet are so human-like.

Those prints now come alive for me

and you can see a couple with a child walking across that ash.

Very nice little story about that because the small individual

actually speeds up at the end of the trail to match...

-He's lagging behind.

-Exactly. It's true.

The stride length changes to match the two adults.

-Saying, "Come on, keep up!"

-Yeah.

And the jaw. You can't see the teeth.

That's the one thing that to me looks a bit more chimp-like.

You can see she's quite prognathic, her face sticks forward quite a bit.

This is obviously different from modern humans,

where our jaws have become quite retracted.

She's fantastic.

By piecing together how these three moved and how they looked

and how similar they were to us today,

I think we've gained a better understanding of not only our family history,

but what it means to be human.

Thanks to everyone here and all the experts

who've helped put flesh on the bones of our three ancient ancestors.

And thank you at home for joining us here

on this four-million-year journey back into our past.

-Goodnight.

-Goodnight.