Homo Erectus Prehistoric Autopsy

Hello and welcome back to Prehistoric Autopsy.

We're at the University of Glasgow

to continue our evolutionary journey back into the past.

Using the latest research,

we're going to recreate in extraordinary anatomical detail

another of our prehistoric ancestors,

one of the earliest humans - Homo erectus.

For two months, we've been rebuilding one individual

from the bones up,

using information gathered from experts around the world.

Recent discoveries are showing homo erectus in a completely new light.

That is a major breakthrough.

It is, yes.

-Now, that is remarkable. This is an old jaw.

-Yeah.

This is a jaw which has lost most of its teeth.

And clues buried deep in the seabed

are revealing how their world started to change.

It's like being given a history book of Earth's climate

and no-one's ripped the pages out.

Homo erectus was around for nearly two million years,

far longer than any other human species.

And at the end of the night, we'll come face to face

with one of these early ancestors.

So let's get started.

Welcome back!

Well, last time, we recreated a Neanderthal,

known as La Ferrassie One.

His kind were around for over 300,000 years.

We found out that he had a large brain,

and he was a skilled hunter and probably had language as well.

Tonight, using these bones, we're going to recreate an individual

from one of the very first species that we can comfortably call human,

known as homo erectus.

But first, let's just recap.

We're here in 2012, and this is us - homo sapiens.

Last time, we discovered we shared the planet

with possibly four other species, including Neanderthals.

And remember this little hobbit down here - Homo floresiensis,

around until 12,000 years ago.

But this is who we're looking at tonight.

Homo erectus lived at the same time as us,

but their story begins away back here - 1.8 million years ago.

They were on the planet far, far longer

than any other single human species.

So what is so special about Homo erectus?

Well, to help us answer those questions, we've got a lab up there

where we'll be putting ourselves and them to the test to find out

how similar we were to them, and they to us.

And if you're wondering why there's a man up there

in his underpants under a sun lamp,

all will be revealed later.

Over here, we've got experimental archaeology

and this is where we're hoping to get inside our ancestors' brains.

And where our experts are looking for clues

into how our ancestors lived.

Back here, Palaeo-artist Viktor Deak

and our team of model makers have been working hard

to create an incredibly accurate reconstruction

of one particular member of this species -

homo erectus.

Someone who hasn't been seen for a very, very long time.

By rebuilding one of these ancient ancestors,

Viktor and the model-making team will help us gain a unique insight

into this remarkable species.

All our early ancestors lived in Africa.

Homo erectus was the first human species to leave,

around 1.8 million years ago.

They spread right across the Middle East and Asia,

getting as far as eastern China.

So, how was Homo erectus related to us?

Intriguingly, many different human species

are believed to have descended from them.

One of these is Homo heidelbergensis,

who in turn, evolved into both Neanderthals and us, Homo sapiens.

They are also thought to be

the ancestor species

of those tiny hobbits,

Homo floresiensis.

All thought to have descended

from Homo erectus

and all living at the same time.

The individual we're interested in tonight

was a young lad walking the Earth 1.5 million years ago.

He is known as Nariokotome boy.

He lived near the Nariokotome River,

which feeds into Lake Turkana, in northern Kenya.

When he died, l.5 million years ago, his body sank into the silt

and became fossilised.

It was a revelation when his skeleton was discovered in l984

because it was still 90% intact.

Tonight, to help us make one of the most scientifically accurate models we can,

we're joined by palaeontologist Professor Scott Simpson

of Case Western Reserve University, in Cleveland, Ohio.

And Scott's been involved in some of the key discoveries of Homo erectus.

These bones are really wonderful, they're an incredibly accurate cast.

So Scott, introduce us to Nariokotome Boy.

Ah, well, this is one of the most complete human ancestor skeletons

that has been recovered, to date.

He's probably aged about eight years old when he died.

But he looks like he'd be older than that

cos he's got both molars here and I would normally say that

looks, to me, like a 12-year-old, not an eight-year-old.

He's very unusual - he has a mixture of traits that show he's young

and some mixtures of traits that show he's old.

So, if he was like a modern human, we'd say he's about 12 years old.

But what we've done

is we've looked at detailed studies of the enamel of the teeth

and we know, now, that he died when he was eight years old.

The one thing that immediately strikes me

is that...he seems very slight.

There is a reason to suspect that he was quite agile,

even just looking at his skeleton, but nevertheless, he is quite slim.

Now Viktor, you've got Nariokotome Boy's skeleton loaded up.

-Yes, I do.

-How are you filling in the missing bits?

Because again, he's quite complete but he's not all there.

Well, what's really wonderful about working like this

is that I can mirror image certain elements that exist

and then fill in any gaps.

So, can you mirror that humerus, there,

and stick it on the other side?

Right, so, here we go, let's see.

Actually, I've got the whole arm set up, so there it is.

Oh, fantastic. And you've put the radii in as well.

Now, we think he might have been doing a fair bit of running,

which we're going to talk about later,

-but can you put him in a running pose for us?

-Yeah, I can.

There he goes!

This is still a virtual skeleton

but a copy of Nariokotome Boy's bones

were delivered to our model makers

and I went along to help them put him together.

Down at the workshop, Jez Gibson-Harris leads the team.

'Another day, another hominin?'

Yes!

Finding such a complete skeleton was a major breakthrough.

Until Nariokotome Boy was unearthed,

only odd remains of Homo erectus had been found.

The missing parts of this cast have been filled in

using techniques like Viktor's computer mirroring.

The feet are thought to have been similar to ours.

An arched foot makes walking and running more efficient.

But the running pose that we've chosen

is a challenge for the model makers.

So, this is our spine.

And the idea is, because he's running,

-we've got an angle on the spine.

-Yeah.

He's leaning forwards.

Running is an exercise in not falling over.

So, I suppose, the challenge for you

is going to be to make this as the freestanding running Nariokotome Boy

-because he's going to want to fall forwards.

-He is.

Yes, the centre of balance is quite far forward

and we've only got him on one leg.

That's nice and straight now.

So looking at Viktor's picture, then, this is the leg in stance,

with the other leg about to swing through, like that.

That's going to be slightly more tricky.

-Because that malleoli should be right round here.

-Right round the side.

If you do that, if you bring that tibia round so the patella,

the kneecap's in the right place,

I think we're pretty much there, I mean, that looks really good.

At the end of tonight's programme,

we'll reveal our complete reconstruction of Nariokotome Boy

and discover what Homo erectus may have looked like in the flesh.

'I think just getting those elements assembled

'means that you start to see somebody.

'He's not just a collection of bones lying on the ground any more.'

So what do you think of the reconstructed skeleton?

Well, I think he looks absolutely fantastic.

-It's absolutely extraordinary. Quite lifelike.

-Very agile.

You get a real sense of movement.

Yeah, and it's great

because now we can see what his skeleton might have looked like

if he was complete.

And there's lots of anatomical features here,

-which have been described as being something to do with running.

-Right.

We talk about the nuchal ligament,

which runs between a bump on the back of the skull and neck.

That's to prevent our head pitching forward.

You can feel it on yourself, or George.

So, George, if you do exactly that and tuck your neck down...

You can feel this quite thick band, in the back of your neck,

running all the way down here.

-Oh, yeah! I can feel that, yeah.

-That's the nuchal ligament.

And he's got low shoulders as well.

So we think he's probably swinging his shoulders from side to side

to counterbalance him while he's running

and a nice flexible lumber spine too.

Yes, so he could do the twist, spin back and forth,

which is also necessary for walking and running.

He had very strong back muscles.

If we see, here, there are deep gutters on either side -

necessary for twisting your body and holding you forward.

It's anchoring the whole of your trunk, down to your pelvis.

And, then also, we think Nariokotome Boy

had quite big bottom muscles as well.

Quite a big gluteus maximus.

He looks really good.

Well, the big gluteus maximus muscles,

we use the gluteus maximus when we get out of a chair or when walking up stairs.

For an animal that's walking and running in ancient Africa,

you're going to need this muscle for turning direction

and slowing yourself down.

Preventing your body from pitching forward.

So, are you convinced by these adaptations to running in Nariokotome Boy?

There's a lot of information out there

suggesting perhaps he was just a long-distance walker.

And because we see that many humans are very well adapted to long-distance walking

and walking, if you have a large territory,

is a very important adaptation to living on the ancient African landscape.

But I think running is certainly one explanation,

explaining the anatomy of Nariokotome.

So, Nariokotome Boy evolved to be a good runner,

but the question is - why?

One of the things that drives evolution is environmental change.

So, what was happening to the world Homo erectus lived in?

For researchers at Columbia University, in New York State,

the answer to that question lies in the seabed.

Professor Peter De Menocal works on a technique

that can reveal what our planet was like millions of years ago.

It measures climate change

and it holds a clue as to why Homo erectus

may have been one of the first long-distance runners.

By analysing Earth cores,

drilled from the seabed off the coast of Africa,

he can pinpoint key environmental shifts in our ancestor's world.

We use ocean sediment cores

because the oceans are the ultimate repository of all sediment.

So the sediment just kind of gets dumped into the ocean very slowly

and continuously over time.

So it's like being given a history book of Earth climate

or earth history and no-one has ripped the pages out.

It's like a continuous record of time.

The accumulation rate of this core is roughly -

that would be equivalent to about 1,000 years.

So that's 1,000 years of accumulation,

2,000, 3,000, 4,000...

In this case, this core goes back 10,000 years in time

but we have another section that actually fits in the bottom of this,

goes back another 10,000.

We have cores that go hundreds of metres back below the seafloor

and that takes us back millions of years into the past.

By looking at subtle colour shifts in the cores,

Peter can read periods of dramatic climate change

in the African landscape across the millennia.

You can see there's something happening in this core,

roughly right around at this time, a colour change.

And this is between 5,000 and 10,000 years ago.

Sediments are green.

Sediments are red.

This redder sediment is the dust that's blown off of west Africa.

And then the absence of that dust here is telling us

that something in the African climate changed.

And this is when we know that the African climate was much wetter than it is today.

It was fully vegetated, there were large lakes.

So Africa was wet here and it's dry here.

Peter's team also analyse the sediment

for fossilised remnants of plant matter.

The types of plants that were growing

tell Peter when the climate was warming up or cooling down.

The swings between hot and wet to cooler and drier

have occurred many times throughout the geological record.

But if we travel back 1.8 million years,

what can we discover about the time that Homo erectus first appeared?

There's this shift that happens right around 1.8 million years ago,

which is a really profound change.

This is the first time that we see modern Savannah grass extend.

If you think of your mind's eye image

of what an African Savannah looks like,

that's when that appears.

It's right around 1.8, 1.6 million years ago.

So, right around the time when Homo erectus appears in the fossil record,

east Africa experiences this really tremendous change in vegetation

from more closed habitats, better watered habitats,

toward much more open vegetation.

With long legs and a runner's physique,

Homo erectus thrived in this new environment.

And they had another adaptation that made them very effective runners.

It's buried deep within the skeleton.

But before we look at that,

there's something I want to explain about his anatomy.

But I'd like you to try something for yourself first.

What I'd like you to do is keep your head entirely still,

and you can try this at home.

First of all, I have to put my glasses on. I have to read this.

Get yourself... Open a book, get a sheet of paper with words on it.

-HE STARTS READING

-Start reading it.

Move it from side to side very quickly. Can you read it?

No, it's gone.

OK, let's try it the other way round.

Hold the piece of paper entirely still

and shake your head from side to side.

"As shown in the two drawings below, the canals..." OK.

-So you can still read it.

-"..In three planes that are..."

So there's something really clever going on

and it's a really clever reflex which involves -

obviously, your eyes moving, and that's the last thing -

but your ears are telling your eyes effectively via a reflex

how your head's moving and keeping your eyes trained on one spot.

Now, why would that be handy for this boy?

It means you can keep your eyes ahead

and you can look at one spot while you're running or jumping,

whatever it is you're doing.

So... We have some bits of anatomy over here.

If I give that to you.

And I'll bring this large ear model over...

The bit of anatomy that we're interested in, which is allowing you to do this,

is deep inside the skull and this is a massive model of it.

And here it is.

So this is the vestibular cochlea apparatus

and here is the cochlea - your organ of hearing -

but here is part of the organ of balance

and also sensing direction changes and accelerations.

These are the semicircular canals.

Now, that's a really massive model and, Scott...

That's not how big they are in real life.

That's the real thing?

That is a real one. So that's a human bony labyrinth.

-It is absolutely minute.

-Isn't it beautiful?

And we have this anatomy for Homo erectus,

so we can get an idea of exactly what this tiny, tiny bit of anatomy

looks like in this ancient ancestor.

Now, in order to do this,

the scientists did NOT saw open the fossils,

what they did instead was do that virtually, using a CT scanner.

And then what they were able to do is reconstruct

what the membranous labyrinth of Homo erectus would have looked like

in three dimensions.

The semicircular canals are a different shape and size

from those of earlier ancestors and other apes.

And what's quite remarkable about this is

that it looks quite similar to ours.

So this suggests perhaps that Homo erectus was very agile

and probably running and jumping.

And Homo erectus had to be agile.

They weren't the only animals out on the savannah.

There were grazing animals like rhinoceros.

They have been around for nearly 17 million years.

But in Homo erectus' world

there were also predatory mammals like this sabre-toothed cat.

They would have been a constant threat.

Even with its smaller sabre teeth, it would have been deadly.

1.8 million years ago, Homo erectus may have been the first human species

to leave Africa and start to spread around the world.

But the ones that stayed behind weren't alone.

They shared their African environment

with as many as four other species of our early ancestors.

So who else was around at the time all this was happening?

Once you go back over a million years, there are some

very different species living alongside those early humans.

Like this bruiser here, Paranthropus boisei.

And here he is. He's such an odd-looking hominin.

I can't believe he's one of our relatives.

-Very strange.

-That's true.

His whole anatomy seems to have been taken over

by jaws and jaw musculature.

He was a dedicated chewer.

I mean, look at this, look at this crest along the top of his head.

So his temporalis muscles,

which are the ones we can feel if we're chewing,

you can feel a muscle working on the side of your head there...

Well, his muscles went right up to the top of his head.

-Ours stop about here, don't they?

-That's right.

Right about here, except theirs, as they got older and older,

grew to the midline and continued growing, forming a sagittal crest.

Something we don't see in modern humans.

Yeah. And then he's got incredibly flared cheek bones.

So that that muscle can get through there, down to the jaw.

But what are all those muscles doing?

Well, there's the jaw. Look at that, those teeth are massive.

Especially when we compare it to the Homo erectus skeleton.

-Yeah, look at that.

-They're almost two times as large.

So these molars are absolutely huge,

he must have been eating really tough foods.

Lots and lots of low quality food. Day in and day out.

His nickname is Nutcracker Man, which kind of suggests that

he's eating very hard foods, but I think recent analyses of his teeth

suggested that he might have been eating grasses as well.

Absolutely. If we look at the microwear,

the small scratches on his teeth, you can see that they ate

lots and lots of grasses that were covered with sand and also included phytoliths,

which are little stones that are found in grass,

and together these wear down the teeth very, very quickly.

Boisei was a species perfectly adapted to its environment.

But when that environment started to change, they were in trouble.

The climate in Africa began swinging between

extremes of wet and dry.

Unable to adapt, Boisei couldn't cope and died out.

But Homo erectus thrived.

The key to their success was their adaptability.

Some estimate that at their peak there may have been

as many as 125,000 of them living across the world,

from Africa, right across Asia, to eastern China.

This seems really bizarre because we normally think of species

adapting to one particular type of environment,

but our ancestors were having to get used to

-a rapidly changing environment.

-That's right,

It shows the complexity of necessary adaptations for Homo erectus.

Different habitats and environments

require different types of adaptations.

In the heat of the African savannah, keeping cool is crucial to survival.

Many animals insulate themselves against the harmful exposure

of the sun with a protective layer of hair.

They rest at the hottest times of the day to avoid overheating.

But that means they have less time to travel and hunt.

If Homo erectus was out running in the heat of the day,

what stopped them overheating?

Could this be the time that our early ancestors lost their hair?

I'm with Professor Peter Wheeler from John Moores University.

Would Homo erectus have been hairy?

That's something we don't know,

but what we can say is that there are good reasons to think

that it would have been advantageous for Homo erectus not to be hairy.

Tell me more, Peter.

Yes. We've got these volunteers, who aren't too dissimilar in physique

to what the Nariokotome Boy might have looked like

had he survived to be an adult.

And they're identical twins

and they've trained to a similar level of fitness.

And we've had them standing under these heat lamps,

which emulate the African sun.

One of the advantages of retaining body hair

is that it acts as a shield.

It prevents a lot of the heat from the sun getting through to the body.

And we've selected clothes that are similar in thermal properties

to that of the hair of living primates.

So, in essence, we have a hairless hominid and a hairy one.

Yes. Now, although the surface of the hair does get very hot -

in this case clothing - because it's insulating,

most of it will be reflected and reradiated back to the environment.

It's the lighter colours that are the warmest areas.

The surfaces on the naked skinned volunteer are hot.

They are the skin being hot itself,

therefore the heat is being absorbed directly by the body.

So while animals are standing still,

their fur keeps them cool by reflecting heat away from the body.

But John's bare skin is absorbing it, so he is getting hotter.

Well, let's see how you fare when you start to run.

We'll turn on fans to create a similar airflow

to when you're actually running.

We have a healthcare professional here.

If you don't feel comfortable, you stop at any time.

OK? Start running.

TREADMILLS BLEEP

Well, Alice, they're running away up here.

Do we know why running would be so important for Homo erectus?

Scott, what do you think?

Homo erectus probably lived in very, very large home ranges.

So that means he had to meander around

and run around or walk around these large home ranges looking for food.

Patrolling territories, if that's appropriate,

but they're really eating high quality food,

whether it's meat or high quality fruits and vegetables.

But these are widely dispersed across the savannah,

so you have to spend a lot of time walking around,

looking for these high quality foods.

So if he's looking for meat, obviously, meat walks around

and probably needs to be hunted, so are we saying he's a hunter?

You know, he probably was a hunter.

Although we often think of 'em hunting elephants and the largest animals out there,

well, they could have been hunting some of those animals -

although it's not likely -

what they're probably eating is smaller animals

that were easy to trap or surprise in the course of a day.

So, they were eating meat

but they weren't the big hunters that we see in Neanderthals.

What about scavenging, because that's another way of getting meat?

If he could walk and run for long distances,

then presumably that would have been an advantage to him.

The problem with scavenged food, though, is that there are

a lot of other animals that are also interested in scavenged food,

like hyenas, lions, jackals and birds of prey.

But running would have been useful in terms of getting away

from other scavengers and predators, I imagine.

True, but only if you can run faster than the other scavengers and predators.

If we're talking about somebody who's running around the savannah, we need to put some muscles on him.

So let's go and see how Viktor's getting on.

Oh, look at this. That's lovely.

So you've got muscles on his body

and muscles appearing on his face as well.

He's still looking quite lean and I think that's right,

he's got very slender bones,

so we're not looking at great, big, chunky musculature.

He looks very lithe, doesn't he?

Right, he would've had not a lot of body fat,

-especially in that environment and climate.

-Yeah.

And as active as he was.

All this information has been fed to our model makers.

Once the muscles have been put on the skeleton,

Nariokotome Boy really does start to look more human.

The team uses modelling clay to form muscles around the skeleton.

For sculptor Reza, making sure they are accurate is tricky work.

Reza, you look a bit nervous.

Well, this is my baby.

Wow, that looks a bit different.

Let me just unwrap the arms and legs.

Well, he's got a very lovely serratus anterior,

I can say that right now.

Look at this lovely muscle right here,

this is the muscle that holds the scapula onto the back of the thorax.

So this is all looking anatomically beautiful. Very accurate.

Thank you.

'Considering Nariokotome Boy was around 1.5 million years ago,

'his body is surprisingly similar to ours.'

We're seeing all of the muscles that we'd see in us.

-These are the same muscles.

-Yes, exactly.

They're in the same places.

-I quite like him without a head.

-THEY LAUGH

Now, we haven't got hands or feet on him,

but at the moment he does look very human, doesn't he?

-Yeah, it does.

-I think that's going to change when we put the head on.

Cos it really is the head which is so different.

Right, yes.

He's got quite a small brain, and quite a distinctive face as well.

There's a couple of tweaks that I think would really help.

He's running and actually we need to get a bit of a twist going on.

So when you're running along...

So you're swinging your...

-You swing your chest the other way to kind of...

-Right, yes.

To counterbalance, cos your leg's trying to spin you off

in that direction.

Yeah, we can do some adjustments there.

-He's coming on really nicely.

-Thank you.

He's really starting to take shape.

Now, our volunteers have really been

working up a sweat on these treadmills,

so now I want to see who's keeping their cool.

-How are you feeling?

-Tough.

-Tough?

-Yeah.

And our naked-skinned human?

-OK.

-OK.

He feels he can keep going.

He's dissipating the heat load that his muscles are producing

much more easily.

And there are two distinct reasons why he is able to do this.

The loss of his body hair means that heat can flow from his body

more easily out into the environment.

The second advantage is the loss of body hair

makes sweating much more effective.

When the sweat is secreted onto the skin's surface,

the increased airflow over the skin

means that sweat is evaporated at a greater rate.

I think you should switch the machines off now

cos I'm worried you're about to have heatstroke.

Now, haul up your shirt there. Look at that.

Now, all that heat has been trapped inside,

his core, his insides, are really heating up.

John on the left there is not nearly as hot underneath,

so the advantages are quite clear.

The advantages are very clear, particularly during activity,

either through long-distance persistence walking,

through the heat of the tropical day or short bursts of intense activity,

such as our volunteers have done here.

There's one other problem with exposed skin in the sun

is that you would have to have dark skin protected by melanin.

What about hair on the head?

One of the reasons we think hair is retained on the head

is that it's actually shielding those areas of the body in a biped

which are most exposed to the strongest fluxes of solar radiation...

-It protects the brain?

-..when the sun is overhead.

It's shielding the brain from overheating.

Steven, how do you feel?

-It was really hard.

-That was really hard.

-Good.

-You could have kept going, I reckon.

Yeah.

Under the searing savannah sun, Nariokotome Boy

could only run during the day if he could keep cool.

Sweating is the most efficient way of losing heat and to do that

he would have needed very little body hair.

This is really interesting

and I find it really intriguing that we could be looking at

the point in our story where our ancestors lost their fur.

That's right. This is very unusual.

Humans are unique among primates because we are naked.

We just don't have the hair that the other primates have.

Perhaps the most compelling reason that we've lost the hair

is that we wanted to shed heat.

That allows us to be active throughout the course of the day,

as apposed to... most mammals rest at noon time.

-And this is exactly what the experiment showed.

-Very clearly.

Hairlessness could mean that we can keep cool in a hot environment.

Perhaps that does mean that our ancestors could have gone out

and perhaps scavenged meat, perhaps hunted meat, in a period of time

when other predators might have been resting in the shade.

-That's right.

-And it's interesting that,

if meat were a more important part of these ancestors' diets,

it's interesting to look at the teeth and see that they're getting smaller

and also to see that Nariokotome Boy has a very different-shaped thorax,

rib cage, and it's been suggested that he's got a shorter gut.

It could very well be, because if we look at the shape of the rib cage,

the rib cage is not as broad, wide or flared out as some of our earlier ancestors.

That means that the space in between the pelvis and the diaphragm,

where our guts live, seems to be a smaller volume.

We have smaller guts.

Which suggest that he was eating better quality food.

The shorter the gut, the better quality the food.

So meat could be an explanation for that, but there could be

another explanation as well why guts and teeth are getting smaller.

It could have been that these guys were cooking their food.

It's controversial because until recently, it was thought humans

DIDN'T control fire until around 400,000 years ago.

But new chemical analysis techniques

may have just put a match to all that.

Cooking with fire is a uniquely human behaviour.

Today, Homo sapiens are the only species to do it,

but that hasn't always been the case.

In Williamstown, Massachusetts, Dr Anne Skinner has been analysing

tiny fragments of ancient animal bones that have been burned.

They were found at a site used by Homo erectus.

And Anne made an extraordinary discovery.

What elements within the bone are you particularly interested in?

The part I'm interested in is the proteins.

And how does the fire affect them?

It breaks down the protein and leaves behind just these small bits

that can be seen even a million to 1.5 million years later.

Using a technique known as electron spin resonance,

she can analyse changes in bone protein.

These reveal what temperature the bones were burned at.

Natural fires from the time of Homo erectus would have been

grassfires that burn at 300 degrees Celsius.

But man-made fires, created in a hearth,

reach much higher temperatures.

So if I have bones that are heated above 300,

and especially above 400, to give us a little leeway here,

then I can be sure that they were not heated in a grassfire,

and hence they have to have been heated

in a fire constructed by hominids.

Anne used her technique to analyse burnt fragments of antelope bones

found in Swartkrans cave in South Africa.

This was a cave where Homo erectus remains had also been found.

Remarkably, she found that the bones had burned at 350 degrees Celsius,

and believes this shows they must have been burnt in a hearth.

I can show that these bones were burned in a fire

that must have been created and controlled at the cave

and that dates to somewhere between 1 and 1.5 million years,

which is older than any other site that has ever been found.

-That is a major breakthrough.

-It is. Yes.

Scientists believed that the only species to have the mental ability

to use fire at this time was Homo erectus.

So from your work at Swartkrans cave,

what are you able to tell about Homo erectus and fire?

Well, the fire itself is interesting,

but the idea that these entities had the ability to even conceive

that they might control their environment,

rather than just letting the environment control them...

Instead of seeing a burning bush and running in the other direction,

to conceptually say, "Hey, we could use that.

"Even if we weren't cooking, we could use it to scare away leopards.

"We could use it to keep warm".

Just thinking that there's something that you could use

in your environment is...takes more effort than you might think.

Anne's findings have rewritten the timeline

on Homo erectus' ability to harness fire.

Evolutionary biologist Dr Rachel Carmody has studied the research.

She believes that the early use of fire could even have

accelerated their development.

This kind of work is really showing us

that humans were controlling fire and were possibly using it

for things like cooking very early on in human evolution.

Cooked food means a more varied, higher energy diet.

This reduces the workload for the gut

and leaves calories spare for the rest of the body.

A fifth of the calories we consume are used to fuel our brains.

There's a theory that a switch to cooked food

is one of the things that encouraged an increase in brain size.

What we see at this point in human evolution

is the beginning of a trade-off, where gut size gets smaller

and so you save energy by having a smaller gut.

But humans seem to have been able to reallocate that saved energy

towards fuelling a larger brain.

So is there a link between a better diet and growing bigger brains?

I find this really intriguing and slightly unsettling

because, for me, this is evolution turned on its head.

Because we're saying that we are saving some energy somewhere,

so that means we can grow a bit of ourselves bigger.

-George, what do you think?

-A chimpanzee spends 47% of its time

chewing and eating and processing food,

whereas humans only spend 4.7%,

so you've got all this extra time and energy to do something with it.

Why not cooking?

While we are looking at size of brains, I've got a very graphic way

of demonstrating how brains are getting bigger

through human evolution and that's over here. And...

Thank you, Scott.

Stick Nariokotome Boy's skull in there.

We've got a range of different humans here from different times

in our story, in fact, these ones aren't even human,

they're ancestors but they're not quite human yet.

This one is perhaps the earliest fossil that we have

which we might be able to call a human ancestor.

This is Toumai, Sahelanthropus tchadensis,

-from about six or seven million years ago.

-That's right.

And these beads represent the volume of the brain. Of the inside...

And this is a pretty tiny brain, isn't it, Scott?

It's just a little bit larger than a chimpanzee

or maybe chimpanzee average size. So it's not very smart.

And then this one is Australopithecus africanus?

Yes, she's from South Africa from 2.5 to 2.8 million years ago.

Also walked upright on two legs like we do and perhaps Sahelanthropus.

And this is the average size of this species' brain.

So there you go, a little bit bigger.

And now we come to Nariokotome Boy and his kind.

So Homo erectus.

Now that volume that you're pouring in there

actually represents an adult of that species.

It does, yes.

His brain is a bit smaller than that but had he grown to be an adult,

then he would have achieved something like that.

It's kind of the average for the species as well, isn't it?

That's right, although there's quite a large range of brain size

in Homo erectus because it spans a very long period of time.

And I recognise that skull. That's your skull.

That's me, that's my skull...

Oh, it's tiny, look!

-Absolutely tiny. Hang on a minute!

-Smaller than Homo erectus.

Hang on a minute! Right, OK...

So this really is one of the weirdest things about us,

is the huge brains that we have.

And our brains have been growing throughout human evolution.

But it's not all about the size of the brains,

it's actually what's going on with those brains and what we're doing with them that's important.

And here's where we turn from fossil bones to archaeology.

We've got Professor Bruce Bradley of Exeter University here,

to tell us about what they're doing with these big brains.

Very interestingly, when we see the beginning of Homo erectus,

we see a quantum change in the way they're making stone tools.

And they're going from very simple stone tools,

where a piece of stone would be picked up and just the end would be

knocked off... Now, we need to put on some safety glasses.

Because this can be dangerous. Sharp things flying around.

And so it's very simply the earliest stone tools, are taking

a piece and just knocking the end off of it to get a sharp edge.

-Yeah, that's sharp.

-Yeah. You know, it's not a brilliant tool.

It's pretty basic, though.

It's pretty basic, and you're just taking the form

that you have naturally, and just knocking the end off of it.

So what do we see when we get to Homo erectus?

Think about that, and then think about doing this.

They're shaping the whole piece, and they're not only doing that,

they're turning it into something much more complex.

There's flaking on two sides, with a straight edge that goes all around.

In order to do that, they must have an idea

of what they're going to end up with.

It isn't just random bashing.

They have a plan in their head to make that shape.

This is a real planned object, and it takes a really different

kind of technique.

So instead of just sort of hitting it with

a stone, what I'm going to be doing is working on this edge here.

And then as I strike pieces, you can see they run across the surface.

So I'm not only shaping an edge,

I'm shaping the whole thing three-dimensionally.

This takes an incredibly different mindset,

a cognition, a way of thinking and seeing things.

So, what we're looking at is like you said - planning.

But what's more interesting is not just that they made these

hand axes, but to get to these hand axes,

particularly in parts of Africa, they had very large pieces of stone.

-I wondered why that was there.

-How do you get this, from this?

What Homo erectus was doing is they were taking

-and making these big things, which we call blanks.

-Yeah.

And then THESE were being turned into the hand axes.

So they're making their own form. Free form.

-So can you get a blank out of there?

-Well, we're going to see...

Oh!

-So...

-Wow.

So this, to me, is like Michelangelo looking at a block of marble,

and saying, "I can see David inside it."

I see three or four Davids in this one.

So, Homo erectus had bigger brains and better tools.

They could cover large distances, and it seems they may even have had fire.

With these skills, they were well equipped to explore territories outside Africa.

But what did they look like?

Right, I'm off to see how Viktor's getting on over here.

Because our Nariokotome Boy

should be starting to look almost finished now.

-I'm just working out the hair...

-You're not revealing the face yet!

No. I've got to keep it a secret for you.

So you're not putting that much hair on the rest of his body.

No. Because of thermo-regulation

his hair covering would have been less.

He's still going to be retaining a bit of furriness

from his ancestors, he's not THAT far removed yet...

-And he's got dark skin.

-Dark skin to help against the sun.

-But looking more like us, actually.

-Definitely.

So it's time to join our model makers in their studio,

where they're going to need a LOT of patience to finish off Nariokotome Boy.

The modellers have finished sculpting Nariokotome Boy's body,

and now it's time to cast the model.

First he's carefully wrapped in fibreglass to make a mould.

Liquid silicone is poured into the mould to create a model with a lifelike skin texture.

The next challenge is to decide how hairless he should be

to allow effective sweating,

and to choose a skin tone which would have given him

adequate protection from the African sun.

The researchers have given us advice on which way to go with the colour of this figure,

and the feedback is we've got this darker brown colour,

and now we've come to the painting stage,

whereby we mix up washes of silicone fluid

and we put in different pigments, create the different washes

that are applied layer upon layer, and these will bring up the skin tones.

But it's quite a long process.

One of the challenges is to get the lighter skin tones

around the feet and around the palms of the hands.

It's looking very shiny at the moment, but once it's complete,

we'll put a matting agent on

and that'll give it a much more natural look.

With their dark, hairless skin and lean physique,

Homo erectus may have left Africa and spread

right across Asia... but they didn't go far north.

And the reason for this may have had

something to do with the colour of their skin.

Well, this is Professor Barbara Boucher

of Queen Mary University of London, who has spent decades

looking into the relationship between skin colour and health.

I mean, he's living in a tropical environment,

so presumably we would expect him to have dark skin to protect his...

You certainly would or he'd be in quite a deal of trouble with sunburn

and skin cancers, and generally uncomfortable.

The trouble is, as you move north, a lot less ultraviolet gets through,

and we need ultraviolet to make vitamin D

because it's one of our essential hormones

and we depend on sunlight to make it.

If you are in the north and you've got very dark skin,

you tend to run out of vitamin D. You just don't make enough.

You're a clinician and a scientist,

so clinically, what is the problem if people are vitamin D deficient?

The first thing you would expect to get is bone disease.

Children, as we well know, get rickets,

and women in pregnancy tend to get soft bones.

If you have a soft bone,

and you're walking about, you tend to squash your pelvis in,

and your pelvis gets narrowed and you can't deliver the baby,

so mother and baby die.

So we've talked about effects on bone. What about immunity?

Is vitamin D important for that as well?

Very important for that.

You need vitamin D to make various compounds that destroy bacteria.

You can reduce the dangers of bad infections

and the risks of viral illness

and perhaps rather reduce the hazards of TB.

This is fascinating.

I think it shows that disease can have a very powerful influence

on how populations grow and spread.

Many diseases leave very little mark on our skeletons,

but when they do, that evidence in ancient bones

can tell us something more about our ancestors and their way of life.

I've been to Germany to look at some controversial new evidence.

In 2007, at the University of Gottingen's School of Anatomy,

Professor Michael Schultz was asked to examine a fragment

of a Homo erectus skull.

Found in a quarry in Turkey, it had a remarkable story to tell.

That's a part of a frontal bone found in Turkey

where they are sawing blocks and making tiles,

and very probably, we must have blocks with the rest of the skull

or even the whole skeleton.

So this means that, in fact, the rest of this skull

could be in tiles like this on somebody's bathroom wall?

That's possible, but I doubt it.

Everyone's going to be looking at their bathroom walls now.

And how old is this skull?

It was dated approximately 500,000 years.

When Michael looked at the inside of the skull,

he saw tiny marks which shouldn't be there.

We have very small granular impressions.

We have also impressions of very small blood vessels,

probably arteries.

Normally you'd expect the surface of that to be quite smooth

and you wouldn't see so many blood vessels?

That's right. We have maybe here new formations of bone.

Something had put pressure on the inside of the skull,

causing pits in the bone.

OK, so we've got pits, and we've got new bone growth,

and also grooves from unusual blood vessels here.

What do you think that means?

We have to be very careful,

but I am convinced that this very probably is caused by TB.

It's remarkable to have this diagnosis of TB, Tuberculosis,

in Homo erectus.

This is a disease which was thought to have emerged

just 10,000 years ago,

yet this skull is 500,000 years old.

When the skull is compared to a modern human skull from a TB victim,

the similarities are startling.

This is really interesting

because we're seeing exactly the same changes.

We can see the pits there and new bone formation.

So we've got a skull from the 19th century that's showing

precisely the same changes as this 500,000-year-old skull.

And we know exactly that this skull is from a young adult

and we know that he died from TB.

So, in fact, what we're looking at

in that much more ancient piece of skull

are the tiny lumps which give TB its name, the tubercles,

-making an impression on the skull here.

-Right, yeah.

Finding evidence of a disease like TB

among simple hunter-gatherers like Homo erectus is revolutionary.

At first sight, I couldn't accept that this might be TB

from 500,000 years ago!

I have to say, Michael, that I was quite sceptical.

But now, with you showing me the signs on this very good cast,

I have to say I'm convinced.

What do you think, Scott? I thought that was fairly convincing evidence

of TB inside that skull.

We have to be cautious perhaps on the identification of tuberculosis.

Given that this could potentially be TB, this is fascinating

because it pushes the origins of TB in humans

back much further than previously thought.

Even quite recently we thought we didn't get TB

until we started farming cattle.

What's interesting is the disease process tells us a lot

about the behaviour and the adaptations of extinct ancestors.

It says something about the way humans are interacting,

populations are interacting across Eurasia.

It's also saying something about how humans are interacting

with other animals on the landscape, like cattle.

Tuberculosis is a pathogen that lives in cattle and other bovids.

It's amazing how much pathology - disease in ancient human remains -

can reveal about our ancestors,

but could it EVEN provide us with an insight into their feelings?

One trait that we think marks us out as human

is the sophistication of our emotions,

like sympathy and compassion.

But can fossilised bones

tell us anything about our ancestors' feelings?

I've been to the Republic of Georgia,

to the small medieval town of Dmanisi.

Here, archaeologists have found remains of Homo erectus

that they believe may do just that.

Professor David Lordkipanidze is leading the excavations.

David, what's that over there? Some kind of animal fossil.

Is that as old as the human fossils you've been finding here?

Yeah, it's 1.8 million years old. It belongs to a deer.

It's a fantastic preservation of bones.

1.8 million years ago, environment was more Africa-like in some ways.

Here was definitely environment more savannah-type on one hand,

but it had also forest elements, it had a wood.

It shows that climate was not as hot as in Africa,

and they had much colder winters here.

These are some of the earliest signs we have

of our ancient ancestors outside Africa.

Surviving in this challenging climate would have been tough.

Professor Lordkipanidze has found a skull

that raises some interesting questions

about how some of them survived at all.

Look at that, that's just beautiful!

Yeah, it's a cast of the Dmanisi hominid.

And it was that complete, it wasn't in pieces?

It was not in pieces. There were some small breaks.

But generally we could...

Isn't that wonderful?

So you know the brain size of this individual,

you know what his face looked like.

Absolutely, and also we have a jaw.

1.8 million years ago, Homo erectus had made it here to Georgia.

That in itself is astonishing.

But what's even more surprising is that this person was toothless.

Now that is remarkable. This is an old jaw.

This is a jaw that's lost most of its teeth.

It looks like the only tooth that could possibly have still been

in the mouth is that one there. Is that a canine?

Yes, it was just one canine.

And we can tell that all of these were lost a long time before death

because the bone of the jaw has shrunk right down.

So we know that must have happened

months or even years before this person died.

This person survived at least a few years without teeth.

Somehow, this toothless person survived against the odds.

The evidence suggests that they were living here

long before our ancestors learned to control fire.

So in the harsh winters, they may only have had raw meat to live on.

These people were depending mostly on meat,

and without teeth it's very difficult to get meat.

So how does this person survive, as a hunter-gatherer,

and with fairly basic technology,

in this environment - with no teeth?

I think this is indirect evidence

of the altruism or compassion.

I'm sure somebody was taking care of this individual.

It's lovely to say, OK, we've potentially got evidence of altruism

and compassion here,

but just to be quite kind of harsh and economical about it,

what kind of advantage could that have brought, in evolutionary terms?

Maybe this person had knowledge which others needed still.

So it was maybe very pragmatic also.

Could it be that compassion contributed

to the success of Homo erectus?

I think it's quite interesting to think that

compassion could have been an important feature of our evolution.

It certainly characterises humans, because our human social relationships are so strong,

and many of the relationships we build are built on friendship and compassion

as opposed to some strict evolutionary need.

Well, there is a chimpanzee skull in a museum in Kent

that clearly hasn't got any teeth, and has obviously had his teeth lost

before he died, so he or she was clearly being looked after in some way.

It's interesting, isn't it, because I think that

when we see that in another species we don't immediately jump in and say

there must be some kind of compassion, some kind of altruism going on here.

But of course, altruism isn't something which is limited to humans anyway.

No, that's right. It's a characteristic of all evolving organisms, social organisms.

So even though we don't know why we're doing it,

altruism may not be entirely unselfish?

No, because humans are so behaviourally plastic

that we can change our behaviour throughout our entire lifetime,

that what we want to do is we want someone who's had a rich

experience and understands where the resources are in tough times.

And understands, can decipher complex social relationships.

So compassion and altruism are useful evolutionarily.

Well, we're nearly at the end of our quest,

but there's one last question -

are there any clues as to how Nariokotome Boy died?

Well, there's nothing that completely hits you

between the eyes, but there might be something going on with his teeth.

If we look right here on the right side of his jaw,

we see that there's an area of erosion.

-Right here between his premolar and molar.

-It's always the teeth, isn't it?!

-It is.

-Is that an abscess?

Well, it's some type of inflammatory response, so he probably has an infection going on.

Well, I had a bad abscess in my jaw a week ago,

and it was so painful.

I think it's interesting to think about how infection might have affected our ancestors as well,

cos if you had an abscess in your jaw... What happened after that?

Well, I removed part of it and then I got antibiotics!

Otherwise I don't know what I'd have done.

You know, this is subtle, it may not have been the thing which killed him - but it could have been.

Yet again, it's amazing the amount of detail we've been able to glean from just a handful of bones.

Over six months, Viktor and our model makers have pieced together

the skeleton of this tall and agile runner.

Carefully sculpting muscles to reflect a physique fuelled by meat eating,

and adding the finishing touch of a hairless sweating skin,

that made him so well adapted

for hunting and scavenging on the savannah.

And now he's finished.

None of us have seen him yet,

but we're finally about to meet him in the flesh.

-Shall we go and have a look?

-Absolutely.

Do you want to come and have a look, everybody? This is it, this is it.

-VIKTOR:

-Can't wait to show you.

-I'm pretty excited about it.

-You all ready?

-Right then, Viktor...

-One, two, three!

-The real Nariokotome.

Wow!

He looks a bit different from the last time I saw him.

A face from one and a half million years ago.

The face, I'm really happy with.

-This is an eight-year-old.

-Yeah, that's quite shocking.

That blows me away, because my eight-year-olds were, like, this tall.

He's a big eight-year-old.

The hair he HAS retained is totally credible,

that would be a very good protective barrier against the radiation from the sun.

And then he's lost hair on the rest of his body.

So he would have been able to sweat, cool down.

Yes, so he's got quite a large surface area

but that surface area isn't absorbing rays from the sun.

What would he think if he saw us now? What would he make of us?

I'm really quite moved by it.

I've only ever seen Nariokotome Boy's bones before,

and suddenly here he is amongst us.

He's lovely.

Well, with the help of experts around the world and the people

in this room, we've been able to create our very own Nariokotome Boy.

In our last programme, tomorrow, we'll be travelling back 3.2 million years

to meet one of our very earliest ancestors...

a female who walked on two legs...

called Lucy.

I've been to the States to see what the fossilised remains

of the world's oldest child are revealing about

how Lucy's species moved, and about the origins of childhood.

Here is an individual, still growing its brain,

and still learning from the parents.

Alice has been learning how techniques

borrowed from the aeronautical industry can cast light

on when our early ancestors left the trees.

That's amazing. We've got a very, very different pattern in the way

-the forces are spreading throughout the bone.

-Yeah.

And I caught up with some of our closest living relatives,

to find out if they can give us any clues as to how Lucy

and her species might have communicated.

And we'll be finding out the price she had to pay to walk upright.

-Join us back here, next time. Goodnight.

-Goodnight.