0:00:04 > 0:00:08Hello and welcome back to Prehistoric Autopsy.
0:00:08 > 0:00:09We're at the University of Glasgow
0:00:09 > 0:00:13to continue our evolutionary journey back into the past.
0:00:13 > 0:00:15Using the latest research,
0:00:15 > 0:00:19we're going to recreate in extraordinary anatomical detail
0:00:19 > 0:00:21another of our prehistoric ancestors,
0:00:21 > 0:00:25one of the earliest humans - Homo erectus.
0:00:26 > 0:00:28For two months, we've been rebuilding one individual
0:00:28 > 0:00:30from the bones up,
0:00:30 > 0:00:34using information gathered from experts around the world.
0:00:36 > 0:00:40Recent discoveries are showing homo erectus in a completely new light.
0:00:40 > 0:00:42That is a major breakthrough.
0:00:42 > 0:00:44It is, yes.
0:00:44 > 0:00:47- Now, that is remarkable. This is an old jaw.- Yeah.
0:00:47 > 0:00:49This is a jaw which has lost most of its teeth.
0:00:49 > 0:00:51And clues buried deep in the seabed
0:00:51 > 0:00:54are revealing how their world started to change.
0:00:54 > 0:00:57It's like being given a history book of Earth's climate
0:00:57 > 0:00:59and no-one's ripped the pages out.
0:01:00 > 0:01:04Homo erectus was around for nearly two million years,
0:01:04 > 0:01:07far longer than any other human species.
0:01:07 > 0:01:10And at the end of the night, we'll come face to face
0:01:10 > 0:01:12with one of these early ancestors.
0:01:12 > 0:01:14So let's get started.
0:01:27 > 0:01:28Welcome back!
0:01:28 > 0:01:32Well, last time, we recreated a Neanderthal,
0:01:32 > 0:01:34known as La Ferrassie One.
0:01:34 > 0:01:36His kind were around for over 300,000 years.
0:01:36 > 0:01:40We found out that he had a large brain,
0:01:40 > 0:01:44and he was a skilled hunter and probably had language as well.
0:01:44 > 0:01:49Tonight, using these bones, we're going to recreate an individual
0:01:49 > 0:01:52from one of the very first species that we can comfortably call human,
0:01:52 > 0:01:54known as homo erectus.
0:01:56 > 0:01:57But first, let's just recap.
0:01:57 > 0:02:01We're here in 2012, and this is us - homo sapiens.
0:02:01 > 0:02:03Last time, we discovered we shared the planet
0:02:03 > 0:02:07with possibly four other species, including Neanderthals.
0:02:07 > 0:02:11And remember this little hobbit down here - Homo floresiensis,
0:02:11 > 0:02:14around until 12,000 years ago.
0:02:14 > 0:02:17But this is who we're looking at tonight.
0:02:17 > 0:02:20Homo erectus lived at the same time as us,
0:02:20 > 0:02:25but their story begins away back here - 1.8 million years ago.
0:02:25 > 0:02:28They were on the planet far, far longer
0:02:28 > 0:02:30than any other single human species.
0:02:30 > 0:02:33So what is so special about Homo erectus?
0:02:33 > 0:02:37Well, to help us answer those questions, we've got a lab up there
0:02:37 > 0:02:40where we'll be putting ourselves and them to the test to find out
0:02:40 > 0:02:44how similar we were to them, and they to us.
0:02:44 > 0:02:47And if you're wondering why there's a man up there
0:02:47 > 0:02:49in his underpants under a sun lamp,
0:02:49 > 0:02:51all will be revealed later.
0:02:51 > 0:02:55Over here, we've got experimental archaeology
0:02:55 > 0:02:59and this is where we're hoping to get inside our ancestors' brains.
0:02:59 > 0:03:02And where our experts are looking for clues
0:03:02 > 0:03:05into how our ancestors lived.
0:03:05 > 0:03:08Back here, Palaeo-artist Viktor Deak
0:03:08 > 0:03:11and our team of model makers have been working hard
0:03:11 > 0:03:14to create an incredibly accurate reconstruction
0:03:14 > 0:03:16of one particular member of this species -
0:03:16 > 0:03:17homo erectus.
0:03:17 > 0:03:22Someone who hasn't been seen for a very, very long time.
0:03:24 > 0:03:26By rebuilding one of these ancient ancestors,
0:03:26 > 0:03:31Viktor and the model-making team will help us gain a unique insight
0:03:31 > 0:03:33into this remarkable species.
0:03:35 > 0:03:37All our early ancestors lived in Africa.
0:03:39 > 0:03:42Homo erectus was the first human species to leave,
0:03:42 > 0:03:45around 1.8 million years ago.
0:03:46 > 0:03:49They spread right across the Middle East and Asia,
0:03:49 > 0:03:51getting as far as eastern China.
0:03:54 > 0:03:56So, how was Homo erectus related to us?
0:03:56 > 0:04:00Intriguingly, many different human species
0:04:00 > 0:04:03are believed to have descended from them.
0:04:03 > 0:04:05One of these is Homo heidelbergensis,
0:04:05 > 0:04:10who in turn, evolved into both Neanderthals and us, Homo sapiens.
0:04:12 > 0:04:14They are also thought to be
0:04:14 > 0:04:15the ancestor species
0:04:15 > 0:04:16of those tiny hobbits,
0:04:16 > 0:04:18Homo floresiensis.
0:04:19 > 0:04:21All thought to have descended
0:04:21 > 0:04:22from Homo erectus
0:04:22 > 0:04:25and all living at the same time.
0:04:25 > 0:04:29The individual we're interested in tonight
0:04:29 > 0:04:33was a young lad walking the Earth 1.5 million years ago.
0:04:33 > 0:04:36He is known as Nariokotome boy.
0:04:38 > 0:04:40He lived near the Nariokotome River,
0:04:40 > 0:04:44which feeds into Lake Turkana, in northern Kenya.
0:04:45 > 0:04:50When he died, l.5 million years ago, his body sank into the silt
0:04:50 > 0:04:51and became fossilised.
0:04:53 > 0:04:57It was a revelation when his skeleton was discovered in l984
0:04:57 > 0:05:00because it was still 90% intact.
0:05:02 > 0:05:06Tonight, to help us make one of the most scientifically accurate models we can,
0:05:06 > 0:05:09we're joined by palaeontologist Professor Scott Simpson
0:05:09 > 0:05:13of Case Western Reserve University, in Cleveland, Ohio.
0:05:13 > 0:05:17And Scott's been involved in some of the key discoveries of Homo erectus.
0:05:17 > 0:05:20These bones are really wonderful, they're an incredibly accurate cast.
0:05:20 > 0:05:23So Scott, introduce us to Nariokotome Boy.
0:05:23 > 0:05:27Ah, well, this is one of the most complete human ancestor skeletons
0:05:27 > 0:05:28that has been recovered, to date.
0:05:28 > 0:05:31He's probably aged about eight years old when he died.
0:05:31 > 0:05:33But he looks like he'd be older than that
0:05:33 > 0:05:36cos he's got both molars here and I would normally say that
0:05:36 > 0:05:39looks, to me, like a 12-year-old, not an eight-year-old.
0:05:39 > 0:05:42He's very unusual - he has a mixture of traits that show he's young
0:05:42 > 0:05:44and some mixtures of traits that show he's old.
0:05:44 > 0:05:48So, if he was like a modern human, we'd say he's about 12 years old.
0:05:48 > 0:05:49But what we've done
0:05:49 > 0:05:52is we've looked at detailed studies of the enamel of the teeth
0:05:52 > 0:05:54and we know, now, that he died when he was eight years old.
0:05:54 > 0:05:57The one thing that immediately strikes me
0:05:57 > 0:06:00is that...he seems very slight.
0:06:00 > 0:06:03There is a reason to suspect that he was quite agile,
0:06:03 > 0:06:06even just looking at his skeleton, but nevertheless, he is quite slim.
0:06:06 > 0:06:11Now Viktor, you've got Nariokotome Boy's skeleton loaded up.
0:06:11 > 0:06:14- Yes, I do.- How are you filling in the missing bits?
0:06:14 > 0:06:17Because again, he's quite complete but he's not all there.
0:06:17 > 0:06:20Well, what's really wonderful about working like this
0:06:20 > 0:06:23is that I can mirror image certain elements that exist
0:06:23 > 0:06:25and then fill in any gaps.
0:06:25 > 0:06:27So, can you mirror that humerus, there,
0:06:27 > 0:06:28and stick it on the other side?
0:06:28 > 0:06:31Right, so, here we go, let's see.
0:06:31 > 0:06:33Actually, I've got the whole arm set up, so there it is.
0:06:33 > 0:06:37Oh, fantastic. And you've put the radii in as well.
0:06:37 > 0:06:41Now, we think he might have been doing a fair bit of running,
0:06:41 > 0:06:42which we're going to talk about later,
0:06:42 > 0:06:45- but can you put him in a running pose for us?- Yeah, I can.
0:06:45 > 0:06:47There he goes!
0:06:47 > 0:06:49This is still a virtual skeleton
0:06:49 > 0:06:51but a copy of Nariokotome Boy's bones
0:06:51 > 0:06:53were delivered to our model makers
0:06:53 > 0:06:56and I went along to help them put him together.
0:07:02 > 0:07:06Down at the workshop, Jez Gibson-Harris leads the team.
0:07:06 > 0:07:07'Another day, another hominin?'
0:07:07 > 0:07:09Yes!
0:07:09 > 0:07:13Finding such a complete skeleton was a major breakthrough.
0:07:13 > 0:07:15Until Nariokotome Boy was unearthed,
0:07:15 > 0:07:19only odd remains of Homo erectus had been found.
0:07:19 > 0:07:22The missing parts of this cast have been filled in
0:07:22 > 0:07:26using techniques like Viktor's computer mirroring.
0:07:27 > 0:07:30The feet are thought to have been similar to ours.
0:07:30 > 0:07:34An arched foot makes walking and running more efficient.
0:07:34 > 0:07:36But the running pose that we've chosen
0:07:36 > 0:07:38is a challenge for the model makers.
0:07:41 > 0:07:43So, this is our spine.
0:07:43 > 0:07:45And the idea is, because he's running,
0:07:45 > 0:07:48- we've got an angle on the spine. - Yeah.
0:07:48 > 0:07:50He's leaning forwards.
0:07:50 > 0:07:52Running is an exercise in not falling over.
0:07:52 > 0:07:55So, I suppose, the challenge for you
0:07:55 > 0:07:59is going to be to make this as the freestanding running Nariokotome Boy
0:07:59 > 0:08:02- because he's going to want to fall forwards.- He is.
0:08:02 > 0:08:04Yes, the centre of balance is quite far forward
0:08:04 > 0:08:06and we've only got him on one leg.
0:08:08 > 0:08:10That's nice and straight now.
0:08:11 > 0:08:16So looking at Viktor's picture, then, this is the leg in stance,
0:08:16 > 0:08:20with the other leg about to swing through, like that.
0:08:20 > 0:08:23That's going to be slightly more tricky.
0:08:23 > 0:08:27- Because that malleoli should be right round here. - Right round the side.
0:08:27 > 0:08:29If you do that, if you bring that tibia round so the patella,
0:08:29 > 0:08:31the kneecap's in the right place,
0:08:31 > 0:08:34I think we're pretty much there, I mean, that looks really good.
0:08:34 > 0:08:37At the end of tonight's programme,
0:08:37 > 0:08:41we'll reveal our complete reconstruction of Nariokotome Boy
0:08:41 > 0:08:47and discover what Homo erectus may have looked like in the flesh.
0:08:47 > 0:08:49'I think just getting those elements assembled
0:08:49 > 0:08:52'means that you start to see somebody.
0:08:52 > 0:08:56'He's not just a collection of bones lying on the ground any more.'
0:09:00 > 0:09:03So what do you think of the reconstructed skeleton?
0:09:03 > 0:09:05Well, I think he looks absolutely fantastic.
0:09:05 > 0:09:08- It's absolutely extraordinary. Quite lifelike.- Very agile.
0:09:08 > 0:09:11You get a real sense of movement.
0:09:11 > 0:09:12Yeah, and it's great
0:09:12 > 0:09:15because now we can see what his skeleton might have looked like
0:09:15 > 0:09:16if he was complete.
0:09:16 > 0:09:18And there's lots of anatomical features here,
0:09:18 > 0:09:21- which have been described as being something to do with running.- Right.
0:09:21 > 0:09:24We talk about the nuchal ligament,
0:09:24 > 0:09:26which runs between a bump on the back of the skull and neck.
0:09:26 > 0:09:28That's to prevent our head pitching forward.
0:09:28 > 0:09:31You can feel it on yourself, or George.
0:09:31 > 0:09:34So, George, if you do exactly that and tuck your neck down...
0:09:34 > 0:09:36You can feel this quite thick band, in the back of your neck,
0:09:36 > 0:09:38running all the way down here.
0:09:38 > 0:09:40- Oh, yeah! I can feel that, yeah. - That's the nuchal ligament.
0:09:40 > 0:09:42And he's got low shoulders as well.
0:09:42 > 0:09:46So we think he's probably swinging his shoulders from side to side
0:09:46 > 0:09:48to counterbalance him while he's running
0:09:48 > 0:09:50and a nice flexible lumber spine too.
0:09:50 > 0:09:53Yes, so he could do the twist, spin back and forth,
0:09:53 > 0:09:55which is also necessary for walking and running.
0:09:55 > 0:09:57He had very strong back muscles.
0:09:57 > 0:10:00If we see, here, there are deep gutters on either side -
0:10:00 > 0:10:02necessary for twisting your body and holding you forward.
0:10:02 > 0:10:05It's anchoring the whole of your trunk, down to your pelvis.
0:10:05 > 0:10:08And, then also, we think Nariokotome Boy
0:10:08 > 0:10:09had quite big bottom muscles as well.
0:10:09 > 0:10:12Quite a big gluteus maximus.
0:10:12 > 0:10:14He looks really good.
0:10:14 > 0:10:16Well, the big gluteus maximus muscles,
0:10:16 > 0:10:19we use the gluteus maximus when we get out of a chair or when walking up stairs.
0:10:19 > 0:10:22For an animal that's walking and running in ancient Africa,
0:10:22 > 0:10:24you're going to need this muscle for turning direction
0:10:24 > 0:10:25and slowing yourself down.
0:10:25 > 0:10:28Preventing your body from pitching forward.
0:10:28 > 0:10:31So, are you convinced by these adaptations to running in Nariokotome Boy?
0:10:31 > 0:10:33There's a lot of information out there
0:10:33 > 0:10:35suggesting perhaps he was just a long-distance walker.
0:10:35 > 0:10:40And because we see that many humans are very well adapted to long-distance walking
0:10:40 > 0:10:42and walking, if you have a large territory,
0:10:42 > 0:10:47is a very important adaptation to living on the ancient African landscape.
0:10:47 > 0:10:51But I think running is certainly one explanation,
0:10:51 > 0:10:53explaining the anatomy of Nariokotome.
0:10:53 > 0:10:57So, Nariokotome Boy evolved to be a good runner,
0:10:57 > 0:10:58but the question is - why?
0:10:58 > 0:11:02One of the things that drives evolution is environmental change.
0:11:02 > 0:11:06So, what was happening to the world Homo erectus lived in?
0:11:06 > 0:11:09For researchers at Columbia University, in New York State,
0:11:09 > 0:11:12the answer to that question lies in the seabed.
0:11:16 > 0:11:20Professor Peter De Menocal works on a technique
0:11:20 > 0:11:24that can reveal what our planet was like millions of years ago.
0:11:24 > 0:11:27It measures climate change
0:11:27 > 0:11:30and it holds a clue as to why Homo erectus
0:11:30 > 0:11:33may have been one of the first long-distance runners.
0:11:35 > 0:11:36By analysing Earth cores,
0:11:36 > 0:11:39drilled from the seabed off the coast of Africa,
0:11:39 > 0:11:44he can pinpoint key environmental shifts in our ancestor's world.
0:11:44 > 0:11:46We use ocean sediment cores
0:11:46 > 0:11:49because the oceans are the ultimate repository of all sediment.
0:11:49 > 0:11:52So the sediment just kind of gets dumped into the ocean very slowly
0:11:52 > 0:11:54and continuously over time.
0:11:54 > 0:11:57So it's like being given a history book of Earth climate
0:11:57 > 0:12:00or earth history and no-one has ripped the pages out.
0:12:00 > 0:12:02It's like a continuous record of time.
0:12:02 > 0:12:05The accumulation rate of this core is roughly -
0:12:05 > 0:12:08that would be equivalent to about 1,000 years.
0:12:08 > 0:12:10So that's 1,000 years of accumulation,
0:12:10 > 0:12:132,000, 3,000, 4,000...
0:12:13 > 0:12:16In this case, this core goes back 10,000 years in time
0:12:16 > 0:12:20but we have another section that actually fits in the bottom of this,
0:12:20 > 0:12:22goes back another 10,000.
0:12:22 > 0:12:25We have cores that go hundreds of metres back below the seafloor
0:12:25 > 0:12:28and that takes us back millions of years into the past.
0:12:31 > 0:12:34By looking at subtle colour shifts in the cores,
0:12:34 > 0:12:37Peter can read periods of dramatic climate change
0:12:37 > 0:12:41in the African landscape across the millennia.
0:12:41 > 0:12:43You can see there's something happening in this core,
0:12:43 > 0:12:46roughly right around at this time, a colour change.
0:12:46 > 0:12:49And this is between 5,000 and 10,000 years ago.
0:12:49 > 0:12:51Sediments are green.
0:12:51 > 0:12:52Sediments are red.
0:12:52 > 0:12:56This redder sediment is the dust that's blown off of west Africa.
0:12:56 > 0:12:59And then the absence of that dust here is telling us
0:12:59 > 0:13:02that something in the African climate changed.
0:13:02 > 0:13:06And this is when we know that the African climate was much wetter than it is today.
0:13:06 > 0:13:08It was fully vegetated, there were large lakes.
0:13:08 > 0:13:11So Africa was wet here and it's dry here.
0:13:11 > 0:13:15Peter's team also analyse the sediment
0:13:15 > 0:13:18for fossilised remnants of plant matter.
0:13:18 > 0:13:21The types of plants that were growing
0:13:21 > 0:13:24tell Peter when the climate was warming up or cooling down.
0:13:25 > 0:13:29The swings between hot and wet to cooler and drier
0:13:29 > 0:13:34have occurred many times throughout the geological record.
0:13:34 > 0:13:37But if we travel back 1.8 million years,
0:13:37 > 0:13:42what can we discover about the time that Homo erectus first appeared?
0:13:43 > 0:13:47There's this shift that happens right around 1.8 million years ago,
0:13:47 > 0:13:49which is a really profound change.
0:13:49 > 0:13:52This is the first time that we see modern Savannah grass extend.
0:13:52 > 0:13:54If you think of your mind's eye image
0:13:54 > 0:13:56of what an African Savannah looks like,
0:13:56 > 0:13:57that's when that appears.
0:13:57 > 0:13:59It's right around 1.8, 1.6 million years ago.
0:14:01 > 0:14:05So, right around the time when Homo erectus appears in the fossil record,
0:14:05 > 0:14:09east Africa experiences this really tremendous change in vegetation
0:14:09 > 0:14:12from more closed habitats, better watered habitats,
0:14:12 > 0:14:15toward much more open vegetation.
0:14:15 > 0:14:18With long legs and a runner's physique,
0:14:18 > 0:14:21Homo erectus thrived in this new environment.
0:14:22 > 0:14:27And they had another adaptation that made them very effective runners.
0:14:27 > 0:14:30It's buried deep within the skeleton.
0:14:31 > 0:14:32But before we look at that,
0:14:32 > 0:14:37there's something I want to explain about his anatomy.
0:14:37 > 0:14:39But I'd like you to try something for yourself first.
0:14:39 > 0:14:42What I'd like you to do is keep your head entirely still,
0:14:42 > 0:14:43and you can try this at home.
0:14:43 > 0:14:47First of all, I have to put my glasses on. I have to read this.
0:14:47 > 0:14:50Get yourself... Open a book, get a sheet of paper with words on it.
0:14:50 > 0:14:52- HE STARTS READING - Start reading it.
0:14:52 > 0:14:56Move it from side to side very quickly. Can you read it?
0:14:56 > 0:14:57No, it's gone.
0:14:57 > 0:15:00OK, let's try it the other way round.
0:15:00 > 0:15:01Hold the piece of paper entirely still
0:15:01 > 0:15:04and shake your head from side to side.
0:15:04 > 0:15:09"As shown in the two drawings below, the canals..." OK.
0:15:09 > 0:15:13- So you can still read it. - "..In three planes that are..."
0:15:13 > 0:15:15So there's something really clever going on
0:15:15 > 0:15:18and it's a really clever reflex which involves -
0:15:18 > 0:15:21obviously, your eyes moving, and that's the last thing -
0:15:21 > 0:15:25but your ears are telling your eyes effectively via a reflex
0:15:25 > 0:15:29how your head's moving and keeping your eyes trained on one spot.
0:15:29 > 0:15:31Now, why would that be handy for this boy?
0:15:31 > 0:15:33It means you can keep your eyes ahead
0:15:33 > 0:15:36and you can look at one spot while you're running or jumping,
0:15:36 > 0:15:37whatever it is you're doing.
0:15:37 > 0:15:42So... We have some bits of anatomy over here.
0:15:42 > 0:15:44If I give that to you.
0:15:44 > 0:15:48And I'll bring this large ear model over...
0:15:48 > 0:15:51The bit of anatomy that we're interested in, which is allowing you to do this,
0:15:51 > 0:15:55is deep inside the skull and this is a massive model of it.
0:15:55 > 0:15:56And here it is.
0:15:56 > 0:16:00So this is the vestibular cochlea apparatus
0:16:00 > 0:16:04and here is the cochlea - your organ of hearing -
0:16:04 > 0:16:07but here is part of the organ of balance
0:16:07 > 0:16:10and also sensing direction changes and accelerations.
0:16:10 > 0:16:12These are the semicircular canals.
0:16:12 > 0:16:15Now, that's a really massive model and, Scott...
0:16:15 > 0:16:17That's not how big they are in real life.
0:16:17 > 0:16:19That's the real thing?
0:16:19 > 0:16:23That is a real one. So that's a human bony labyrinth.
0:16:23 > 0:16:26- It is absolutely minute. - Isn't it beautiful?
0:16:26 > 0:16:29And we have this anatomy for Homo erectus,
0:16:29 > 0:16:33so we can get an idea of exactly what this tiny, tiny bit of anatomy
0:16:33 > 0:16:35looks like in this ancient ancestor.
0:16:35 > 0:16:38Now, in order to do this,
0:16:38 > 0:16:42the scientists did NOT saw open the fossils,
0:16:42 > 0:16:46what they did instead was do that virtually, using a CT scanner.
0:16:46 > 0:16:50And then what they were able to do is reconstruct
0:16:50 > 0:16:54what the membranous labyrinth of Homo erectus would have looked like
0:16:54 > 0:16:56in three dimensions.
0:16:56 > 0:17:01The semicircular canals are a different shape and size
0:17:01 > 0:17:05from those of earlier ancestors and other apes.
0:17:05 > 0:17:08And what's quite remarkable about this is
0:17:08 > 0:17:10that it looks quite similar to ours.
0:17:10 > 0:17:14So this suggests perhaps that Homo erectus was very agile
0:17:14 > 0:17:17and probably running and jumping.
0:17:19 > 0:17:21And Homo erectus had to be agile.
0:17:21 > 0:17:25They weren't the only animals out on the savannah.
0:17:25 > 0:17:28There were grazing animals like rhinoceros.
0:17:28 > 0:17:32They have been around for nearly 17 million years.
0:17:32 > 0:17:34But in Homo erectus' world
0:17:34 > 0:17:39there were also predatory mammals like this sabre-toothed cat.
0:17:39 > 0:17:41They would have been a constant threat.
0:17:41 > 0:17:45Even with its smaller sabre teeth, it would have been deadly.
0:17:46 > 0:17:521.8 million years ago, Homo erectus may have been the first human species
0:17:52 > 0:17:55to leave Africa and start to spread around the world.
0:17:55 > 0:17:59But the ones that stayed behind weren't alone.
0:17:59 > 0:18:01They shared their African environment
0:18:01 > 0:18:07with as many as four other species of our early ancestors.
0:18:07 > 0:18:09So who else was around at the time all this was happening?
0:18:09 > 0:18:12Once you go back over a million years, there are some
0:18:12 > 0:18:16very different species living alongside those early humans.
0:18:16 > 0:18:19Like this bruiser here, Paranthropus boisei.
0:18:19 > 0:18:23And here he is. He's such an odd-looking hominin.
0:18:23 > 0:18:25I can't believe he's one of our relatives.
0:18:25 > 0:18:27- Very strange.- That's true.
0:18:27 > 0:18:29His whole anatomy seems to have been taken over
0:18:29 > 0:18:32by jaws and jaw musculature.
0:18:32 > 0:18:34He was a dedicated chewer.
0:18:34 > 0:18:37I mean, look at this, look at this crest along the top of his head.
0:18:37 > 0:18:39So his temporalis muscles,
0:18:39 > 0:18:42which are the ones we can feel if we're chewing,
0:18:42 > 0:18:45you can feel a muscle working on the side of your head there...
0:18:45 > 0:18:48Well, his muscles went right up to the top of his head.
0:18:48 > 0:18:50- Ours stop about here, don't they? - That's right.
0:18:50 > 0:18:53Right about here, except theirs, as they got older and older,
0:18:53 > 0:18:56grew to the midline and continued growing, forming a sagittal crest.
0:18:56 > 0:18:58Something we don't see in modern humans.
0:18:58 > 0:19:03Yeah. And then he's got incredibly flared cheek bones.
0:19:03 > 0:19:05So that that muscle can get through there, down to the jaw.
0:19:05 > 0:19:07But what are all those muscles doing?
0:19:07 > 0:19:11Well, there's the jaw. Look at that, those teeth are massive.
0:19:11 > 0:19:13Especially when we compare it to the Homo erectus skeleton.
0:19:13 > 0:19:16- Yeah, look at that. - They're almost two times as large.
0:19:16 > 0:19:18So these molars are absolutely huge,
0:19:18 > 0:19:21he must have been eating really tough foods.
0:19:21 > 0:19:24Lots and lots of low quality food. Day in and day out.
0:19:24 > 0:19:27His nickname is Nutcracker Man, which kind of suggests that
0:19:27 > 0:19:30he's eating very hard foods, but I think recent analyses of his teeth
0:19:30 > 0:19:32suggested that he might have been eating grasses as well.
0:19:32 > 0:19:35Absolutely. If we look at the microwear,
0:19:35 > 0:19:37the small scratches on his teeth, you can see that they ate
0:19:37 > 0:19:41lots and lots of grasses that were covered with sand and also included phytoliths,
0:19:41 > 0:19:43which are little stones that are found in grass,
0:19:43 > 0:19:45and together these wear down the teeth very, very quickly.
0:19:47 > 0:19:51Boisei was a species perfectly adapted to its environment.
0:19:51 > 0:19:55But when that environment started to change, they were in trouble.
0:19:55 > 0:19:58The climate in Africa began swinging between
0:19:58 > 0:20:01extremes of wet and dry.
0:20:01 > 0:20:04Unable to adapt, Boisei couldn't cope and died out.
0:20:09 > 0:20:11But Homo erectus thrived.
0:20:12 > 0:20:16The key to their success was their adaptability.
0:20:16 > 0:20:19Some estimate that at their peak there may have been
0:20:19 > 0:20:23as many as 125,000 of them living across the world,
0:20:23 > 0:20:27from Africa, right across Asia, to eastern China.
0:20:31 > 0:20:35This seems really bizarre because we normally think of species
0:20:35 > 0:20:37adapting to one particular type of environment,
0:20:37 > 0:20:40but our ancestors were having to get used to
0:20:40 > 0:20:42- a rapidly changing environment. - That's right,
0:20:42 > 0:20:46It shows the complexity of necessary adaptations for Homo erectus.
0:20:46 > 0:20:48Different habitats and environments
0:20:48 > 0:20:50require different types of adaptations.
0:20:51 > 0:20:55In the heat of the African savannah, keeping cool is crucial to survival.
0:20:58 > 0:21:01Many animals insulate themselves against the harmful exposure
0:21:01 > 0:21:05of the sun with a protective layer of hair.
0:21:06 > 0:21:10They rest at the hottest times of the day to avoid overheating.
0:21:10 > 0:21:14But that means they have less time to travel and hunt.
0:21:15 > 0:21:18If Homo erectus was out running in the heat of the day,
0:21:18 > 0:21:20what stopped them overheating?
0:21:20 > 0:21:25Could this be the time that our early ancestors lost their hair?
0:21:28 > 0:21:31I'm with Professor Peter Wheeler from John Moores University.
0:21:31 > 0:21:33Would Homo erectus have been hairy?
0:21:33 > 0:21:36That's something we don't know,
0:21:36 > 0:21:39but what we can say is that there are good reasons to think
0:21:39 > 0:21:43that it would have been advantageous for Homo erectus not to be hairy.
0:21:43 > 0:21:44Tell me more, Peter.
0:21:44 > 0:21:47Yes. We've got these volunteers, who aren't too dissimilar in physique
0:21:47 > 0:21:50to what the Nariokotome Boy might have looked like
0:21:50 > 0:21:51had he survived to be an adult.
0:21:51 > 0:21:54And they're identical twins
0:21:54 > 0:21:56and they've trained to a similar level of fitness.
0:21:56 > 0:21:59And we've had them standing under these heat lamps,
0:21:59 > 0:22:01which emulate the African sun.
0:22:01 > 0:22:04One of the advantages of retaining body hair
0:22:04 > 0:22:06is that it acts as a shield.
0:22:06 > 0:22:09It prevents a lot of the heat from the sun getting through to the body.
0:22:09 > 0:22:13And we've selected clothes that are similar in thermal properties
0:22:13 > 0:22:15to that of the hair of living primates.
0:22:15 > 0:22:19So, in essence, we have a hairless hominid and a hairy one.
0:22:19 > 0:22:24Yes. Now, although the surface of the hair does get very hot -
0:22:24 > 0:22:27in this case clothing - because it's insulating,
0:22:27 > 0:22:30most of it will be reflected and reradiated back to the environment.
0:22:30 > 0:22:33It's the lighter colours that are the warmest areas.
0:22:33 > 0:22:38The surfaces on the naked skinned volunteer are hot.
0:22:38 > 0:22:41They are the skin being hot itself,
0:22:41 > 0:22:45therefore the heat is being absorbed directly by the body.
0:22:45 > 0:22:47So while animals are standing still,
0:22:47 > 0:22:52their fur keeps them cool by reflecting heat away from the body.
0:22:52 > 0:22:57But John's bare skin is absorbing it, so he is getting hotter.
0:22:57 > 0:22:59Well, let's see how you fare when you start to run.
0:22:59 > 0:23:02We'll turn on fans to create a similar airflow
0:23:02 > 0:23:03to when you're actually running.
0:23:03 > 0:23:06We have a healthcare professional here.
0:23:06 > 0:23:09If you don't feel comfortable, you stop at any time.
0:23:09 > 0:23:11OK? Start running.
0:23:11 > 0:23:14TREADMILLS BLEEP
0:23:19 > 0:23:21Well, Alice, they're running away up here.
0:23:21 > 0:23:25Do we know why running would be so important for Homo erectus?
0:23:25 > 0:23:26Scott, what do you think?
0:23:26 > 0:23:30Homo erectus probably lived in very, very large home ranges.
0:23:30 > 0:23:33So that means he had to meander around
0:23:33 > 0:23:36and run around or walk around these large home ranges looking for food.
0:23:36 > 0:23:39Patrolling territories, if that's appropriate,
0:23:39 > 0:23:41but they're really eating high quality food,
0:23:41 > 0:23:44whether it's meat or high quality fruits and vegetables.
0:23:44 > 0:23:46But these are widely dispersed across the savannah,
0:23:46 > 0:23:48so you have to spend a lot of time walking around,
0:23:48 > 0:23:50looking for these high quality foods.
0:23:50 > 0:23:53So if he's looking for meat, obviously, meat walks around
0:23:53 > 0:23:56and probably needs to be hunted, so are we saying he's a hunter?
0:23:56 > 0:23:58You know, he probably was a hunter.
0:23:58 > 0:24:02Although we often think of 'em hunting elephants and the largest animals out there,
0:24:02 > 0:24:04well, they could have been hunting some of those animals -
0:24:04 > 0:24:05although it's not likely -
0:24:05 > 0:24:08what they're probably eating is smaller animals
0:24:08 > 0:24:10that were easy to trap or surprise in the course of a day.
0:24:10 > 0:24:12So, they were eating meat
0:24:12 > 0:24:15but they weren't the big hunters that we see in Neanderthals.
0:24:15 > 0:24:18What about scavenging, because that's another way of getting meat?
0:24:18 > 0:24:20If he could walk and run for long distances,
0:24:20 > 0:24:22then presumably that would have been an advantage to him.
0:24:22 > 0:24:25The problem with scavenged food, though, is that there are
0:24:25 > 0:24:28a lot of other animals that are also interested in scavenged food,
0:24:28 > 0:24:30like hyenas, lions, jackals and birds of prey.
0:24:30 > 0:24:33But running would have been useful in terms of getting away
0:24:33 > 0:24:36from other scavengers and predators, I imagine.
0:24:36 > 0:24:39True, but only if you can run faster than the other scavengers and predators.
0:24:39 > 0:24:43If we're talking about somebody who's running around the savannah, we need to put some muscles on him.
0:24:43 > 0:24:47So let's go and see how Viktor's getting on.
0:24:47 > 0:24:48Oh, look at this. That's lovely.
0:24:48 > 0:24:50So you've got muscles on his body
0:24:50 > 0:24:52and muscles appearing on his face as well.
0:24:52 > 0:24:55He's still looking quite lean and I think that's right,
0:24:55 > 0:24:58he's got very slender bones,
0:24:58 > 0:25:02so we're not looking at great, big, chunky musculature.
0:25:02 > 0:25:04He looks very lithe, doesn't he?
0:25:04 > 0:25:07Right, he would've had not a lot of body fat,
0:25:07 > 0:25:09- especially in that environment and climate.- Yeah.
0:25:09 > 0:25:11And as active as he was.
0:25:11 > 0:25:14All this information has been fed to our model makers.
0:25:14 > 0:25:17Once the muscles have been put on the skeleton,
0:25:17 > 0:25:21Nariokotome Boy really does start to look more human.
0:25:26 > 0:25:30The team uses modelling clay to form muscles around the skeleton.
0:25:30 > 0:25:36For sculptor Reza, making sure they are accurate is tricky work.
0:25:36 > 0:25:37Reza, you look a bit nervous.
0:25:37 > 0:25:40Well, this is my baby.
0:25:41 > 0:25:44Wow, that looks a bit different.
0:25:46 > 0:25:50Let me just unwrap the arms and legs.
0:25:50 > 0:25:52Well, he's got a very lovely serratus anterior,
0:25:52 > 0:25:53I can say that right now.
0:25:53 > 0:25:55Look at this lovely muscle right here,
0:25:55 > 0:25:59this is the muscle that holds the scapula onto the back of the thorax.
0:25:59 > 0:26:02So this is all looking anatomically beautiful. Very accurate.
0:26:02 > 0:26:04Thank you.
0:26:04 > 0:26:09'Considering Nariokotome Boy was around 1.5 million years ago,
0:26:09 > 0:26:13'his body is surprisingly similar to ours.'
0:26:13 > 0:26:18We're seeing all of the muscles that we'd see in us.
0:26:18 > 0:26:21- These are the same muscles. - Yes, exactly.
0:26:21 > 0:26:22They're in the same places.
0:26:23 > 0:26:27- I quite like him without a head. - THEY LAUGH
0:26:27 > 0:26:29Now, we haven't got hands or feet on him,
0:26:29 > 0:26:32but at the moment he does look very human, doesn't he?
0:26:32 > 0:26:35- Yeah, it does.- I think that's going to change when we put the head on.
0:26:35 > 0:26:39Cos it really is the head which is so different.
0:26:39 > 0:26:40Right, yes.
0:26:40 > 0:26:44He's got quite a small brain, and quite a distinctive face as well.
0:26:44 > 0:26:50There's a couple of tweaks that I think would really help.
0:26:50 > 0:26:53He's running and actually we need to get a bit of a twist going on.
0:26:53 > 0:26:55So when you're running along...
0:26:55 > 0:26:58So you're swinging your...
0:26:58 > 0:27:01- You swing your chest the other way to kind of...- Right, yes.
0:27:01 > 0:27:04To counterbalance, cos your leg's trying to spin you off
0:27:04 > 0:27:06in that direction.
0:27:06 > 0:27:08Yeah, we can do some adjustments there.
0:27:08 > 0:27:11- He's coming on really nicely. - Thank you.
0:27:13 > 0:27:15He's really starting to take shape.
0:27:15 > 0:27:17Now, our volunteers have really been
0:27:17 > 0:27:19working up a sweat on these treadmills,
0:27:19 > 0:27:22so now I want to see who's keeping their cool.
0:27:22 > 0:27:25- How are you feeling?- Tough.
0:27:25 > 0:27:26- Tough?- Yeah.
0:27:26 > 0:27:29And our naked-skinned human?
0:27:29 > 0:27:30- OK.- OK.
0:27:30 > 0:27:32He feels he can keep going.
0:27:32 > 0:27:34He's dissipating the heat load that his muscles are producing
0:27:34 > 0:27:35much more easily.
0:27:35 > 0:27:39And there are two distinct reasons why he is able to do this.
0:27:39 > 0:27:42The loss of his body hair means that heat can flow from his body
0:27:42 > 0:27:45more easily out into the environment.
0:27:45 > 0:27:48The second advantage is the loss of body hair
0:27:48 > 0:27:50makes sweating much more effective.
0:27:50 > 0:27:54When the sweat is secreted onto the skin's surface,
0:27:54 > 0:27:55the increased airflow over the skin
0:27:55 > 0:27:58means that sweat is evaporated at a greater rate.
0:27:58 > 0:28:01I think you should switch the machines off now
0:28:01 > 0:28:05cos I'm worried you're about to have heatstroke.
0:28:05 > 0:28:09Now, haul up your shirt there. Look at that.
0:28:09 > 0:28:12Now, all that heat has been trapped inside,
0:28:12 > 0:28:15his core, his insides, are really heating up.
0:28:15 > 0:28:21John on the left there is not nearly as hot underneath,
0:28:21 > 0:28:24so the advantages are quite clear.
0:28:24 > 0:28:27The advantages are very clear, particularly during activity,
0:28:27 > 0:28:30either through long-distance persistence walking,
0:28:30 > 0:28:33through the heat of the tropical day or short bursts of intense activity,
0:28:33 > 0:28:35such as our volunteers have done here.
0:28:35 > 0:28:38There's one other problem with exposed skin in the sun
0:28:38 > 0:28:41is that you would have to have dark skin protected by melanin.
0:28:41 > 0:28:43What about hair on the head?
0:28:43 > 0:28:46One of the reasons we think hair is retained on the head
0:28:46 > 0:28:49is that it's actually shielding those areas of the body in a biped
0:28:49 > 0:28:53which are most exposed to the strongest fluxes of solar radiation...
0:28:53 > 0:28:55- It protects the brain? - ..when the sun is overhead.
0:28:55 > 0:28:57It's shielding the brain from overheating.
0:28:57 > 0:28:59Steven, how do you feel?
0:28:59 > 0:29:01- It was really hard. - That was really hard.
0:29:01 > 0:29:03- Good.- You could have kept going, I reckon.
0:29:03 > 0:29:04Yeah.
0:29:05 > 0:29:08Under the searing savannah sun, Nariokotome Boy
0:29:08 > 0:29:12could only run during the day if he could keep cool.
0:29:12 > 0:29:16Sweating is the most efficient way of losing heat and to do that
0:29:16 > 0:29:19he would have needed very little body hair.
0:29:19 > 0:29:21This is really interesting
0:29:21 > 0:29:24and I find it really intriguing that we could be looking at
0:29:24 > 0:29:27the point in our story where our ancestors lost their fur.
0:29:27 > 0:29:29That's right. This is very unusual.
0:29:29 > 0:29:31Humans are unique among primates because we are naked.
0:29:31 > 0:29:34We just don't have the hair that the other primates have.
0:29:34 > 0:29:37Perhaps the most compelling reason that we've lost the hair
0:29:37 > 0:29:38is that we wanted to shed heat.
0:29:38 > 0:29:42That allows us to be active throughout the course of the day,
0:29:42 > 0:29:45as apposed to... most mammals rest at noon time.
0:29:45 > 0:29:48- And this is exactly what the experiment showed.- Very clearly.
0:29:48 > 0:29:53Hairlessness could mean that we can keep cool in a hot environment.
0:29:53 > 0:29:56Perhaps that does mean that our ancestors could have gone out
0:29:56 > 0:29:59and perhaps scavenged meat, perhaps hunted meat, in a period of time
0:29:59 > 0:30:02when other predators might have been resting in the shade.
0:30:02 > 0:30:04- That's right. - And it's interesting that,
0:30:04 > 0:30:07if meat were a more important part of these ancestors' diets,
0:30:07 > 0:30:10it's interesting to look at the teeth and see that they're getting smaller
0:30:10 > 0:30:14and also to see that Nariokotome Boy has a very different-shaped thorax,
0:30:14 > 0:30:18rib cage, and it's been suggested that he's got a shorter gut.
0:30:18 > 0:30:22It could very well be, because if we look at the shape of the rib cage,
0:30:22 > 0:30:25the rib cage is not as broad, wide or flared out as some of our earlier ancestors.
0:30:25 > 0:30:29That means that the space in between the pelvis and the diaphragm,
0:30:29 > 0:30:32where our guts live, seems to be a smaller volume.
0:30:32 > 0:30:34We have smaller guts.
0:30:34 > 0:30:37Which suggest that he was eating better quality food.
0:30:37 > 0:30:40The shorter the gut, the better quality the food.
0:30:40 > 0:30:43So meat could be an explanation for that, but there could be
0:30:43 > 0:30:46another explanation as well why guts and teeth are getting smaller.
0:30:46 > 0:30:50It could have been that these guys were cooking their food.
0:30:50 > 0:30:54It's controversial because until recently, it was thought humans
0:30:54 > 0:30:57DIDN'T control fire until around 400,000 years ago.
0:30:57 > 0:31:00But new chemical analysis techniques
0:31:00 > 0:31:02may have just put a match to all that.
0:31:05 > 0:31:09Cooking with fire is a uniquely human behaviour.
0:31:09 > 0:31:12Today, Homo sapiens are the only species to do it,
0:31:12 > 0:31:15but that hasn't always been the case.
0:31:17 > 0:31:21In Williamstown, Massachusetts, Dr Anne Skinner has been analysing
0:31:21 > 0:31:26tiny fragments of ancient animal bones that have been burned.
0:31:26 > 0:31:30They were found at a site used by Homo erectus.
0:31:30 > 0:31:34And Anne made an extraordinary discovery.
0:31:36 > 0:31:40What elements within the bone are you particularly interested in?
0:31:40 > 0:31:43The part I'm interested in is the proteins.
0:31:43 > 0:31:45And how does the fire affect them?
0:31:45 > 0:31:51It breaks down the protein and leaves behind just these small bits
0:31:51 > 0:31:56that can be seen even a million to 1.5 million years later.
0:31:58 > 0:32:02Using a technique known as electron spin resonance,
0:32:02 > 0:32:06she can analyse changes in bone protein.
0:32:06 > 0:32:10These reveal what temperature the bones were burned at.
0:32:12 > 0:32:15Natural fires from the time of Homo erectus would have been
0:32:15 > 0:32:19grassfires that burn at 300 degrees Celsius.
0:32:19 > 0:32:23But man-made fires, created in a hearth,
0:32:23 > 0:32:26reach much higher temperatures.
0:32:26 > 0:32:30So if I have bones that are heated above 300,
0:32:30 > 0:32:34and especially above 400, to give us a little leeway here,
0:32:34 > 0:32:38then I can be sure that they were not heated in a grassfire,
0:32:38 > 0:32:41and hence they have to have been heated
0:32:41 > 0:32:45in a fire constructed by hominids.
0:32:46 > 0:32:51Anne used her technique to analyse burnt fragments of antelope bones
0:32:51 > 0:32:55found in Swartkrans cave in South Africa.
0:32:55 > 0:33:00This was a cave where Homo erectus remains had also been found.
0:33:00 > 0:33:06Remarkably, she found that the bones had burned at 350 degrees Celsius,
0:33:06 > 0:33:10and believes this shows they must have been burnt in a hearth.
0:33:10 > 0:33:14I can show that these bones were burned in a fire
0:33:14 > 0:33:18that must have been created and controlled at the cave
0:33:18 > 0:33:21and that dates to somewhere between 1 and 1.5 million years,
0:33:21 > 0:33:25which is older than any other site that has ever been found.
0:33:25 > 0:33:28- That is a major breakthrough. - It is. Yes.
0:33:28 > 0:33:34Scientists believed that the only species to have the mental ability
0:33:34 > 0:33:37to use fire at this time was Homo erectus.
0:33:38 > 0:33:41So from your work at Swartkrans cave,
0:33:41 > 0:33:45what are you able to tell about Homo erectus and fire?
0:33:45 > 0:33:48Well, the fire itself is interesting,
0:33:48 > 0:33:53but the idea that these entities had the ability to even conceive
0:33:53 > 0:33:56that they might control their environment,
0:33:56 > 0:33:59rather than just letting the environment control them...
0:33:59 > 0:34:02Instead of seeing a burning bush and running in the other direction,
0:34:02 > 0:34:05to conceptually say, "Hey, we could use that.
0:34:05 > 0:34:09"Even if we weren't cooking, we could use it to scare away leopards.
0:34:09 > 0:34:12"We could use it to keep warm".
0:34:12 > 0:34:15Just thinking that there's something that you could use
0:34:15 > 0:34:19in your environment is...takes more effort than you might think.
0:34:22 > 0:34:25Anne's findings have rewritten the timeline
0:34:25 > 0:34:29on Homo erectus' ability to harness fire.
0:34:30 > 0:34:35Evolutionary biologist Dr Rachel Carmody has studied the research.
0:34:35 > 0:34:38She believes that the early use of fire could even have
0:34:38 > 0:34:41accelerated their development.
0:34:41 > 0:34:45This kind of work is really showing us
0:34:45 > 0:34:49that humans were controlling fire and were possibly using it
0:34:49 > 0:34:54for things like cooking very early on in human evolution.
0:34:54 > 0:34:59Cooked food means a more varied, higher energy diet.
0:34:59 > 0:35:01This reduces the workload for the gut
0:35:01 > 0:35:05and leaves calories spare for the rest of the body.
0:35:05 > 0:35:09A fifth of the calories we consume are used to fuel our brains.
0:35:09 > 0:35:12There's a theory that a switch to cooked food
0:35:12 > 0:35:16is one of the things that encouraged an increase in brain size.
0:35:16 > 0:35:19What we see at this point in human evolution
0:35:19 > 0:35:23is the beginning of a trade-off, where gut size gets smaller
0:35:23 > 0:35:26and so you save energy by having a smaller gut.
0:35:26 > 0:35:29But humans seem to have been able to reallocate that saved energy
0:35:29 > 0:35:31towards fuelling a larger brain.
0:35:33 > 0:35:37So is there a link between a better diet and growing bigger brains?
0:35:37 > 0:35:41I find this really intriguing and slightly unsettling
0:35:41 > 0:35:44because, for me, this is evolution turned on its head.
0:35:44 > 0:35:47Because we're saying that we are saving some energy somewhere,
0:35:47 > 0:35:50so that means we can grow a bit of ourselves bigger.
0:35:50 > 0:35:54- George, what do you think? - A chimpanzee spends 47% of its time
0:35:54 > 0:35:56chewing and eating and processing food,
0:35:56 > 0:35:58whereas humans only spend 4.7%,
0:35:58 > 0:36:02so you've got all this extra time and energy to do something with it.
0:36:02 > 0:36:04Why not cooking?
0:36:04 > 0:36:07While we are looking at size of brains, I've got a very graphic way
0:36:07 > 0:36:09of demonstrating how brains are getting bigger
0:36:09 > 0:36:13through human evolution and that's over here. And...
0:36:13 > 0:36:15Thank you, Scott.
0:36:15 > 0:36:17Stick Nariokotome Boy's skull in there.
0:36:17 > 0:36:21We've got a range of different humans here from different times
0:36:21 > 0:36:24in our story, in fact, these ones aren't even human,
0:36:24 > 0:36:27they're ancestors but they're not quite human yet.
0:36:27 > 0:36:31This one is perhaps the earliest fossil that we have
0:36:31 > 0:36:34which we might be able to call a human ancestor.
0:36:34 > 0:36:36This is Toumai, Sahelanthropus tchadensis,
0:36:36 > 0:36:39- from about six or seven million years ago.- That's right.
0:36:39 > 0:36:44And these beads represent the volume of the brain. Of the inside...
0:36:44 > 0:36:48And this is a pretty tiny brain, isn't it, Scott?
0:36:48 > 0:36:50It's just a little bit larger than a chimpanzee
0:36:50 > 0:36:54or maybe chimpanzee average size. So it's not very smart.
0:36:54 > 0:36:57And then this one is Australopithecus africanus?
0:36:57 > 0:37:01Yes, she's from South Africa from 2.5 to 2.8 million years ago.
0:37:01 > 0:37:06Also walked upright on two legs like we do and perhaps Sahelanthropus.
0:37:06 > 0:37:09And this is the average size of this species' brain.
0:37:09 > 0:37:10So there you go, a little bit bigger.
0:37:10 > 0:37:14And now we come to Nariokotome Boy and his kind.
0:37:14 > 0:37:16So Homo erectus.
0:37:16 > 0:37:19Now that volume that you're pouring in there
0:37:19 > 0:37:22actually represents an adult of that species.
0:37:22 > 0:37:23It does, yes.
0:37:23 > 0:37:27His brain is a bit smaller than that but had he grown to be an adult,
0:37:27 > 0:37:29then he would have achieved something like that.
0:37:29 > 0:37:32It's kind of the average for the species as well, isn't it?
0:37:32 > 0:37:35That's right, although there's quite a large range of brain size
0:37:35 > 0:37:38in Homo erectus because it spans a very long period of time.
0:37:38 > 0:37:42And I recognise that skull. That's your skull.
0:37:42 > 0:37:44That's me, that's my skull...
0:37:44 > 0:37:45Oh, it's tiny, look!
0:37:45 > 0:37:48- Absolutely tiny. Hang on a minute! - Smaller than Homo erectus.
0:37:48 > 0:37:51Hang on a minute! Right, OK...
0:37:51 > 0:37:55So this really is one of the weirdest things about us,
0:37:55 > 0:37:57is the huge brains that we have.
0:37:57 > 0:38:00And our brains have been growing throughout human evolution.
0:38:00 > 0:38:03But it's not all about the size of the brains,
0:38:03 > 0:38:08it's actually what's going on with those brains and what we're doing with them that's important.
0:38:08 > 0:38:11And here's where we turn from fossil bones to archaeology.
0:38:11 > 0:38:15We've got Professor Bruce Bradley of Exeter University here,
0:38:15 > 0:38:20to tell us about what they're doing with these big brains.
0:38:20 > 0:38:23Very interestingly, when we see the beginning of Homo erectus,
0:38:23 > 0:38:27we see a quantum change in the way they're making stone tools.
0:38:27 > 0:38:30And they're going from very simple stone tools,
0:38:30 > 0:38:34where a piece of stone would be picked up and just the end would be
0:38:34 > 0:38:37knocked off... Now, we need to put on some safety glasses.
0:38:37 > 0:38:41Because this can be dangerous. Sharp things flying around.
0:38:41 > 0:38:45And so it's very simply the earliest stone tools, are taking
0:38:45 > 0:38:49a piece and just knocking the end off of it to get a sharp edge.
0:38:49 > 0:38:53- Yeah, that's sharp.- Yeah. You know, it's not a brilliant tool.
0:38:53 > 0:38:55It's pretty basic, though.
0:38:55 > 0:38:57It's pretty basic, and you're just taking the form
0:38:57 > 0:39:00that you have naturally, and just knocking the end off of it.
0:39:00 > 0:39:03So what do we see when we get to Homo erectus?
0:39:03 > 0:39:06Think about that, and then think about doing this.
0:39:06 > 0:39:10They're shaping the whole piece, and they're not only doing that,
0:39:10 > 0:39:14they're turning it into something much more complex.
0:39:14 > 0:39:17There's flaking on two sides, with a straight edge that goes all around.
0:39:17 > 0:39:20In order to do that, they must have an idea
0:39:20 > 0:39:22of what they're going to end up with.
0:39:22 > 0:39:23It isn't just random bashing.
0:39:23 > 0:39:27They have a plan in their head to make that shape.
0:39:27 > 0:39:30This is a real planned object, and it takes a really different
0:39:30 > 0:39:33kind of technique.
0:39:33 > 0:39:36So instead of just sort of hitting it with
0:39:36 > 0:39:40a stone, what I'm going to be doing is working on this edge here.
0:39:40 > 0:39:45And then as I strike pieces, you can see they run across the surface.
0:39:45 > 0:39:47So I'm not only shaping an edge,
0:39:47 > 0:39:50I'm shaping the whole thing three-dimensionally.
0:39:50 > 0:39:54This takes an incredibly different mindset,
0:39:54 > 0:39:56a cognition, a way of thinking and seeing things.
0:39:56 > 0:40:00So, what we're looking at is like you said - planning.
0:40:00 > 0:40:02But what's more interesting is not just that they made these
0:40:02 > 0:40:05hand axes, but to get to these hand axes,
0:40:05 > 0:40:09particularly in parts of Africa, they had very large pieces of stone.
0:40:09 > 0:40:13- I wondered why that was there. - How do you get this, from this?
0:40:13 > 0:40:15What Homo erectus was doing is they were taking
0:40:15 > 0:40:19- and making these big things, which we call blanks.- Yeah.
0:40:19 > 0:40:22And then THESE were being turned into the hand axes.
0:40:22 > 0:40:26So they're making their own form. Free form.
0:40:26 > 0:40:30- So can you get a blank out of there? - Well, we're going to see...
0:40:32 > 0:40:33Oh!
0:40:33 > 0:40:36- So...- Wow.
0:40:36 > 0:40:40So this, to me, is like Michelangelo looking at a block of marble,
0:40:40 > 0:40:43and saying, "I can see David inside it."
0:40:43 > 0:40:45I see three or four Davids in this one.
0:40:48 > 0:40:52So, Homo erectus had bigger brains and better tools.
0:40:52 > 0:40:57They could cover large distances, and it seems they may even have had fire.
0:40:57 > 0:41:02With these skills, they were well equipped to explore territories outside Africa.
0:41:02 > 0:41:06But what did they look like?
0:41:06 > 0:41:09Right, I'm off to see how Viktor's getting on over here.
0:41:09 > 0:41:12Because our Nariokotome Boy
0:41:12 > 0:41:16should be starting to look almost finished now.
0:41:16 > 0:41:21- I'm just working out the hair... - You're not revealing the face yet!
0:41:21 > 0:41:23No. I've got to keep it a secret for you.
0:41:23 > 0:41:26So you're not putting that much hair on the rest of his body.
0:41:26 > 0:41:29No. Because of thermo-regulation
0:41:29 > 0:41:32his hair covering would have been less.
0:41:32 > 0:41:35He's still going to be retaining a bit of furriness
0:41:35 > 0:41:37from his ancestors, he's not THAT far removed yet...
0:41:37 > 0:41:42- And he's got dark skin. - Dark skin to help against the sun.
0:41:42 > 0:41:44- But looking more like us, actually. - Definitely.
0:41:44 > 0:41:47So it's time to join our model makers in their studio,
0:41:47 > 0:41:52where they're going to need a LOT of patience to finish off Nariokotome Boy.
0:41:55 > 0:41:58The modellers have finished sculpting Nariokotome Boy's body,
0:41:58 > 0:42:01and now it's time to cast the model.
0:42:02 > 0:42:06First he's carefully wrapped in fibreglass to make a mould.
0:42:07 > 0:42:13Liquid silicone is poured into the mould to create a model with a lifelike skin texture.
0:42:15 > 0:42:18The next challenge is to decide how hairless he should be
0:42:18 > 0:42:20to allow effective sweating,
0:42:20 > 0:42:23and to choose a skin tone which would have given him
0:42:23 > 0:42:26adequate protection from the African sun.
0:42:26 > 0:42:30The researchers have given us advice on which way to go with the colour of this figure,
0:42:30 > 0:42:36and the feedback is we've got this darker brown colour,
0:42:36 > 0:42:38and now we've come to the painting stage,
0:42:38 > 0:42:42whereby we mix up washes of silicone fluid
0:42:42 > 0:42:46and we put in different pigments, create the different washes
0:42:46 > 0:42:51that are applied layer upon layer, and these will bring up the skin tones.
0:42:51 > 0:42:52But it's quite a long process.
0:42:52 > 0:42:55One of the challenges is to get the lighter skin tones
0:42:55 > 0:42:59around the feet and around the palms of the hands.
0:42:59 > 0:43:03It's looking very shiny at the moment, but once it's complete,
0:43:03 > 0:43:05we'll put a matting agent on
0:43:05 > 0:43:07and that'll give it a much more natural look.
0:43:07 > 0:43:11With their dark, hairless skin and lean physique,
0:43:11 > 0:43:14Homo erectus may have left Africa and spread
0:43:14 > 0:43:19right across Asia... but they didn't go far north.
0:43:19 > 0:43:21And the reason for this may have had
0:43:21 > 0:43:24something to do with the colour of their skin.
0:43:24 > 0:43:27Well, this is Professor Barbara Boucher
0:43:27 > 0:43:30of Queen Mary University of London, who has spent decades
0:43:30 > 0:43:34looking into the relationship between skin colour and health.
0:43:34 > 0:43:36I mean, he's living in a tropical environment,
0:43:36 > 0:43:39so presumably we would expect him to have dark skin to protect his...
0:43:39 > 0:43:43You certainly would or he'd be in quite a deal of trouble with sunburn
0:43:43 > 0:43:46and skin cancers, and generally uncomfortable.
0:43:46 > 0:43:50The trouble is, as you move north, a lot less ultraviolet gets through,
0:43:50 > 0:43:53and we need ultraviolet to make vitamin D
0:43:53 > 0:43:56because it's one of our essential hormones
0:43:56 > 0:43:59and we depend on sunlight to make it.
0:43:59 > 0:44:02If you are in the north and you've got very dark skin,
0:44:02 > 0:44:05you tend to run out of vitamin D. You just don't make enough.
0:44:05 > 0:44:07You're a clinician and a scientist,
0:44:07 > 0:44:12so clinically, what is the problem if people are vitamin D deficient?
0:44:12 > 0:44:14The first thing you would expect to get is bone disease.
0:44:14 > 0:44:17Children, as we well know, get rickets,
0:44:17 > 0:44:20and women in pregnancy tend to get soft bones.
0:44:20 > 0:44:21If you have a soft bone,
0:44:21 > 0:44:24and you're walking about, you tend to squash your pelvis in,
0:44:24 > 0:44:28and your pelvis gets narrowed and you can't deliver the baby,
0:44:28 > 0:44:29so mother and baby die.
0:44:29 > 0:44:32So we've talked about effects on bone. What about immunity?
0:44:32 > 0:44:35Is vitamin D important for that as well?
0:44:35 > 0:44:36Very important for that.
0:44:36 > 0:44:40You need vitamin D to make various compounds that destroy bacteria.
0:44:40 > 0:44:42You can reduce the dangers of bad infections
0:44:42 > 0:44:44and the risks of viral illness
0:44:44 > 0:44:47and perhaps rather reduce the hazards of TB.
0:44:47 > 0:44:48This is fascinating.
0:44:48 > 0:44:52I think it shows that disease can have a very powerful influence
0:44:52 > 0:44:54on how populations grow and spread.
0:44:57 > 0:45:01Many diseases leave very little mark on our skeletons,
0:45:01 > 0:45:05but when they do, that evidence in ancient bones
0:45:05 > 0:45:09can tell us something more about our ancestors and their way of life.
0:45:11 > 0:45:14I've been to Germany to look at some controversial new evidence.
0:45:17 > 0:45:22In 2007, at the University of Gottingen's School of Anatomy,
0:45:22 > 0:45:25Professor Michael Schultz was asked to examine a fragment
0:45:25 > 0:45:27of a Homo erectus skull.
0:45:32 > 0:45:35Found in a quarry in Turkey, it had a remarkable story to tell.
0:45:37 > 0:45:42That's a part of a frontal bone found in Turkey
0:45:42 > 0:45:45where they are sawing blocks and making tiles,
0:45:45 > 0:45:49and very probably, we must have blocks with the rest of the skull
0:45:49 > 0:45:51or even the whole skeleton.
0:45:51 > 0:45:53So this means that, in fact, the rest of this skull
0:45:53 > 0:45:57could be in tiles like this on somebody's bathroom wall?
0:45:57 > 0:45:59That's possible, but I doubt it.
0:45:59 > 0:46:01Everyone's going to be looking at their bathroom walls now.
0:46:03 > 0:46:05And how old is this skull?
0:46:05 > 0:46:09It was dated approximately 500,000 years.
0:46:11 > 0:46:14When Michael looked at the inside of the skull,
0:46:14 > 0:46:17he saw tiny marks which shouldn't be there.
0:46:18 > 0:46:22We have very small granular impressions.
0:46:22 > 0:46:26We have also impressions of very small blood vessels,
0:46:26 > 0:46:28probably arteries.
0:46:28 > 0:46:31Normally you'd expect the surface of that to be quite smooth
0:46:31 > 0:46:33and you wouldn't see so many blood vessels?
0:46:33 > 0:46:38That's right. We have maybe here new formations of bone.
0:46:40 > 0:46:43Something had put pressure on the inside of the skull,
0:46:43 > 0:46:45causing pits in the bone.
0:46:48 > 0:46:52OK, so we've got pits, and we've got new bone growth,
0:46:52 > 0:46:56and also grooves from unusual blood vessels here.
0:46:56 > 0:46:58What do you think that means?
0:46:58 > 0:46:59We have to be very careful,
0:46:59 > 0:47:04but I am convinced that this very probably is caused by TB.
0:47:06 > 0:47:09It's remarkable to have this diagnosis of TB, Tuberculosis,
0:47:09 > 0:47:11in Homo erectus.
0:47:13 > 0:47:17This is a disease which was thought to have emerged
0:47:17 > 0:47:18just 10,000 years ago,
0:47:18 > 0:47:23yet this skull is 500,000 years old.
0:47:24 > 0:47:28When the skull is compared to a modern human skull from a TB victim,
0:47:28 > 0:47:31the similarities are startling.
0:47:32 > 0:47:33This is really interesting
0:47:33 > 0:47:35because we're seeing exactly the same changes.
0:47:35 > 0:47:38We can see the pits there and new bone formation.
0:47:38 > 0:47:41So we've got a skull from the 19th century that's showing
0:47:41 > 0:47:44precisely the same changes as this 500,000-year-old skull.
0:47:44 > 0:47:48And we know exactly that this skull is from a young adult
0:47:48 > 0:47:52and we know that he died from TB.
0:47:52 > 0:47:53So, in fact, what we're looking at
0:47:53 > 0:47:55in that much more ancient piece of skull
0:47:55 > 0:47:59are the tiny lumps which give TB its name, the tubercles,
0:47:59 > 0:48:02- making an impression on the skull here.- Right, yeah.
0:48:02 > 0:48:06Finding evidence of a disease like TB
0:48:06 > 0:48:11among simple hunter-gatherers like Homo erectus is revolutionary.
0:48:11 > 0:48:15At first sight, I couldn't accept that this might be TB
0:48:15 > 0:48:17from 500,000 years ago!
0:48:17 > 0:48:20I have to say, Michael, that I was quite sceptical.
0:48:20 > 0:48:24But now, with you showing me the signs on this very good cast,
0:48:24 > 0:48:27I have to say I'm convinced.
0:48:27 > 0:48:30What do you think, Scott? I thought that was fairly convincing evidence
0:48:30 > 0:48:32of TB inside that skull.
0:48:32 > 0:48:36We have to be cautious perhaps on the identification of tuberculosis.
0:48:36 > 0:48:40Given that this could potentially be TB, this is fascinating
0:48:40 > 0:48:44because it pushes the origins of TB in humans
0:48:44 > 0:48:46back much further than previously thought.
0:48:46 > 0:48:49Even quite recently we thought we didn't get TB
0:48:49 > 0:48:50until we started farming cattle.
0:48:50 > 0:48:53What's interesting is the disease process tells us a lot
0:48:53 > 0:48:57about the behaviour and the adaptations of extinct ancestors.
0:48:57 > 0:48:59It says something about the way humans are interacting,
0:48:59 > 0:49:01populations are interacting across Eurasia.
0:49:01 > 0:49:04It's also saying something about how humans are interacting
0:49:04 > 0:49:06with other animals on the landscape, like cattle.
0:49:06 > 0:49:10Tuberculosis is a pathogen that lives in cattle and other bovids.
0:49:10 > 0:49:14It's amazing how much pathology - disease in ancient human remains -
0:49:14 > 0:49:15can reveal about our ancestors,
0:49:15 > 0:49:20but could it EVEN provide us with an insight into their feelings?
0:49:26 > 0:49:29One trait that we think marks us out as human
0:49:29 > 0:49:31is the sophistication of our emotions,
0:49:31 > 0:49:33like sympathy and compassion.
0:49:35 > 0:49:37But can fossilised bones
0:49:37 > 0:49:40tell us anything about our ancestors' feelings?
0:49:41 > 0:49:43I've been to the Republic of Georgia,
0:49:43 > 0:49:46to the small medieval town of Dmanisi.
0:49:47 > 0:49:52Here, archaeologists have found remains of Homo erectus
0:49:52 > 0:49:54that they believe may do just that.
0:49:56 > 0:50:01Professor David Lordkipanidze is leading the excavations.
0:50:02 > 0:50:05David, what's that over there? Some kind of animal fossil.
0:50:05 > 0:50:08Is that as old as the human fossils you've been finding here?
0:50:08 > 0:50:12Yeah, it's 1.8 million years old. It belongs to a deer.
0:50:12 > 0:50:15It's a fantastic preservation of bones.
0:50:15 > 0:50:201.8 million years ago, environment was more Africa-like in some ways.
0:50:20 > 0:50:26Here was definitely environment more savannah-type on one hand,
0:50:26 > 0:50:30but it had also forest elements, it had a wood.
0:50:30 > 0:50:34It shows that climate was not as hot as in Africa,
0:50:34 > 0:50:38and they had much colder winters here.
0:50:39 > 0:50:42These are some of the earliest signs we have
0:50:42 > 0:50:45of our ancient ancestors outside Africa.
0:50:45 > 0:50:49Surviving in this challenging climate would have been tough.
0:50:49 > 0:50:52Professor Lordkipanidze has found a skull
0:50:52 > 0:50:54that raises some interesting questions
0:50:54 > 0:50:58about how some of them survived at all.
0:50:58 > 0:51:01Look at that, that's just beautiful!
0:51:01 > 0:51:05Yeah, it's a cast of the Dmanisi hominid.
0:51:05 > 0:51:08And it was that complete, it wasn't in pieces?
0:51:08 > 0:51:12It was not in pieces. There were some small breaks.
0:51:12 > 0:51:15But generally we could...
0:51:15 > 0:51:17Isn't that wonderful?
0:51:17 > 0:51:19So you know the brain size of this individual,
0:51:19 > 0:51:21you know what his face looked like.
0:51:21 > 0:51:24Absolutely, and also we have a jaw.
0:51:25 > 0:51:311.8 million years ago, Homo erectus had made it here to Georgia.
0:51:31 > 0:51:34That in itself is astonishing.
0:51:34 > 0:51:40But what's even more surprising is that this person was toothless.
0:51:40 > 0:51:42Now that is remarkable. This is an old jaw.
0:51:42 > 0:51:44This is a jaw that's lost most of its teeth.
0:51:44 > 0:51:47It looks like the only tooth that could possibly have still been
0:51:47 > 0:51:50in the mouth is that one there. Is that a canine?
0:51:50 > 0:51:51Yes, it was just one canine.
0:51:51 > 0:51:55And we can tell that all of these were lost a long time before death
0:51:55 > 0:51:58because the bone of the jaw has shrunk right down.
0:51:58 > 0:52:00So we know that must have happened
0:52:00 > 0:52:03months or even years before this person died.
0:52:03 > 0:52:09This person survived at least a few years without teeth.
0:52:11 > 0:52:16Somehow, this toothless person survived against the odds.
0:52:17 > 0:52:20The evidence suggests that they were living here
0:52:20 > 0:52:24long before our ancestors learned to control fire.
0:52:24 > 0:52:29So in the harsh winters, they may only have had raw meat to live on.
0:52:30 > 0:52:34These people were depending mostly on meat,
0:52:34 > 0:52:38and without teeth it's very difficult to get meat.
0:52:38 > 0:52:43So how does this person survive, as a hunter-gatherer,
0:52:43 > 0:52:46and with fairly basic technology,
0:52:46 > 0:52:49in this environment - with no teeth?
0:52:49 > 0:52:51I think this is indirect evidence
0:52:51 > 0:52:56of the altruism or compassion.
0:52:56 > 0:53:00I'm sure somebody was taking care of this individual.
0:53:00 > 0:53:04It's lovely to say, OK, we've potentially got evidence of altruism
0:53:04 > 0:53:05and compassion here,
0:53:05 > 0:53:11but just to be quite kind of harsh and economical about it,
0:53:11 > 0:53:15what kind of advantage could that have brought, in evolutionary terms?
0:53:15 > 0:53:19Maybe this person had knowledge which others needed still.
0:53:20 > 0:53:23So it was maybe very pragmatic also.
0:53:23 > 0:53:27Could it be that compassion contributed
0:53:27 > 0:53:29to the success of Homo erectus?
0:53:32 > 0:53:34I think it's quite interesting to think that
0:53:34 > 0:53:39compassion could have been an important feature of our evolution.
0:53:39 > 0:53:43It certainly characterises humans, because our human social relationships are so strong,
0:53:43 > 0:53:47and many of the relationships we build are built on friendship and compassion
0:53:47 > 0:53:50as opposed to some strict evolutionary need.
0:53:50 > 0:53:54Well, there is a chimpanzee skull in a museum in Kent
0:53:54 > 0:53:59that clearly hasn't got any teeth, and has obviously had his teeth lost
0:53:59 > 0:54:03before he died, so he or she was clearly being looked after in some way.
0:54:03 > 0:54:05It's interesting, isn't it, because I think that
0:54:05 > 0:54:08when we see that in another species we don't immediately jump in and say
0:54:08 > 0:54:11there must be some kind of compassion, some kind of altruism going on here.
0:54:11 > 0:54:15But of course, altruism isn't something which is limited to humans anyway.
0:54:15 > 0:54:19No, that's right. It's a characteristic of all evolving organisms, social organisms.
0:54:19 > 0:54:22So even though we don't know why we're doing it,
0:54:22 > 0:54:25altruism may not be entirely unselfish?
0:54:26 > 0:54:29No, because humans are so behaviourally plastic
0:54:29 > 0:54:31that we can change our behaviour throughout our entire lifetime,
0:54:31 > 0:54:34that what we want to do is we want someone who's had a rich
0:54:34 > 0:54:37experience and understands where the resources are in tough times.
0:54:37 > 0:54:41And understands, can decipher complex social relationships.
0:54:41 > 0:54:45So compassion and altruism are useful evolutionarily.
0:54:45 > 0:54:47Well, we're nearly at the end of our quest,
0:54:47 > 0:54:48but there's one last question -
0:54:48 > 0:54:52are there any clues as to how Nariokotome Boy died?
0:54:52 > 0:54:55Well, there's nothing that completely hits you
0:54:55 > 0:54:59between the eyes, but there might be something going on with his teeth.
0:54:59 > 0:55:01If we look right here on the right side of his jaw,
0:55:01 > 0:55:03we see that there's an area of erosion.
0:55:03 > 0:55:06- Right here between his premolar and molar. - It's always the teeth, isn't it?!
0:55:06 > 0:55:08- It is.- Is that an abscess?
0:55:08 > 0:55:12Well, it's some type of inflammatory response, so he probably has an infection going on.
0:55:12 > 0:55:16Well, I had a bad abscess in my jaw a week ago,
0:55:16 > 0:55:18and it was so painful.
0:55:18 > 0:55:22I think it's interesting to think about how infection might have affected our ancestors as well,
0:55:22 > 0:55:25cos if you had an abscess in your jaw... What happened after that?
0:55:25 > 0:55:28Well, I removed part of it and then I got antibiotics!
0:55:28 > 0:55:31Otherwise I don't know what I'd have done.
0:55:31 > 0:55:35You know, this is subtle, it may not have been the thing which killed him - but it could have been.
0:55:35 > 0:55:42Yet again, it's amazing the amount of detail we've been able to glean from just a handful of bones.
0:55:44 > 0:55:48Over six months, Viktor and our model makers have pieced together
0:55:48 > 0:55:51the skeleton of this tall and agile runner.
0:55:52 > 0:55:56Carefully sculpting muscles to reflect a physique fuelled by meat eating,
0:55:56 > 0:56:01and adding the finishing touch of a hairless sweating skin,
0:56:01 > 0:56:02that made him so well adapted
0:56:02 > 0:56:06for hunting and scavenging on the savannah.
0:56:06 > 0:56:08And now he's finished.
0:56:09 > 0:56:11None of us have seen him yet,
0:56:11 > 0:56:15but we're finally about to meet him in the flesh.
0:56:15 > 0:56:17- Shall we go and have a look? - Absolutely.
0:56:17 > 0:56:21Do you want to come and have a look, everybody? This is it, this is it.
0:56:21 > 0:56:24- VIKTOR:- Can't wait to show you. - I'm pretty excited about it.
0:56:24 > 0:56:27- You all ready?- Right then, Viktor...
0:56:27 > 0:56:30- One, two, three! - The real Nariokotome.
0:56:30 > 0:56:32Wow!
0:56:32 > 0:56:36He looks a bit different from the last time I saw him.
0:56:36 > 0:56:39A face from one and a half million years ago.
0:56:39 > 0:56:43The face, I'm really happy with.
0:56:43 > 0:56:46- This is an eight-year-old. - Yeah, that's quite shocking.
0:56:46 > 0:56:49That blows me away, because my eight-year-olds were, like, this tall.
0:56:49 > 0:56:51He's a big eight-year-old.
0:56:51 > 0:56:54The hair he HAS retained is totally credible,
0:56:54 > 0:56:57that would be a very good protective barrier against the radiation from the sun.
0:56:57 > 0:56:59And then he's lost hair on the rest of his body.
0:56:59 > 0:57:03So he would have been able to sweat, cool down.
0:57:03 > 0:57:06Yes, so he's got quite a large surface area
0:57:06 > 0:57:09but that surface area isn't absorbing rays from the sun.
0:57:09 > 0:57:13What would he think if he saw us now? What would he make of us?
0:57:13 > 0:57:15I'm really quite moved by it.
0:57:15 > 0:57:18I've only ever seen Nariokotome Boy's bones before,
0:57:18 > 0:57:21and suddenly here he is amongst us.
0:57:21 > 0:57:22He's lovely.
0:57:22 > 0:57:26Well, with the help of experts around the world and the people
0:57:26 > 0:57:31in this room, we've been able to create our very own Nariokotome Boy.
0:57:31 > 0:57:36In our last programme, tomorrow, we'll be travelling back 3.2 million years
0:57:36 > 0:57:39to meet one of our very earliest ancestors...
0:57:39 > 0:57:42a female who walked on two legs...
0:57:42 > 0:57:43called Lucy.
0:57:43 > 0:57:47I've been to the States to see what the fossilised remains
0:57:47 > 0:57:51of the world's oldest child are revealing about
0:57:51 > 0:57:56how Lucy's species moved, and about the origins of childhood.
0:57:56 > 0:58:00Here is an individual, still growing its brain,
0:58:00 > 0:58:02and still learning from the parents.
0:58:03 > 0:58:06Alice has been learning how techniques
0:58:06 > 0:58:09borrowed from the aeronautical industry can cast light
0:58:09 > 0:58:12on when our early ancestors left the trees.
0:58:12 > 0:58:16That's amazing. We've got a very, very different pattern in the way
0:58:16 > 0:58:19- the forces are spreading throughout the bone.- Yeah.
0:58:19 > 0:58:22And I caught up with some of our closest living relatives,
0:58:22 > 0:58:26to find out if they can give us any clues as to how Lucy
0:58:26 > 0:58:29and her species might have communicated.
0:58:31 > 0:58:36And we'll be finding out the price she had to pay to walk upright.
0:58:36 > 0:58:40- Join us back here, next time. Goodnight.- Goodnight.