0:00:08 > 0:00:11They say this is where it all began.
0:00:15 > 0:00:17That we are all children of Africa.
0:00:21 > 0:00:24But if so, why do we look so different?
0:00:26 > 0:00:33And how on earth could a handful of African families become a whole world full of people?
0:00:44 > 0:00:50I'm Alice Roberts, medical doctor and anthropologist.
0:00:50 > 0:00:52I'm fascinated by what bones,
0:00:52 > 0:00:55stones,
0:00:55 > 0:01:00and even our bodies can reveal about the distant past.
0:01:02 > 0:01:07I'm going in search of where the first people were born
0:01:07 > 0:01:11and how they began their journey to populate the world.
0:01:14 > 0:01:17'Leaving Africa was virtually impossible,
0:01:17 > 0:01:23'but new evidence suggests just one tiny group might have done it.'
0:01:23 > 0:01:25I just think it's absolutely remarkable.
0:01:25 > 0:01:28Isn't that amazing? It's stunning.
0:01:29 > 0:01:35'Can I find their trail out of Africa and across the world and discover
0:01:35 > 0:01:41'how those journeys changed them to become who we are today?'
0:01:44 > 0:01:49Come with me in the footsteps of our ancestors, on the most epic adventure ever undertaken.
0:02:12 > 0:02:16Ask yourself, where do you come from?
0:02:16 > 0:02:20How did the first humans become you?
0:02:20 > 0:02:24It's a surprisingly tricky question.
0:02:25 > 0:02:31And in search of an answer, I'm starting in East Africa.
0:02:31 > 0:02:34I've dreamt about coming to this place since I was a teenager.
0:02:47 > 0:02:50As unlikely as it sounds, palaeontologists now think
0:02:50 > 0:02:55they have a pretty good idea of where we modern humans first appeared.
0:02:55 > 0:02:59And I'm trying to get there.
0:02:59 > 0:03:03But it is in one of the most remote parts of the continent.
0:03:16 > 0:03:19I'm heading to Africa's Great Rift Valley,
0:03:19 > 0:03:22and the Omo River in Ethiopia.
0:03:32 > 0:03:36Very few foreigners ever come here.
0:03:43 > 0:03:48The place I'm trying to reach lies on the far western side of the Omo.
0:03:50 > 0:03:53There are no bridges for hundreds of miles,
0:03:53 > 0:03:58so my best option is the slightly leaky passenger ferry...
0:03:58 > 0:04:01past the crocodiles.
0:04:29 > 0:04:32That's quite a welcoming committee.
0:04:35 > 0:04:36Hello.
0:05:00 > 0:05:06I'm looking for the route taken by a scientific expedition about 40 years ago.
0:05:11 > 0:05:17They stumbled across perhaps the most important clue about the beginning of our species.
0:05:20 > 0:05:25I've got map co-ordinates, but there are no obvious tracks to follow.
0:05:29 > 0:05:34I think what I'm going to do is head to Kibish, the nearest village, and get some local help.
0:06:01 > 0:06:04'Kibish is home to the Nyangatom tribe.'
0:06:04 > 0:06:06Soya, salaam.
0:06:06 > 0:06:08- How are you?- I'm well. How are you?
0:06:08 > 0:06:10I'm fine.
0:06:13 > 0:06:16- I need to find a very particular place.- Mm-hm.
0:06:18 > 0:06:22'My only chance of help is if the chief agrees.'
0:06:26 > 0:06:28THEY SPEAK IN DIALECT
0:06:29 > 0:06:31Soya, can you tell him why I'm here?
0:06:31 > 0:06:35Can you say that I'm here to find the place where people were digging?
0:06:51 > 0:06:54This all sounds very promising.
0:06:57 > 0:07:02- He said someone was digging. - "Someone was digging..." - And he found something like bone,
0:07:02 > 0:07:07and, I don't know, he said that the bone had stayed there for a long time.
0:07:07 > 0:07:09When can we go? Can you ask them?
0:07:09 > 0:07:12THEY SPEAK IN DIALECT
0:07:12 > 0:07:14- Let's go now.- We can go now?
0:07:27 > 0:07:30'I'm not sure that these guys know where they're going.
0:07:34 > 0:07:37'But they seem to have come prepared for something.'
0:07:37 > 0:07:40Why is he carrying a gun?
0:07:40 > 0:07:42HE ASKS IN DIALECT
0:07:44 > 0:07:45For protection.
0:07:45 > 0:07:48For protection from whom?
0:07:48 > 0:07:50- For protection from enemies.- Right.
0:07:50 > 0:07:55Like Surma, Turkana...and Mursi.
0:07:55 > 0:08:00- So these are other tribes? - Yeah, they're other tribes. - Are they likely to attack us?
0:08:03 > 0:08:07- Yeah, they just come to attack them. - So there's always fighting going on?
0:08:07 > 0:08:09- Yeah, they're always fighting. - Right.
0:08:17 > 0:08:22'It's noon and the temperature has soared into the 40s.
0:08:32 > 0:08:35'Although I've wanted to come here for years,
0:08:35 > 0:08:41'after four hours in this searing heat, I'm not sure I'm going to make it.'
0:08:48 > 0:08:51- So what are they saying? - They say it's there.- Really?
0:08:51 > 0:08:54- Yeah.- That's where it was found? Just here? Just there?
0:08:54 > 0:08:56Just there.
0:09:13 > 0:09:18Well, this is it. This is the place, because this is where
0:09:18 > 0:09:24the earliest human remains in the entire world were discovered.
0:09:24 > 0:09:26It's been really difficult to find it.
0:09:26 > 0:09:31It's taken us four hours to walk here and we've been on a circuitous route through the bush
0:09:31 > 0:09:34and it seems really strange that
0:09:34 > 0:09:36there's nothing to mark it,
0:09:36 > 0:09:39because this is such an important place
0:09:39 > 0:09:42in our story.
0:09:42 > 0:09:45And it's as close as I can get
0:09:45 > 0:09:48to where we all began.
0:09:48 > 0:09:49Amazing.
0:10:04 > 0:10:07'And this is what the archaeologists discovered.'
0:10:10 > 0:10:14This is a cast of the skull that was found here
0:10:14 > 0:10:17and which was dated to 195,000 years ago.
0:10:17 > 0:10:22I think, considering it's so old, it's remarkably complete.
0:10:22 > 0:10:25OK, the fragile face bones are missing,
0:10:25 > 0:10:27but most of the brain case is here.
0:10:27 > 0:10:30We can see the size of the brain
0:10:30 > 0:10:34and we can see this very characteristic forehead.
0:10:34 > 0:10:39'No other remains of our species even approaching this age
0:10:39 > 0:10:43'have been found anywhere else on the planet.
0:10:49 > 0:10:54'This is as near as we can get to the origin of our species.'
0:11:02 > 0:11:07There's something very special about sitting here, looking out at the Omo.
0:11:07 > 0:11:14I could be on the banks of any African river, apart from the fact we know that this landscape
0:11:14 > 0:11:19has been home to humans, people like you and me,
0:11:19 > 0:11:22for nearly 200,000 years.
0:11:25 > 0:11:31So if this is where we first appeared, what did we come from?
0:11:34 > 0:11:39The evidence suggests that the very first human-like creatures
0:11:39 > 0:11:42evolved in Africa over 4 million years ago.
0:11:42 > 0:11:45They were much more ape-like than us.
0:11:45 > 0:11:48A series of human species
0:11:48 > 0:11:52with gradually bigger brains came and went.
0:11:52 > 0:11:58The most recent, and only surviving, is our own species -
0:11:58 > 0:12:01Homo sapiens, modern humans.
0:12:08 > 0:12:14Here is a skull of one of our nearest ancient human relatives, Homo heidelbergensis.
0:12:14 > 0:12:19If we compare it with this modern skull, some things just leap out at you.
0:12:19 > 0:12:23This heidelbergensis skull has an enormous brow ridge
0:12:23 > 0:12:29and a swept-back, sloping forehead - much steeper in the modern skull.
0:12:29 > 0:12:33In fact, the whole brain case here is much rounder.
0:12:35 > 0:12:38Using the skull of the ancient human,
0:12:38 > 0:12:41experts have reconstructed his face...
0:12:43 > 0:12:48..to reveal our flatter-headed, beetle-browed predecessor.
0:12:54 > 0:13:00Contrast with this reconstruction of a very old but modern human,
0:13:00 > 0:13:06and I think you'll agree that she looks a lot more like me.
0:13:09 > 0:13:15But if East Africa is where the first humans were born, there are some big questions to answer.
0:13:19 > 0:13:23Are we all descended from black Africans?
0:13:23 > 0:13:27If so, why do most of us look so different?
0:13:36 > 0:13:41And how could a handful of people from such an isolated place
0:13:41 > 0:13:44go on to colonise first Africa...
0:13:45 > 0:13:47..and then the rest of the world?
0:13:54 > 0:14:00So what do we know about these shadowy first families?
0:14:00 > 0:14:05200,000 years ago, it's likely there were so few of them,
0:14:05 > 0:14:12living such a precarious existence, that today they'd be classified as an endangered species.
0:14:15 > 0:14:21Life was fragile and the African savannah was a dangerous place.
0:14:42 > 0:14:45Well, I'm going to be spending the night out here in the bush,
0:14:45 > 0:14:48presumably something our ancestors did all the time.
0:14:48 > 0:14:51But years of living in civilisation have softened me.
0:14:52 > 0:14:58I've got a big torch here, so if anything comes by I can get a better look at it in the dark.
0:14:58 > 0:15:06And I've got this little camera so I can make a video diary throughout the night
0:15:06 > 0:15:08and talk about what comes along.
0:15:08 > 0:15:09I'm doing this for real.
0:15:09 > 0:15:13I'm going to be out here all night and I really am quite scared.
0:15:36 > 0:15:38ANIMAL CHATTERS
0:15:42 > 0:15:46- WHISPERING:- It's just amazing the amount of noises you suddenly hear.
0:15:46 > 0:15:48About half an hour ago, there was the sound,
0:15:48 > 0:15:53a really distinct sound, of something lapping water.
0:15:53 > 0:15:55Maybe a hyena, maybe a leopard.
0:15:55 > 0:15:59It sounded like a big cat. Literally like a cat lapping up milk.
0:16:01 > 0:16:04Hopefully nothing can get through that.
0:16:11 > 0:16:17I suddenly feel really vulnerable as an animal which is designed to be out in the daylight.
0:16:17 > 0:16:21I mean, we can't see very well at night,
0:16:21 > 0:16:26hearing's all right, just about enough to get you feeling scared.
0:16:28 > 0:16:31- And sense of smell as well. - SHE SNIFFS
0:16:31 > 0:16:34Compared to all those other animals, might as well not have it.
0:16:40 > 0:16:43- ROARING - Did you hear that?
0:16:46 > 0:16:49- I'm scared now. - HOWLING
0:16:53 > 0:16:56HOWLING RESUMES
0:16:56 > 0:16:59Is that a...? Is that a lion?
0:16:59 > 0:17:01Is that a leopard?
0:17:06 > 0:17:08Is that...?
0:17:10 > 0:17:11Is that a hyena?
0:17:14 > 0:17:17HOWLING
0:17:17 > 0:17:19Oh, I don't like that noise.
0:17:19 > 0:17:22That's really spooky.
0:17:34 > 0:17:39That's got to be one of the most frightening nights of my life.
0:17:39 > 0:17:45I did get some sleep, but then I got woken up by these horrendous noises.
0:17:45 > 0:17:48Sometimes it was hyenas
0:17:48 > 0:17:51and then there was something that sounded like a stand-off
0:17:51 > 0:17:55between a hyena and leopard or something. I don't know what it was.
0:17:55 > 0:17:56Awful noises.
0:17:56 > 0:17:59Really, really scary.
0:18:07 > 0:18:10With the return of the crew, I pluck up my courage
0:18:10 > 0:18:14and look for signs of the animals that I heard in the night.
0:18:18 > 0:18:20Oh, just look at this.
0:18:20 > 0:18:24This is a big male leopard paw print and there
0:18:24 > 0:18:28are large hyena prints as well.
0:18:28 > 0:18:33So these predators, these carnivores, were literally here,
0:18:33 > 0:18:38about 25 metres away from where I was sleeping, underneath that tree.
0:18:38 > 0:18:41They sounded really close during the night.
0:18:41 > 0:18:43I can see now that they were.
0:18:51 > 0:18:57At night time especially, our ancestors must have been very vulnerable.
0:18:57 > 0:19:00So how did those first families survive,
0:19:00 > 0:19:04let alone go on to spread across the world?
0:19:15 > 0:19:20In the hope of finding out more, I'm heading south to Namibia.
0:19:33 > 0:19:36I'm meeting one of the last groups of hunter-gatherers
0:19:36 > 0:19:40on this continent - the bushmen of the Kalahari.
0:19:40 > 0:19:42What's your name?
0:19:42 > 0:19:44My name is Sedre.
0:19:44 > 0:19:47- Se... Sedre?- Sedre.
0:19:51 > 0:19:56Their way of life is the closest I can find to that of our ancestors.
0:20:01 > 0:20:05The bushmen are expert hunters.
0:20:07 > 0:20:15But before I see how they do it, I want to persuade Kun and Au to take part in a little experiment.
0:20:15 > 0:20:18Kun...
0:20:18 > 0:20:22I need to check your body temperature using this. Is that all right?
0:20:22 > 0:20:25I'm going to put it in your ear, like that.
0:20:25 > 0:20:28Right, I'm just going to pop it in there.
0:20:31 > 0:20:35- ELECTRONIC BEEP - Lovely. 36.2.
0:20:35 > 0:20:39- Oh, I see.- That's how hot you are. - That's my ears.
0:20:39 > 0:20:40- Yes.- OK.
0:20:40 > 0:20:45Au, I need to do it to you as well. There we go. It's ready
0:20:45 > 0:20:46to take your temperature.
0:20:46 > 0:20:51- ELECTRONIC BEEP - Right, 35.8.
0:20:51 > 0:20:54You're even cooler. You're very cool.
0:20:54 > 0:20:56THEY SPEAK IN DIALECT
0:20:58 > 0:21:01It's turned into a competition.
0:21:14 > 0:21:19'Humans usually hunt in the day, so I want to see how our bodies cope with this blazing heat.'
0:21:19 > 0:21:22It's a pretty relentless pace.
0:21:22 > 0:21:26'We're looking for the trail of an antelope.'
0:21:36 > 0:21:38What have you found?
0:21:43 > 0:21:47Right, this is really exciting. We've got an oryx track
0:21:47 > 0:21:50and we're gonna follow it. I'm gonna have to be really quiet now.
0:21:58 > 0:22:01'We've got to move fast to gain on the oryx.
0:22:10 > 0:22:16'We've been walking and running for over an hour when we find more prints.
0:22:16 > 0:22:19'But not the ones we were hoping for.'
0:22:21 > 0:22:23THEY SPEAK IN DIALECT
0:22:23 > 0:22:28I think we give up the chase at this point. The animal has been chased by a hyena.
0:22:28 > 0:22:30We don't know if it lived to tell the tale either.
0:22:30 > 0:22:32But no dinner for us.
0:22:36 > 0:22:40'It's now just past midday and the temperature is in the high 30s.
0:22:40 > 0:22:45'So what effect has all this running in the heat had on our body temperatures?'
0:22:46 > 0:22:5137.4, so a bit hotter than you were before.
0:22:51 > 0:22:53I'll try you as well.
0:22:53 > 0:22:55ELECTRONIC BEEP
0:22:55 > 0:23:00- Ooh, 36.7. Cooler than him. - THE MEN LAUGH
0:23:00 > 0:23:02Now what about me? Let's take mine.
0:23:05 > 0:23:08ELECTRONIC BEEP
0:23:08 > 0:23:10It's 36.9. We've beaten him!
0:23:10 > 0:23:13'Incredibly, our temperatures have barely risen.'
0:23:13 > 0:23:17The key to this is that we're all regulating our body temperatures, even in this heat.
0:23:24 > 0:23:27And this is the secret - we keep cool by sweating,
0:23:27 > 0:23:32something humans do more effectively than most mammals.
0:23:32 > 0:23:38Not having fur, we can sweat from glands all over our bodies,
0:23:38 > 0:23:44which allows us to keep moving in pursuit of prey for hours without overheating...
0:23:46 > 0:23:52..even in the middle of the day, when most big predators are just trying to keep cool.
0:23:55 > 0:24:01And there are other things about your body designed specifically for running.
0:24:03 > 0:24:05And this is one of them.
0:24:05 > 0:24:10Yes, it's a foot and it is brilliantly designed to provide spring.
0:24:10 > 0:24:13The ligaments and tendons support the sprung arches of the foot,
0:24:13 > 0:24:16so that every time our foot hits the ground,
0:24:16 > 0:24:19the spring stores and then releases energy,
0:24:19 > 0:24:21making running more efficient.
0:24:24 > 0:24:27And there's a really important muscle in our bums.
0:24:27 > 0:24:33Our gluteus maximus muscle is huge and we hardly use it at all when we're walking.
0:24:33 > 0:24:36But it comes into its own when we run.
0:24:41 > 0:24:44So all of these adaptations suggest that running,
0:24:44 > 0:24:51especially over long distances, was really important to our early ancestors.
0:24:56 > 0:25:02But there was something else that may have really given our ancient ancestors the edge.
0:25:02 > 0:25:05SHE SPEAKS IN LANGUAGE WITH PALATAL CLICKS
0:25:10 > 0:25:15'Language. The ability to communicate and plan.'
0:25:19 > 0:25:22Red, yellow, green.
0:25:22 > 0:25:23How do you say it?
0:25:23 > 0:25:25THEY ANSWER WITH PALATAL CLICK
0:25:29 > 0:25:32'We don't know when people started to speak,
0:25:32 > 0:25:40'but there's evidence that languages like this, click languages, may be the oldest in the world.
0:25:41 > 0:25:44SHE SPEAKS IN LANGUAGE WITH PALATAL CLICKS
0:25:46 > 0:25:51'So it's possible the first families sounded a bit like this.'
0:25:51 > 0:25:55It is an amazing language. Every sentence is peppered with these
0:25:55 > 0:25:58clicks and tutting noises that are consonants.
0:25:58 > 0:26:00They're just very unlike any consonants
0:26:00 > 0:26:03that I'm used to pronouncing, so I'm struggling with it.
0:26:03 > 0:26:07- So this is... - SHE ATTEMPTS PALATAL CLICK
0:26:13 > 0:26:15See, I think it's easier to say "yellow"!
0:26:19 > 0:26:25'And it's a type of language that could have been crucial to our ancestors' survival.'
0:26:27 > 0:26:30It may be that these click languages have been around for so long
0:26:30 > 0:26:34because they're particularly useful during hunting.
0:26:34 > 0:26:37Apparently, when the bushmen are stalking an animal, they drop
0:26:37 > 0:26:44their voices to a whisper, so they're talking almost entirely in clicks, which make a lot of sense to me.
0:26:44 > 0:26:48The clicks are high-pitched noises - they don't travel far through the bush,
0:26:48 > 0:26:51so the hunters aren't going to scare off their quarry.
0:27:01 > 0:27:06Equipped with language and hunting skills, we flourished.
0:27:07 > 0:27:10And began to do something else - spread out.
0:27:12 > 0:27:15We don't know for sure which routes they took,
0:27:15 > 0:27:19but new evidence shows that very early on, modern humans
0:27:19 > 0:27:23were living at the extreme southern edge of the continent.
0:27:28 > 0:27:31I'm heading along the South African coast
0:27:31 > 0:27:33to a place called Pinnacle Point.
0:27:39 > 0:27:41Today, it's a playground for the rich.
0:27:41 > 0:27:46But during the construction of this golf course,
0:27:46 > 0:27:51archaeologists discovered something amazing deep beneath the fairway.
0:28:02 > 0:28:07This could be the oldest known dwelling of our species anywhere in the world.
0:28:13 > 0:28:15So, this is where you've been digging.
0:28:15 > 0:28:17This is the oldest part of the cave.
0:28:17 > 0:28:20What are the dates here then, as we go down through these layers?
0:28:20 > 0:28:25These layers date from 130,000 to 167,000 years ago.
0:28:25 > 0:28:29- It's just so incredibly ancient. - It's amazing.
0:28:29 > 0:28:35- Did you know how important what you were excavating really was? - Not until we got those dates.
0:28:35 > 0:28:38But, yeah. Amazing, stunning.
0:28:44 > 0:28:48The evidence in this cave reveals that those ancient families were
0:28:48 > 0:28:52behaving in ways quite unlike previous species of human.
0:28:54 > 0:28:58That's not from this cave, is it? Cos I recognise this. This is a hand-axe.
0:28:58 > 0:29:03Yes, that's more typical of what you would find from about 1.5 million years ago
0:29:03 > 0:29:07- to about 300,000 years ago. - So what sort of thing were you finding in the cave, then?
0:29:07 > 0:29:09OK, tools like these.
0:29:09 > 0:29:13Blades and points are much more typical of what we find here.
0:29:13 > 0:29:17Made on quartzite, locally available on the beach down here.
0:29:17 > 0:29:20In our oldest levels here, alongside these types of tools,
0:29:20 > 0:29:24- we also have these very small bladelet tools.- These are tiny.
0:29:24 > 0:29:29'What could such minute blades have been used for?'
0:29:29 > 0:29:35Obviously these weren't used just in your hand, like this, so how would they have been used?
0:29:35 > 0:29:38It's more likely that those were set in some kind of a handle
0:29:38 > 0:29:41to make a compound tool, maybe something more like this.
0:29:41 > 0:29:47This is a series of small blades set into a handle for use as a knife.
0:29:47 > 0:29:48Yes, I think that would work.
0:29:48 > 0:29:53So you think that's how these stone tools were used then, as a knife?
0:29:53 > 0:29:58That's one possibility. It's also possible they would have been used for hunting weapons.
0:30:01 > 0:30:07'Kyle and his team have discovered you can make some lethal weapons with these bladelets.'
0:30:07 > 0:30:09This one looks particularly vicious.
0:30:09 > 0:30:12This is one interpretation of how
0:30:12 > 0:30:14those small-back blades might have been mounted.
0:30:17 > 0:30:19The advantage to this would be
0:30:19 > 0:30:21that there's these barbs that would prevent
0:30:21 > 0:30:27the tip from pulling out immediately and would inflict a greater injury.
0:30:29 > 0:30:34So by 160,000 years ago, those early resourceful families
0:30:34 > 0:30:37seemed to have colonised much of Africa.
0:30:48 > 0:30:51But what about the rest of the world?
0:30:53 > 0:31:01How did some of those ancient wanderers get out of Africa to become me and perhaps you?
0:31:01 > 0:31:06It's one of the most baffling mysteries of our origins.
0:31:16 > 0:31:21Africa south of the Sahara is cut off from the rest of the planet.
0:31:23 > 0:31:26To the west, south
0:31:26 > 0:31:29and east - ocean.
0:31:32 > 0:31:37To the north, the vast deserts of the Sahara and Arabia.
0:31:41 > 0:31:47So could there be another way that people first appeared all over the world?
0:31:50 > 0:31:55Did they, as some have suggested, evolve separately on different continents?
0:31:55 > 0:31:57It's a huge question.
0:32:02 > 0:32:08A different branch of science is beginning to provide very surprising answers.
0:32:08 > 0:32:12To find out more, I've come to Cape Town.
0:32:14 > 0:32:17Cape Town today is a world city with representatives
0:32:17 > 0:32:21of just about every group and creed you can possibly imagine.
0:32:21 > 0:32:24And every single one of these people
0:32:24 > 0:32:29unknowingly carries inside them a story of their ancient ancestors.
0:32:29 > 0:32:37That's because buried in the genes of each of us is an indelible record of our past.
0:32:41 > 0:32:48By studying DNA from people all over the world, geneticists are piecing together that ancient story.
0:32:49 > 0:32:53Cape Town, a product of its colonial past, has citizens
0:32:53 > 0:32:59who bring their own genetic stories from every corner of the planet.
0:33:00 > 0:33:04And the minute differences in their DNA provide clues about
0:33:04 > 0:33:11the ancient migrations that led our species to colonise the world.
0:33:11 > 0:33:13Thanks again, folks, for coming.
0:33:13 > 0:33:16This is the tree of humanity.
0:33:16 > 0:33:20'Geneticist Raj Ramesar has used these differences to help
0:33:20 > 0:33:26'build a global family tree by tracing genes down the female line.
0:33:28 > 0:33:31'Our modern genes are the branches of the tree
0:33:31 > 0:33:35'and geneticists have followed them back in time
0:33:35 > 0:33:36'to find our ancient roots.
0:33:38 > 0:33:43'The DNA of everyone alive today fits somewhere on this tree.
0:33:45 > 0:33:50'Although it's not always obvious exactly where you fit.'
0:33:50 > 0:33:54Stephen, where do you think your maternal heritage stems from?
0:33:54 > 0:33:56Probably Southern Europe.
0:33:56 > 0:33:59The Italian community - that's where my family comes from.
0:33:59 > 0:34:04Well, actually, you are on a European branch but you're on a European branch up here.
0:34:04 > 0:34:09That's much more Northern Europe. So I'm very sorry, you're not Italian, you're a Laplander!
0:34:09 > 0:34:10LAUGHTER
0:34:10 > 0:34:15But follow the branches back to the beginning and the tree reveals
0:34:15 > 0:34:21that ultimately, we all have our roots in the same place.
0:34:21 > 0:34:24There's no question from the genetic data that is generated
0:34:24 > 0:34:26on the people here, as well as other studies
0:34:26 > 0:34:29that have been done, that humanity arose in Africa.
0:34:29 > 0:34:33That's where the depth of this thick trunk illustrates
0:34:33 > 0:34:37where the majority of humanity can look for its roots.
0:34:37 > 0:34:39So because we originated in Africa, there's been more time
0:34:39 > 0:34:43for branches to develop here than there has been anywhere else?
0:34:43 > 0:34:45Yeah, that's a crucial point.
0:34:45 > 0:34:49Humanity has spent most of its life in Africa.
0:34:49 > 0:34:52- I'm African! - LAUGHTER
0:34:52 > 0:34:55- Yes, my cousin!- We all are.
0:34:55 > 0:35:01Absolutely. It's only more recently that we see this aspect of the tree.
0:35:02 > 0:35:08'But the really amazing thing is what the tree tells us about those who left Africa.
0:35:10 > 0:35:13'You might expect lots of branches,
0:35:13 > 0:35:18'lots of genetic lineages, leaving Africa at different times.
0:35:20 > 0:35:25'But instead, the rest of the world connects back to Africa
0:35:25 > 0:35:28'through one thin branch.
0:35:28 > 0:35:32'What does that mean?'
0:35:32 > 0:35:36There was a single branching out of Africa.
0:35:36 > 0:35:41It amounts to, historically, a single band of individuals leaving the African continent.
0:35:41 > 0:35:47So that was the original migration out of Africa that we can track with DNA.
0:35:47 > 0:35:50From there, there were branchings out in many different directions,
0:35:50 > 0:35:57into Europe, into the rest of Asia, Eurasia, to the north and then down
0:35:57 > 0:36:01to Australia and Japan and ultimately to the Americas on the other side.
0:36:01 > 0:36:06'Geneticists across the world have come to the same conclusions.
0:36:06 > 0:36:14'Everyone outside Africa descends from not many, but just one tiny group of pioneers.'
0:36:14 > 0:36:17I just think it's absolutely remarkable. Isn't that amazing?
0:36:17 > 0:36:20It's stunning, yeah.
0:36:20 > 0:36:22Oh, wow, man!
0:36:29 > 0:36:32It may be that others tried too.
0:36:32 > 0:36:35But their descendants have not survived.
0:36:38 > 0:36:40So the genetics tells us our species
0:36:40 > 0:36:47made just one successful attempt to leave and this wasn't a mass exodus.
0:36:47 > 0:36:52It was a small group of people taking one route out of Africa.
0:36:52 > 0:36:58And everybody in the world today who isn't African is descended from that handful of people.
0:36:58 > 0:37:01It's just mind-boggling to think how different the
0:37:01 > 0:37:07world would be today if it weren't for that small group of pioneers.
0:37:07 > 0:37:09And it begs the next question -
0:37:09 > 0:37:12which route did they take?
0:37:14 > 0:37:19The genetics may be convincing, but the geography is a huge problem.
0:37:26 > 0:37:31For these early families, deserts and oceans would have been massive obstacles.
0:37:37 > 0:37:40But we know they did it somehow.
0:37:42 > 0:37:49From this map, I think there are perhaps four possible routes out of Africa.
0:37:49 > 0:37:53Across the Strait of Gibraltar here, so a bit of a sea-crossing.
0:37:53 > 0:37:55From Tunisia, up through Sicily and Italy -
0:37:55 > 0:37:57even more sea to cross there.
0:37:57 > 0:38:01Down here, across the mouth of the Red Sea,
0:38:01 > 0:38:04but you'd need a boat for that as well.
0:38:04 > 0:38:08Or here, through the Sahara and Sinai deserts.
0:38:08 > 0:38:11Well, all of those routes have their challenges,
0:38:11 > 0:38:14but we know that it was just one of them that was taken.
0:38:14 > 0:38:16So which one was it?
0:38:22 > 0:38:25It's a real puzzle, but could it be
0:38:25 > 0:38:27that the world was different back then?
0:38:30 > 0:38:33Well, there is a way to find out.
0:38:37 > 0:38:41We've asked a team of Britain's leading climate scientists to work out how
0:38:41 > 0:38:45the global environment has changed,
0:38:45 > 0:38:49going back over thousands of years.
0:38:52 > 0:38:55And the answer is in here. With this climate computer,
0:38:55 > 0:38:59I can look at the changing environment over time.
0:38:59 > 0:39:06Starting at 140,000 years ago, we're moving towards the present.
0:39:06 > 0:39:11Forests and grasslands are green and deserts, light brown.
0:39:14 > 0:39:15Now this is interesting.
0:39:15 > 0:39:20125,000 years ago, there's a change in the climate.
0:39:20 > 0:39:26It's been very dry in this area and then suddenly it gets greener.
0:39:29 > 0:39:33And the world's biggest, driest,
0:39:33 > 0:39:37most-impassable desert briefly blossoms.
0:39:46 > 0:39:48For just a few thousand years,
0:39:48 > 0:39:52the Sahara, Sinai
0:39:52 > 0:39:57and Arabian deserts were lush and green.
0:40:00 > 0:40:07So it looks like 125,000 years ago it would have been possible for our ancestors to have walked
0:40:07 > 0:40:11through the Sahara and leave Africa to the northeast.
0:40:15 > 0:40:19I'm after some evidence that at least one band of pioneers
0:40:19 > 0:40:22made it to the other side of the Sahara
0:40:22 > 0:40:26and through that northern exit to the rest of the world.
0:40:32 > 0:40:36I'm on my way to Israel and the site of an intriguing discovery.
0:40:40 > 0:40:45But one which may present as many questions as answers.
0:40:49 > 0:40:54Back in the 1930s, an international team of archaeologists
0:40:54 > 0:40:57was excavating here at Skhul Cave.
0:41:02 > 0:41:06But it's what was found outside the cave that was really interesting.
0:41:06 > 0:41:10The archaeologists dug down through 1.5m of soil just here,
0:41:10 > 0:41:15finding masses and masses of stone tools.
0:41:15 > 0:41:20But as they got down close to the bedrock, they found something even more exciting -
0:41:20 > 0:41:24human burials. Ten of them.
0:41:32 > 0:41:34When the bones were dated, they were found to be
0:41:34 > 0:41:37about 100,000 years old -
0:41:37 > 0:41:42the oldest modern-human remains outside Africa.
0:41:48 > 0:41:52The dates fit well with that greening of the Sahara.
0:41:54 > 0:41:59So could these people be the pioneers I'm looking for,
0:41:59 > 0:42:03whose descendants went on to populate the rest of the world?
0:42:08 > 0:42:14Some of their remains are now kept in the Rockefeller Museum in Jerusalem.
0:42:20 > 0:42:23This skeleton is incredibly well-preserved.
0:42:23 > 0:42:26And the main reason for that is that the bodies at Skhul
0:42:26 > 0:42:29weren't just left on the surface of the ground.
0:42:29 > 0:42:32They were deliberately buried.
0:42:32 > 0:42:37And not only that, they were buried with objects, with shell beads,
0:42:37 > 0:42:42and one of them even had a boar's jaw enclosed in its arms.
0:42:42 > 0:42:45Surely this is further evidence
0:42:45 > 0:42:49for modern ways of thinking and behaving.
0:42:49 > 0:42:51For spirituality,
0:42:51 > 0:42:56and perhaps even a belief in the afterlife.
0:43:06 > 0:43:10But not everything here is what it seems.
0:43:10 > 0:43:14These people may well have been the first to leave Africa,
0:43:14 > 0:43:18but it looks like they can't be our ancestors...
0:43:18 > 0:43:21because the trail then dries up.
0:43:21 > 0:43:25All evidence of modern humans disappears.
0:43:27 > 0:43:31It looks like these families died out completely...
0:43:35 > 0:43:39..around 90,000 years ago, when the Middle Eastern Sahara
0:43:39 > 0:43:45returned to desert, and life here became impossible.
0:43:57 > 0:44:01For our species, it seems that this was a dead end
0:44:01 > 0:44:05and it shows just how fragile our existence was,
0:44:05 > 0:44:11and what a massive impact climate change could have on a human population.
0:44:11 > 0:44:14But it wasn't the end of the human journey.
0:44:14 > 0:44:19So where was that elusive route out of Africa?
0:44:22 > 0:44:27The Sahara desert once again closed the door on any migration north,
0:44:27 > 0:44:33leaving just one of my four routes out of Africa - the Red Sea.
0:44:33 > 0:44:38If they did try to cross it, the most likely point is at its mouth -
0:44:38 > 0:44:41the Gate of Grief.
0:44:51 > 0:44:55Could at least a few families have broken out of Africa here?
0:44:59 > 0:45:05Below me is the Red Sea, and to the west, the small African state of Djibouti.
0:45:05 > 0:45:07And over to the east, I can just about make out
0:45:07 > 0:45:10the coast of Yemen on the tip of the Arabian Peninsula.
0:45:10 > 0:45:17At this point, it is just 30km between Africa and Arabia.
0:45:21 > 0:45:2730km of sea is still a big problem if you don't have a sea-going vessel.
0:45:29 > 0:45:34But from about 90,000 years ago, something interesting began to happen.
0:45:37 > 0:45:41The very same climate change that had turned the Sahara back to desert
0:45:41 > 0:45:44had another impact.
0:45:44 > 0:45:46It made sea levels drop.
0:45:49 > 0:45:51And at the Gate of Grief,
0:45:51 > 0:45:57the gap between Africa and Arabia became much smaller.
0:46:00 > 0:46:08As sea levels fell, the distance across the Red Sea at this point dropped to just 11km.
0:46:08 > 0:46:13So perhaps here at last was a chance to risk everything,
0:46:13 > 0:46:19to cross the Gate of Grief and take a step into the unknown.
0:46:22 > 0:46:27And geneticists working for this series have been able to estimate
0:46:27 > 0:46:31how many people made that leap out of Africa,
0:46:31 > 0:46:33whichever way they took.
0:46:39 > 0:46:43They estimate the size of this group that made the crossing
0:46:43 > 0:46:46from Africa to Arabia was just a few hundred people.
0:46:46 > 0:46:54And geneticists have now tested the DNA of thousands and thousands of non-Africans
0:46:54 > 0:46:57and not one single person has been found
0:46:57 > 0:47:02who can't trace their ancestry back to this tiny group of wanderers.
0:47:06 > 0:47:09It may have been just a single tribe.
0:47:12 > 0:47:18And whatever you look like, if you're not African, you descend from them.
0:47:28 > 0:47:32But getting beyond the Red Sea may have been the easy bit.
0:47:37 > 0:47:42I'm leaving Africa to travel deep into Arabia.
0:47:45 > 0:47:50And here I'm confronted by another great mystery.
0:47:56 > 0:48:02How could those pioneers have survived here?
0:48:05 > 0:48:13Back then, most of Arabia was brutal desert, pretty much as it is today.
0:48:16 > 0:48:20Is it really possible that a handful of Stone-Age people
0:48:20 > 0:48:27could have trekked through hundreds of miles of this and gone on to populate the whole world?
0:48:34 > 0:48:38Well, here's one man who looks like he knows how to get around in the desert.
0:48:43 > 0:48:50Archaeologist Jeff Rose has spent years scouring Arabia for evidence of our earliest ancestors.
0:48:59 > 0:49:02And he's come to meet me in Oman.
0:49:05 > 0:49:09- Jeff.- Hello.- Hello, how are you?
0:49:09 > 0:49:14- So, Jeff, why are we in this desolate place?- It's actually quite a special location.
0:49:14 > 0:49:17You see all these black rocks that are lying across the surface?
0:49:17 > 0:49:21Yeah, there's a particular concentration of them just round here.
0:49:21 > 0:49:26Well, they're not really rocks. They're all ancient stone tools made by early humans.
0:49:26 > 0:49:28If we just pick this piece up here,
0:49:28 > 0:49:32it's got this flat surface and this surface with flake scars on it.
0:49:32 > 0:49:34And they've done some re-touch on it.
0:49:34 > 0:49:38They've hit it here and here to create this chisel-like edge.
0:49:38 > 0:49:40So that can't have occurred naturally?
0:49:40 > 0:49:43No. This couldn't have occurred naturally
0:49:43 > 0:49:46because of the pattern of scars that we see here. It's called a burin.
0:49:46 > 0:49:51They would have been used for working soft materials - hides, leather, bone, wood,
0:49:51 > 0:49:54anything like that - for carving tools out of that.
0:49:54 > 0:49:56- So it's a little bit like a chisel? - Yeah.
0:49:56 > 0:49:59It's amazing to pick up a stone tool just lying on the surface.
0:49:59 > 0:50:04You get used to it working in Arabia cos they're everywhere. They cover the surface everywhere.
0:50:04 > 0:50:10- If they've got flat surfaces on, are they likely to be...?- Just about anything you see that's flat-lying.
0:50:10 > 0:50:16- Even things like that? - That's from the edge of a blade, so that's called "cortex".- Yeah.
0:50:16 > 0:50:21A lot of times they leave that cortex on because if you're using it, you're not gonna cut yourself.
0:50:21 > 0:50:25So you can see how they would have held it. Something like that.
0:50:25 > 0:50:29- That makes a neat little knife. - Exactly.- OK, so what is the date of this site?
0:50:29 > 0:50:32- I'm putting you on the spot here! - Well, it's hard to say.
0:50:32 > 0:50:36It's a surface site, so it's impossible to date anything specifically.
0:50:36 > 0:50:39But from that technology, from that core I showed you, we can say
0:50:39 > 0:50:43it's anywhere between 70,000 and 12,000 years ago and maybe even earlier.
0:50:43 > 0:50:49- As long ago as 70,000 years? - There was a site that was recently found on the Red Sea coast in Yemen
0:50:49 > 0:50:52that was dated to about 70,000 years ago and it's the same technology.
0:51:01 > 0:51:05So there were people here 70,000 years ago.
0:51:05 > 0:51:10I find that really difficult to believe because at that time
0:51:10 > 0:51:15the landscape would have been just as dry and harsh as it is today.
0:51:15 > 0:51:20I mean, OK, there's stone to make tools out of.
0:51:20 > 0:51:22But where were they living?
0:51:37 > 0:51:43The biggest problem for those pioneering families would have been the lack of water.
0:51:45 > 0:51:51But a few short miles from these arid mountains, I'm in for a surprise.
0:52:14 > 0:52:20Well, just look at this. I'm only two miles away from the desert here, but I could be in rural Somerset.
0:52:20 > 0:52:22If it weren't for
0:52:22 > 0:52:24the camels!
0:52:24 > 0:52:26I'm definitely in Arabia.
0:52:38 > 0:52:45This place, near the coast of Oman, sits right on the edge of the monsoon region of the Indian Ocean.
0:52:49 > 0:52:55Every year, the monsoons turn this valley into a green oasis...
0:52:56 > 0:53:01..somewhere you can imagine our ancestors flourishing.
0:53:06 > 0:53:10But this is a green island in the middle of the desert.
0:53:10 > 0:53:15The desert stretches on for hundreds of miles around here.
0:53:15 > 0:53:20So how did our ancestors move through Arabia...
0:53:20 > 0:53:25to reach the world beyond?
0:53:30 > 0:53:35There's no way they could have done it without more widespread sources of fresh water.
0:53:40 > 0:53:42But where are they?
0:54:06 > 0:54:12I'm at sea just off the coast of Oman, a coastline that our ancestors may have passed along.
0:54:12 > 0:54:16Except that 70,000 years ago, the coast wouldn't have been there
0:54:16 > 0:54:18because the sea level was much lower -
0:54:18 > 0:54:22it was up to 50km in that direction.
0:54:29 > 0:54:36And Jeff Rose thinks that the key to our ancestors' journey along this coast lies at the bottom of the sea.
0:54:37 > 0:54:40One of the strangest things about Arabia
0:54:40 > 0:54:43is we have this dry surface, this completely arid landscape,
0:54:43 > 0:54:46and yet beneath the surface there are heaps of fresh water
0:54:46 > 0:54:51that's bubbling, running towards the coast, and coming up directly beneath us.
0:54:51 > 0:54:55Down below, if you were to dive down with a canteen, you could fill it up with fresh water.
0:54:55 > 0:55:00- So the springs down there are still working?- Yes. There's heaps of fresh water coming towards the coast.
0:55:00 > 0:55:03Only when the sea level was lower would it have been available.
0:55:03 > 0:55:08It really shows why that coastline was so important for early humans moving out of Africa.
0:55:16 > 0:55:22So around 70,000 years ago, the Arabian coastline was very different to today.
0:55:28 > 0:55:32Freshwater springs bubbled up all the way along it.
0:55:32 > 0:55:38If our ancestors attempted this route, they would have found a lifeline...
0:55:39 > 0:55:44..stretching all the way from the Red Sea to the Persian Gulf...
0:55:47 > 0:55:52..a place which back then was a great fertile plain.
0:55:57 > 0:56:00So the Gulf as we know it today didn't exist.
0:56:00 > 0:56:03It was a vast, green, lush plain.
0:56:03 > 0:56:06Green and lush. You had estuaries and rivers and lakes.
0:56:06 > 0:56:10It was probably the most important place in Southwest Asia for all early humans
0:56:10 > 0:56:14because so much fresh water was available at that time.
0:56:14 > 0:56:18- So they had everything they needed for survival.- It sounds idyllic. - It was.
0:56:23 > 0:56:29Finding the route that our ancestors took out of Africa has been challenging.
0:56:29 > 0:56:32But I really think that this could have been it.
0:56:36 > 0:56:41And it's perhaps no wonder, with the obstacles they faced,
0:56:41 > 0:56:45that there seems to have been just one successful attempt.
0:56:47 > 0:56:50A massive leap in our ancestors' journey.
0:56:56 > 0:57:02Africa was the original home of our species and it was our only home
0:57:02 > 0:57:09for tens of thousands of years until a small handful of people made their way out of Africa.
0:57:09 > 0:57:15And it was their descendants that went on to colonise the rest of the world.
0:57:15 > 0:57:21I'm going to try to trace their footsteps as we continue on the Great Human Journey.
0:57:28 > 0:57:31'Come with me as I travel right across the world...'
0:57:31 > 0:57:34This is looking like a pretty big footprint.
0:57:34 > 0:57:39'..in search of the traces left by our ancestors.'
0:57:39 > 0:57:43- That's the original? - Yes, all original.- I didn't know any of it had survived.
0:57:45 > 0:57:51'I want to know how so few people could have populated the rest of the planet.'
0:57:51 > 0:57:56That makes us re-think all of our theories about early Americans.
0:57:59 > 0:58:00'Facing the unimaginable...
0:58:02 > 0:58:05'..rival species...
0:58:05 > 0:58:08'and even near extinction...'
0:58:08 > 0:58:12I don't think I've ever been so cold in my entire life.
0:58:12 > 0:58:17'..to reach the most distant corners of the world.'
0:58:17 > 0:58:20I'm worried we're gonna get swept in by these breakers.
0:58:25 > 0:58:30'And how did those journeys change us into who we are today?'
0:58:48 > 0:58:50Subtitles by Red Bee Media Ltd
0:58:50 > 0:58:52E-mail subtitling@bbc.co.uk