0:00:04 > 0:00:07This is our world.
0:00:08 > 0:00:11We have shaped it in our image.
0:00:11 > 0:00:13Made it our own.
0:00:15 > 0:00:18We are now the only humans in existence.
0:00:18 > 0:00:20Absolute rulers of the Earth.
0:00:21 > 0:00:24But there was a time when we shared this planet with other,
0:00:24 > 0:00:28very different types of human.
0:00:31 > 0:00:37By the time our ancestors left Africa around 100,000 years ago,
0:00:37 > 0:00:40most of these "others" had gone extinct.
0:00:42 > 0:00:44But not all.
0:00:49 > 0:00:53Other species had made the journey out of Africa before us.
0:00:53 > 0:00:58Smart, strong and well adapted to their environment,
0:00:58 > 0:01:01they were the dominant species on the planet.
0:01:08 > 0:01:11So what happened when our worlds collided?
0:01:12 > 0:01:16Why, despite all their advantages,
0:01:16 > 0:01:19were those others driven to extinction?
0:01:20 > 0:01:25Why, against the odds, did we win the Battle For Planet Earth?
0:02:09 > 0:02:12Around 100,000 years ago,
0:02:12 > 0:02:17a new species of human arrived in what is now India.
0:02:18 > 0:02:22The colour of their skin betrayed their African origins.
0:02:28 > 0:02:30They had language.
0:02:30 > 0:02:34They lived in small, tightly-bonded family groups.
0:02:35 > 0:02:39These were Homo sapiens - modern people.
0:02:41 > 0:02:43They were us.
0:02:47 > 0:02:49Their numbers were few,
0:02:49 > 0:02:54and from Africa they had begun to spread slowly across the world.
0:02:56 > 0:02:58But Asia was already occupied.
0:02:58 > 0:03:01Home to a different human species -
0:03:01 > 0:03:03Homo erectus.
0:03:08 > 0:03:13Erectus was a fascinating species, it lasted for a very long time.
0:03:13 > 0:03:15It's really the longest-lived human species we know about.
0:03:18 > 0:03:22These are people that are being very mobile, in open country,
0:03:22 > 0:03:23to get to their food,
0:03:23 > 0:03:27and often to get to their food ahead of the competition.
0:03:27 > 0:03:29So in that sense, they're very like us
0:03:29 > 0:03:32in terms of their overall body shape and body build.
0:03:51 > 0:03:53No water.
0:03:54 > 0:03:55Come.
0:03:55 > 0:03:57Although physically similar,
0:03:57 > 0:04:00any chance of a peaceful co-existence
0:04:00 > 0:04:03between Homo sapiens and Homo erectus
0:04:03 > 0:04:07was shattered by a cataclysmic event
0:04:07 > 0:04:10that took place over 2,000 miles away.
0:04:19 > 0:04:22The eruption of Mount Toba in south-east Asia.
0:04:24 > 0:04:2774,000 years ago,
0:04:27 > 0:04:31it erupted on a scale that no human had experienced before or since.
0:04:32 > 0:04:35It's certainly the largest volcanic eruption
0:04:35 > 0:04:37of the last two million years
0:04:37 > 0:04:39and erupted a huge amount of material.
0:04:41 > 0:04:43And because of its magnitude,
0:04:43 > 0:04:46it's been classed as a super-volcanic eruption.
0:04:49 > 0:04:55The fallout from the eruption extended as far as the Indian sub-continent.
0:04:56 > 0:04:59We've got areas, particularly in East India,
0:04:59 > 0:05:02where the ash reaches six metres in thickness.
0:05:04 > 0:05:08Ash fall from the eruption filled the atmosphere with toxic chemicals...
0:05:10 > 0:05:15..turning rain to acid that poisoned lakes and rivers...
0:05:16 > 0:05:19..intensifying the struggle for survival.
0:05:20 > 0:05:23In the aftermath of the Toba eruption,
0:05:23 > 0:05:27you might have increased competition because, remember,
0:05:27 > 0:05:30plants and animals are suffering
0:05:30 > 0:05:33and these small groups of hunter-gatherers
0:05:33 > 0:05:37are competing for diminished resources
0:05:37 > 0:05:40and so that may have caused some situations
0:05:40 > 0:05:43where there was conflict between groups.
0:05:57 > 0:06:02Based on the latest archaeological and scientific evidence,
0:06:02 > 0:06:07this is a dramatisation of a world forged by the Toba eruption.
0:06:08 > 0:06:13A time which shaped the fates of two different but closely related species.
0:06:14 > 0:06:17Us...and them.
0:06:17 > 0:06:19Leave it.
0:06:19 > 0:06:21Water!
0:06:21 > 0:06:24Wait! Baako, wait!
0:06:29 > 0:06:31Drink.
0:06:31 > 0:06:34Don't drink it! What are you doing?
0:06:34 > 0:06:36How do you know the water is good?
0:06:36 > 0:06:38People were here. They lived here.
0:06:41 > 0:06:44Why do you think they left?
0:06:50 > 0:06:54The people, did they go to the mountains for clean water?
0:06:56 > 0:06:59These are NOT people!
0:07:06 > 0:07:09As the once-lush Indian landscape turned to desert,
0:07:09 > 0:07:15clean water became scarce and increasingly hard to find.
0:07:30 > 0:07:33We'll find somewhere for you to rest.
0:07:35 > 0:07:37Up there.
0:07:39 > 0:07:45The Toba eruption was so vast, it would have affected the whole planet.
0:07:45 > 0:07:49In the aftermath, human numbers fell dramatically.
0:07:50 > 0:07:52We were threatened with extinction.
0:07:54 > 0:07:59In India, the struggle to survive would have been particularly harsh.
0:08:01 > 0:08:04This was erectus territory.
0:08:04 > 0:08:10For thousands of years, erectus had been one of Asia's most successful predators.
0:08:13 > 0:08:18The arrival of modern humans would have threatened their world.
0:08:18 > 0:08:21We're talking a different species of human.
0:08:21 > 0:08:25Erectus was a much more ancient species of human.
0:08:25 > 0:08:27So we've got this very strong brow ridge at the front,
0:08:27 > 0:08:30a long and low skull. A big face.
0:08:30 > 0:08:34Overall bigger teeth than us. If we had the lower jaw,
0:08:34 > 0:08:36there wouldn't be a chin on the lower jaw.
0:08:36 > 0:08:39So overall, much more robust. The skull is thicker,
0:08:39 > 0:08:41muscle markings are very strong.
0:08:50 > 0:08:53She's sleeping, but needs water.
0:09:00 > 0:09:03What are they if they're not people?
0:09:06 > 0:09:08All I know, I know from stories.
0:09:10 > 0:09:11And from my father.
0:09:15 > 0:09:18They move fast, like us.
0:09:18 > 0:09:20They hunt.
0:09:21 > 0:09:23They kill.
0:09:26 > 0:09:28If someone comes near...
0:09:29 > 0:09:32..they will snap a twig.
0:09:32 > 0:09:34- And Mother will hear. - You will hear them.
0:09:34 > 0:09:36I will come with you!
0:09:37 > 0:09:40Stay with your mother, she needs you.
0:09:43 > 0:09:45If I do not return,
0:09:45 > 0:09:46keep our family alive.
0:10:11 > 0:10:14The first human species to walk fully upright,
0:10:14 > 0:10:17erectus, would have made formidable opponents.
0:10:19 > 0:10:25This is a cast of a thigh bone or femur of Homo erectus from Africa.
0:10:25 > 0:10:30It tells us Homo erectus was similar to us below the neck.
0:10:30 > 0:10:33More particularly, this ridge on the back of their thigh bone,
0:10:33 > 0:10:38this is the pilaster, and it grows in response to running.
0:10:38 > 0:10:41People today who have similar kinds of ridges on their femurs
0:10:41 > 0:10:44and have femurs of similar sorts of shape like this
0:10:44 > 0:10:45tend to be very good runners.
0:10:45 > 0:10:48We're talking about people, Olympic athletes.
0:10:50 > 0:10:54If they were around today, chasing people around, you'd be in trouble.
0:10:56 > 0:10:59These guys were like wolves with knives.
0:10:59 > 0:11:02With bodies beautifully evolved for running,
0:11:02 > 0:11:08erectus were the first human species to hunt big game.
0:11:08 > 0:11:11To begin with, erectus was scavenging,
0:11:11 > 0:11:15so picking up the meat from other animals that had done the killing.
0:11:15 > 0:11:20But by the end of their time, they were certainly big game hunters,
0:11:20 > 0:11:22and were capable big game hunters.
0:11:26 > 0:11:32Hunting big prey would have required erectus to work co-operatively, in packs.
0:12:20 > 0:12:21Mother.
0:12:31 > 0:12:34SCREAM
0:14:08 > 0:14:11Cunning carnivores at the very top of the food chain,
0:14:11 > 0:14:16erectus were armed with a lethal stone weapon.
0:14:16 > 0:14:17It looks just like a rock.
0:14:19 > 0:14:21But if you look more carefully,
0:14:21 > 0:14:23you can see it has a very sharp cutting edge
0:14:23 > 0:14:25that goes around its circumference.
0:14:25 > 0:14:29It's also thin, a cross section, so you have a very sharp edge.
0:14:29 > 0:14:31And from what we can reconstruct of its use,
0:14:31 > 0:14:34it was used mainly for cutting the limbs off of an animal.
0:14:34 > 0:14:37It's the Stone Age equivalent of a chainsaw.
0:14:40 > 0:14:43For cutting through skin. Cutting through muscle.
0:14:43 > 0:14:45Cutting through tendons.
0:14:45 > 0:14:50If you're using this as a weapon, it would create a pretty nasty slashing wound.
0:14:50 > 0:14:53Like that. Yeah, it's all-purpose knife.
0:15:10 > 0:15:11No, go away!
0:15:12 > 0:15:14Mother!
0:15:16 > 0:15:18Leave us alone! No!
0:15:27 > 0:15:30Although we think of necklaces as a way of dressing up,
0:15:30 > 0:15:35for our ancestors, they had a much more important role.
0:15:39 > 0:15:43Recent human cultures used beads and other personal adornments
0:15:43 > 0:15:45to transmit information, in a way.
0:15:45 > 0:15:49Certain combinations of shells can symbolically convey information
0:15:49 > 0:15:51about the person wearing them.
0:15:54 > 0:15:56Personal adornments, symbols like this,
0:15:56 > 0:15:58can be ways that people can establish
0:15:58 > 0:16:02communications and relationships across great distances,
0:16:02 > 0:16:05so it's kind of like a passport when you think about it.
0:16:05 > 0:16:10Beads like these helped us to identify friend from foe,
0:16:10 > 0:16:13allowing us to form alliances with others.
0:16:14 > 0:16:17- Where's your father? - He went to find water.
0:16:17 > 0:16:19They took him.
0:16:19 > 0:16:22- Who took him?- Did they see you?
0:16:22 > 0:16:25Did they see you? Did they see you?
0:16:43 > 0:16:45To the rock. Quick!
0:16:53 > 0:16:57The ability to track evolved with the ability to hunt.
0:16:57 > 0:17:02Homo erectus were the first humans to systematically track their prey,
0:17:02 > 0:17:06using scent, sight and sound.
0:17:07 > 0:17:11Their large brains could interpret signs,
0:17:11 > 0:17:15work out the movements of their prey, making them deadly hunters.
0:17:16 > 0:17:20Our ancestors, however, had a significant advantage.
0:17:23 > 0:17:28We had learned to anticipate the thoughts and behaviours of others,
0:17:28 > 0:17:30and use that knowledge to outsmart them.
0:17:32 > 0:17:34Find your footprints where you came down.
0:17:34 > 0:17:37Step in them backwards.
0:17:37 > 0:17:39Backwards!
0:17:48 > 0:17:50Keep going.
0:17:59 > 0:18:00Stop!
0:18:11 > 0:18:13What are you staring at?
0:18:23 > 0:18:26HE ROARS
0:18:26 > 0:18:28Go! Stay on the rock.
0:18:47 > 0:18:48They have father's spear!
0:18:49 > 0:18:53There is no evidence that Homo erectus made spears.
0:18:54 > 0:18:59Even if they had, they couldn't have used them the way we do.
0:19:00 > 0:19:06Their shoulders lacked the ability to twist, so their palms faced forwards,
0:19:06 > 0:19:09instead of hanging sideways as with modern humans.
0:19:10 > 0:19:15So even if they had invented the spear, they may not have been able to throw it.
0:19:16 > 0:19:22In the hands of our ancestors, the spear became a very effective weapon.
0:19:24 > 0:19:29The most important advantage of this kind of weapon is that it allows the person using it
0:19:29 > 0:19:31to put some distance between them and the tip of the spear.
0:19:31 > 0:19:34Whereas with a hand axe, you're using the weapon close up.
0:19:34 > 0:19:38In this case, you have a long distance between yourself, your hands,
0:19:38 > 0:19:40and the part of the tool that's doing the killing.
0:19:43 > 0:19:45The spear was also effective close up.
0:19:48 > 0:19:51Here you can see the kind of wound it makes. A big slashing wound.
0:19:51 > 0:19:54You can see the point's inside the abominable cavity there
0:19:54 > 0:19:59and the animal's moving, the movement of that point will cause damage,
0:19:59 > 0:20:03it will cause haemorrhage, cause the animal to bleed out and die more quickly.
0:20:04 > 0:20:07The spear wasn't our ancestors' only weapon.
0:20:07 > 0:20:11- I will keep you safe. - Not with a spear.
0:20:11 > 0:20:13The point is sharp.
0:20:13 > 0:20:15Hmm. "The point is sharp."
0:20:15 > 0:20:18Throw a spear once, then what?
0:20:20 > 0:20:22Keep watch.
0:20:36 > 0:20:41At some point in the distant past, they developed something very new.
0:20:49 > 0:20:51One spear. Many stones!
0:20:51 > 0:20:53Here.
0:20:57 > 0:20:59The slingshot, like the spear,
0:20:59 > 0:21:04gave our ancestors the ability to strike and kill from a distance.
0:21:04 > 0:21:08If you hit a small animal with this, it's like hitting you or I with a car.
0:21:08 > 0:21:10It'll crush bones, it'll stop it in its tracks.
0:21:10 > 0:21:13This is a weapon that allows you to go after birds in flight,
0:21:13 > 0:21:16rabbits on the move, deer, creatures like this.
0:21:16 > 0:21:19It also has value as an offensive weapon in warfare.
0:21:19 > 0:21:21You know, David and Goliath.
0:21:21 > 0:21:23These things are really dangerous, no joke.
0:21:23 > 0:21:29Even in modern conflicts, people armed with these things have been known to kill other people.
0:21:29 > 0:21:33It can cause devastating injuries, one of these things against a limb will break a bone.
0:21:33 > 0:21:35If it hits your head, it can kill you.
0:21:39 > 0:21:44In the 1.8 million years Homo erectus had been on the planet,
0:21:44 > 0:21:48their weapons technology hadn't progressed beyond the hand axe.
0:21:48 > 0:21:53A highly effective, multi-purpose weapon, it was portable,
0:21:53 > 0:21:59simple to make, easy to replace and the perfect tool to cut, sever and smash.
0:22:01 > 0:22:05But it was limiting in one crucial way.
0:22:08 > 0:22:12To kill, erectus had to get close.
0:23:05 > 0:23:10For the first time, Homo erectus faced competition from a species
0:23:10 > 0:23:14who weren't bigger, stronger or more numerous,
0:23:14 > 0:23:19but who simply thought about things in a different way.
0:23:20 > 0:23:23It's worked. They've gone.
0:23:31 > 0:23:33You drank bad water.
0:23:36 > 0:23:37You should know better.
0:23:51 > 0:23:52Water?
0:23:52 > 0:23:54What else?
0:24:01 > 0:24:06Fragments of fossilised ostrich egg shells from the Thar desert in India
0:24:06 > 0:24:12suggest that our ancestors may have used these eggs to store and transport water.
0:24:12 > 0:24:17Just as the San bushmen in Africa have been doing for centuries.
0:24:19 > 0:24:24This ability to plan ahead was something our hominid rivals lacked.
0:24:26 > 0:24:31Homo sapiens' brain is about a third larger than Homo erectus' brain, and that tells you something.
0:24:31 > 0:24:33Brains are expensive tissues.
0:24:33 > 0:24:35It costs a lot of calories to grow a big brain.
0:24:35 > 0:24:38So there has to be some payoff for that extra brain.
0:24:38 > 0:24:42We think the payoff for Homo sapiens is more complex thought,
0:24:42 > 0:24:46where they are able to plan more complex activities, store more information.
0:24:46 > 0:24:50Homo erectus wasn't stupid, but Homo sapiens may have had some key advantages
0:24:50 > 0:24:54as a consequence of having a larger, more complex brain.
0:24:55 > 0:24:59Another advantage we had was language.
0:25:00 > 0:25:04Differences between our and their linguistic abilities
0:25:04 > 0:25:07can be seen by comparing skulls.
0:25:08 > 0:25:12The part of the brain that controls language and speech production
0:25:12 > 0:25:14is located right around here.
0:25:14 > 0:25:16And you can see these parts of the Homo sapiens' brain
0:25:16 > 0:25:18are very much enlarged.
0:25:18 > 0:25:21That part of the skull bows outward quite a bit,
0:25:21 > 0:25:23and so there's more brain in that part of the head.
0:25:23 > 0:25:25On the corresponding part of Homo erectus' skull,
0:25:25 > 0:25:27the brain is relatively small.
0:25:27 > 0:25:30So the Homo erectus brain is not devoting a lot of space
0:25:30 > 0:25:33to the parts of the brain that controls language and speech.
0:25:33 > 0:25:36One of the crucial elements of Homo sapiens' adaptations
0:25:36 > 0:25:39is that it combines complex planning,
0:25:39 > 0:25:42developed in the front of the brain here, with language,
0:25:42 > 0:25:45with the ability to spread complex plans from one individual
0:25:45 > 0:25:48to the other individual, to another individual.
0:25:51 > 0:25:55- Where's it from?- Far from here.
0:25:56 > 0:25:58Before they came and chased us out.
0:25:59 > 0:26:01Us? You were with others?
0:26:01 > 0:26:03My son...
0:26:04 > 0:26:07..his wife, their baby boy.
0:26:10 > 0:26:11Enough!
0:26:11 > 0:26:13Don't drink it all!
0:26:14 > 0:26:17There's more water nearby.
0:26:20 > 0:26:22No, there isn't.
0:26:22 > 0:26:23Here, on higher ground.
0:26:23 > 0:26:25There's been no rain.
0:26:25 > 0:26:28- But father said... - Your father was wrong!
0:26:31 > 0:26:32There is no water here.
0:26:34 > 0:26:36But away from the rock...
0:26:38 > 0:26:42..across the sand, there is water.
0:26:42 > 0:26:45More water than you can imagine.
0:26:45 > 0:26:47How do you know?
0:26:52 > 0:26:53My father told me.
0:26:56 > 0:26:57He came from the water.
0:27:00 > 0:27:02Inside there is food.
0:27:02 > 0:27:04Not in that one, not now.
0:27:12 > 0:27:14There is no food on this mountain,
0:27:14 > 0:27:17but at the water...
0:27:21 > 0:27:24..there is more food than you can eat.
0:27:24 > 0:27:29Imagination, the ability to visualise what can't be seen,
0:27:29 > 0:27:33would prove another defining advantage for our species.
0:27:41 > 0:27:46Like us, erectus are believed to have lived in small family groups.
0:27:48 > 0:27:55There is evidence that they cared for each other, and looked after the sick and injured.
0:27:55 > 0:27:59There are some hints that they may have had a sense of compassion.
0:27:59 > 0:28:02Comparable to the things we feel about one another.
0:28:02 > 0:28:06There are fossils from the site of Dmanisi in Georgia
0:28:06 > 0:28:07that hint at this.
0:28:07 > 0:28:10One fossil in particular had lost all of its teeth,
0:28:10 > 0:28:12either to an infection or to old age, or to both,
0:28:12 > 0:28:15and this individual was so severely handicapped
0:28:15 > 0:28:17that it would have had to have assistance.
0:28:17 > 0:28:20Some other member of its group would have had to help it
0:28:20 > 0:28:23basically chew its food in order for this individual to survive.
0:28:25 > 0:28:28Erectus moved around in search of food
0:28:28 > 0:28:31and rarely settled for any length of time.
0:28:32 > 0:28:38They were using the landscape, they were travelling from one place to another.
0:28:38 > 0:28:42And they were probably gathering resources, gathering, you know,
0:28:42 > 0:28:47plants and they were occasionally, obviously, butchering animals.
0:28:47 > 0:28:52So these were, in a sense, small groups of hunters and gatherers.
0:28:56 > 0:29:01But after the Toba eruption, there was not much left to gather.
0:29:01 > 0:29:03Ash killed off vegetation,
0:29:03 > 0:29:08leaving little in the way of fruit, nuts and tubers to eat.
0:29:09 > 0:29:11They have food.
0:29:11 > 0:29:14Meat would have been highly valued.
0:29:14 > 0:29:15They have food!
0:29:15 > 0:29:18- Meat?- We must leave.
0:29:18 > 0:29:20- What about father? - Forget your father!
0:29:20 > 0:29:23- We must wait for him!- Huh, wait!
0:29:25 > 0:29:28WHISPERS: There are no animals here.
0:29:29 > 0:29:32I know that smell!
0:29:39 > 0:29:41Tell him.
0:29:49 > 0:29:52- Tonight, we stay here.- What?!
0:29:53 > 0:29:55This is where he will come.
0:29:55 > 0:29:58He will not come.
0:29:58 > 0:30:01He's a brave man.
0:30:01 > 0:30:02He's strong.
0:30:14 > 0:30:16At first light, we go.
0:30:18 > 0:30:19With or without him.
0:30:47 > 0:30:49Father's alive.
0:30:50 > 0:30:52I know he is.
0:30:55 > 0:30:57WANGARI GRUMBLES IN HER SLEEP
0:30:59 > 0:31:01WANGARI SNORES
0:31:05 > 0:31:08- She even talks in her sleep!- Shhh.
0:31:08 > 0:31:11Respect your elders.
0:31:16 > 0:31:18She talks too much.
0:31:18 > 0:31:20I don't like her.
0:31:20 > 0:31:24I don't like her, but she knows things.
0:31:30 > 0:31:33And she has water.
0:31:35 > 0:31:38We could take the water and leave her.
0:31:38 > 0:31:41Shall we?
0:31:41 > 0:31:42Go back to sleep.
0:32:07 > 0:32:09HE GRUNTS WITH EFFORT
0:32:11 > 0:32:13HE COUGHS
0:32:19 > 0:32:20Baako.
0:32:23 > 0:32:24Baako!
0:32:29 > 0:32:31Father!
0:32:42 > 0:32:45HE ROARS
0:32:52 > 0:32:54She's gone.
0:33:05 > 0:33:09Like other large predators, erectus were territorial,
0:33:09 > 0:33:14hunting within boundaries and defending their territory from other competition.
0:33:18 > 0:33:20She left this.
0:33:21 > 0:33:26Territory based on high ground would have been especially prized,
0:33:26 > 0:33:28because it makes spotting prey easier.
0:33:32 > 0:33:34I saw father on that ridge...
0:33:36 > 0:33:38..with the others.
0:33:39 > 0:33:43Anything that strayed into their territory would have been treated as food.
0:33:55 > 0:33:56Don't be afraid.
0:34:18 > 0:34:20Footprints.
0:34:22 > 0:34:23Everywhere.
0:34:55 > 0:35:01Recent studies suggest that erectus were infected by tapeworms,
0:35:01 > 0:35:03which you get from eating raw meat.
0:35:03 > 0:35:08It seems that erectus liked his food red and bloody,
0:35:08 > 0:35:11even though he could have cooked it.
0:35:11 > 0:35:13HE SNIFFS
0:35:15 > 0:35:18- They were here.- Where are they now?
0:35:19 > 0:35:22I don't know.
0:35:22 > 0:35:24Just stay here...
0:35:25 > 0:35:27..and watch.
0:36:04 > 0:36:05Father?
0:36:08 > 0:36:10HE GASPS
0:36:17 > 0:36:18Mother!
0:36:18 > 0:36:23On some occasions, Homo erectus's hunger for meat
0:36:23 > 0:36:26seems to have got the better of them.
0:36:26 > 0:36:30The fossilised remains of an erectus found in Kenya
0:36:30 > 0:36:33shows signs of vitamin A poisoning,
0:36:33 > 0:36:37probably caused by eating too much animal liver.
0:36:41 > 0:36:46Excessive vitamin A causes tissue around bones to tear and bleed.
0:36:48 > 0:36:51This person would have been in agony for months.
0:36:51 > 0:36:58To survive as long as they did, they must have been cared for by other members of the group.
0:37:05 > 0:37:06Baako!
0:37:11 > 0:37:14Friend or enemy? Think!
0:38:06 > 0:38:08HE SIGHS
0:38:10 > 0:38:11Father.
0:38:16 > 0:38:18He'll protect you.
0:38:32 > 0:38:33It's yours now.
0:38:41 > 0:38:44Would Homo erectus haven eaten a Homo sapiens, given the chance?
0:38:44 > 0:38:46My guess is, "Yeah."
0:38:46 > 0:38:49They probably didn't view each other as members of the same species,
0:38:49 > 0:38:53and just as humans today will eat chimpanzees as bush meat,
0:38:53 > 0:38:56Homo erectus may have felt the same way about Homo sapiens.
0:39:01 > 0:39:03They may also have been cannibals.
0:39:05 > 0:39:07Homo erectus bones have been discovered
0:39:07 > 0:39:14with cut marks, suggesting that the flesh was prised off the skeleton.
0:39:23 > 0:39:24Quick!
0:39:27 > 0:39:29Toka?
0:39:39 > 0:39:40Ta!
0:39:49 > 0:39:51ERECTUS YELLS
0:39:52 > 0:39:54HE HOWLS IN AGONY
0:39:54 > 0:39:56Go, Mother. Go!
0:40:04 > 0:40:07THEY CALL TO EACH OTHER
0:40:07 > 0:40:09Keep going!
0:40:24 > 0:40:26No!
0:40:34 > 0:40:35Up here, quick!
0:40:50 > 0:40:52Muka, halla.
0:40:52 > 0:40:54HE GROWLS IN FRUSTRATION
0:41:11 > 0:41:13Muka.
0:41:25 > 0:41:27I can't go any further.
0:41:27 > 0:41:30- Keep going.- No you go, run.
0:41:35 > 0:41:36They're coming.
0:41:44 > 0:41:46This way. This way! Quick!
0:42:17 > 0:42:21A unique and crucial development of every human species
0:42:21 > 0:42:25was to harness the power of fire.
0:42:25 > 0:42:29Erectus were the first human species to use fire.
0:42:29 > 0:42:31Time is the currency of evolution.
0:42:31 > 0:42:33If you have more time, you can do more things.
0:42:33 > 0:42:37You can do more of the same thing or you can experiment and do different things.
0:42:37 > 0:42:39But it's all underwritten by having time,
0:42:39 > 0:42:43and fire is one way of providing that kind of time.
0:42:43 > 0:42:46Without fire, you're not human.
0:42:46 > 0:42:51Both species used fire for warmth, and to cook and dry meat.
0:42:51 > 0:42:54Cooking makes meat a more digestible substance
0:42:54 > 0:42:57and so it reduces the time one has to spend time chewing,
0:42:57 > 0:42:59frees you up to do other things.
0:42:59 > 0:43:05But our ancestors were the first to exploit its full range of possibilities.
0:43:20 > 0:43:24When they left Africa, our ancestors most likely followed the coastline
0:43:24 > 0:43:29as they moved into Arabia, India, South East Asia and beyond.
0:43:31 > 0:43:35Close to the sea, they were guaranteed food and fresh water,
0:43:35 > 0:43:38flowing from rivers into the sea.
0:43:38 > 0:43:44But after Toba, their ability to range freely was dramatically curtailed.
0:43:45 > 0:43:47Them or us?
0:43:50 > 0:43:52Does it matter?
0:43:53 > 0:43:55Mother?
0:44:18 > 0:44:21To escape from this eruption-ravaged land,
0:44:21 > 0:44:24our ancestors faced a huge problem.
0:44:28 > 0:44:30The Thar desert.
0:44:33 > 0:44:39It forms a long, natural barrier between the Indian interior and the sea.
0:44:43 > 0:44:46It has been there for hundreds of thousands of years,
0:44:46 > 0:44:52growing and contracting in response to the changing climatic conditions.
0:45:06 > 0:45:11After Toba, the desert dramatically expanded.
0:45:13 > 0:45:17So this would have brought colder and drier conditions
0:45:17 > 0:45:20into the north east of India and this would have...
0:45:22 > 0:45:26probably enhanced aridity.
0:45:26 > 0:45:30So areas such as the Thar desert, for example, may have expanded,
0:45:30 > 0:45:34or areas like the Indo-Gangetic plain may have been particularly arid.
0:45:36 > 0:45:40You might have thought that a desert, hundreds of miles wide,
0:45:40 > 0:45:44would have trapped any humans in the Indian interior.
0:45:44 > 0:45:51But there is archaeological evidence that people did attempt to make the journey across it.
0:45:51 > 0:45:52How much further?
0:45:54 > 0:45:55Keep walking.
0:46:01 > 0:46:02How far?
0:46:07 > 0:46:08I don't know.
0:46:15 > 0:46:16Look!
0:46:34 > 0:46:37Follow me. We'll lose them in the storm.
0:46:49 > 0:46:50Faster!
0:46:50 > 0:46:54- I can't!- They're coming. - Keep going.
0:46:57 > 0:46:59THEY COUGH
0:47:01 > 0:47:03- Aro!- Heeya-ha!
0:47:05 > 0:47:08Wa! Waa!
0:47:11 > 0:47:13Walk like this.
0:47:37 > 0:47:39Wait! Stop!
0:47:39 > 0:47:43- We can't stop.- Sit!
0:47:43 > 0:47:45There's nowhere to hide.
0:47:45 > 0:47:47If you want to stay, stay, we're going.
0:47:50 > 0:47:55Here, walk in this and you walk like a wounded animal.
0:47:55 > 0:47:59Round and round, backwards and forwards, you lose yourself forever.
0:47:59 > 0:48:00Do you hear me?
0:48:01 > 0:48:04Do you hear me?!
0:48:50 > 0:48:54No-one can be quite sure how our ancestors made it.
0:48:54 > 0:48:57Perhaps by finding water in dry river beds,
0:48:57 > 0:49:02as many indigenous people in Africa and Asia still do today.
0:49:04 > 0:49:08Even in apparently dry river beds, after long droughts,
0:49:08 > 0:49:15water can still be found in underground reservoirs beneath the sand.
0:49:15 > 0:49:16If you know where to look.
0:49:51 > 0:49:53Heko?
0:49:57 > 0:49:59Heko!
0:50:04 > 0:50:06Heko. Heko!
0:50:24 > 0:50:26Heko.
0:50:26 > 0:50:28Heko.
0:50:43 > 0:50:47The ability to find water in the dry times would have been
0:50:47 > 0:50:51invaluable knowledge, passed down the generations.
0:50:53 > 0:50:58And all rivers, dry or flowing, eventually, lead to the sea.
0:51:17 > 0:51:19Come on.
0:51:33 > 0:51:34Don't drink it.
0:51:50 > 0:51:52Get back!
0:53:24 > 0:53:28Archaeologists working in Jawalpuram in India
0:53:28 > 0:53:30have found the sort of stone tools
0:53:30 > 0:53:35made by modern humans buried beneath a thick layer of Toba ash.
0:53:35 > 0:53:41Alongside our tools were those of Homo erectus.
0:53:41 > 0:53:46Above the ash, only our tools are found.
0:53:46 > 0:53:50The lack of evidence of erectus after the Toba eruption
0:53:50 > 0:53:55suggests that they might have been wiped out in India, never to return.
0:53:55 > 0:53:59In other parts of Asia, they hung on.
0:53:59 > 0:54:02Fossilised skulls from Indonesia
0:54:02 > 0:54:07show Homo erectus living here until as recently as 30,000 years ago.
0:54:07 > 0:54:13A descendent of theirs, Homo floresiensis, nicknamed the Hobbits,
0:54:13 > 0:54:16lived until about 18,000 years ago.
0:54:16 > 0:54:19But then, having successfully walked the earth
0:54:19 > 0:54:25for almost two million years, this other human species disappeared.
0:54:25 > 0:54:30I think it is remarkable that we have these different human species,
0:54:30 > 0:54:32and, you know, even 100, 000 years ago
0:54:32 > 0:54:35we've still got several human species on Earth
0:54:35 > 0:54:36and that's strange for us.
0:54:36 > 0:54:40We're the only survivors of all of those great evolutionary experiments in how to be human.
0:54:42 > 0:54:44They did go extinct.
0:54:44 > 0:54:49And that, of course, was unfortunate for them,
0:54:49 > 0:54:53but it made a new opportunity for species like ourselves.
0:54:53 > 0:54:57The passing of Homo erectus was a tragedy.
0:54:57 > 0:55:00We think of ourselves as so unique and special and all the rest of this,
0:55:00 > 0:55:04and we do so because there's such a huge gulf between ourselves
0:55:04 > 0:55:08and our nearest primate relatives - gorillas, chimpanzees and bonobos.
0:55:08 > 0:55:12If that gap were populated by other hominids, if we had others,
0:55:12 > 0:55:18we'd see that gap as not so much a gulf but rather a continuum with steps on the way.
0:55:18 > 0:55:21We'd still think of ourselves as special but maybe not so special...
0:55:21 > 0:55:24A little dose of humility wouldn't hurt.
0:55:25 > 0:55:28If you went back in time and changed a few parameters
0:55:28 > 0:55:33of climate and geography, then we could have ended up with a completely different outcome.
0:55:33 > 0:55:35Maybe these species would all still be around,
0:55:35 > 0:55:41maybe modern humans would never have evolved and we'd still have these other species on Earth and not us.
0:55:50 > 0:55:56The Toba eruption may have changed the destiny of our species,
0:55:56 > 0:55:58socially and biologically.
0:55:58 > 0:56:02Experts believe that our large brains, significantly different from
0:56:02 > 0:56:07those of our closest relatives, are the product of an intense process of
0:56:07 > 0:56:15natural selection which occurred during a period of extreme hardship when population numbers were low.
0:56:15 > 0:56:20You're home.
0:56:20 > 0:56:22People.
0:56:25 > 0:56:30Socially too, Toba left a mark on our species.
0:56:30 > 0:56:36Evidence reveals that social networking in surviving humans increased.
0:56:38 > 0:56:44Through the exchange of gifts, ideas and even people between groups,
0:56:44 > 0:56:51our social relationships strengthened and became insurance policies against bad times,
0:56:51 > 0:56:54greatly increasing our chances of survival.
0:56:56 > 0:56:59As climatic conditions improved,
0:56:59 > 0:57:04our ancestors spread around the world, hugging the coastlines,
0:57:04 > 0:57:09coming in contact with other Homo sapien groups, forging new alliances.
0:57:11 > 0:57:13Then 32,000 years ago,
0:57:13 > 0:57:20our ancestors finally arrived in Europe, to confront the final challenge
0:57:20 > 0:57:24in our Battle for the Planet - The Neanderthals.
0:57:30 > 0:57:35The way Neanderthals are treated in the popular media is very unfair.
0:57:35 > 0:57:37I mean, they were highly evolved humans,
0:57:37 > 0:57:39in their own way as evolved as we are.
0:57:42 > 0:57:45There's no other event in human evolution
0:57:45 > 0:57:49that captures the public imagination like the encounters
0:57:49 > 0:57:52between Homo sapiens and Neanderthals.
0:58:05 > 0:58:08Subtitles by Red Bee Media Ltd
0:58:08 > 0:58:11E-mail subtitling@bbc.co.uk