0:00:14 > 0:00:22Even before we knew we were related, we'd always known there was part of them in us,
0:00:22 > 0:00:25and part of us in them.
0:00:32 > 0:00:35We can see ourselves in their faces.
0:00:37 > 0:00:40We share a long family history.
0:00:44 > 0:00:46A sense of adventure.
0:00:46 > 0:00:48Courage.
0:00:53 > 0:00:55A society and its battles.
0:00:59 > 0:01:04There is an understanding of life and death here.
0:01:06 > 0:01:11What makes us human may not be uniquely human after all.
0:01:14 > 0:01:18There are wild monkeys all around the world,
0:01:18 > 0:01:22yet only recently have we discovered just how extraordinary they are.
0:01:34 > 0:01:39Jodhpur in India, and the monkey gods are awake.
0:01:42 > 0:01:44Monkeys were here first.
0:01:46 > 0:01:51We have a handful of other closer cousins, rare forest apes.
0:01:51 > 0:01:56But monkeys represent the blueprints on which we are all based.
0:01:59 > 0:02:04Some monkeys live with us, and perhaps live more like us than any other animal.
0:02:14 > 0:02:17HORNS BEEPING, SHOUTING
0:02:18 > 0:02:22We have no idea what they think and feel.
0:02:22 > 0:02:24We can, however, guess.
0:02:26 > 0:02:31And there are lots of different scientific theories.
0:02:32 > 0:02:37We do know they want to find out about everything,
0:02:37 > 0:02:39whatever the risks.
0:02:45 > 0:02:48Toque macaques will try anything new,
0:02:48 > 0:02:54imagining rewards behind every closed drawer, tasting every new food.
0:03:05 > 0:03:07DOG BARKS
0:03:07 > 0:03:10SMASH!
0:03:32 > 0:03:3440 million years ago,
0:03:34 > 0:03:37in the ancient tropical forests,
0:03:37 > 0:03:39there were monkeys.
0:03:44 > 0:03:49Our monkey ancestors may have looked a little like this.
0:03:49 > 0:03:50Tiny.
0:03:51 > 0:03:58In the tropical forests of Ecuador lives the pygmy marmoset, the smallest monkey in the world.
0:03:58 > 0:04:02It's the size of a hamster, and it hunts like a cat.
0:04:05 > 0:04:10Yet this monkey is closer to us than to cat or hamster.
0:04:10 > 0:04:17The eyes face forward and see in 3D and colour, and have a powerful brain behind them.
0:04:17 > 0:04:22Hands have fingerprints, and claws are long fingernails.
0:04:24 > 0:04:29Being able to grasp physical objects also helps your understanding.
0:04:30 > 0:04:34You learn things are there even if you can't see them.
0:04:35 > 0:04:39Navigating around a tree is more complicated than flat ground.
0:04:43 > 0:04:49Marmosets hold places and objects in their minds.
0:04:52 > 0:04:57Once you can picture things, you can perhaps imagine improvements.
0:04:57 > 0:05:02The marmoset family seem to. They "farm" sap from trees.
0:05:02 > 0:05:06Taking bites out of the bark has no immediate benefit.
0:05:06 > 0:05:08The bark is spat out.
0:05:10 > 0:05:15The family makes ordered holes like planting a field of cabbages.
0:05:15 > 0:05:19A few days later, a harvest of sugary gum has emerged.
0:05:26 > 0:05:32Planning ahead is clever, but so are your neighbours, waiting for you to do all the work.
0:05:34 > 0:05:39The family next door launches raids every few days.
0:05:44 > 0:05:47The owners are chased off.
0:05:47 > 0:05:52And the invaders gobble up as much sap as they can.
0:05:55 > 0:06:00The owners scent mark, which seems to give them new confidence.
0:06:00 > 0:06:04They rally their forces, charge and chase off the neighbours.
0:06:25 > 0:06:31A long time ago, the monkey mind turned to improving their world,
0:06:31 > 0:06:33and farming and warfare took root.
0:06:36 > 0:06:41Monkeys lived together to defend food and watch for predators,
0:06:41 > 0:06:46and numerous little societies sprang up.
0:06:55 > 0:07:00Each species made its own discoveries and customs.
0:07:00 > 0:07:05Marmosets and tamarins will often share childcare.
0:07:05 > 0:07:13The female emperor tamarin nearly always has twins, and she persuades two males to help look after them.
0:07:15 > 0:07:22Their mother carries them, with the two fathers, neither certain of paternity, obediently in tow.
0:07:22 > 0:07:28When mum wants to offload the kids, she signals to her mates with her tongue.
0:07:38 > 0:07:45An obsession with their young, we now realise, is one of the things that is basic to all monkeys.
0:07:58 > 0:08:05The infants have a father each to look after them, so mum goes to feed on nectar.
0:08:06 > 0:08:09There's something curious about monkey babies.
0:08:09 > 0:08:14The silver leaf monkey, for example, has orange young.
0:08:14 > 0:08:18It's risky with predators around, it advertises defencelessness.
0:08:18 > 0:08:23But to the family, it says, "Help me, look after me."
0:08:24 > 0:08:32Adults respond by worrying more, and devoting more time than if the baby wasn't so obviously vulnerable.
0:08:33 > 0:08:37So young monkeys can stay being babies longer.
0:08:39 > 0:08:44Childhood in monkeys is not primarily about a growing body, but a growing mind.
0:08:44 > 0:08:48A young brain searches for understanding in slow stages,
0:08:48 > 0:08:53hands reaching out, working out what things are, and how they work.
0:09:17 > 0:09:24A baby monkey slowly builds its understanding of the world and of others around them.
0:09:27 > 0:09:34As physical growing slows down, so monkeys have time to wise up.
0:09:54 > 0:09:57Awareness dawns in infancy.
0:09:58 > 0:10:02Intelligence awakes and takes control.
0:10:17 > 0:10:22These white-faced capuchins in Central America are very clever.
0:10:22 > 0:10:29In fact, capuchin monkeys have a larger brain for their size than any of our closer ape cousins.
0:10:31 > 0:10:36One group near the coast is able to track the tides.
0:10:36 > 0:10:41When the water retreats, clams are exposed, and easy to collect.
0:10:44 > 0:10:48But not so easy to open.
0:10:48 > 0:10:54The trick is to roll and bang the clams hard, and often for a long time.
0:11:10 > 0:11:13The thought of what's inside is what keeps them going.
0:11:13 > 0:11:16It's hardly fast food.
0:11:19 > 0:11:24Monkeys, like us, imagine food they can't yet see, and it drives them on.
0:11:28 > 0:11:35After ten minutes, the clams start to weaken and the capuchins can pull open the shells.
0:11:35 > 0:11:40If you're disappointed, it can only be because you've imagined more.
0:11:44 > 0:11:46Opening clams is just the beginning.
0:11:46 > 0:11:51Some troops have discovered how to get the best out of termite mounds,
0:11:51 > 0:11:54or reach water by using their tail as a sponge.
0:11:56 > 0:11:58The young learn from their parents.
0:11:58 > 0:12:03They have what scientists call a culture. Monkey culture.
0:12:06 > 0:12:12But the most important things for monkeys to understand are their fellow monkeys.
0:12:12 > 0:12:17Outsmarting each other can make the difference between life and death.
0:12:21 > 0:12:26Most animals are wary of outsiders, and defend their territory.
0:12:26 > 0:12:31In monkeys, this has become a battle of wits.
0:12:33 > 0:12:40The capuchins move around like chess pieces, testing their defences, trying to trap unwary scouts.
0:12:48 > 0:12:50SCREECHING
0:12:53 > 0:12:56Previous battles and old grudges fuel the aggression.
0:12:59 > 0:13:06In monkey society, everyone is an individual, and different rules can apply.
0:13:06 > 0:13:09Friends fight for each other.
0:13:09 > 0:13:14Rivals and foreigners can be killed if you can catch them.
0:13:30 > 0:13:35Our feelings for friends and enemies are chillingly similar.
0:13:35 > 0:13:39This is part of our nature too.
0:14:21 > 0:14:26More capuchins are killed by each other than by any predator.
0:14:30 > 0:14:36The invaders retreat, with nothing gained from the battle except injuries.
0:14:37 > 0:14:45If murder and morality have roots in our past, then so too does compassion.
0:14:45 > 0:14:49The fighters return, and are soothed and nursed.
0:15:29 > 0:15:35Hands that when they were tiny explored the world and opened a mind,
0:15:35 > 0:15:39now demonstrate a gentle understanding of others.
0:15:52 > 0:15:57Grooming does more than clean wounds and remove parasites.
0:15:57 > 0:16:00It shows respect and affection.
0:16:03 > 0:16:07Monkeys' attention to their health goes even further.
0:16:07 > 0:16:11Some monkeys have discovered a few simple medicines.
0:16:11 > 0:16:19The leaves of the Piper plant are antiseptic, and used by people here in Costa Rica as an insect repellent.
0:16:19 > 0:16:23When a capuchin finds a Piper plant, they all become very excited,
0:16:23 > 0:16:28sharing, rubbing, disinfecting, and turning it into a party.
0:16:28 > 0:16:33Self-medication becomes a social event.
0:16:33 > 0:16:37We do the same. Think of tea and alcohol.
0:17:01 > 0:17:05A need to try everything is an extraordinary way to survive in the jungle.
0:17:10 > 0:17:16Here are leaves that can cure disease or repel insects, feed you or poison you.
0:17:24 > 0:17:31Knowledge, technology and culture are rooted here in the forest, in the hands of monkeys.
0:17:40 > 0:17:45In Sri Lanka, toque macaques fish for caterpillars.
0:17:45 > 0:17:52The caterpillars hang from the end of silk threads, but monkey hands can reel them in.
0:17:57 > 0:18:02Local knowledge and their unique culture are what they live by.
0:18:02 > 0:18:09They know a nearby lake is guarded by a six-foot monkey-eating monitor lizard.
0:18:16 > 0:18:23Trust monkeys to find a way to reach the delicious lily flowers, safe from the monitor lizard.
0:18:23 > 0:18:31Only the high born, the dominant in the monkey society are allowed to use these overhanging branches.
0:18:38 > 0:18:43Those at the bottom of the social scale have to take bigger risks.
0:18:46 > 0:18:50They take turns to watch for the monitor lizard.
0:18:51 > 0:18:55While the guards are alert, it's pretty safe.
0:18:56 > 0:19:03These lower ranking toque macaques will actually dive for lily roots and bulbs.
0:19:03 > 0:19:07Little of this amazing behaviour is instinctive.
0:19:07 > 0:19:11It was discovered, learned, and passed down the generations.
0:19:12 > 0:19:18Keeping an eye out for your family and friends is an important part of their culture too.
0:19:28 > 0:19:34Instincts in animals generally are automatic, restrictive but reliable.
0:19:34 > 0:19:38But learning can be forgotten, and concentration can lapse.
0:20:15 > 0:20:17SQUEALING
0:20:36 > 0:20:42What must a monkey guard feel when a youngster is lost on their watch?
0:21:12 > 0:21:18We can't know what they are thinking, but they behave in a way that we imagine we recognise.
0:21:21 > 0:21:25Another of the troop has been killed in a fight.
0:21:27 > 0:21:29He was the leader.
0:21:29 > 0:21:32It was a battle for control of the group.
0:21:34 > 0:21:38They are unusually silent as they gather around.
0:21:38 > 0:21:43The victorious new leader watches from the side, his injuries ignored.
0:21:43 > 0:21:45He does not interfere.
0:21:49 > 0:21:55Some who brought about the old leader's downfall are now tender and respectful.
0:22:04 > 0:22:08For many years he had been an ally, or a mate.
0:22:08 > 0:22:13He'd been a caring father to a whole generation of young.
0:23:02 > 0:23:08As scientists trace human qualities and feelings further back in time,
0:23:08 > 0:23:14so modern monkeys seem less "animal", more like rediscovered relatives.
0:23:17 > 0:23:21Many are very rare, like the golden lion tamarin.
0:23:21 > 0:23:23There's so much to discover.
0:23:23 > 0:23:29Why does the white uakari in the Amazon think a red face a good sign?
0:23:31 > 0:23:36Or the golden snub-nosed monkey in China have blue eye shadow?
0:23:38 > 0:23:42Why does the emperor tamarin have a moustache?
0:23:42 > 0:23:46The weirdest may be the proboscis monkey in Borneo,
0:23:46 > 0:23:50with a 9" nose, and a fermenting stomach like a cow.
0:23:53 > 0:23:57Perhaps the most beautiful is the Douc monkey of Cambodia.
0:23:59 > 0:24:03Every monkey has its own different character and story.
0:24:05 > 0:24:07FEROCIOUS GROWLING
0:24:10 > 0:24:14Howler monkeys call to declare territory.
0:24:15 > 0:24:19Lions roar and nightingales sing for the same reason.
0:24:21 > 0:24:24Howlers have a silent duet too.
0:24:24 > 0:24:29It's a love song, though in us it would be considered a little rude.
0:24:54 > 0:24:57All animals instinctively pair together.
0:24:57 > 0:25:01But if monkeys are at all sensitive,
0:25:01 > 0:25:04if they can guess what another monkey may be thinking,
0:25:04 > 0:25:09if they have memories and make plans for the future,
0:25:09 > 0:25:13it must be surprisingly close to how we feel.
0:25:43 > 0:25:48We give words to thoughts and feelings.
0:25:48 > 0:25:53Without words, is thinking even possible?
0:25:53 > 0:25:58The jungle to us may seem a cacophony of meaningless sounds.
0:26:06 > 0:26:12Each animal listens to its own calls, and usually tunes out the rest.
0:26:12 > 0:26:15But some monkeys are multilingual.
0:26:23 > 0:26:27Guenons live here and there are several species of them.
0:26:27 > 0:26:31Each has its own calls for communicating with other members of its troop.
0:26:36 > 0:26:41These Diana monkeys have joined an army of other guenons -
0:26:41 > 0:26:45a United Nation of monkeys, and that requires them to understand each other.
0:26:48 > 0:26:51On the forest floor live sooty mangabeys.
0:26:51 > 0:26:55They specialize in gathering fallen nuts.
0:26:55 > 0:27:01Above are red colobus, spot-nosed and putty-nosed guenons,
0:27:01 > 0:27:05black and white colobus, Campbell's guenon,
0:27:05 > 0:27:09and the Diana monkey which live mainly in the upper canopy.
0:27:09 > 0:27:13These monkeys all behave as though they're one troop,
0:27:13 > 0:27:17moving through the forest together, resting together,
0:27:17 > 0:27:19and all looking out for predators.
0:27:19 > 0:27:24On the forest floor the sooty mangabey
0:27:24 > 0:27:28can rely on the eyes and ears above and relax, thanks to the alliance.
0:27:32 > 0:27:36If a red colobus spots something like a snake,
0:27:36 > 0:27:40it gives the red colobus alarm call for, "Snake".
0:27:40 > 0:27:44A spot-nosed guenon reacts immediately.
0:27:44 > 0:27:47If a Diana monkey high in the tree sees an eagle,
0:27:47 > 0:27:51the alarm goes up, "Eagle" and all the monkeys look up.
0:27:51 > 0:27:54Each species has a different alarm call,
0:27:54 > 0:27:56but they all understand each other.
0:27:56 > 0:28:01With 8 different monkeys, and about 15 calls each,
0:28:01 > 0:28:04that's 120 different sounds.
0:28:04 > 0:28:07The Mangabeys see a leopard. All the other monkeys call, "Leopard",
0:28:07 > 0:28:12in their own way, but there are other calls in there too.
0:28:12 > 0:28:14Diana monkeys have been the most studied.
0:28:14 > 0:28:18Their ability to understand other species
0:28:18 > 0:28:23gives scientists a running translation of other monkey calls.
0:28:23 > 0:28:27If Diana monkeys hear a string of calls by a Campbell's guenon, say,
0:28:27 > 0:28:30they behave as if they were hearing a sentence.
0:28:30 > 0:28:35Some calls add detail - "Maybe," or "Not urgent."
0:28:35 > 0:28:38With another guenon, if the sounds are in a different order,
0:28:38 > 0:28:40it means something else.
0:28:40 > 0:28:43Grammar, the basis of true language,
0:28:43 > 0:28:46was once thought of as uniquely human.
0:28:46 > 0:28:51Chimps have not yet been shown to have this ability in the wild -
0:28:51 > 0:28:53only monkeys and people.
0:28:53 > 0:28:57Diana monkeys also have a voice box more like ours,
0:28:57 > 0:29:00so alarm calls may be only a small part of their vocabulary.
0:29:03 > 0:29:06If talking is an ancient monkey ability,
0:29:06 > 0:29:11we should find something similar in other monkeys around the world.
0:29:11 > 0:29:14In forests from Africa to South America
0:29:14 > 0:29:19scientists have found monkeys whose calls refer to predators.
0:29:19 > 0:29:23But do they ever use sounds for things when they can't see them,
0:29:23 > 0:29:26when they are just thinking about them?
0:29:30 > 0:29:36The white faced capuchins in Costa Rica live by streams full of danger.
0:29:36 > 0:29:39They are nervous, maybe imagining death
0:29:39 > 0:29:42lurking under every log or pile of leaves.
0:29:42 > 0:29:45They too have put sounds to some of their fears,
0:29:45 > 0:29:49and have different calls for different predators.
0:29:51 > 0:29:53A call goes up, "Snake!"
0:29:53 > 0:29:58The whole troop leaps out of the water and up into the trees.
0:30:01 > 0:30:06They soon calm down. Once noticed, most predators are of little danger.
0:30:06 > 0:30:10The warning system is built on trust and honesty.
0:30:10 > 0:30:16Yet, very occasionally, some monkeys deliberately shout an alarm call
0:30:16 > 0:30:18when there is no snake there.
0:30:18 > 0:30:21The reason for this deception
0:30:21 > 0:30:25lies in the fact that monkey society is very competitive.
0:30:25 > 0:30:29The leaders often take food from subordinates.
0:30:29 > 0:30:33The problem for a low-status monkey is not just finding food,
0:30:33 > 0:30:38it's hanging on to it, and sometimes they have to be a little crafty.
0:30:41 > 0:30:44Suppose a subordinate is acting a little strangely,
0:30:44 > 0:30:46watching the others closely.
0:30:50 > 0:30:54He then could, without any obvious panic, call, "Snake,"
0:30:54 > 0:30:56and everybody leaps out of the water.
0:31:03 > 0:31:05While the others are looking for snakes,
0:31:05 > 0:31:08he could sneak down and recover a fallen bird's egg
0:31:08 > 0:31:10he could have been hiding.
0:31:19 > 0:31:22The leaders slowly return to the pool.
0:31:22 > 0:31:27It seems that lying may be as old as language itself.
0:31:27 > 0:31:32If our little manipulator is spotted with his egg, he's in big trouble.
0:31:38 > 0:31:43This sort of deception has been noticed in several species.
0:31:43 > 0:31:47It shows they imagine things when they're not visible,
0:31:47 > 0:31:50and it implies they are beginning to think about
0:31:50 > 0:31:53what each other may be thinking about.
0:31:56 > 0:32:01Millions of years ago some monkeys reached this point,
0:32:01 > 0:32:05and then took another huge leap into the unknown.
0:32:05 > 0:32:08They left the forest.
0:32:23 > 0:32:28Open grassland is a hard place in which to survive.
0:32:28 > 0:32:30Fruits and flowers are scarce.
0:32:30 > 0:32:35There's nowhere to escape, and some very dangerous predators.
0:32:51 > 0:32:55Baboons have grown larger than forest monkeys
0:32:55 > 0:32:59and 80 or so baboons stick together for defence.
0:32:59 > 0:33:01They are wary and aggressive.
0:33:08 > 0:33:11The big males will often go on the attack.
0:33:48 > 0:33:50The young are helpless.
0:33:50 > 0:33:53Most animals here run from birth.
0:33:53 > 0:33:57Gazelles and baboons feed together, both watching for predators.
0:34:00 > 0:34:05The baboons make do with tough plants, insects and grass mainly.
0:34:10 > 0:34:12The fawns assume the baboons are allies,
0:34:12 > 0:34:16and don't realise that monkeys also eat meat.
0:34:21 > 0:34:23GROWLING
0:34:38 > 0:34:41When our ancestors left the trees,
0:34:41 > 0:34:44we changed too, and became more predatory and dangerous
0:34:44 > 0:34:46than the apes and monkeys
0:34:46 > 0:34:49we left behind in the forest.
0:34:53 > 0:34:58There's more to learn in larger and more volatile societies.
0:34:58 > 0:35:04All monkeys can be murderous, but baboons seem closer to violence,
0:35:04 > 0:35:08as though anger and frustration were just under the surface.
0:35:08 > 0:35:12The lower ranking males find failing ambition very stressful,
0:35:12 > 0:35:16and become neurotic, with high blood pressure and ulcers.
0:35:18 > 0:35:23High ranking males are dictatorial bullies while their power lasts,
0:35:23 > 0:35:27but when deposed become ill and have symptoms of depression.
0:35:31 > 0:35:34Baboon society shares many of our problems.
0:35:34 > 0:35:37We're psychologically similar.
0:35:37 > 0:35:40Of course there are huge differences,
0:35:40 > 0:35:45but if you want to imagine your early ancestor on a hunt, think baboon.
0:36:49 > 0:36:55A clever political mind is essential in large groups.
0:36:55 > 0:36:58So the cleverest monkeys should be found
0:36:58 > 0:37:02in the biggest troops, equivalent to our towns or cities.
0:37:05 > 0:37:11In the Simien Mountains of Ethiopia live huge herds of geladas.
0:37:14 > 0:37:18Speeded up, they move like an army.
0:37:41 > 0:37:44Groups of mothers and their young,
0:37:44 > 0:37:49a harem, gather together to form troops of up to 800 monkeys.
0:37:51 > 0:37:56Geladas' hands are usually busy plucking grass instead of grooming,
0:37:56 > 0:38:02so to keep in touch, geladas have become the chattiest of all monkeys.
0:38:03 > 0:38:07The gossipy banter can sound to scientists
0:38:07 > 0:38:11like sentences with words or even names for each other.
0:38:11 > 0:38:16Most agree it's often used to defuse tension.
0:38:20 > 0:38:24In geladas, there's a lot to be tense about.
0:38:26 > 0:38:29There are gangs of young males
0:38:29 > 0:38:33trying to steal away the women from the family harems.
0:38:34 > 0:38:39Each handful of females is guarded by a single male, the harem master.
0:38:43 > 0:38:47The spare boys try and tempt the girls away,
0:38:47 > 0:38:50hoping the resident father figure doesn't notice.
0:38:55 > 0:38:58The males flash teeth at each other.
0:38:58 > 0:38:59They may fight,
0:38:59 > 0:39:01but it's usually just showing off,
0:39:01 > 0:39:02in case the girls are watching.
0:39:04 > 0:39:07There's a lot of flirting on both sides.
0:39:09 > 0:39:12And then if an innocent looking female is tempted to wander off
0:39:12 > 0:39:16past her guardian, he has to decide what to do.
0:39:18 > 0:39:20Girls mostly sneak off secretly for affairs.
0:39:20 > 0:39:24This is a blatant challenge to his authority.
0:39:27 > 0:39:29The illicit couple just sit.
0:39:29 > 0:39:34The suitor seems to be using his hand to hide his grimace.
0:39:34 > 0:39:37He probably doesn't want trouble.
0:39:37 > 0:39:43Chimps, baboons and macaques may also try to look innocent when they break the rules.
0:39:44 > 0:39:47This is a complicated social problem.
0:39:47 > 0:39:54Using your brain to control societies is called Machiavellian Intelligence,
0:39:54 > 0:39:56after a sixteenth century courtier
0:39:56 > 0:39:59who wrote on manipulating political power.
0:39:59 > 0:40:02Instead of launching into an attack,
0:40:02 > 0:40:05the politician here tries to grab a baby.
0:40:05 > 0:40:10Monkey etiquette dictates nobody attacks anyone holding a baby,
0:40:10 > 0:40:12so they are like living flak jackets.
0:40:12 > 0:40:16The mothers are worried, and quickly scoop up the youngest.
0:40:18 > 0:40:21Here, the two males face each other.
0:40:21 > 0:40:25The family man backs towards one of his more loyal wives,
0:40:25 > 0:40:26calling for support.
0:40:28 > 0:40:33One of the youngsters suddenly switches from mother to father.
0:40:33 > 0:40:36This should calm things down.
0:40:36 > 0:40:37With the youngster attached,
0:40:37 > 0:40:41the father is protected, and the harem should unite.
0:40:44 > 0:40:46But it can go wrong.
0:40:59 > 0:41:03The youngster is slipping off. The family are frantic.
0:41:06 > 0:41:10The harem master has no protection from attack.
0:41:17 > 0:41:23The bachelor is finally driven off, with a little help from the mothers.
0:41:26 > 0:41:29But the fathers are meant to guard the precious young.
0:41:29 > 0:41:32He knows he's in all sorts of trouble.
0:41:32 > 0:41:37If the infant dies, the mothers may not support him again.
0:41:44 > 0:41:48Our brain too, wrestles with our own similar problems.
0:41:48 > 0:41:51We are as social and as competitive.
0:41:59 > 0:42:04Intelligence sweeps in through monkey evolution,
0:42:04 > 0:42:08to apes and us, and leaves a chilling legacy.
0:42:10 > 0:42:14Becoming clever can mean being controlling,
0:42:14 > 0:42:16stressed, perhaps unhappy.
0:42:16 > 0:42:20The females are plotting, worrying for their young.
0:42:20 > 0:42:24He worries about other males stealing his girls.
0:42:24 > 0:42:28All of them are thinking about whom they can trust.
0:42:31 > 0:42:35Is this the pinnacle of monkey brainpower?
0:42:35 > 0:42:37Monkeys also set us on a path
0:42:37 > 0:42:42towards co-operation, planning, tool-making and technology.
0:42:42 > 0:42:46The cleverest monkey perhaps took that path too.
0:43:02 > 0:43:05Stone slabs have been found in the forests of Brazil
0:43:05 > 0:43:08that have been worn into hollows,
0:43:08 > 0:43:13apparently by prehistoric people, using stone hammers.
0:43:20 > 0:43:24It turns out they were not made by humans at all.
0:43:27 > 0:43:30A bearded capuchin monkey starts the processing of palm nuts
0:43:30 > 0:43:33by tapping them to see if they are ripe.
0:43:41 > 0:43:47There are only 20 or 30 monkeys in a group, with fewer social pressures.
0:43:47 > 0:43:51They are thinkers and doers, not chatterers.
0:43:51 > 0:43:57The ripest palm nuts are stripped of their outer case ready to be dropped
0:43:57 > 0:44:02on to the ground to dry out, which will take about three days.
0:44:02 > 0:44:06Each stage seems very well co-ordinated,
0:44:06 > 0:44:11a routine in a monkey culture, choreographed to perfection.
0:44:11 > 0:44:16Tapping again tells the monkeys which ones are ready.
0:44:44 > 0:44:47The next stage may take place
0:44:47 > 0:44:49at the other end of the valley,
0:44:49 > 0:44:51the nut-cracking site.
0:44:51 > 0:44:54The hammers are of a harder stone,
0:44:54 > 0:44:56brought up from the river beds
0:44:56 > 0:44:57by the monkeys.
0:44:57 > 0:45:00They are heavy - some as heavy as the monkey itself.
0:45:03 > 0:45:05Palm nuts are extremely hard
0:45:05 > 0:45:06and difficult to crack open.
0:45:06 > 0:45:10It only works if you get it exactly right.
0:45:18 > 0:45:21Somehow these clever monkeys
0:45:21 > 0:45:23get amazingly good at it.
0:45:55 > 0:45:59Collecting a ripe nut has taken days of harvesting,
0:45:59 > 0:46:02testing, ripening, transportation,
0:46:02 > 0:46:05collecting tools and choosing sites,
0:46:05 > 0:46:07not forgetting years of learning
0:46:07 > 0:46:09in the nut-cracking school.
0:46:17 > 0:46:21The Year Two class is still wrestling with the basics.
0:46:27 > 0:46:30The sounds echo through the forest.
0:46:34 > 0:46:37Jaguars know it's monkeys at work.
0:46:39 > 0:46:42The capuchins always select their sites carefully,
0:46:42 > 0:46:45preferably below the edge of the escarpment.
0:46:48 > 0:46:52But it's more than just an escape route.
0:47:08 > 0:47:11We are increasingly realising
0:47:11 > 0:47:15we are not the only intelligent life on the planet.
0:47:31 > 0:47:3640 million years ago, it seems, there were creatures with hands and eyes
0:47:36 > 0:47:39who took great care of their babies
0:47:39 > 0:47:41because they took a long time to grow up.
0:47:43 > 0:47:49The story has ended up with us, seeing ourselves in their faces.
0:47:52 > 0:47:54We can be proud of the fact
0:47:54 > 0:48:00that what makes us human isn't just human after all.
0:48:18 > 0:48:20Subtitles by Red Bee Media Ltd
0:48:20 > 0:48:23E-mail subtitling@bbc.co.uk