0:00:03 > 0:00:05Planet Earth.
0:00:07 > 0:00:09Millions of different species.
0:00:10 > 0:00:14But a few are special.
0:00:16 > 0:00:18Born to thrive.
0:00:27 > 0:00:29These are the opportunists.
0:00:33 > 0:00:34The collaborators.
0:00:38 > 0:00:39The survivors.
0:00:42 > 0:00:46So, what is it that makes these animals so successful?
0:00:48 > 0:00:51By exploring the details deep beneath the skin,
0:00:51 > 0:00:56we'll discover the unique features that set some species apart.
0:00:59 > 0:01:01In this series, new behaviour,
0:01:01 > 0:01:04and the very latest scientific discoveries
0:01:04 > 0:01:07will throw fresh insight
0:01:07 > 0:01:10into the wonder of animals.
0:01:21 > 0:01:26Humans may have the most complex brains on the planet...
0:01:27 > 0:01:31..but we've got some relatives that aren't far behind.
0:01:38 > 0:01:40The great apes.
0:01:44 > 0:01:49In this episode, we'll reveal how different parts of their brains
0:01:49 > 0:01:53have been adapted over time by their anatomy...
0:01:56 > 0:01:57..their ingenuity...
0:02:01 > 0:02:04..and their sociability.
0:02:04 > 0:02:07These three forces have shaped the evolution
0:02:07 > 0:02:11of one of the most intelligent groups of animals on the planet.
0:02:13 > 0:02:17But our journey starts with the simplest of beginnings,
0:02:17 > 0:02:20one part of their anatomy.
0:02:28 > 0:02:31And that part
0:02:31 > 0:02:34is the hand.
0:02:44 > 0:02:46The great apes, orang-utans,
0:02:46 > 0:02:48gorillas, chimpanzees
0:02:48 > 0:02:53and, of course, us, all benefit by having a form of opposable thumb.
0:02:54 > 0:02:57This is a thumb which is capable of moving
0:02:57 > 0:03:01so it can touch the other digits on the hand,
0:03:01 > 0:03:05but of course, the other great apes use them in different ways.
0:03:15 > 0:03:19Gorillas spend most of their time on the ground.
0:03:19 > 0:03:23They use their hands to select and manipulate their food.
0:03:29 > 0:03:34In the trees, chimpanzees and orang-utans hold branches
0:03:34 > 0:03:39with opposable toes, as well as thumbs.
0:03:44 > 0:03:50What they all have in common is the ability to grasp objects...
0:03:54 > 0:03:58..with a dexterity that few other species have.
0:04:00 > 0:04:04And it's this dexterity that has allowed the primate brain
0:04:04 > 0:04:07to really flex its muscles.
0:04:13 > 0:04:18Delicate hand movements take concentration and control,
0:04:18 > 0:04:23the more intricate the hand movement the more brain power is required.
0:04:26 > 0:04:31And there are few movements more intricate than using a tool.
0:04:33 > 0:04:37Chimps fish for termites with handmade rods.
0:04:50 > 0:04:52Palm branches act as a pestle,
0:04:52 > 0:04:56to soften the tree's edible heart.
0:05:05 > 0:05:09And folded leaves make sponges for gathering water.
0:05:18 > 0:05:21Orang-utans also use branches as tools...
0:05:27 > 0:05:31..to get fruit that would otherwise be out of reach.
0:05:32 > 0:05:35And those that live near humans
0:05:35 > 0:05:38sometimes even try our tools.
0:05:41 > 0:05:44These actions may look simple
0:05:44 > 0:05:48but what's going on inside the apes' head is highly complex.
0:05:50 > 0:05:54Many parts of the brain work together to create these movements,
0:05:54 > 0:05:59but one part in particular is key.
0:06:02 > 0:06:04The cerebellum.
0:06:06 > 0:06:09This is the part of the brain that enables us
0:06:09 > 0:06:12to move our limbs in an accurate and controlled way,
0:06:12 > 0:06:18and recent research has found that it's crucial for tool use.
0:06:23 > 0:06:24Over many generations,
0:06:24 > 0:06:29those that learned how to use their hands survived better.
0:06:30 > 0:06:34So, as the more dexterous individuals thrived,
0:06:34 > 0:06:38gradually bigger brains evolved.
0:06:44 > 0:06:48But there's a lot more to dexterity than just having an opposable thumb.
0:06:54 > 0:06:58This chimp is doing something that a lot of animals can't.
0:07:03 > 0:07:07Many animals can only use their hands symmetrically.
0:07:11 > 0:07:15The great apes, however, can use their hands asymmetrically.
0:07:17 > 0:07:22Both at the same time and in different ways.
0:07:25 > 0:07:28For us, it's such an ordinary ability
0:07:28 > 0:07:30that we simply take it for granted.
0:07:32 > 0:07:38But asymmetrical bi-manuality, as it's known, is, in fact,
0:07:38 > 0:07:42a complicated skill and it takes a lot of brain power.
0:07:45 > 0:07:49Once again, the cerebellum is hard at work.
0:07:52 > 0:07:56It's communicating via a huge number of connections
0:07:56 > 0:08:01with another key part of the brain, the motor cortex.
0:08:03 > 0:08:07This part controls the movement of the body's muscles
0:08:07 > 0:08:09and in the great apes,
0:08:09 > 0:08:16the largest area of the motor cortex is devoted to the hands.
0:08:22 > 0:08:25All the great apes have evolved
0:08:25 > 0:08:27an enlarged motor cortex and cerebellum
0:08:27 > 0:08:29compared to other primates...
0:08:31 > 0:08:35..allowing them to use both of their hands independently.
0:08:45 > 0:08:49But whilst using tools takes dexterity,
0:08:49 > 0:08:54actually designing them and building them
0:08:54 > 0:08:57takes something altogether different,
0:08:57 > 0:08:59ingenuity.
0:09:04 > 0:09:09The orang-utans of North-West Sumatra feed mostly on fruit.
0:09:14 > 0:09:19But when the swamp forests flood, the waters bring in rich nutrients
0:09:19 > 0:09:23and in their wake, an abundance of insects,
0:09:23 > 0:09:27a welcome break from their usual diet.
0:09:27 > 0:09:31Although they are more difficult to collect.
0:09:32 > 0:09:35The orang-utans, however, have come up with a solution.
0:09:37 > 0:09:39They break off a branch,
0:09:39 > 0:09:41strip off the twigs...
0:09:43 > 0:09:44..fray one end...
0:09:47 > 0:09:52..and then, dip the stick into holes in the trees,
0:09:52 > 0:09:56to get honey and termites.
0:09:58 > 0:10:03They've designed and built a makeshift spoon.
0:10:08 > 0:10:10As well as constructing tools,
0:10:10 > 0:10:15great apes devise strategies for using them.
0:10:21 > 0:10:23A flurry of recent research
0:10:23 > 0:10:27has revealed that chimpanzees actually plan ahead...
0:10:32 > 0:10:35..collecting useful objects before they're needed
0:10:35 > 0:10:39and then, taking these tool kits to the feeding site.
0:10:44 > 0:10:49If they haven't got quite the right one for the job,
0:10:49 > 0:10:53they use a sequence of up to five different objects
0:10:53 > 0:10:56to get the tool they need.
0:11:02 > 0:11:05This ability to problem solve
0:11:05 > 0:11:10gives apes access to food that would otherwise be unobtainable.
0:11:17 > 0:11:22Ingenuity and innovation exercise the brain.
0:11:22 > 0:11:25Compared with less resourceful animals,
0:11:25 > 0:11:28great apes have bigger, executive brains,
0:11:28 > 0:11:32that's the neocortex, the top layer,
0:11:32 > 0:11:35and the striatum, deep within.
0:11:35 > 0:11:38Parts of the neocortex are crucial to innovation
0:11:38 > 0:11:42as they inhibit old patterns of behaviour and generate new ones.
0:11:43 > 0:11:48So, over time, devising ingenious ways to get food
0:11:48 > 0:11:51favoured an expansion of the brain.
0:11:58 > 0:12:02But apes aren't born intelligent.
0:12:02 > 0:12:06Their brains have to be programmed with the right information.
0:12:10 > 0:12:12They have to learn.
0:12:19 > 0:12:21And they don't just learn by watching.
0:12:27 > 0:12:31One research team from the University of Zurich,
0:12:31 > 0:12:35believe they have evidence that apes actively teach their young.
0:12:39 > 0:12:42In the tropical rainforests of the Ivory Coast,
0:12:42 > 0:12:46an important food source is nuts.
0:12:52 > 0:12:54Nuts are energy rich,
0:12:54 > 0:12:58but only if you can crack the shell.
0:13:00 > 0:13:02By numbering rocks,
0:13:02 > 0:13:07scientists were able to analyse how the chimpanzees used them as tools.
0:13:10 > 0:13:14This is the hammer,
0:13:14 > 0:13:18and this is the anvil.
0:13:22 > 0:13:27Adult chimps can crack open 130 nuts in an hour.
0:13:34 > 0:13:39It takes ten years for the young chimps to fully acquire this skill.
0:13:46 > 0:13:49The study found that when their young are present,
0:13:49 > 0:13:52adults often leave their hammers by the anvil
0:13:52 > 0:13:54whilst they're collecting nuts,
0:13:54 > 0:13:58to give the infants a chance to have a go.
0:14:07 > 0:14:10The scientists also observed mothers
0:14:10 > 0:14:13showing their young how to position the nut correctly.
0:14:20 > 0:14:24Acting for the benefit of others like this
0:14:24 > 0:14:27is a crucial part of collaboration...
0:14:29 > 0:14:34..the first step towards building a cohesive social group.
0:14:45 > 0:14:49Most great apes live in communities.
0:14:49 > 0:14:54In chimpanzees, these communities can number up to 150 individuals.
0:15:01 > 0:15:05So, this means developing complex relationships.
0:15:10 > 0:15:13They must learn who to greet...
0:15:21 > 0:15:23..who to play with...
0:15:30 > 0:15:33..and when to work together as a team.
0:15:37 > 0:15:41All of which requires a bigger brain and once again,
0:15:41 > 0:15:43many parts are at work.
0:15:46 > 0:15:50But crucially, a tiny region called the amygdala.
0:15:52 > 0:15:54Recent research has found
0:15:54 > 0:15:58that primates living in large social groups have a bigger amygdala.
0:16:00 > 0:16:04It's thought that this part of the brain may have evolved
0:16:04 > 0:16:07to deal with an increasingly complex social life.
0:16:12 > 0:16:14It's the same within humans.
0:16:16 > 0:16:19The more complex a person's social network,
0:16:19 > 0:16:22the greater the volume of the amygdala.
0:16:26 > 0:16:28This part of the brain enables great apes
0:16:28 > 0:16:32to form relationships and function as a team.
0:16:40 > 0:16:45And at no time is collaboration more important in chimp society
0:16:45 > 0:16:47than when it comes to a hunt.
0:16:54 > 0:16:58Their prey, the colobus monkey,
0:16:58 > 0:17:00is fast and light.
0:17:06 > 0:17:10To catch it, the chimps must work together.
0:17:40 > 0:17:43Certain members will herd the colobus...
0:17:46 > 0:17:49..driving the monkeys into a trap...
0:17:50 > 0:17:54..where a second group will make the kill.
0:17:55 > 0:17:58COMMOTION
0:18:09 > 0:18:14SCREECHING
0:18:31 > 0:18:34But this controlled aggression
0:18:34 > 0:18:36is not always directed at prey.
0:18:36 > 0:18:40SCREECHING
0:18:40 > 0:18:43Chimps can turn on each other.
0:18:48 > 0:18:52If a territory is under threat from other communities,
0:18:52 > 0:18:56the chimps will fight to protect it
0:18:56 > 0:19:00and secure access to the best food.
0:19:12 > 0:19:16But not all great apes are quite so aggressive.
0:19:16 > 0:19:20There is a species that's followed the path of peace
0:19:20 > 0:19:22and it all began one million years ago.
0:19:48 > 0:19:53Back then, this central African land was occupied by two ape species.
0:19:58 > 0:20:01The ancestor of modern-day chimpanzees...
0:20:03 > 0:20:07..and gorillas, their ecological rivals.
0:20:13 > 0:20:16Until...so as one theory goes,
0:20:16 > 0:20:19a massive drought drove the gorillas away
0:20:19 > 0:20:22from the south side of the River Congo.
0:20:26 > 0:20:31The chimpanzee ancestors now had the southern jungles to themselves
0:20:31 > 0:20:35with little competition for resources.
0:20:36 > 0:20:39And with plenty of food to go round,
0:20:39 > 0:20:41what's the point in fighting?
0:20:43 > 0:20:47Over hundreds of thousands of years,
0:20:47 > 0:20:50aggression gradually became a less prominent trait.
0:20:57 > 0:21:02And those chimpanzee ancestors south of the Congo River
0:21:02 > 0:21:06evolved into today's bonobo.
0:21:11 > 0:21:14This evolutionary theory has been put forward
0:21:14 > 0:21:18by scientists from America's Duke University,
0:21:22 > 0:21:26And it may explain why the social behaviour of bonobos
0:21:26 > 0:21:29is so different to that of chimpanzees.
0:21:36 > 0:21:40Famous for their love of sex over war...
0:21:42 > 0:21:46..bonobos seem to have replaced aggression with seduction
0:21:46 > 0:21:48as a means of resolving conflict.
0:21:53 > 0:21:57But their bonding instincts run far deeper than this.
0:22:00 > 0:22:05Tests done by the scientists found that whilst chimpanzees
0:22:05 > 0:22:07will fight over food...
0:22:09 > 0:22:12..bonobos will actually share theirs.
0:22:14 > 0:22:16Even with strangers.
0:22:21 > 0:22:26So, how did this gentler trait evolve in bonobo society?
0:22:30 > 0:22:33The Duke University anthropologists
0:22:33 > 0:22:36have again possibly come up with an answer.
0:22:41 > 0:22:44Could it be that bonobos have gone through
0:22:44 > 0:22:47a process known as "self-domestication" -
0:22:47 > 0:22:50a bit like the process that dogs have gone through
0:22:50 > 0:22:52in their evolution from wolves?
0:22:55 > 0:22:58Generation after generation of selectively breeding
0:22:58 > 0:23:00for more passive dogs,
0:23:00 > 0:23:04means that their wolf-like aggression has diminished.
0:23:07 > 0:23:11Leaving them, just like the bonobos,
0:23:11 > 0:23:14altogether more friendly.
0:23:17 > 0:23:21But according to the theory, over hundreds of thousands of years,
0:23:21 > 0:23:27some species are actually capable of domesticating themselves.
0:23:30 > 0:23:32Like the bonobos.
0:23:34 > 0:23:36So, a million years ago,
0:23:36 > 0:23:39on the south side of the Congo River,
0:23:39 > 0:23:44as the ancestor chimpanzees enjoyed a land of plenty,
0:23:44 > 0:23:47there was less call for violence.
0:23:50 > 0:23:53And therefore, the females were able to choose
0:23:53 > 0:23:56to breed with less aggressive males.
0:23:59 > 0:24:03In this way, over many generations,
0:24:03 > 0:24:06the bonobos domesticated themselves...
0:24:11 > 0:24:14..becoming a more gentle species of ape.
0:24:17 > 0:24:20But even more remarkably,
0:24:20 > 0:24:26they now show a trait that was once believed to be uniquely human.
0:24:26 > 0:24:30This orphan bonobo is playing with his friend,
0:24:30 > 0:24:33but it soon gets rough.
0:24:36 > 0:24:38The mother of the victim intervenes
0:24:38 > 0:24:41and reprimands the orphan by biting his finger,
0:24:41 > 0:24:44whilst another mother tries to stop her.
0:24:57 > 0:25:00What's remarkable is how the rest of the group
0:25:00 > 0:25:02react to the injured orphan.
0:25:17 > 0:25:20They show empathy.
0:25:24 > 0:25:28Two young bonobos come to see how the orphan is.
0:25:48 > 0:25:51Empathetic behaviour of this kind
0:25:51 > 0:25:54is regularly observed in bonobos.
0:26:03 > 0:26:07Empathy is a complex emotion.
0:26:08 > 0:26:11The fact that bonobos are capable of it
0:26:11 > 0:26:16proves that their reduced aggression is more than skin deep.
0:26:19 > 0:26:23It's down to a difference in their brains.
0:26:27 > 0:26:30Scientists from Emory University in Atlanta,
0:26:30 > 0:26:34have found that parts of the brain crucial to feeling empathy
0:26:34 > 0:26:37and regulating emotion, the limbic structures,
0:26:37 > 0:26:41are more developed in bonobos than in chimpanzees.
0:26:44 > 0:26:48In bonobos, these areas contain more grey matter
0:26:48 > 0:26:51and have a thicker connection between the amygdala
0:26:51 > 0:26:56and the anterior cingulate which helps moderate social behaviour.
0:26:59 > 0:27:03When the bonobos sense that their actions are causing distress,
0:27:03 > 0:27:07that pathway works to reduce their aggressive behaviour.
0:27:10 > 0:27:14What's remarkable about bonobos' empathy is their ability
0:27:14 > 0:27:19to show compassion to strangers, as well as to others in their group.
0:27:24 > 0:27:26As one of our closest living relatives,
0:27:26 > 0:27:30researchers are now investigating to see if there are similarities
0:27:30 > 0:27:35between the social tolerance of bonobos and that of humans.
0:27:42 > 0:27:47What's certain is that bonobos have crossed an imaginary line
0:27:47 > 0:27:51that was once thought to separate us from our ape relatives.
0:27:58 > 0:28:02The ability to feel and respond to the emotions of others.
0:28:12 > 0:28:15The great apes' anatomy has enabled them
0:28:15 > 0:28:18to use their hands with exquisite precision.
0:28:26 > 0:28:30They've developed ingenious strategies for designing tools,
0:28:30 > 0:28:33which have kept their big brains fed.
0:28:36 > 0:28:40In turn, allowing them to navigate the complex relationships
0:28:40 > 0:28:43that come from living in a society.
0:28:45 > 0:28:48Dexterity, ingenuity and sociability
0:28:48 > 0:28:51have all played their part in the evolution
0:28:51 > 0:28:55of one of the most complex brains in the animal kingdom
0:28:55 > 0:28:59and that is the wonder of great apes.