Nat Geo_Smarter Than an Ape
Transcript
00:00Meet the relatives.
00:06These are our closest cousins, the great apes.
00:11We like to think we're different.
00:14But a few million years ago, we were just the same.
00:21Now we dominate the planet.
00:25Somehow, we humans have left apes far behind.
00:30Or have we?
00:33Through a series of experiments, we'll prove that apes are much closer to us than anyone thought.
00:39Startling images reveal that their instant memory is far superior to ours.
00:45Apes can understand hundreds of words.
00:49They have a form of language.
00:53And they use more complex tools than anyone realized.
00:58By looking at the differences and similarities between apes and us,
01:03we may find the secret ingredient that makes apes apes and humans human.
01:08Apes apes and humans human.
01:17Of the 10 million or more different species in the world,
01:22some creatures are much closer to us than others.
01:26We share 40% of our DNA with worms.
01:3060% of our genes with chickens.
01:3380% with mice.
01:35And nearly 100% with these, the great apes.
01:44Our DNA is so similar because humans evolved from the same branch of the tree of life.
01:51Our most distant cousin among the great apes is the orangutan.
01:55They split away from us 11 million years ago.
02:00Today, orangutans live only in Asia.
02:02They spend almost all their time in the trees.
02:05We don't look much like them, but we share up to 96.4% of our DNA.
02:13Then, about 8 million years ago, the branch leading to gorillas split off.
02:20Gorillas are the largest of all the great apes.
02:23They may look fierce, but these are gentle vegetarians.
02:27They live in pockets of rainforest across Africa, and we share as much as 97.7% of their DNA.
02:38Around 5 million years ago, another branch split away.
02:42This produced our nearest living relatives, the chimps and bonobos.
02:48Bonobos are the so-called hippies of the ape world.
02:51They use sex to keep the peace.
02:53But their range is limited to a small area of the Congo.
02:58Chimpanzees live right across equatorial Africa.
03:02They are altogether less peaceful.
03:05Both chimps and bonobos share over 98% of their DNA with us.
03:12Now, the chimpanzee showboat starring that veteran of the boards, Captain Roy.
03:18Even before we knew about DNA, we knew that apes were a lot like us.
03:24They can do many things as well as we can.
03:28Sometimes better.
03:31But despite these similarities, apes are still swinging from tree to tree,
03:36and we are travelling through space.
03:40So how did this happen?
03:42What do we have that apes don't?
03:45Well, we have a lot in common.
03:48So how did this happen?
03:50What do we have that apes don't?
03:53What exactly is in that 1.6% difference of DNA that makes us human?
04:00Our first experiment is a simple test of recognition.
04:04We take it for granted that self-recognition is a fundamental building block of human society.
04:13We exist as individuals, each with our own unique features.
04:21Scientists believe self-recognition is essential for our survival.
04:25We can live in large groups because we recognize similar features to our own in others.
04:30We can tell friend from foe.
04:37But is self-recognition uniquely human?
04:40Show a monkey a mirror, and it thinks it's another monkey.
04:44It attacks.
04:46It attacks.
04:48It attacks.
04:50It attacks.
04:52It attacks.
04:53It attacks.
04:56But how will our closer relatives, the great apes, react when faced with their own image?
05:03This three-year-old chimpanzee has never seen a mirror before.
05:13He's not sure what to make of it.
05:16Erect fur is usually a sign of fear or anger.
05:26But his fear is soon replaced by curiosity.
05:46This chimp appears to know that that's her tongue and those are her teeth.
05:53Chimpanzees seem to have a concept of the bodily self that allows them to look into a mirror and say,
06:00that image is equivalent to this body.
06:06But how can we prove that humans and chimpanzees really identify the figure in the mirror as themselves?
06:15Psychologists have a well-known test for this. It's called the mark test.
06:22A researcher marks a child's cheek.
06:25The child then looks in a mirror.
06:32He moves his hand up to the mark.
06:35He recognizes himself.
06:39By the age of two, half of all children tested can recognize themselves.
06:44Soon, they all do.
06:51So, can our ape cousins pass this test?
06:58A keeper places a mark on a female orangutan.
07:03Next, they put her in front of a mirror.
07:06She has seen her reflection before, but this time she notices that something has changed.
07:12Her hand goes to the mark.
07:25All the great apes, gorillas, orangutans, chimps and bonobos can pass the mark test
07:31All the great apes, gorillas, orangutans, chimps and bonobos can pass the mark test by a certain age.
07:40But we don't recognize just ourselves, we recognize other people too.
07:45Is this what separates us from the apes?
07:50At the Primate Research Institute in Japan, a chimp takes a voice recognition test.
07:57She's played a one-second clip of a voice.
08:01She's then shown two photographs and has to identify the correct image from just hearing that short sound bite.
08:09First, she hears an ape sound, she recognizes the sound instantly and selects the right ape.
08:15Now, she hears a human voice.
08:18She sees an ape and a human face and picks the human face.
08:23She seems to recognize the difference between ape and human sounds.
08:27Finally, she hears another human voice.
08:31But this time, she's shown two human faces.
08:36She selects the correct picture.
08:39From hearing just that one-second clip, she can distinguish not just different ape voices, but different human voices too.
08:51This chimp has an 80% success rate for the test.
08:55So, what differences have we uncovered so far?
08:59We've tested both humans and apes and found that they recognize themselves.
09:05Both are self-aware.
09:08So far, there is little difference.
09:17But why is it so important for apes to be self-aware?
09:22Scientists need to understand how apes relate to each other.
09:26Most great apes live in large groups.
09:29They can identify every face in their group.
09:32They know who to avoid and who to make alliances with.
09:39But in humans, group awareness is a stepping stone to something far more important.
09:47Maybe our most amazing feature, kindness.
09:56Over here!
09:57Ape!
10:00Ape!
10:04A bonobo lies injured. He's hurt his arm in a fight and is in pain.
10:15The others appear to sympathize.
10:18It's as if they understand that he's feeling pain.
10:21Astonishingly, apes show acts of caring even outside their group.
10:29We tend to think of gorillas as violent and dangerous.
10:33Wrong.
10:37A zoo near Chicago.
10:41A three-year-old boy falls 20 feet into an enclosure.
10:45The fall knocks him unconscious.
10:47All around him, gorillas weighing up to 180 kilograms.
10:53Upper hose reel! Upper hose reel!
10:57But then, a female gorilla picks him up and cradles him in her arms as if he were one of her own.
11:05She then gently places the boy down in front of her zookeeper's door.
11:11It's a touching, almost human moment.
11:13But we can't know the gorilla's true motives.
11:18To find that secret ingredient that makes us human, we need to conduct more experiments.
11:31Tools are an essential part of our everyday life.
11:37For years, gorillas have been used as tools.
11:41For years, the classic textbook definition of humans was man the toolmaker.
11:47We were said to be the only species that used tools.
11:53For two and a half million years, we have hammered and forged implements from the earth.
11:59We manufactured amazingly complex tools, and with them, created the modern world.
12:05Surely our toolmaking ability makes us unique.
12:12But in the 1960s, researchers discovered chimpanzees laying sticks across ant trails to make ant kebabs.
12:22And they used leaves as sponges to mop up water for drinking.
12:27But these are simple tools, nothing like our complex toolmaking.
12:31So, can apes fashion tools and use them in a complex way like humans?
12:46Cricket Sands and Dave Morgan of the Wildlife Conservation Society are on an expedition to one of the remotest parts of Africa, the Gualogo Triangle, in the Republic of Congo.
12:57For the last six years, they've been coming here to study chimpanzees in the wild.
13:06Sands and Morgan are looking for signs of chimpanzee tool use.
13:11They suspect that chimps have reached a far higher level of sophistication in fashioning tools than we currently believe.
13:18On the edge of a forest trail, they spot some sticks lying on a termite's nest.
13:27Scientists have known for years that chimps use sticks to catch termites.
13:32What's unusual here is that there's evidence of different types of tools.
13:36Sands and Morgan need to know if the chimps are responsible.
13:41They set up a series of hidden cameras and wait.
13:48Two days later, a group of chimpanzees triggers one of the cameras.
13:53The chimpanzees are not aware that the camera is being used to capture the chimpanzees.
13:58The camera is being used to capture the chimpanzees.
14:01Two days later, a group of chimpanzees triggers one of the cameras.
14:08Despite their efforts to hide it, the chimpanzees have spotted it.
14:13It's probably the first man-made object they've seen, and they're curious.
14:19One chimpanzee even makes a tool to probe the camera.
14:24Over the next few months, triggered by heat, the cameras will capture anything that comes into range.
14:32Back at camp, Sands and Morgan review the tapes. The results are astonishing.
14:40They show for the first time chimps using two different tools as they forage for food.
14:46You can see several individuals arriving on the scene, several with tools in their mouths.
14:51They're carrying to the termite nest.
14:54Look, he's got the end of the tool, he's pressing on it with his foot, trying to push it into the ground as far as he can.
15:00The chimps use the large stick to break open the nest.
15:04Then the footage reveals the chimps reshaping the second, thinner stick.
15:09This is an adult female who's actually making a brush tip on a herbaceous herb.
15:15She's pulling it through her molars and she's making a nice brush with the end of the tool.
15:20She then straightens it and inserts it into the termite nest.
15:24No one has filmed this before.
15:30Sands and Morgan may have recorded evidence of one of the most astonishing discoveries in chimpanzee history.
15:38So if you just were to insert this blunt end, the termites wouldn't be able to bite as well.
15:43Their mandibles just aren't as large as that, they can't grasp around it.
15:47But if you make a brush by pulling this through your teeth,
15:54even pulling a fiber apart,
15:57even pulling a fiber apart,
16:06then you've made a nice brush and you can insert this into the nest.
16:10In tests, Sands and Morgan have found that the brush catches ten times more termites than a plain stick.
16:18And now that we've opened the surface of the nest, we need to follow with a second tool.
16:27So you can feel tiny vibrations on the tools as they bite the ends of the brush stem.
16:38Here we have a major soldier, a few workers.
16:43Did okay, probably not as good as a chimp.
16:46After they've got the termites in their hand and gone,
16:50they'll withdraw them and put them in their mouth and chew on them very quickly.
16:55Some very smart chimp invented the brush tip stem tool, they should patent that.
17:00It's amazing, it really does increase their efficiency.
17:03It's the first time anyone has recorded chimpanzees using two tools with different functions to achieve their goal.
17:11Sands and Morgan's research reveals that chimpanzee tool use is far more complex than anyone thought.
17:18Humans and apes seem to share more similarities than differences.
17:26While their customs and traditions stay local, ours can spread right round the world.
17:33Somehow primate societies do not develop as fast as ours.
17:48This is Lake Victoria in Uganda.
17:52And this is researcher Victoria Horner.
17:55She's developed a simple but brilliant experiment that could explain how we came to be the most successful species on the planet.
18:03Strangely, it's because there are some tasks we do worse than chimpanzees.
18:08We present both chimpanzees and children with this box, this is the black box.
18:13And it's completely opaque, you can't see the inside of the box, you can't see how it works at all.
18:19And inside this there is a food reward for chimpanzees, or for human children there's a little sticker.
18:28Horner demonstrates the long sequence of actions Jessica must use to get the reward.
18:43She reloads the box. It's now Jessica's turn to show she's learned what she's seen.
19:14She successfully picks up the complicated sequence of actions and gets her reward.
19:25Next, Horner and her boxes make the 15-minute journey to nearby Ngamba Island.
19:33Horner demonstrates a simple but brilliant experiment that could explain how we came to be the most successful species on the planet.
19:43She demonstrates the movements to Billy.
19:55Now, it's Billy's turn. Will she copy the actions?
20:13Just like Jessica, the chimpanzee copies the actions and gets her reward.
20:44But Horner has just been toying with both ape and child.
20:48This experiment is not about how apes learn, it's about understanding how humans learn.
20:55Back at the school, she swaps the boxes.
20:58We then present them with what we call the clear box.
21:05And this one is structurally identical to the black box.
21:09But this time, all of the walls of the box are made of see-through material.
21:14And actually, there's a full ceiling which runs right around the top here.
21:18So that all the actions to the top are irrelevant.
21:22They're pretend nonsense actions.
21:25And the sticker, or the food reward, is actually located in this tube at the front.
21:30Jessica can now see that poking the stick in the top is pointless.
21:35And yet, the only action she needs to do is the last one.
21:43But for some reason, Jessica sticks faithfully to what she's learned.
21:48Even though she can see that the first actions are unnecessary, she carefully repeats them.
21:56Finally, she gets the reward.
22:00Oh, no! Very good!
22:05It's not just Jessica.
22:07Horner has tested children around the world, and they all copy her actions.
22:12Not one of them takes the shortcut.
22:15What we found was actually rather surprising.
22:18We found that the children copied everything that I did,
22:23no matter whether they had the black box or the see-through box.
22:27And they all copied my actions.
22:30And they all copied my actions.
22:33And they all copied my actions.
22:36And they all copied my actions.
22:40So what will Billy do?
22:49She goes straight for the sweet.
22:55This isn't unusual.
22:57In trials with a dozen chimpanzees, Horner has found that two times out of three, chimpanzees take the shortcut.
23:10It's a start towards explaining why humans and apes are so different.
23:17Imitation and copying accurately is a huge part of our development as humans.
23:22It's how we learn language, it's how we learn to interact with objects
23:25and acquire cultural behaviors and lots of the complex things that we do as humans.
23:30And it's a little as if it's a sort of default for us to copy accurately.
23:34By copying others, we acquire thousands of skills and customs.
23:40In Victoria Horner's experiment, apes and humans both get their reward, but in different ways.
23:53Victoria Horner's experiment has revealed the first significant difference between humans and apes.
23:59But are there others?
24:01So far, we have outstripped our ape cousins.
24:05Our achievements are on a different level.
24:08We build roads and skyscrapers, invent iPods and atom bombs.
24:13We transform deserts into cities and put men on the moon.
24:20Is it the fact that humans learn by copying?
24:24Is it the fact that humans learn by copying?
24:27Or is there something else in our DNA that enables us to do all this?
24:36One difference between ape and human brains is sheer size.
24:40By the time we're adults, our brain will be three times the size of a chimpanzee's.
24:47Along with this large brain comes an extremely powerful memory.
24:53All of us can remember millions of pieces of information.
24:56In fact, we generally assume we have the best memories on the planet.
25:02Think again.
25:03You're about to witness one of the most incredible feats of memory ever filmed.
25:09And it's not human.
25:16Professor Tetsuro Matsuzawa at the Kyoto Primate Research Institute in Japan
25:21has devised a memory test for the chimpanzees.
25:28His star pupil is a seven-year-old chimpanzee.
25:33Show him the numbers one to nine, and he'll put them in the right order,
25:37pointing to them one by one.
25:40Every time he gets it right,
25:42he receives a treat, a tiny piece of apple or half a raisin.
25:48But now, the researchers make things difficult.
25:53As soon as the chimp presses the number one, the rest of the numbers are hidden.
25:59He has to remember where the numbers were
26:02and press the white squares in numerical order.
26:06The positioning of the numbers is important.
26:09He gets it right time after time, with lightning speed and 100% accuracy.
26:18In 0.65 seconds, he can remember the numerals in which position.
26:28Now, it's your turn.
26:31Did you get them? No? Try again.
26:34This time, we'll run the sequence at half speed.
26:43Still too difficult? Try at a quarter speed.
26:47Back to full speed, and you get an idea
26:49of how extraordinary this chimpanzee's memory is.
26:56Now, it's your turn.
27:00Did you get them? No? Try again.
27:05This time, we'll run the sequence at half speed.
27:10Still too difficult? Try at a quarter speed.
27:17So, how do humans compare?
27:21No one knows why, but children tend to be better than adults
27:24at this sort of short-term memory task.
27:27We've asked some nine-year-olds to have a go.
27:32They take a lot longer studying the numbers before they start,
27:36and even then, most of the time, they only get four or five right.
27:46Occasionally, they do a little better.
27:52Not bad, but now watch the chimpanzee again.
27:59It seems that chimps' short-term memory is superior to ours.
28:10Scientists believe the chimpanzee's short-term memory helps it survive.
28:15They can take an instant inventory of their surroundings,
28:18locate food and avoid enemies.
28:23Our common ancestor of humans and chimpanzees
28:26may have had such a capability
28:29of immediately memorising things at a glance.
28:36Scientists think we lost this instant memory
28:39in a trade-off for a far more powerful mental ability.
28:46This trade-off represents one of the most important breakthroughs
28:50in human development.
28:52Language.
28:55In the wild, ape vocalisation may not have developed much
28:59since the chimps and bonobos split away from us around five million years ago.
29:05But since we split away from our ape ancestors,
29:08our brains have developed sophisticated ways to take in information.
29:12They learn by trial and error or by passive observation.
29:16We communicate ideas and discuss ways to solve problems.
29:22And it's not just language.
29:24What makes us unique may be something even more fundamental.
29:31We cooperate.
29:34At the Max Planck Institute in Leipzig, Germany,
29:37this researcher is finding out how far humans will go to help others.
29:46He looks like the clumsiest scientist on the planet,
29:49but his butter-fingered experiments have a serious purpose.
29:56They reveal that even the most intelligent chimpanzees
30:00They reveal that even tiny children cooperate instinctively.
30:15Do apes share this instinct to help out, or is something limiting them?
30:21The Chimpanzee Sanctuary on Ngamba Island in Uganda
30:26is a leading centre for studying chimpanzee behaviour.
30:31When the chimpanzees come in from the forest to eat,
30:34it allows researcher Alicia Melis to conduct experiments
30:38in as near to wild conditions as possible.
30:41She wants to know what chimpanzees are thinking when they cooperate.
30:46Is it really that they understand what's going on?
30:49Is it really that they understand there is something like they have to do together?
30:53Is it really that they understand that they need a partner?
30:57Melis tests just how far one chimp will go to assist another.
31:03She places a long plank next to the cage where the chimpanzees will be.
31:10OK, so I'm going to put some food here in the two dishes
31:14on both ends of this platform.
31:19That's five pieces there and another five pieces here.
31:27She then runs a rope from the plank to the cage.
31:34When the ends of the rope are close together like this,
31:37one chimp can get the food.
31:48Melis resets the experiment.
31:50This time the ends of the rope are spaced further apart,
31:53so one chimp can't pull both at the same time.
32:00Next, Melis places another chimp in the neighbouring cage.
32:06They lock the door between the two cages.
32:12Now the only way for the chimp to get the food is to work with a partner.
32:19So what will the chimpanzee do?
32:26He realises he can't do it on his own and removes the peg to release the other chimp.
32:34They pull the rope together.
32:40In this situation, the chimpanzees help each other.
32:44But just one small change tips the delicate balance.
32:54This time there's just as much food as before,
32:57but now it's all on one tray in the middle of the plank.
33:04Will the two chimps still help each other as humans would?
33:15Both hold the rope and one of them pulls the plank in.
33:24But the dominant chimpanzee grabs all the food.
33:33The experiment is repeated.
33:39But now the second chimpanzee refuses to help.
33:42He knows he won't get any food.
33:47When it comes to sharing, chimps will only go so far.
33:52Perhaps this is the dividing line between apes and humans.
33:58We share intentions, we communicate our goals,
34:02and crucially, we're not just serving our own selfish needs.
34:08The final part of our cooperation experiment
34:11reveals how we are able to share intentions in a way that apes never can.
34:19A researcher places a piece of food under one of two cups.
34:25The chimp has to choose the cup where the food is hidden.
34:31The researcher reaches for the cup with the food.
34:38And the chimp goes straight for it.
34:45You set up a situation where you're competing with the chimpanzee
34:48and you reach for it like you're trying to get it yourself
34:51in competition with the chimp.
34:53Then they see that and they make the inference
34:55that must be where the food is.
34:57If he's trying to get in there, that must be where the food is.
35:01But just a slightly different gesture changes everything.
35:06Instead of reaching for it,
35:09the researcher points towards where the food is hidden.
35:14Half the time, the chimpanzee picks the wrong cup.
35:18It doesn't understand that the researcher is trying to help it.
35:23Perfect.
35:24I don't think that the chimpanzee is trying to help it.
35:27I think that the researcher is trying to help it.
35:31I don't think chimpanzees quite understand
35:34that you're trying to inform them of something helpfully.
35:37In their natural state, chimps don't just point to some food
35:40for another chimp and say,
35:42here's some food if you'd like it.
35:44I don't want it right now. You can have it.
35:46Chimpanzees apparently only understand intentions
35:49from a selfish viewpoint.
35:51They only cooperate if they think
35:53they will gain something from their actions.
35:57Here's the same test.
35:59Here's the same test.
36:01This time with an 18-month-old child.
36:10The child gets the idea immediately.
36:15There's something in our genetic makeup
36:17that from an early age allows us to work together
36:20towards a common goal.
36:22We read and trust each other's intentions.
36:25It seems this could be what makes us human.
36:30On the journey between human and ape, something changed.
36:36At some point, our brains began to develop differently.
36:43Now, scientists think they know when and how this change happened.
36:51We've come to Philadelphia,
36:53where this discovery was made by pure chance.
36:57Hansel Stedman, at the University of Pennsylvania,
37:00studies muscular dystrophy.
37:05To understand the disease better,
37:07he decided to compare human muscle cells
37:10with those in the great apes.
37:13He noticed something unusual in some of the cells
37:16in one particular ape.
37:20It was a tumor.
37:22He noticed something unusual in some of the cells
37:25in one particular muscle, the jaw muscle.
37:31He took a thin slice of chimpanzee
37:33and a thin slice of human jaw muscle
37:36and compared them under a microscope.
37:40We're looking at a razor-thin section
37:43of one of the jaw-closing muscles from a great ape.
37:47These red cells seen in cross-section
37:49are a chimpanzee's biting muscle fibers.
37:53But when Stedman looked at the human jaw muscle,
37:56the difference was immediately obvious.
37:59The human biting muscle fibers at the bottom
38:02are one-third the size of the great apes.
38:06This isn't just an isolated case.
38:08Every human jaw muscle looks the same.
38:13Stedman has discovered that in the jaw muscle
38:16that in the distant past, a genetic mutation occurred.
38:20It made our ancestors' jaw muscles
38:22much weaker than those of the other apes.
38:27You wouldn't think that a weaker jaw
38:29could be an advantage back in the prehistoric era.
38:33But incredibly, it's this genetic mutation
38:36that could be responsible for something even more amazing.
38:41The secret lies in the way muscles attach to bones,
38:45in this case, the skull.
38:48If you take a look at this orangutan skull,
38:51this is an adult male,
38:52this illustrates very nicely
38:54that muscles leave an indelible mark on the bones
38:58where they attach to them.
39:00All the great apes have a crest along the top of their skull.
39:04They need it because their strong jaw muscles need a firm anchor.
39:09But the thick skull has another effect.
39:12It acts like a rigid and inflexible cage on the brain.
39:18In humans, our weak jaw muscle
39:20exerts far less pressure on the skull.
39:24These skulls belong to two different hominid species
39:27living together over two million years ago.
39:30Australopithecus boisei on the left
39:33and Homo erectus on the right.
39:38Anthropologists are convinced
39:40that genetic mutation occurred in one of these hominids,
39:43weakening the jaw muscle
39:45and allowing the skull and brain to expand.
39:48But which one?
39:50The Australopithecus has a large, ape-like jaw muscle,
39:54while the Homo erectus has a much smaller, human-like jaw muscle.
39:59It's this one that has the genetic mutation.
40:03The other dramatic difference, obviously,
40:06is in the size of the brain case.
40:08Homo erectus has a brain that's 50% larger
40:12than Australopithecus boisei.
40:15But when did this happen?
40:18By comparing how genes vary in different species
40:21over millions of years,
40:23Hansel Stedman has calculated
40:25that the strong jaw muscle mutated into the weaker muscle
40:28in our ancestor, Homo erectus,
40:30about 2.4 million years ago.
40:36It's one of the most important moments in our evolutionary history.
40:43And it's all down to a single genetic mutation.
40:47That occurred in one individual at one point in time
40:52when there was a gene pool of interbreeding animals
40:56that all had the normal version of this gene.
40:59And yet, with the passage of time,
41:01the only surviving version of that gene in humans
41:05is the mutant version.
41:07It eclipsed all of the others
41:09that were in that breeding pool at that time
41:11through the process of genetic fixation.
41:14A single genetic mutation,
41:17but powerful enough for our ancestors
41:20to out-compete all other hominids.
41:23But how did these early ancestors of ours
41:26survive with jaw muscles
41:2810 to 50 times weaker than their rivals?
41:32If you know you're going to lose a jaw-to-jaw combat,
41:36then avoid jaw-to-jaw combat altogether.
41:38Find some other way to annihilate your competitors.
41:43And that's what our ancestors did.
41:47They switched from brawn to brain.
41:51Blessed with a larger brain,
41:53our ancestors began to cooperate.
41:56They shared their plans,
41:58developed complex social structures.
42:01This was the first step on a journey
42:04that would ultimately propel us into a different world.
42:10But before modern humans like us
42:12would emerge to conquer the planet,
42:15we needed one more ingredient to really take off.
42:19One more critical event had to happen.
42:22The final piece in the jigsaw.
42:29Over two million years ago, our ancestors changed.
42:36A single genetic mutation in our jaw muscle
42:39allowed our skulls to expand
42:41and our brains to grow far larger than our ape cousins.
42:45But one further change was the final key
42:49to the development of modern human beings.
42:52It was discovered here at Oxford University in England.
42:56In 1996, researchers were studying three generations of one family.
43:0116 of them had a severe speech disorder.
43:19They couldn't produce the delicate movements of tongue and lips
43:23that would let them speak clearly.
43:28Studying their DNA,
43:30the researchers found they all had the same genetic defect.
43:34In modern humans, a gene called FOXP2 is essential for speech.
43:39It's believed that sometime in the past,
43:42a mutation in FOXP2 helped create the neural connections needed
43:46for the movements of our lips and tongues.
43:49But none of the 16 family members in the study
43:52had this mutation.
43:54Now they knew what to look for,
43:56the researchers tried to work out
43:58when the FOXP2 gene changed in our ancestors.
44:02They found it mutated as recently as 200,000 to 300,000 years ago.
44:08So our early ancestors,
44:11who split away from the chimps and bonobos five million years ago,
44:15probably couldn't talk.
44:18It would be millions of years
44:20before our ancestors gained the ability to speak.
44:23It could be the appearance of the FOXP2 mutation
44:27coincided with the emergence of a new species
44:30in an area of sub-Saharan Africa.
44:33Homo sapiens.
44:35Or, more simply, you and I.
44:41Armed with this new linguistic weapon,
44:44Homo sapiens poured out of Africa into Europe and Asia.
44:51This ability to communicate would drive us forward.
44:56We shared knowledge with each other.
44:59We explained and taught, copied and learned.
45:03Each generation built on the knowledge of the last.
45:08If you just look at human history,
45:10we started with very simple technologies
45:12and simple social institutions, for example,
45:14and now we have very complicated ones.
45:16And so we've called this the ratchet effect.
45:18Each generation of children learns whatever they're exposed to.
45:22And then maybe some innovation is made.
45:25Then the next generation of children learns the innovated, the new version.
45:28And then maybe there's a new innovation
45:30and the next generation learns a new version.
45:32Human cultures can ratchet up in complexity over time
45:35and children get them for free.
45:39Our language became complex.
45:41Our technology advanced.
45:43Our culture, richer.
45:48We were propelled in leaps and bounds
45:51into a different league from the other animals.
45:54The primitive forest ape became a modern human.
46:04In many ways we are still similar to the apes.
46:07Tiny differences in our DNA give us the things that make us special.
46:12Brain power, language, complex tools
46:16and our ability to share goals and work together.
46:24But the great apes are special too.
46:27They have incredible physical strength, fast reactions
46:31and a phenomenal short-term memory.
46:34Both of us are adapted for our own environment.
46:41But one difference stands out from all the rest.
46:46Our development has made us incredibly successful.
46:50There are now over 6.6 billion of us on the planet.
46:54Compared to the great apes, an astonishing contrast emerges.
46:59The number of people born in just two days, some 700,000
47:03is greater than the number of all the great apes in the world.
47:08We share most of our DNA with them.
47:12But the tiny amount we don't share makes a world of difference.