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Origins of Us
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00:05The shape of your face, walking on two legs, the way you see the world, what makes you the person
00:17you are. The story of each and every one of us can be traced back millions of years to the
00:28plains of ancient Africa. The answers to the question, what makes us human, lie buried
00:37in the ground in the fossils and other traces of our ancestors, but also lie deep within
00:43our own bodies, in our bones, flesh and genes. As an anatomist, I'm fascinated by the way
00:54our bodies have been sculpted by our ancestors' struggle for survival.
01:05But why did we leave behind the other apes in the forest and stride out into the African
01:14savannah? How did that change the way we looked, give us big muscles in the unlikeliest of places,
01:29and help us to acquire amazing new skills? The story of how we became human describes how
01:39forest-dwelling apes evolved into us. And the story starts millions of years ago with an
01:46ape who stood upright and walked.
01:54The story starts permanent in the forest.
02:05These objects произplanted blooms of archegist groups fairly poetic as their prior control
02:10to mental health, and little by the raw nature of the hardcore generation. And the
02:27Our story began around six million years ago with apes who lived in an ancient African
02:34forest.
02:36In many ways they would have been similar to the apes that still live in the forests
02:40here today.
02:46I'm here in the ancient forest of Kibale in Uganda which covers about 700 square kilometers
02:53and I'm hoping to do something really special and that's to track down some of our closest
02:58living relatives, chimpanzees.
03:08I want to get close enough to see how their bodies work.
03:14But getting near to the wild chimps who live in this dense, wet forest isn't easy.
03:23Francis Muguruzi is my guide.
03:28He's been studying the chimps here for nearly 20 years.
03:39I think we're getting really close now.
03:41Francis, my guide, tells me that he can hear the chimpanzees.
03:43He thinks there's two groups of them, one which is further away somewhere over there but also
03:47a group which is much nearer, perhaps only five or ten minutes away.
03:51so this is really exciting.
04:10Here we go.
04:13Ciao.
04:33Oh, there's lots of them there all around us.
04:45This is just extraordinary. This is my first sight of chimpanzees in the wild.
05:04It's impossible to look at chimpanzees and think that we're not related to them. And
05:09of course, these are our closest living relatives. I mean, look at the way he's sitting there.
05:18We are so closely related to chimpanzees, we share nearly 99% of our DNA with them.
05:28I shouldn't say that's not me.
05:32But although we're genetically close, we are not descended from them.
05:47Looking at chimpanzees helps us understand where we've come from. And that's not because
05:52we've evolved from them. Of course we haven't. But if we trace back each of our family trees far enough,
05:58we reach a point where they come together. We have a common ancestor with chimpanzees going back about
06:05six or seven million years ago. So I'm here visiting my relatives. Now, their ancestors stayed in the forests,
06:14whereas ours moved out. And if we can find out how and why we did that, well, that's the story
06:22of how we became human.
06:27Our evolutionary journey is written into our bodies and into the way we use them. And a chimpanzee's
06:37body is built for a particular way of getting around.
06:49He's passed asleep. Literally just a few meters away.
07:06He's just having a quick look around, but basically he's dozing, lying on his back with his limbs
07:12splayed out. He's got these wonderfully long arms and very short legs. He's a climber.
07:21And his feet are wonderful. He's still got this grasping ability in his feet that we've lost.
07:26He's able to grip onto things and climb. His great toe, his big toe, is out to the side like
07:33that.
07:33So it makes his feet look like hands.
07:37Millions of years ago, our ancestors would have had feet which grasped like this.
07:44And that's something that we've lost.
08:01In six million years, our body plan has become very different, with our long legs and feet for walking on.
08:17It looks as though they're moving quite slowly, but I can assure you they're not.
08:21This is a fairly fast pace to be moving through the jungle.
08:27So what was it that set our ancestors off on a different path?
08:33A path that would lead us to colonise the globe, whilst other apes stayed in the African forest?
08:39And when did we start to change?
08:46It's always been a puzzle.
08:50Until this extraordinary fossil was discovered just a few years ago.
08:58This is Tumai, also known as Sahelanthropus judensis.
09:03And it's not putting it too strongly to say that his discovery caused something of a stir.
09:09He certainly looks like an ape.
09:12And just to convince you of that, I've got a modern chimpanzee skull here.
09:16And you can see how similar the two are.
09:19They've even got a similar sized brain.
09:21But there's something very special about Tumai.
09:25And just to explain that.
09:26First of all, I want to show you the foramen magnum underneath the chimpanzee skull.
09:31This is where the spinal cord exits the skull.
09:34If I hold the chimpanzee skull in that orientation.
09:38So this is as the skull would be in life, with the eye sockets in a vertical plane.
09:44We can see that the foramen magnum exits the skull at this angle.
09:49And in Tumai it's completely different.
09:52The foramen magnum is right underneath the skull.
09:54Which means the skull is balancing on an erect spine.
09:59This isn't any old ape.
10:02This is an ape who stood upright on two legs.
10:06And not only that.
10:08This is a bipedal ape.
10:10Who dates to six to seven million years ago.
10:16This is a hugely significant moment in our story.
10:24It means that Tumai was moving around on two legs.
10:28Very close to the time our ancestors split from chimpanzees.
10:32There's no question he's more chimpanzee like than human.
10:37But Tumai put standing up right at the start of our journey.
10:55In the six million years since Tumai stood upright.
10:59Our skeleton has undergone many changes.
11:05Our bones and muscles have been transformed by this new way of getting around upright on two legs.
11:20I'm a human anatomist and I've studied the structure of the human body.
11:24And I've mainly done that through dissection.
11:26And in fact that's exactly what anatomy means.
11:29It means to take apart.
11:31But today I'm trying out something a bit different.
11:34I'm putting the human body or at least the skeleton back together again.
11:46This skeleton is, as you might expect, white.
11:49But in fact that's because these are dead bones.
11:52Living bones are pink in colour because they're so full of blood.
11:55Anybody that's broken a bone will know that.
11:57A fractured bone bleeds like crazy.
12:03And living bone in our bodies is constantly changing in response to the stresses and strains that we place it
12:10under.
12:10So over a period of years all of the bone in your skeleton is taken away and replaced with new
12:16bone.
12:20But standing up on two legs is dependent on a central yet vulnerable part of our anatomy.
12:27Right in the centre of the skeleton is this wonderful structure, the spine, built up of a series of repeating
12:34vertebrae.
12:35And it forms this beautiful double S shape.
12:42But all of this anatomical beauty comes at a cost.
12:48With this isolated spine you can see the curves really beautifully.
12:52But you can also see something else and that's the increase in size of the individual vertebrae as we go
12:58down.
12:59Until we get to here, the lumbar spine where the vertebrae are absolutely massive.
13:04And that's because they're bearing the weight of everything above them.
13:09So it's not surprising that this is where we tend to get problems with our spines.
13:13And in fact it's the most common reason for visits to GPs.
13:17As we get older the intervertebral discs start to dry out and the inside of them can pop out and
13:23press on the spinal nerves.
13:25And that can be painful.
13:26And also the weight that is borne by the spine moves backwards and now is loaded onto these joints at
13:33the back so they can be painful too.
13:35So standing upright causes us so many problems.
13:40Why did we do it?
13:50The answer is locked away in the dark recesses of time.
13:58Six million years ago the world's climate was becoming colder and drier and the forests of Africa were thinning out.
14:09And where dense jungles gave way to woodlands the apes who lived in them started to change.
14:27You can see what might have happened by looking at apes living today.
14:39Up in the trees some of the best food is in the most inaccessible places.
14:48And being able to reach those highest branches is an obvious advantage.
14:55They are feeding on celsis durandii.
14:58Celsis durandii.
15:00Yes and it's one of their favourite fruits that they feed on.
15:03Oh so they're eating fruits up there are they?
15:04Yes they're eating grapefruits.
15:06And actually there are some that have fallen down on this branch here.
15:11Oh right yeah.
15:13Can I taste it?
15:14Yes we can taste it.
15:15So these little yellow ones are ripe?
15:16Yes they are ripe.
15:18They like it.
15:21Hmm.
15:23It's somehow bitter.
15:24It is bitter.
15:24But for them they're leaky.
15:26That's not one of my favourite fruits.
15:28It can't be your favourite.
15:29Yes.
15:38In an increasingly patchy woodland, being able to stand up to reach fruit on the thinnest branches must have been
15:47a great advantage for our ancestors.
15:52And it's possible that this is what drove the changes in Tumai's body.
15:59He could have been standing upright in the trees.
16:09The latest discoveries show that Tumai was the first of many bipedal apes.
16:17Over the next two million years, fossils like Orarin Tuganensis and Ardipithecus rhamidus show that other apes were also adapting
16:27to their changing environment by standing upright.
16:32They were still essentially climbers, but as the forests thinned, it's thought these apes were spending more time on the
16:39ground.
16:46It's hard to know exactly when our ancestors gave up a life in the trees for living on the ground.
16:57But there is a clue hidden away in our bones.
17:05I've been watching the chimpanzees as they've been climbing and the way their ankles work, so I want to compare
17:11that with my ankle.
17:12Sorry about this, but the boot and the sock are coming off.
17:15Now most of the time I'm walking around on the ground and my foot is at 90 degrees to my
17:21leg.
17:22But I can move the ankle like this, that's called dorsiflexion, to about 20 degrees.
17:31Now compare that with chimpanzees.
17:36To climb efficiently on something vertical, you need to be able to bend your foot up much more than we
17:43can.
17:44When chimps are climbing, they dorsiflex their ankles up to 45 degrees.
17:50The differences in ankle movement between us and them could provide vital evidence in working out exactly when our ancestors
17:59gave up climbing for walking.
18:21To nail down when we became walking rather than climbing apes, scientists at Boston University have been studying the bones
18:29of our ancient ancestors.
18:30With laser-like precision.
18:37They've analysed the remains of every fossil they could lay their hands on.
18:45Including the bones of this truly remarkable fossil, Lucy.
18:53She belongs to a species called Australopithecus afarensis.
18:59This is a replica of Lucy who is one of the most famous, if not the most famous skeletons in
19:05the whole of human evolution.
19:07She's 3.2 million years old and we have so much of her skeleton that we can tell an enormous
19:15amount about her.
19:16She would have stood just over a metre tall.
19:19The length of her arms and her curved fingers suggest that climbing was still really important in the way she
19:27got around.
19:28But recent research is challenging that idea.
19:36There's one area of Lucy's skeleton that's been the focus of Jeremy De Silva's exciting new research.
19:44Lucy has a spectacular ankle and we have some comparisons.
19:49Great, so this is a chimp.
19:50Right.
19:51And this is a human.
19:53And chimpanzees, they do remarkable things with their feet and ankles.
19:57For instance, they could take the top of their foot and press it right up against their shin.
20:01It's amazing flexion, which if you and I tried that, we would snap ligaments and our Achilles, we just aren't
20:09equipped for that kind of motion.
20:10A big ape like a chimpanzee putting all of its body on the foot and on the ankle while it's
20:15climbing like that, it leaves its mark on the bones.
20:20On the left is the bottom of the chimpanzee's tibia or shin bone where it forms the ankle joint and
20:26there's a very obvious trapezoid shape.
20:30On the right is the same area of the human tibia and it's square.
20:36The shape of your bones reflects whether you use your ankles for climbing or for walking.
20:44Okay, so let's have a look at Lisi and compare her.
20:51Well, although she's tiny, the shape of that joint just there is much more human-like.
20:58It is.
20:59And that tells us that her feet were planted firmly on the ground directly underneath her knees, which are adaptations
21:05that we see in upright walking creatures.
21:08Fantastic.
21:09It's amazing to be able to tell so much just from the end of one bone.
21:13Yes, and the magnificent thing about Lisi is that we have so many bones and each one of those bones
21:19tells a fascinating story.
21:26Lucy still appears very ape-like and her brain was similar in size to that of a chimpanzee's.
21:37But becoming a walking ape had fundamentally changed the shape of her body.
21:47By the time we see Australopithecines like Lisi, we can be absolutely sure, beyond a shadow of a doubt, that
21:55our ancestors were standing and walking around on two legs.
22:00And not only that, they were committed to walking.
22:04It was their main way of getting around.
22:11Giving up climbing for walking suggests that our ancestors were moving beyond the confines of the forest.
22:21That they were exploring new habitats.
22:25But walking is a physical skill that takes time to learn.
22:40Just think about what these babies are trying to do.
22:49Balancing on their tiny little feet, defying gravity.
23:05Some of us get the hang of it quicker than others.
23:14And some of us aren't in a rush to do anything.
23:21But most of us will, at some stage in our early childhood, stagger to our feet and walk.
23:31These little ones are just learning to do something that's incredibly difficult.
23:36They've been quite happy for a few months crawling around on all fours.
23:40But now they really want to get up onto two feet and start walking.
23:45And at any point in time, when she cracks it, she'll be balancing on just one foot.
23:55And with each step, this involves coordinating some 200 muscles.
24:06It's an amazing feat of learning.
24:09But there are physical changes too.
24:19As these toddlers learn to walk, their bodies are changing.
24:22They're using their muscles in different ways.
24:25And the muscles will develop accordingly.
24:28And deep inside their bodies, their bones are changing as well.
24:31They'll start to develop the backwards curve in the lower spine.
24:35And the bottom of the spine will push down between the two hip bones.
24:39The hip bones curve forwards.
24:41And the thigh bone also starts to curve forwards and bend inwards.
24:45But what's really interesting is that we don't know how much these changes are programmed
24:51and how much they're appearing, they're developing in response to walking.
24:58And jumping.
25:06It's obvious that the evolution of walking has had a profound impact on our bodies.
25:15And it all started with those ancestors who put one foot in front of the other.
25:37It took millions of years for our ancestors to master the art of standing and then walking.
25:54But walking would fundamentally alter the course of our evolutionary history.
26:11And the next critical step on the long road to becoming human was driven by a new wave of drastic
26:20climate change.
26:23From around three million years ago, East Africa started to dry and the forests shrank back.
26:30A brand new habitat was born.
26:33The savannah.
26:39This was a whole new world rich with opportunity and evolution went into overdrive.
26:47There was an explosion of species taking advantage of the expanding grasslands.
27:01And alongside them were new species of walking apes who strode out on two legs into the changing landscape.
27:11Forming new branches of our family tree.
27:21Giving up climbing for walking meant that this group of apes were in the right place at the right time.
27:31As the forests receded, the walking ape came into its own.
27:36In fact, we know from the fossils that around two million years ago, there were at least six different species
27:42of these hominins.
27:44These apes which habitually walked on two legs.
27:47It was a big, bushy family tree.
27:51But while most of those lineages would eventually die out, one would go on to be extraordinarily successful.
28:06We don't really know why any of the others died out.
28:10But the thought that any of our ancestors could have survived in this arid, open environment is difficult to comprehend.
28:19For a relatively puny forest ape, life on the savannah would surely have been a dangerous proposition.
28:29I am feeling quite nervous and extremely vulnerable out here on the plain.
28:35I am keeping my eyes peeled and I can see some gazelles over there and some zebra.
28:42But I know that there are much more dangerous animals here as well.
28:46I saw some lions earlier and a cheetah.
28:50And there would have been similarly formidable predators here two million years ago.
28:57So how did our ancestors survive on the open savannah?
29:16This extraordinary fossil skeleton of a young male, unearthed here in Kenya, gives us an insight into how our ancestors
29:25managed not only to survive, but to thrive on the savannah.
29:32And I've really enjoyed laying this skeleton out.
29:35I've seen so many pictures of it, but there's nothing quite like being able to handle the real thing.
29:40Well, actually, this is a replica, but it is one of the most famous early human fossils.
29:47And it's just remarkable how much of a skeleton has been preserved, how many bones we have here.
29:54It dates back to one and a half million years ago.
29:58He's called K-N-M-W-T-15-thousand, or perhaps more poetically, Nariya Katomi Boy.
30:07And his bones tell us something really important about a crucial change to our bodies in human evolution.
30:21There are clues all over his skeleton, but the most striking are in the lower half of his body.
30:29Just look at the length of these legs. It is stunning. If I put my leg down beside Nariya Katomi
30:37Boy's leg, you can see that it's practically the same length.
30:40His femur fits along my thigh. His tibia fits quite nicely along my lower leg there.
30:52And these long legs really are an important step forward in human evolution.
30:59This is the first time we've seen somebody who looks human.
31:03He could be walking out there in this landscape and you would not notice that he wasn't one of us.
31:15Nariya Katomi Boy was a member of a species of early humans known as Homo erectus.
31:24He may be nearly two million years old, but his body plan was obviously highly effective, because from the neck
31:32down, he's so similar to us today.
31:37But his brain was only two thirds the size of ours. He didn't get by on his wits alone.
31:48So is there anything else about him that can tell us how he survived out here?
31:54There are plenty of adaptations here to efficient walking, but there are also some surprising changes in this skeleton which
32:02don't seem to be related to walking at all.
32:04He has very large knees and big hips as well.
32:10And in the trunk, he's got a waist. He's got a long, narrow waist.
32:15The first time we've seen this, his shoulders have also dropped down away from the head.
32:21And on the back of his skull, there's the sign of attachment of a very special ligament.
32:28Now, all of those changes are to do with stabilising the trunk, not something you really need while you're walking.
32:37So what was this boy doing that destabilised him?
32:51The best place in the world to understand Nari Kotomi Boy's mysterious physique is not in Africa, but in Boston
32:59at Harvard University.
33:08I've agreed to be the subject in an experiment, so I'm wearing gym kit and I've done these rather odd
33:13items of footwear, which are more like gloves than shoes, but in them I'm effectively barefoot, like our ancestors.
33:26This is the lab of Professor Dan Lieberman.
33:291.2 metres a second.
33:30Here we go. 3, 2, 1.
33:34His groundbreaking research has revealed that the shape and structure of our bodies has been profoundly affected by a particular
33:42form of locomotion.
33:45Just pretend you're strolling along the African savannah.
33:49All of a sudden, you've decided you have to run. Maybe there's a kudu up ahead that you've decided you
33:54want to chase, okay?
33:55It's dinner. We're going to get you up to a nice running speed, maybe about a 10-minute mile.
34:00All right, here we are. You ready to speed up?
34:02Yep, yep.
34:03Here we go. 3, 2, 1.
34:12All right, well, you have a nice gait, nice forefoot strike. As you're running now, you're much less stable than
34:17when you're walking, right?
34:18You're not falling over.
34:20Yep.
34:20But you ought to be, because every time you hit the ground, your body wants to fall forward on your
34:25chin.
34:31Staying balanced whilst running is hard.
34:35As we run, our legs throw our bodies out to the left and right.
34:41Our shoulders and arms swing in the opposite direction to try to keep us on the straight and narrow.
34:50But it's not enough. We need another crucial element to stay balanced.
34:58Our long, narrow waists. They allow us to twist whilst we run, which is vital to counteracting the destabilizing forces
35:10of our legs.
35:13So another challenge when you're running is your head, right? Every time you hit the ground, your head wants to
35:18pitch forward really fast.
35:19So your arm attaches to a ligament that's unique to humans, called the nuchal ligament, which is right in the
35:25back of your head.
35:26Just as your head wants to pitch forward, the weight of your arm is connected in the midline to this
35:31ligament, and it pulls your head back.
35:34This ligament isn't huge, but it's vital for keeping us balanced when we run.
35:43The attachment of that ligament is very obvious in the skull of Nariya Kotomi boy.
35:50It fixes on this ridge.
35:53Like us, it seems he had a nuchal ligament to stop his head pitching forward whilst he ran.
36:02So all these different parts of our anatomy are long waists, low shoulders, and the nuchal ligament in the back
36:09of our neck seem to be adaptations to running.
36:13They were there in Nariya Kotomi boy. Our basic body plan goes back nearly two million years.
36:20But there's one other really important bit of anatomy when it comes to running, and that's in our bums.
36:32You know what's nice about this? I'm not the person on the treadmill. Usually it's me.
36:38And it's not a bone, but a muscle. It's called the gluteus maximus.
36:43We're going to put electrodes on your gluteus maximus, which is the largest muscle in your body, but they're different
36:48portions, and we want to get this upper portion here.
36:51Brilliant. On both sides? On both sides. Both cheeks.
36:53And I can use this stuff to get a good contact? That's good, yeah.
36:57To see what effect the muscle has, I need to be wired up with some electrodes.
37:02And I suspect that they won't be filming you as you put these on.
37:05No, you won't be filming me as you put these on.
37:08All right.
37:16So, with my bottom fully wired up, and Professor Lieberman at the controls of the treadmill, it's time to fire
37:27up my gluteus maximus.
37:34To begin with, all I need to do is walk.
37:39And then Professor Lieberman turns up the power.
37:43And I'm going to bring you up to run.
37:45Okay. Nice slow run.
37:52Every time this muscle contracts, a signal is sent to the computer.
37:57The stronger the contraction, the larger the signal.
38:08All right, you can stop. I'm going to stop you now.
38:13The differences between how my gluteus maximus works when I'm walking, compared with when I'm running, are displayed on the
38:20computer screen.
38:22So, this is you walking, right? And this is your left gluteus maximus in red, and your right gluteus maximus
38:28in green.
38:29And you can see that when, say, for example, your right foot hits the ground in a walk, right, at
38:33this moment, right here in time.
38:34Yeah.
38:35Your gluteus maximus turns on just a little bit, right? And it's basically acting to push your leg back as
38:41you're walking.
38:42Okay.
38:42Okay, so now let's go to your running. Bam.
38:45So here you are walking, here you are running. And you can see, look at the gluteus maximus, look how
38:49much harder it's working.
38:50It's an enormous effect. You don't really need your gluteus maximus to walk, but you can't run without the gluteus
38:55maximus.
38:56So really, in order to be a good runner, you have to have a good strong butt.
39:00You cannot run very easily as a biped without a big gluteus maximus.
39:07So, the muscles in my bottom, your bottom, and every human bottom on Earth, have been shaped by the fact
39:24that our ancestors evolved a body built to run.
39:30But this running body wasn't built for raw speed. It evolved to run long distances. Our ancestors were endurance runners.
39:46In a developed country, so few of us run on a regular basis that it really is remarkable to reflect
39:52how much our bodies have been shaped by running.
39:56And I think even the fittest amongst us lead a relatively sedentary lifestyle compared with our ancient ancestors,
40:04for whom running wasn't a choice. It wasn't a recreational activity. It was essential to survival.
40:15Being able to run long distances could have given Nari Katomi boy an important advantage.
40:24He could hunt or compete with other scavengers for meat.
40:31But running in this hot environment may have changed our bodies in other unexpected ways.
40:57In the searing heat of the African savannah, running for any length of time can be deadly.
41:06Keeping cool is critical to survival.
41:13Other animals lose heat and control their core body temperature by panting and by avoiding the hottest part of the
41:20day.
41:22Few animals hunt in the midday sun.
41:28But it's thought our ancestors were able to exploit this niche because they developed something incredibly effective.
41:41One of the really important ways that we keep cool whilst running is this. Sweat.
41:53But in order for sweating to work, we needed to lose our ape-like body hair.
42:01One of the most obvious differences between us and other apes is our hairlessness.
42:06But in fact, we're not really naked apes at all because our bodies are covered in these very tiny, fine
42:12hairs.
42:12So maybe it's more accurate to say that we are fur-less.
42:18And amongst those fine hairs on our skin are the pores of up to 4 million sweat glands.
42:26Which can pump out as much as 3 litres of sweat an hour.
42:35So combined with that furlessness, this means that we can very effectively and efficiently lose body heat from the surface
42:43of our skin through the evaporation of sweat.
42:47Now when you're running, you're generating much more internal body heat than you do whilst walking.
42:53And when you're running in a hot place like this, the need to get rid of all that heat is
42:58even more pressing.
42:59So this combination of furlessness and sweatiness has been put forward as just one of the physical adaptations that evolved
43:08in our ancestors for endurance running.
43:17And that means, in the heat and over a long distance, we can run down any animal on the planet.
43:24Because we can keep cool, and they can't.
43:31Our long distance runner's body became our secret weapon.
43:42It took nearly 5 million years of evolution to get from Tumai to Nariya Katomi Boy.
43:51In that time, our ancestors had abandoned the forest for the savannah.
43:58And had gone from being four-limbed climbers to two-legged runners.
44:09And standing up on two legs had an important knock-on effect.
44:14It freed up our arms.
44:18The anatomy of our legs was completely transformed as our ancestors became consummate runners and walkers.
44:26But what about our arms and our hands?
44:28I've got a really mobile shoulder.
44:31I have a forearm, which I can rotate 180 degrees, and a grasping hand.
44:38Now, these are all relics of our tree-living ancestry.
44:43But we took those old adaptations and used them for something completely new.
44:49Something that, in turn, would shape our future.
44:54And that was making tools.
45:04As far as we know, the first stone toolmaker was Homo habilis.
45:11Appearing around two and a half million years ago.
45:15And every human species since has refined and developed that tool-making ability.
45:23But we aren't the only animal to use tools.
45:29So what is it about being human that makes our tools so special?
45:42To find out, I've come to the Uganda Wildlife Education Centre.
45:47Hello, hello. I've got stuff in my pockets here.
45:51Hello. Hello, little one. Hello. Hello, hello.
45:57This is a place of sanctuary for young chimpanzees rescued from poachers.
46:02You're biting me. Oh, I know.
46:04I'm here to see how they use tools, but they just want to play.
46:11No, no, don't look at that. Don't look up there.
46:15So this is Nipper, who's three and a half and has about as much energy as a human toddler, I
46:22would say.
46:22You don't want to walk, do you? You want to be carried.
46:26Come on then, Nipper.
46:29As part of their rehabilitation, the chimps here are encouraged to do things they naturally do in the wild.
46:36What's this on here?
46:37One of them is termite fishing.
46:39Look at that.
46:40The centre has built this concrete copy of a termite mound, which is full of honey rather than insects.
46:49This little three and a half year old certainly knows what he's up to.
46:53Look at that.
46:56He's poking this twig into the hole and then putting it back out again with honey on it.
47:06There's no doubt these chimps can use tools, but it falls a little short of human tool use.
47:13And this might be linked to the way they hold them.
47:16If I was holding this twig, I'm choosing to hold it like that and pushing my thumb down to anchor
47:22it in my hand.
47:23The nipper is holding it like that.
47:28It's less dextrous.
47:30It's actually more difficult to guide the twig in.
47:35So could the secret to human tool use be in the way we use our hands?
47:46Our hands move with incredible precision.
47:50They contain a quarter of the bones in the body.
47:55Surprisingly, our fingers themselves have few muscles in them.
47:58They're mainly moved by tendons from the forearm.
48:03Yet, anatomically, our fingers and thumbs are very similar to those of our chimpanzee cousins.
48:11The extraordinary thing about chimpanzee hands is when you look at them, they look on the surface quite similar to
48:16ours.
48:16And in fact, inside they've got the same bones, the same muscles.
48:19So why do we use them so differently?
48:22There must be something going on which makes our hands unique and uniquely able to make and use tools.
48:40To unlock the mystery of the human hand, I've come to the capital of the United States, Washington DC.
48:50Here, new research is shedding light on the evolution of our hands.
49:11This is Professor Brian Richmond, and for his test I need to have one of my hands wrapped up in
49:17some very technical electronic equipment.
49:27This very strange glove-like contraption looks like I'm about to play a bizarre virtual reality computer game.
49:33But in fact, these blue strips are pressure transducers which are going to allow me to capture information about how
49:41my hand works in real time.
49:44And you can see it on the screen behind me.
49:49The special strips in the glove measure the pressure I'm generating through each of my fingers.
49:56From left to right on the screen you can see the force applied to the little finger, ring, middle finger,
50:04index finger and thumb.
50:07The bones and joints of our hands, the muscles and the nerves that supply them are set up in such
50:13a way that we have incredibly fine control over the movement of our hands.
50:19But it's not really about moving our hands freely in space.
50:23It's about the pressure that we can apply to objects.
50:30That looks so easy, but tell that to a chimpanzee.
50:36Chimpanzees usually hold a piece of fruit in two hands to eat it.
50:41They don't seem to be able to apply enough pressure with their fingers to bite into it whilst holding it
50:47with just one hand.
50:49In chimpanzees, all of the fingers are very firmly attached within the hand.
50:54But in our hand, the third is firmly attached and the others are more mobile, particularly the fifth finger.
51:00So we can move that little finger within the hand much more than an ape can.
51:04And we can even rotate that little finger around to meet with the thumb on the other side.
51:09It's almost like having a little thumb on the other side.
51:11It is, it's facing the thumb across the palm.
51:14Precisely.
51:14So it allows you to grasp around an object.
51:17So with my electronic glove fully activated, it's time to test just how powerful my flexible little finger is.
51:25And look at that. That's right, you have, you can see the pressure on your little finger and your thumb
51:29on the other side.
51:35Our hands are, they're so mobile that they can conform in any variety of ways to handle any variety of
51:42objects.
51:42And that's what makes our hands so special compared to the hands of other monkeys and apes.
51:47But there's something else which we have and chimpanzees don't.
51:52It's very obvious when you compare the bones.
51:55The thumb in a human hand is just so much longer and thicker.
51:58Yeah.
52:01You think of how powerful a chimpanzee's hand is.
52:04And ironically the thumb is quite weak compared to the big powerful thumb that we have.
52:09Yeah.
52:10But that big thumb is a relatively new bit of anatomy.
52:14It's only been around for the last two and a half million years.
52:19And it first appears in Homo habilis, our ancestor who made those early stone tools.
52:29It seems more than a coincidence that big thumbs appear at the same time as stone tools.
52:34And it's always been thought that the two are linked.
52:39Fortunately, we have the technology to put that theory to the test.
52:44OK, I'm ready. I've got the hammer stone in my hand that's strapped up to the monitors.
52:49So stand well back.
52:51OK.
52:56There you go. Good.
52:59So if our big thumbs are important for making stone tools, you'd expect to see a large pressure spike on
53:06the screen for my thumb.
53:12What was actually going on with my fingers and thumb?
53:14So we can see right here that you have force on your thumb, but you have just as much force
53:19on your other fingers as well.
53:21I don't see particularly high force on the thumb.
53:24Why on earth, then, did our thumb become so big and strong?
53:30If it's not making stone tools, could it be linked to how we use them?
53:36Let's see what happens when I cut some meat.
53:39That's great. Good.
53:41You can see it's sharp. It's really cutting in, right?
53:43It's incredible. Yeah.
53:45Look at that.
53:46OK. Let's see how your thumb is doing.
53:49Oh, and look at that. The thumb pressure is very high.
53:53It's as high or higher than it is on the fingers.
53:59That's really interesting. It's a very different pattern from when I was making the tool.
54:03Absolutely. And what that tells us is that your thumb is having to really forcefully pinch that tool while it's
54:10being used.
54:10And that's not what we saw when you made a tool.
54:12So this tells us that maybe it's using a tool that's more important and helps explain the evolution of a
54:18big, robust thumb instead of making a tool.
54:24For the first time, it's becoming clear that it's how our ancestors used the tools they made that shaped our
54:32anatomy.
54:36The bones in our hands developed as our ancestors' behavior changed.
54:44It's fascinating to look at the shape and the function of our hands today and to realize how that has
54:51been brought about through evolution.
54:54We think about our thumbs being so important, but it turns out our little fingers are incredibly important as well.
55:00And what's really amazing is that our hands have changed because of something that we've done.
55:07It's not just about adapting to our environments. It's about adapting to things that we've made.
55:14The tools that we have created have shaped our hands.
55:22And that ability to use tools didn't just transform our anatomy. It utterly changed our world.
55:40Dexterous and powerful hands were fundamentally important to the success of our ancestors.
55:52Our species, Homo sapiens, only appeared on the planet around 200,000 years ago.
55:59But we are the most successful human species ever.
56:09With our hands, we could make the tools and technology which allowed us to colonize every corner of the globe.
56:21But they also enabled us to do much more than that.
56:31They gave us the means to transform the world around us.
56:50Like this dynamically, we can receive an opportunity to transform our roots in life.
56:51This is a superhuman pioneers attraction such as ''Theosier space''
56:51... and which they remainedDo 11 years ago,
56:53Want to be sure to transform our innate bodies?
56:53How do they recognize that we are or the others bite?
56:53And we'll see each other Deixa-in-amas.
57:02I thought our enemies erle себя about the astral completely.
57:04We weren't paying attention to для dessas art.어서
57:12But it all started back in Africa with an ape who got up on two legs and walked.
57:26Our bones and muscles form the foundations of two fundamentally human characteristics.
57:32We are bipedal apes and we are toolmakers.
57:37On our long legs we strode out of our continent of origin and went on to colonise the globe.
57:44But the dexterity of our hands enabled us to make tools and transform our environment.
57:51And I think it's really humbling to realise that our greatest achievements are
57:58our most advanced technology, soaring architecture, exquisite art and music,
58:04they all depend on an unpredictable series of anatomical adjustments
58:10that changed our ancestors into walkers and runners and sculpted the hand of the toolmaker.
58:35Our brand new series on the history of electricity continues this week.
58:40The final part of Shock and Awe is here on Thursday at 11.
58:44Hill.
58:47Hill.
58:50Hill.
58:54Raul.
58:56You
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