(soft music) - I've known and met a lot of great fossils, but Lucy is the paleo rockstar.

- We look at her and we see a tiny human almost.

- I remember seeing the reconstruction of Lucy's skeleton.

That was it.

I was hooked.

- The discovery of Lucy really hit paleoanthropology like a sledgehammer.

- Lucy's species gave up being good in the trees in favor of being good walking on two feet on the ground.

- When I discovered Lucy, I had no idea that she would have this extraordinary impact.

- Before Lucy came along, we were mesmerized by an idea of human evolution as being a slow and steady history of sort of linear improvement.

- Lucy has impacted so many people, even big guys like Barack Obama.

- She's the best known member of the human family.

- Well, there's this skull and there's this skull, and then suddenly they're presented with this almost complete skeleton.

- I've been joking that she's sort of the Taylor Swift of human fossils and she was the benchmark which was used to compare all finds of older hominins after her discovery in 1974.

- Lucy was the first specimen that gave us an idea of how humans worked.

By 3.2 million years, human ancestors were working on two feet.

- And of course we're very curious.

It's like a detective story 3.2 million years ago with most of the evidence gone, what can you make of what evidence is still there?

- When we think about earlier human ancestors, we always think about like them being much smaller than ourselves, right?

But sometimes, when you look at, you know, their jaws like what I have in my hand, this is a Lucy's species, australopithecus afarensis, and it's really huge.

And you wonder like what were they doing with all these big teeth?

Why do they have big teeth?

What were they eating?

Understanding what they were doing with their teeth, understanding their size.

All of the information that we try to get from like the bits and pieces of fossils that we find are really critical.

But sometimes when we're lucky, we find partial skeletons like Lucy's.

- A lot of science has sprung from first, a single, then what became a small pile of bones, and it keeps coming.

Hi, I'm Catherine Anaya.

We're inside the Institute of Human Origins at Arizona State University.

50 years after the bones were discovered in Africa, the science spawned by the Lucy fossil is still growing.

These are casts of her bones and this is a recreation of what Lucy might have looked like.

I'm a bit taller than one and a half meters, five feet, one inches tall, a full grown adult.

Scientists are sure Lucy was fully adult too, but only about one meter or three and a half feet tall when she was alive.

We can't know exactly what she looked like in life, so this reimagined model combines both science and art.

It's an interesting story on its own, a story we will dig into along the way.

Studying Lucy speaks to our need to know who we are and where we come from.

Lucy is connected to those questions in ways that touch not just our past but also our present, and even our future.

- Yeah, I study, you know, slips and falls and how people fall, and falling is inclusive of walking.

- [Catherine] No fossils here.

- Are we still same as Lucy?

I believe yes, we are.

- [Catherine] This is a biomechanics lab at Arizona State University.

- So we had to study walking and we had to go really back, way back, all the way down to Lucy.

- [Catherine] They're working on problems, like how to create new devices to predict and prevent older people from falling, and on solutions like an exoskeleton leg that might help us walk longer or carry heavy loads.

- We are always unstable, so we are basically falling and catching ourselves, falling and catching ourselves very, very precarious type of control system if you think about it.

- [Catherine] All this is about the future, not the past.

- If you look at our gait, our gait is amazing.

It is very, very efficient.

- [Catherine] Lucy is right here in this lab.

- The risk and the efficiency that we face today is still the same today, same as Lucy faced, we're facing that same thing today.

- [Catherine] Lucy and her kind were doing something risky, standing up.

- Lucy was a big deal.

We thought that she was bipedal, right?

The information came from her bone structures.

Looking at the pelvic girdle, her pelvic girdle is little a y and it can be incorporated with lots of muscles.

So the first requirement for bipedalism is upright.

You gotta be upright.

- Toes, feet, knees, hips, legs, they all have to come together in just the right way for us to walk the way we do, upright.

The search for fossils that led to Lucy's discovery began in Africa with the discovery of just one of those essential parts, two bones that come together to form a knee joint.

- I've had the extraordinary opportunity to work in Africa beginning in 1970.

And in 1972, I was working closely with a French geologist named Maurice Taieb, and we were exploring an area that was literally terra incognito.

It was the northeastern part of Africa's Great Rift Valley, a place known as the Afar Triangle.

And it was absolutely littered with fossil bones that we knew were older than three million years in age.

And we were hoping to find remains of our human ancestors at that time because we had really literally just fragments of fossils from other sites in the Rift Valley.

The discovery of the first evidence of early humans in this area known as Hadar came in 1973 when I found this little knee joint.

It's the bottom end of the thigh bone and the top end of the shin bone.

And what's important about this is how did it function?

Because it would tell us something about whether these creatures walked upright or were on four legs, for example.

And as you move it through its paces, it's identical to our own.

In fact, I showed this to an orthopedic surgeon when I was in Cleveland and he said that's exactly like the replacements we put in modern human knees.

It's got all of the anatomy and I won't go into the details, but it's got all the detail anatomy of how these bones fit together that's identical to our own.

So we knew that this came from a human ancestor, but we didn't know who that was and had all of the features of walking upright, which was very important.

But we didn't know who it belonged to, we didn't know what species it belonged to.

So this spurred us on to return in 1974 to see if we could find more complete remains of early humans at that site.

- So a lot of looking to find just two small but important leg bones.

Important because they point clearly to a creature that, like us, was walking upright.

Perhaps more important, simply because they made Donald Johanson hungry to go back to Ethiopia to search for more bones.

- And in 1974, on our second expedition to this area, I was out surveying with one of my graduate students, Tom Gray.

And in this area we had found a beautiful, to us, a beautiful pig skull.

And we were going to position it or put it exactly on our maps.

And as we looked around, there weren't many fossils, and it was noon and it was 110 degrees or something or other.

And we were tired and we were heading back to our Land Rover to go back to the field camp.

- [Catherine] Don Johanson and Tom Gray were about to call it a day.

Out of persistence or just plain habit, Johanson looked at the ground one more time.

- One of the questions that people often ask me about what happened on that fateful November 24th day 50 years ago was what was the first specimen of Lucy that I identified?

And I looked down at the ground, always looking for fossils, and it was this little piece, this little piece here, part of an elbow that caught my eye, and I picked it up, I looked at it and saw that it didn't look like a monkey, didn't look like an antelope, it didn't look like anything but perhaps a human ancestor.

And that is what led to the Lucy skeleton.

And as I looked up the slope, I could see parts of a skeleton.

I saw part of a femur, the thigh bone, I saw chunks of mandible, I saw shards of a cranium.

And I realized that there was a partial skeleton here and we knew from the geology that it was older than three million years.

And it turned out that we have about 40% of a single skeleton, which is popularly known as Lucy, named after the Beatles song, "Lucy in the Sky with Diamonds."

It was playing in camp that night and I thought that she was a female because of her diminutive size.

And someone suggested, "Well, why don't you call her Lucy?"

And it stuck and in many, many ways she has become the touchstone for people who become interested in paleoanthropology, the study of human origins, and arguably is probably the best known fossil human ancestor of the 20th century.

- Like most of the really big discoveries in science, finding the Lucy fossils answered some questions, but asked many more.

How old was she?

What did she eat?

How far could she move?

And perhaps the most natural question of all, what did Lucy look like?

Remember that Donald Johanson found mostly just chunks and bits of scattered bones.

They all had to be rebuilt into something like their original shape.

Now, 50 years later, a very special artist has taken that work and added a whole lot of additional research to recreate Lucy.

- With the face, there has to be more there than just a mannequin.

You have to be able to connect with that face.

You have to look into the eyes and feel that there's a presence there.

Otherwise you might as well not have done the reconstruction because you're trying to get across the point to viewers that this is a creature that actually lived and breathed and felt pain and felt joy and felt sorrow.

And so you need to get a look in the eyes that signifies a presence there, that builds up over time as you're working on a reconstruction.

So I'll be working late at night for example, and I'll be reading my notes, and I look up, and suddenly be startled by these eyes looking at me.

And when that happens, I know that I'm starting to succeed in bringing out a presence there.

That's a strictly non-scientific aspect of this kind of work, but I think it's very important in a reconstruction is to bring that presence into the eyes and the face.

What I hope observers get from this reconstruction is, first of all, a sense that this is a living being that lived somewhere back in our past, in this case a little over three million years.

I also want them to see that in many ways she shares features with great apes.

In many other ways, she shares features with modern humans.

Not that that completely describes her anatomy, she has many unique features, but she does have primitive features that are inherited from her ape ancestors, and she also has derived features that are held in common with modern humans that great apes don't have.

So she is in many ways a mix of features and I hope that comes across in the first instant of viewers looking at her.

- It's taken decades of work to unlock the secrets of the Lucy skeleton.

Did Lucy look and move like us, or more like our closest relative, the chimpanzee?

With some help from the California Academy of Sciences, let me show you why those questions matter.

(light music) Lucy and chimps both have an elongated skull with a small brain case.

Faces and jaws that jut out from the brain case under the skull.

Working our way down the body, both have shoulder blades and joints that are suited for climbing trees.

They both have long arms and hands with curved fingers.

Now let's put one of us in the picture.

Lucy and humans share a spine connection beneath the skull to keep the head steady.

Like us, Lucy has a robust broad basin-shaped pelvis to support the upper body and hold it upright.

Like us, she's got angled thigh bones that place the weight directly over strong knee joints.

And like us, compact arched feet that support the full body weight with every step.

I can do this with my thumbs across my palms, but none of us can really do that with our big toe.

Chimps can and that's why they can climb so much better than we do.

But because our big toes are straighter than chimps, we're better than they are at walking upright and running.

So what about Lucy?

For science, Lucy's big toe is a big deal.

- Lucy herself doesn't have any feet, but we have other fossils, we have footprints, and we have more recent specimens that show that Lucy's big toes were in line with the rest of her digits.

- We do have another foot from Hadar that has the big toe.

So that individual belongs to the same species.

So our knowledge of what the big toe looked like in australopithecus afarensis is not specifically from Lucy, it's from other individuals who were found here at the site.

- And it's pretty much immobilized in humans, you can't get motion out of that joint.

- The big toe in bipedality is one of the most important elements in our foot because that's how we toe off.

We toe off with our big toe.

- So, land on our heel, rock over our foot bones, toe off, off our big toe.

- The whole weight is being transferred to the ground through the big toe.

So the whole idea of bipedality in australopithecus afarensis has been tested not only from the shape of the bones of the foot, but also the traces that they left behind in the form of footprints at 3.6 million years ago.

- She had an arch on her foot, her foot is stiff, gives her a spring in her step, and it's just every bit like yours or mine.

And that means that she was really good at walking on two feet, but what she wasn't good at is climbing trees because if you only have one or two hands to grab onto trees and your feet aren't very good at it, you're not very good in the trees.

I can climb trees, I'm not very good at it.

So afarensis, Lucy's species, gave up being good in the trees in favor of being good walking on two feet on the ground.

This would've been especially important for a female who most of her adult life would've been carrying a child and having only one hand to use to move around in the trees.

So sure, they may have gone on the trees, but they weren't very good at it.

And the most important thing for these animals was walking on the ground on two feet, that's what natural selection cared about.

- You can see that we're bumping into more very natural and very fun questions about Lucy.

Lucy's pelvis tells us that she was female.

Her teeth tell us that she was an adult.

Those two facts point to a natural question, was Lucy a mother?

And if so, what might her babies have looked like?

There's no way to know for sure, of course, but some new finds have been made after Lucy was found that give us some great hints.

- So the the Dikika child is a fossil that I discovered at the site called Dikika in Ethiopia back in 2000.

And when discovered, we saw the skull, which was an almost complete skull.

It belongs to the Lucy's species, australopithecus afarensis, but it's a juvenile, and it's almost 60% complete compared to Lucy, which is 40%.

So when put together, the Dikika child represents the earliest and most complete child ever discovered in the history of paleoanthropology.

At the time of death, she was two and a half years, and she died 3.3 million years ago, which is 150,000 years before Lucy.

She was a child, so there is a difference in terms of morphology between the juveniles, the young individuals, and the adults like Lucy.

But if the Dikika child was to grow to be a grownup, then she would've looked like Lucy, obviously.

After Lucy, we also had found grownup with males, but the children were missing.

Therefore, the discovery of the Dikika child completes the family because now we have the adults from Hadar and we have the child from Dikika.

- So what's it like on the ground in Africa looking for fossils?

Hard work.

Let me give you just a glimpse of some of the terrain of Hadar, Ethiopia.

This is where the bones of Lucy and bones of others of her species have been found.

Layers of soft crumbling rocks and soil shot through with fossils everywhere you look, bones of mammals and reptiles, all from different and distant time periods.

- I've had a blast!

Now, albeit the first day of fossil hunting was very hot.

- It is a lot.

I would say it's draining both mentally and physically.

- I think I have sometimes like a picture of a certain hominin in my head sometimes, when I look and a certain outcrop and there are some outcrops that you expect you'll find something and then you go there, there's nothing.

- The steep slopes tend to be where the fossils are found best, so you're not just walking across flat ground, you're going up hills, you're going down hills, you're going up hills, you're going down hills.

My name is Irene.

I am currently an Assistant Professor of Anatomy at the West Virginia School of Osteopathic Medicine, which I know sounds kind of weird, but it's because I am a biological anthropologist by training and in fact a lot of paleontologists and biological anthropologists work in medical schools and teach anatomy because we have this really great link from what humans look like on the inside today to what our fossil ancestors looked like.

That's sort of how I got to be connected.

I went to graduate school at Arizona State.

- It's kind of, I don't wanna get my expectations too high on if I can find a hominin, but I am looking, anytime that you see me walking around, I'm steady looking at the ground trying to find something.

I'm Jyreh, I'm a third year PhD student at the University of Texas at Austin and I study hominin fossil preservation.

Yeah, so the story of Lucy in any intro or introductory bio anthropology course when you get to the hominin and human evolution section, Lucy is a big component.

- You will think you'll find what you are looking for and you have something in your head and then you are just working and then working and then working and sometimes you find interesting stuff.

My name is Blade Redae and I'm a Postdoctoral Researcher at the IHO Institute of Human Origin at ASU.

- You know, we have so much data on fossil hominins and we know sort of a lot about the timeline of when they're revolving, and how they change, and why they might be changing.

And we don't always know that for other animals.

And so part of the idea is that we can use these other animals to test like, "Oh, do we think there's a change in climate?"

And that's why the hominins are changing.

- For me, a good day in the field is when you find either a hominin or like older one stone tools or a cut mark.

And I would really, really get excited and then I try to to find like what was the role of how were they using tools to access meat or not.

And then if they were like, to what extent.

- It's always like, "Oh, what can I find today?"

Or "What cool or unusual bone can I find and identify today?"

Especially since this is my first time fossil hunting, it's a good practice for me to actually identify things that I've learned in the classroom.

Now I can actually use it out in the field, which is pretty nice, but for me personally, it's also showing other people of color and other students of color like, "Hey, you can actually get out of the country and go do work just like this."

- Finding fossil bones is one challenge, figuring out how old they are is another.

To unlock the full story of any fossil, you have to understand the geology, the layers in which they're found.

In many ways, to understand the bones, you have to understand the stones.

- It's hot and dirty, I mean every aspect of it, whether you are looking for fossils or doing geology or archeology, the only way to do it is to cover a lot of ground, both laterally and vertically.

I am Chris Campisano, I am Associate Professor at the School of Human Evolution and Social Change at Arizona State University as well as a Research Scientist at the Institute of Human Origin.

- This place is huge (laughs) and it goes on and on and on.

It's 100 degrees and it's a blazing sun.

I'm Beverly and I'm a Professor at Case Western Reserve University, and I ask questions about the links between changes in the environment and the evolution of animal life over timescales of hundreds of million years to the last few thousand years.

- There is what I observed in the field looking at the soil, but really until I break inside of it and really look at a microscope, there's a lot more that we can find out.

My name is Evan Madill, I am a PhD Student of Geology at Case Western Reserve University.

- So I sort of wanna know where the fizz is, where the carbonate is, and where it's not.

I'm Naomi Levin, I'm a Faculty Member at the University of Michigan.

My research is to reconstruct what landscapes and organisms were like in the past using geochemistry.

And we've gotta scramble, we wanna get to a specific interval and we've gotta scramble up to it, so sometimes it takes digging a foot hole with a pick and to sort of get in there, but we really want something quite specific, so we have to scramble, slide, I'm actually constantly testing the rock to see what fizzes, so what is carbonate?

If it fizzes, I put the acid on it and so it creates little bubbles of gas that shows the reaction.

Then it basically bubbles up and fizzes.

- The steps expose the different layers of rock that represent really the environment at each point in time.

I'm Dan, I'm a Professor at the University of Tennessee, Knoxville.

Then I also try to find traces of life, plant roots, or burrows of animals.

When those well-developed soils occur, I can actually see them from the bottom to the top to characterize what that soil was like at that particular point in time.

- Lucy was found in an area of Ethiopia called the Afar Desert.

It's a harsh and challenging place to work or live, but it's home to the Afar people.

And for the past 50 years, they've been an important part of the search for new fossils.

(soft music) - So the Afar are the inhabitants of the Hadar area and Afar region.

They primarily are pastoralists with goats and sheep and camels, and periodically cows.

They often frequent the towns even if they are pastoralists out in the field here, they rely on the region for grazing and they move often.

The Awash River is obviously a major source of water for their livestock and they are irreplaceable for our project, we use them as fossil finders, as guards for us, as helpers to set up camp and do various other things.

And of course we're on their land, so we try to integrate with them as much as possible and have a good relationship with them.

We typically hire far more than we need just so that we can help out.

And they have been key to this project finding some of the most major fossil finds since the '70s.

So they are just as much part of the Hadar Project as we are.

- Here's one more question science hasn't answered yet, did Lucy and her species have language?

Did they speak?

That's a question scientists are still discussing now 50 years after her discovery.

Donald Johanson, the man who found Lucy is looking back at Lucy, but also looking forward.

He wants us to ask some big questions of ourselves and of our shared human future.

Since Lucy can't speak for herself, let's give the final word to Donald Johanson, the man who found her.

(gentle music) - Extinction is forever, and if we go extinct, there'll never be humans again on this planet.

Paleontologists estimate that more than 95% of all life that existed on the planet has gone extinct.

Studying our ancestry links us to the natural world.

We know that we have been crafted by natural selection over millions of years.

Species have come and species have gone.

And I feel we are at a crucial point in the history of humankind where we must make the right choices so that our species will exist long into the future and our descendants will think back and look at us.

We will never see Lucy's species again, and we will never see Neanderthals again.

They survived, but they didn't survive to present day.

We are alone.

We are a sole species on this planet, we have inherited whether we like it or not, that incredible responsibility, frightening responsibility to be protectors rather than destroyers of this planet.

The future of the planet, the future of our species, the future of our descendants, the future of all of our fellow travelers now rests very firmly within our hands.

(light music)