Kromdraai: Children From The Cradle Of Humankind

In a remote part of southern Africa is a UNESCO World Heritage Site, known as the Cradle of Humankind. More fossil hominids have been found in this valley than anywhere else in the world. Yet the story of our origins is still full of gaps.

And despite the archaeological treasures found in this unique place, we still do not know what the first humans were like or how they came into being, because hardly any fossils from the relevant period have been found. However, the paleoanthropologist Jose Braga has recently begun excavating at Kromdrai, in a sector of the hill that has not previously been explored. The fossil bones now being unearthed might well provide the precious missing clues needed to answer the riddle of our origins.

It is a dizzying thought. Solving the mystery of the first humans would not just mean finding out what they were like and how they emerged in the prehistoric savannah. Above all, it would mean finally comprehending what caused us to diverge from the other primates and made us human.

Jose Braga may look like a character from an adventure yarn, but he is one of the world's most highly regarded paleoanthropologists. Equally at home in the dust of the African bush or in a research laboratory, he has spent his entire life seeking to fathom our origins. For thirty years he has been coming up against the same obstacle, vital pages are missing from the history of humankind.

Whole sections of our family tree are at blank. When we look into the origin of the subspecies to which all present humans belong, Homo sapiens sapiens, most everyone agrees that all humans who inhabit the Earth today have an African origin somewhere around one hundred thousand years old. However, if we delve much further into the past, over a period that is twenty times older, about two million years ago, we realize there isn't a consensus.

The genus Homo appeared at that time, while others delved deeper into humanity's origin around three million years ago. Given this, there is a broad debate and a total lack of consensus. Professor Braga is convinced that if there is one place that can provide answers, it is in South Africa, in this valley, fifty kilometres northwest of Johannesburg.

Most of the fossils on which current knowledge about our history is based, were found here, in the cradle of humankind. Around seven million years ago, one particular branch of the tree of evolution split off from the great apes to form the hominins, a group that includes pre-humans and humans. Over the years, several pre-human Australopithecus skeletons from over three million years ago have been found.

All the finds from after two million years ago indicate that by then, Australopithecus had completely disappeared and humans had arrived. But for the moment, nothing is known about the transition from Australopithecus to humans. The period between three and two million years ago is a blank.

No hominid fossil from this period has enabled scientists to solve the mystery of how humans emerged. The mystery Professor Braga has been attempting to solve all these years, here, in the cradle of humankind. In the early two thousands, he was put in charge of one of the valley's emblematic sites, the hill of Kromdrai.

He was the first Frenchman to inherit one of these archaeological jewels. But it was a jewel that had lost its sparkle. Although promising fossil evidence was found at Kromdrai when the site was first discovered in the nineteen thirties, very little had been found since, and interest in the site had gradually waned.

During their first ten years of excavation, the French team unearthed few important finds. It looked as if the seam really was exhausted. But Professor Braga's intuition prompted him to keep looking.

He decided to try a different approach, and use new technologies to analyse the site. Professor Braga believes the Kromdrai site is bigger than is generally thought. To test this hypothesis, he has a photogrammetric survey done of an area extending beyond the historical excavation site.

By comparing the resulting three-D map with soil chemistry analysis, he hopes to detect additional locations with fossil-bearing potential. The results reveal Kromdrai in a totally new light, extending northwards from the historical excavation site is an area that is geologically similar to it. Professor Braga decides to excavate the new sector, even though it has always been thought that it contained no fossils.

He has an inner sense that this totally unexplored area will yield astonishing finds. After all, this is the cradle of humankind, the place where the greatest paleoanthropological discoveries occurred. Surely Kromdrai can be no exception.

So why is this area so uniquely rich in fossils? The level of soil erosion here is among the lowest in the world. Stratas several million years old have remained intact.

By a geological fluke, the valley has provided a safe haven for ancient fossils through the ages. This extraordinary permanence makes it easy to reconstruct the landscape at the time of the first humans. It would have looked almost exactly the same as it does today.

These hills were home to the earliest humans. Before they have even started to explore the subsoil, the archaeologists are on the trail of our distant ancestors. They dig energetically in the new excavation area.

Professor Braga's hypothesis about the true extent of the Kromdrai site is soon confirmed. But he scarcely imagines how right he was. And he has not yet grasped the full implications of this miniscule find.

Look, that's a tooth bud. A primate tooth bud. Damn, I'm in the maxillary.

What is this? What is this? That's beautiful.

It looks like an inferior permanent tooth bud. It's not that bone. No, no, that's not a bebon.

It is a fantastic find for the start of an excavation. The archaeologists haven't just unearthed a few odd teeth. They can already make out the jawbone.

Damn, it's hominin. Exceptional. This is unique.

The paleoanthropologist has recognised a member of our genus at a glance. Once the fossil has been cleaned and assembled, he realises how important it is. An almost complete lower jawbone of a hominin child, in a perfect state of preservation.

Now the challenge is to find out what genus the child belonged to. Was it an Australopithecus, a human, or perhaps a representative of the mysterious transitional period between the two? To move the investigation forward, Professor Braga has asked Benjamin Moreno, a medical imaging specialist, to create a digital double of the precious fossil.

Features invisible to the naked eye are revealed with amazing precision. So, we've integrated the data that you provided to us on the mandible of the crumb dry child, and we've also segmented all of the tooth buds, It's extraordinary. Absolutely extraordinary.

Here, I've never seen that on Australopithecus. On Australopithecus, you never have central or lateral incisors of this width. This characteristic confirms the visual impression I had when I found this mandible.

We'll add additional criteria to affirm. I mean, affirm that we're dealing here with a human mandible. The shape and position of teeth are specific to each species.

The teeth rooted in the mandible stopped growing at the stage they had reached when the child died, offering a fantastic snapshot. Professor Braga is now certain that the mandible belongs to a member of the genus Homo. But where does the individual belong on the tree of evolution?

This baby from Chrome Dr has an association of characteristics that is completely new. It's both modern and primitive at the same time. You see this little canine, for example?

It has very primitive characteristics of Australopithecus. We have a completely new mix of Australopithecus characteristics and ultra-modern characteristics that we've never seen on such ancient fossils. Clearly human characteristics, without a doubt.

And if we had found this individual when he was a few years older, we wouldn't have that information. So, the fact it's a baby. In fact, the information is essential ?

Yes, because today we don't yet have a very clear idea of what makes a human millions of years ago. I'm convinced this is its growing stages. And to be able to say this, we have to find human babies.

And we have one in front of us. The fact that the child died so young is a boon for paleoanthropologists. Professor Braga is convinced that a species' defining characteristics are to be found in a jawbone that is still developing, and disappear once the jaw is fully formed.

This young human has retained much of his Australopithecus inheritance. Everything about this baby suggests that it belongs to the transition period. But Professor Braga has to check that he is right by dating the finds scientifically.

Now that we have our Chrome Dr child, the problems begin. There are problems I like and problems I don't like. I love this one, but it'll be complicated because we'll have to date this fossil, especially to know if it's older than two million years, or from after two million years.

I'm absolutely convinced it's older than two million years, but that's not enough. We'll have to prove it. This is just the start of a thrilling archaeological experience.

Dating the chrome-dry child is a challenging and highly complex task. None of the usual techniques such as DNA analysis or carbon-fourteen dating are possible with remains this ancient. The age of the fossil has to be worked out indirectly by dating the soil layer in which it was found.

That is easier said than done. The site will have to be painstakingly excavated for chronological clues. Professor Braga has assembled a team of experienced geologists to assist him with this mammoth task.

First, they need to work out how the subsoil is structured in the new excavation area, a near-rectangle bounded by calcareous rock walls that are in an advanced state of degradation in places. Do you have the impression that the blocks are completely altered? Absolutely.

You have the impression that all this was fucked, like you said? Yes, there must have been water but not circulating water. Before the excavation can continue, the team has to work out why this stagnant water was there, and what it reveals about the geological history of the site.

That history might contain precious information about the period in which the chrome-dry child lived. The clue to how chrome-dry subsoil formed is to be found just a mile away, in the bowels of the famous Sterkfontein site. It was here, in these underground galleries, that Littlefoot, the most complete australopithecus skeleton ever found, was discovered in nineteen ninety-four.

Pastologist Laurent Bruxelles led the team of geologists who succeeded in dating Littlefoot. After years of research, they established that the layer in which the fossil was found was three-point-seven million years old. Laurent specialises in caves.

He knows this labyrinth like the palm of his hand, and has studied each stage of its formation. We arrive in the galleries which have kept the traces of the cave's formation. There.

We see the process taking place here. Below the water table, all that is bathed in water that flows very slowly and will gradually wash away the carbonates or magnesium solutions, and anything non-soluble or less soluble will remain in place. As the valleys widen, the groundwater level goes down, and the very porous ghost rock will tend to disintegrate into itself.

And so we have caves that are tens of kilometers long and are veritable labyrinths where one can get lost. The history of the Sterkfontein cave spectacularly reveals the true nature of the chrome-dry site. The geologists have seen rocks that have undergone the same process of digestion at the dig.

Both sites belong to a single underground network. This visible surface rift is the remains of a collapsed gallery that was part of it. Until Professor Braga's team arrived, excavations at chrome-dry were restricted to this narrow strip of land.

In fact, it opens onto a much larger chamber that had gone unnoticed by earlier archaeologists. Incredible as it may seem, the area now being excavated at chrome-dry was once the interior of an underground cave. It has lost its rock ceiling and has been completely filled in.

This is where the chrome-dry child was found. Now the archaeologists need to understand the process by which the cave was filled. It is the only way to date the precious fossil and get a step closer to knowing who our ancestors were.

We're in one of the great rooms of Sterkfontein. It's about thirty meters long and twenty meters wide, and about thirty meters high. It's exactly the size of the Kromdrae site.

It's interesting because we have the cave here before it got filled. Today we still have a vault separating us from the surface. It's a good ten meters of rocks.

But we must imagine, if we continue the geological evolution, that little by little, as erosion thins the vault, one day an entry will form. And in through the entry falls pebbles, earth, plants, but also animals which will constitute all the fossils that we are looking for. It will gradually form a mound in an hourglass form, a natural hourglass that contains passing time.

And these rooms are temporal traps, meaning we've kept for several tens of thousands of years or several hundreds of thousands of years the memory of what was happening on the outside. The cave continued to fill up until the aperture was blocked, for instance by a rock slide. The absolute stillness inside the cave enabled the bones to fossilise.

In tandem with this delicate process, stalagmites gradually formed on the talus. Meanwhile, the rock ceiling was eroded from outside. When it reopened, a talus from a more recent period formed on top of the earlier one.

At chrome-dry, the entire ceiling and the top of the talus were eventually eroded, bringing fossils from the dawn of time to the surface. So here we have a sort of snapshot of what Kromdrae could have been like four, five or six million years ago, before the room was connected with the surface. And this room is a sight in the making.

The day when erosion opens the vault, a mound will form, and we will record a new part of the evolution of man. The Sturckfontein chamber mirrors the long-vanished chamber at chrome-dry, providing a fantastic opportunity to go several million years back in time and work out how these amazing fossil traps operated. At chrome-dry, the infill in the former cave looks uniform.

But electromagnetic analysis reveals that it is made up of different talus deposits piled up on top of each other. Each one contains the memory of a specific period. The geologists endeavour to trace the contours of the talus in which the human jawbone was found.

Professor Braga concentrates the excavations here, in the hope of finding chronological clues that will help date the chrome-dry child. Ah, a tooth. See, this is a very pretty Bovet incisor.

Very nice. Jean-Baptiste Fourvel is an expert on animal fossils. He can identify a species and its level of evolution from just a fragment.

Careful, it's fragile. Right. The clues it provides might enable him to estimate when the animal was alive.

A femur. Is it bovid? Yes.

The palaeontologist concludes that these bovine bone fragments belong to a small antelope. The chrome-dry child's clan lived in this African landscape and would have shared their territory with this species. What can the bone fragment tell us about their environment?

I'll try to restore all the links in the chain from the death of the animal until the day we took it from the ground. And all these elements allow me to finally describe the ecosystem in which the hominins evolved. Based on what I identified in Cromdry, we are still in an environment that is quite open, like savanna, a wooded savanna.

We have springbok, a small antelope that still lives in herds. The way antelopes live today is very similar, or at least comparable, to species of two million years ago, or even earlier. So it's a safe bet that the environment we have in Cromdry is quite close to this wooded savanna.

But although the bone provides clues to the animal's environment, it comes from a species whose anatomy is known to have remained virtually unchanged for millions of years, so it is no help with dating. The team needs to find remains from species whose anatomy altered more significantly over time. After only a few hours digging, a compact block has been extracted from the area where the fossils were found.

Where the earth has been loosened, the team can make out more fossil bones. But in order to study them, they will need to clear away a thick coating of sediment. In his field laboratory, Jean-Baptiste Fourvel attacks the hardened sediment with a dentist drill.

It is a tricky process. The fossils must on no account be damaged. I thought it was a feline, but I didn't get any further than that.

When it's cleaned, I'm going to have the whole palate and the whole face of a saber-toothed feline a little over two million years old, like a Meganteria. The discovery of the Meganterian fossil is a real turning point, because it is known when this species appeared and died out. It appeared about three million years ago, and became extinct just under two million years ago.

At last, the archaeologists have a date range for the chrome-dry child's jawbone, which came from the same talus. Their hopes soar. These findings take them a step closer to the transition period between Australopithecus and Homo.

A time when a fearsome predator reigned over the savannah. It is vital to narrow the date range for the chrome-dry child, to determine precisely when humankind as a whole first appeared. An undertaking of such importance calls for close cooperation between the various specialists on the team.

The next stage of the investigation will once again draw on the resources of geology. The collapsed cave contains an odd vertical concretion. It looks as if it had been set on top of the talus the archaeologists have been excavating.

Laurent Bruxelles has studied it at length. Here is the Kromdrae stalagmite. It's very important because it is the only one we know of in the cradle of humanity that is in place.

This stalagmite can be dated. We know how to do analyses on it and determine when it was formed. The drops of water that formed this stalagmite long ago contained minute quantities of uranium.

Over time, this element was slowly and steadily replaced by lead, creating a natural atomic clock. By measuring the ratio of uranium to lead, the geologists have been able to estimate the stalagmite's age. It is between two and two point three million years old.

So the talus on which it formed, the one containing the chrome-dry child, must be older. The stalagmite provides spectacular confirmation of the dates inferred from the saber-toothed cat fossil, and takes us even further back, beyond the two million year mark. A body of corroborating evidence now confirms that the chrome-dry child lived during the transition period, between Australopithecus and Homo, the blank every paleoanthropologist longs to fill in.

Finally, what the Kromdrae site documents is exactly what we are missing at Sterkfontein. Here we have the link between the appearance of Australopithecus and the appearance of the genus Homo. In Sterkfontein, it corresponds to a time when there was erosion, so we lost these levels.

We have them here in Kromdrae, and it is here that we'll be able to make the link between all the stories of the entire cradle of humanity. The discovery of the chrome-dry child really is as important as Professor Braga divined. We now know that it is the earliest human child ever found.

Given how crucial fossil children are to modern paleoanthropology, the research being conducted in the laboratory takes on a new importance. It might at last shed light on the first humans, and tell us how they differed from Australopithecus and from modern humans. Between two and three million years ago, all the fossils we have we can almost put in the palm of my hand today.

And these fossils, among them, we have no children. Now in Chrome Dr, we have a child. And thanks to the characteristics we observe on it, we can define what a human could have been two million years ago.

We did a three-D scene from the data you provided us, to compare the mandible of a modern two-year-old baby, with the mandible of the crumb dry child, and with the mandible of the tongue child. Right, the Iconocostal Rhythmicus baby. The first Australopithecus to be discovered, known as the Tong child, was found in nineteen twenty-four, also in South Africa.

But at the time, scholars were only interested in adult's bones. So the official discovery of the genus had to wait for over a decade. This unique fossil of a young Australopithecus is vital for the comparisons Professor Braga wants to conduct.

So the Australopithecus child in red, Chrome Dr child in blue, the actual child. So now if you can do a profile, a mid-sagittal profile, we can cut half of the chin to see a chin symphysis. Super.

You see, the Tongue child really doesn't have a chin. It's completely oblique. You see, the human Chrome Dr child's profile is very vertical on the anterior portion.

He's very far from that. Not only because his chin recedes much less than that of the Tongue child, but even the width of this region, called the symphysis, is much smaller. This is added to the morphology of this tooth that's already moving away from Australopithecus.

So we have a whole set of characteristics that allow us to establish a portrait of this human child and that allow us to say that it is much closer to a modern child than to an Australopithecus. This is a real intellectual revolution. Much more modern than what we thought until now.

We'll have to push the analyses further because in recent years everything that until now has been used to consider that we had a human several million years ago, all these criteria have fallen. Bipedalism, tools, the large brain, these three characteristics have fallen. We know that the tool is Australopithecus.

We know that bipedalism is Australopithecus. We know that the large brain is after the first humans. On the other hand, more and more we think the criteria we must absolutely explore to define humanity, to define the first homos, are criteria linked to human development.

And here, because we have a fossil of a baby, we can answer this question for the first time. This human child, over two million years old, has only just begun to reveal its secrets. No paleoanthropologist could have predicted that it would be this modern.

The next stage is the most exciting but also the most difficult, identifying the characteristics that allowed us to enter the world of human beings. In tandem with this totally new type of anatomical exploration, the field investigation into the origins of our genus continues. As he reconstructs each stage of the cave's history, Laurent Bruxelles gleans more information about the lifestyles of the first humans.

There is a time when the cave functions as a trap. The animals fall into it or animal remains fall. They accumulate in the cave.

Then there is a time when the entrance is eroded enough so that the animals can enter the cave on their own and use it as a shelter. Thanks to the work of Jean-Baptiste, we can see this passage very well, the moment when we pass from the trap to the carnivore layer. And we see it not only in the nature of the deposits, that's what geology indicates, but also with the fauna, which paleontology indicates.

What I observe on the bone, at least the upper part, in large part anyway, is an occupation by predators. We can't exclude that part of the bones are the result of another phenomenon. The geologists have added a crucial chapter to the history of Krondrei, which must have occurred before the rock ceiling had totally disappeared.

The cave must have continued to fill until the talus reached the aperture in the ceiling, allowing live animals to make their way inside. At the time when humankind emerged, Krondrei was used as a den by predators, and most of the fossils found in the talus are their prey. But where did the first humans fit into this daunting ecosystem?

Human is an opportunist. He eats meat, but is not a great hunter. He takes advantage of the carcasses that are provided by other large predators, big cats in particular.

It's funny to think that two million years ago, we were mainly scavengers. We profit from what others killed. We are also prey.

We are easily eaten. So finding the remains of our ancestors in Cromdry, who are the prey, it's exciting. All the questions this poses about how we've changed, how we've evolved, that's very exciting.

To learn more about the first humans, the team needs to find more fossils. Comparing the Krondrei child with an Australopithecus and a modern human of the same age was a necessary stage, but it's not enough. To redefine what it means to be human, they need to compare this child with the other hominin genus from the same period, Paranthropus.

Etymologically, Paranthropus means next to human. The reason scholars chose this name was that Paranthropus is our closest relative, descended like us from Australopithecus. It probably appeared during the same period as the genus Homo.

The very first Paranthropus was discovered right here in Krondrei, almost eighty years ago. The South African paleoanthropologist Francis Thackeray played a part in the story of this amazing discovery. In nineteen thirty-eight, a young schoolboy was walking from Stoke-Fontaine to his school and he discovered some teeth sticking out.

He knocked the teeth out with a stone and he took it to Dr Robert Broome. And together, this schoolboy, Gert de Blanche, with Robert Broome, had discovered a very important specimen of Paranthropus robustus. They found the fossil, but they did not record the exact position where the fossil had been found.

I tried to solve the mystery by doing chemical analysis in the rocks with the fossil, and then I excavated some of the rocks from the site and did a similar chemical analysis. So we plotted it all on a big map and we were able to say this is probably the spot where the skull was found seventy years before. And then, we excavated, Jose Braga and I, and we found a tooth that belongs to the same skull.

So it was through chemistry that we were able to relocate the exact position of the skull. The first humans and the first Paranthropus are completely different. They're completely different in many ways.

Paranthropus had a spectacular facial morphology with an overdevelopment of the chewing muscle. And so, these animals were very specialized in eating hard vegetables. They were vegetarians.

The first humans were not at all. Geochemical studies show that the first humans were already opportunistic. Plants and also meat in sufficient quantities so that we find geochemical signatures of it inside early human teeth.

For the next stage of his investigation into our origins, Professor Braga needs to compare the development of human and Paranthropus children over two million years ago. He is convinced that child development holds the key to what sets us apart from the other primates. But there is a major hurdle to overcome.

He already has the human Krondrei child, but so far no primitive Paranthropus child has ever been found. The only solution is to go back and look for more fossils, using technology to identify the best place to look. Mtombem Golei, a South African studying for a doctorate in archaeology, is tasked with analysing the spatial pattern of the fossil finds and using statistics to determine where they should keep excavating.

My specific area of studies is on the three-D reconstruction of the site and understanding spatial patterning using three-D digitization methods. These are actually the fossils, whose coordinates we've collected using the total station. In red, you have the bovids, and in green, you have the hominins, and in yellow, you have carnivores.

So what we found from our three-D spatial analysis is that we actually have four main clusters. Cluster one and two contain the most fossils, so this is the most dense region of the site. Archaeology is a very destructive process, and part of the discovery is destruction, but my focus within my PhD is to ensure that we can actually preserve data in such a way that future generations can have an image of what it looked like before it was removed.

Compared to the Apartheid times, I think now there's a lot more knowledge and awareness of this, and a lot more representation as well. So me, for example, being a black woman studying this, it's very rare, but we are pioneering and opening spaces for us to know our history and disseminate it as well. Professor Braga decides to dig a trench through the areas identified by Mtombem Golei as the most promising.

That, I think, is probably a piece of tusk. It's completely in a puzzle. There are pieces of ivory everywhere.

It's the kind of fossil you can't do anything with. Its only interest is that it indicates a dip. Like that, I think.

Benji, come look at this later. I think there's a piece of tusk at an angle opposite to the Paranthropus. Its orientation is like that.

Right, it's clearly north to south. And that's good because it corresponds to the hypothesis that there's another entry and another origin for the material. Chronological order ?

Older, of course. That indicates a much longer and more complex story. An elephant's tusk that is of no interest in itself has created a sensation.

It is positioned in counterslope to the talus the team have been excavating, which means it belongs to a different layer that comes from another aperture in the cave roof. This talus is partly covered by the one containing the first human and Paranthropus fossils. So it is older.

But what period does it date from? The archaeologists are on tenterhooks. They might find anything in this unknown terrain.

This level is very rich. This is bone. All of this yellow here is bone.

To know what it is, we'll have to dig it out. But it's too hard to dig out with this small tool. We'll need a stronger method.

The aggregate is unbelievably hard. Removing the fossil from it will take a very long time, and exposure to the air could seriously damage the bones. To take no risks, large blocks have been cut out using an angle grinder and transferred to the laboratory at Sterkfontein, where the fossils will be extracted from them.

This atmospheric cabinet of curiosities belongs to a legendary paleoanthropologist, Ron Clarke, who discovered Littlefoot, the founding Australopithecus specimen, here in nineteen ninety-four. As well as being the world's greatest expert on pre-humans, he is the most enigmatic. Only his friend Jose is allowed inside his lair, perhaps because Clarke himself is curious.

He asks about the finds. This piece corresponds to the right maxilla of that specimen. It still needs some preparation.

This is yours. This is already piquing my interest. This doesn't look like a parenthesis between you and me.

And at the moment in the matrix it's not that easy to tell. But if you look at the premaxilla, it doesn't look like Homer. And also, It's 2 52 I look at this, the more I feel that it's one of these.

For the first time now at chrome dry, you have an Australopithecus. And I'm sure of that. I'm so pleased for you.

And I'm pleased for the science, because this adds so much to our knowledge of the way these hominids were developing and the different species that existed at any one time. So, well done. No wonder even Ron Clarke has lost his legendary composure.

Already this partially cleaned fossil has revealed a staggering archaeological sequence, making Kronji the only site in the world to contain the complete transition from Australopithecus to Paranthropus and Homo. The three pieces needed to complete the puzzle of our origins. This Australopithecus is very close to the separation.

It is perhaps one of the last Australopithecus in the population, which will then give us Paranthropus and the first humans. Another important point in chrome-dry is that, in the layer immediately above where we found the skull, we have the oldest Paranthropus on one side and the oldest humans on the other. So, in these layers, we actually have the transition, the moment when it happens.

Finding Australopithecus far from the separation or finding Paranthropus long after the separation It's very interesting, of course. The more Australopithecus or Paranthropus skulls we have, it's great, but that's not what interests me. What I want is the blank page, the moment of separation.

That's what interests me. Professor Braga knows how incredibly lucky he is. This is every paleoanthropologist's dream, to be where humankind began.

We're tickling our ancestors. Above all, we're tickling their descendants. So, chrome-dry is a time machine.

Yet a crucial piece of the puzzle is still missing. For Professor Braga, comparing the development of human and Paranthropus children over two million years ago is of capital importance. From the outset, he has been convinced that this is the key to the behaviours that define being human.

But the dig is almost over. The chance of finding a baby Paranthropus child seems to have slipped through their fingers. Or has it?

What if Kronji has a last surprise in store, just as the team are on the point of leaving? I have the bottom teeth. I have another dental row.

Look! It's beautiful. It going here Oh, that's great.

And there's more beautiful. The world's first known baby Paranthropus face. Every time I come here, I ask myself, what would you like to find?

And each time, the answer is the same. A baby Paranthropus or a human baby. Welcome, baby Paranthropus.

This child will teach us a lot of things when we compare him to the human baby, whose mamma we all smelt. As if Kronji had answered the paleoanthropologist's call, the long-awaited discovery occurs. Although it is broken, the jawbone is in a perfect state of preservation.

It will be possible to reconstruct it in the laboratory. Professor Braga now has everything he needs to compare the primitive Paranthropus baby with the team's first find, the oldest human baby ever discovered. It is the culmination of ten years' hard work.

In fact, this little baby Paranthropus is the new star of South African paleoanthropology, The first skull of a baby Paranthropus that we know today in the world. Thanks to synchrotron imaging, we are now going to get inside the tooth and look at the structures that are five microns thick. And these structures correspond to the thickness of the enamel that will be deposited in a baby Paranthropus or in a human baby in the space of twenty-four hours.

A bit the same principle is for tree rings. The greater the thickness, deposited in twenty-four hours, the more speed of tooth formation was implied. And that's exactly what we observed.

The small Paranthropus have a speed of growth which is clearly superior to that observed in the first humans. So that's the first thing. And the second thing is geochemistry, of course.

The two great chemical forms of calcium, when we dose them over the entire height of the tooth of this little human or this little Paranthropus, allows us to see how the ratio between these two isotopes could have varied over the course of the formation of this tooth. And that's very important. Because when we go from an essentially maternal diet to a solid diet, well, this isotope ratio will change.

In fact, what we discovered is that Paranthropus babies were weaned very soon after birth, certainly around birth or only a few months after birth, while baby humans were weaned much later, probably around the age of three. So that obviously has implications in terms of social structuring. Because raising a baby that is weaned very early and raising a baby that is weaned much later means a complete difference in the investment on the part of the group, in particular on the part of the parents.

Studying present-day great apes shows that social organisation is closely linked to the length of childhood. This is true for all present and past primates and could help piece together the lifestyle of the first humans. Sabrina Krief is an eminent primatologist based at the Musée de l'Homme in Paris.

If we look at gorillas, weaning is much closer to birth than in chimpanzees where infancy is long. Before weaning, the entire metabolism will be concentrated on the brain's development, which is growing, and its cognitive capacities are developing. The other functions, including locomotion functions, will be put on standby.

Clearly, the young chimpanzee stays gripped to his mother and completely dependent on the mother's locomotion and protection. The community plays a very big role in defending its most vulnerable individuals. Young gorillas become more independent earlier than young chimpanzees, yet contrary to what one might think, this earlier autonomy reduces their learning period, shortening this period when individuals are like sponges.

In chimpanzees, we see that this is the period when they will learn to handle tools, and that takes time for the observation of other individuals. When I observe chimpanzees, I feel close to them. For me, they are part of my family.

And it's true that when we imagine the first humans, we imagine this environment and this way of living in society. What makes the big difference is that their tools have remained the same. We know that there is a transmission, but there has been no change, modification or improvement of their tools.

That's what makes the difference between human cultures which are cumulative and which little by little arrive at very sophisticated tools, and the chimpanzee society whose tools remain relatively similar, reproduce from generation to generation. Childhood lasted much longer in primitive humans than in Paranthropus, in the same way that infancy lasts longer in chimpanzees than in gorillas. This startling analogy with present-day great apes sheds light on the social organisation of hominins over two million years ago.

The earliest human communities were entirely structured around the need to protect infants, who remained vulnerable for much longer than the young of other primates. The additional burden meant the community was more exposed to the dangers of the savannah. But this social organisation offered a decisive advantage.

It made it easier to pass on knowledge between generations. History teaches us, chrome dry teaches us, that the human strategy was the good one since Paranthropus disappeared one million years ago. Humans, from their origin, had a very original development mode compared to what was previously known in Australopithecus and Paranthropus.

The first humans' reproduction strategy, which consisted of making babies very needy in energy to develop their brains, but also babies who needed a lot of attention from the group and from their parents. This was ultimately the winning strategy. It prevailed and allowed our species today to colonize the entire planet from ancestral species that, I am convinced, most certainly lived in the same way as us, at least as far as their relationship with their children is concerned.

The spectacular finds made at Cromdrey have finally told their secret, a secret more than two million years old. The children from the cradle of humankind are the oldest infant hominins ever found. Their teeth contain the story of how Paranthropus and humankind came into being.

Professor Braga's intuition was correct. The key to defining hominin species lies in the first years of life. What makes a species part of the human family, from the earliest humans to ourselves, is not the development, or using tools, or having a bigger brain, but the way we bring up our children and organise our societies to protect and educate them.

Suddenly our remote ancestors seem touchingly close. The long quest for knowledge has achieved its aim and redefined the very notion of being human.