Why Didn't Humans Evolve Into This?

追加: 2026-05-12

[00:00:00]Sirens ring out. The spacecraft crashes into the planet and the engine slowly wors into silence. You undo your harness and fall out of the vessel. And then you realize you are not alone.

[00:00:14]You are surrounded by strangelooking creatures shorter than you are with arms longer than their legs. In some ways they are familiar, reminding you of humans. But their stockiness and the monstrous shape of their heads quickly tells you they are not.

[00:00:32]Beyond the small crowd that is gathered, a city sprawled into the distance, but it is not like any city that you've seen before. Tall buildings rise out of a thick treed landscape. These squat creatures grip long ropes within human strength, hoisting cargo to great heights with giant pulleys. Up close, you can see that they most certainly are not human, and their clothing and makeup emphasizes their differences. Bony ridges run up the back of their skulls, and many of them have painted their skull ridges in bright reds, purples, and whites. One creature places an enormous nut into its mouth and crushes it in a single bite. The others chew incessantly, their huge teeth grinding away at handful after handful of coarse grass. Eventually, you take out your scanner and point it towards these creatures. A picture of the strange ape man flashes on the screen. Species identified. Homo robustus.

[00:01:34]You've never heard of homo robustus, but part of the name rings a bell. You search on your scanner for related species and find paranthropus robustus.

[00:01:44]But paranthropus is a long deadad genus of homminin that went extinct around 1 million years ago.

[00:01:56]You have crossed into another reality.

[00:01:59]One where our more robust evolutionary relatives have survived until today.

[00:02:04]Though alien to behold, they reflect what the real Paranthropus species actually look like. Their powerful sagittal crests rose up over their skull like a fin. Their massive teeth four times the size of ours filled strong jaws whose muscles distorted the shape of their faces and gave them a bite as strong as a hyena. And their grip strength was equal to that of a gorilla.

[00:02:28]These remarkable creatures lived alongside many other hominins, including some which scientists think were our early ancestors. And so what exactly was Paranthropus? What did they evolve from?

[00:02:41]And what relation are they to us? And of course, where did they go? Why did our branch of ancestors survive when they did not?

[00:03:06]Human minds have imagined and discovered brand new creations for the entirety of our history. From the stone tools fashioned by our earliest human ancestors through the explosion of art and culture in the last 100,000 years and into the many inventions of recorded history, the story of humans is a story of discovery. And indeed, so begins the 400page illustrated encyclopedia, The Book, The Ultimate Guide to Rebuilding a Civilization. The Book was created by an international group of artists, scientists, architects, and designers.

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[00:04:28]In 1335, a strange skull was found in a gravel pit near Clarenfort in Austria.

[00:04:35]It was longer than a human arm and ended in a curved muzzle like a beak. This discovery confirmed the stories the villagers had heard as children. A water dragon had once terrorized their town.

[00:04:47]It had hidden in the mists and its blood curdling roar had pierced the cold, rainy nights. It had wre havoc, flooding the nearby river Glenn, stalking travelers and threatening all who live nearby. Indeed, that was how Claron foot got its name. Clar means wailing or lamenting, and foot is a crossing.

[00:05:06]Legend has it that a local juke offered a reward to anyone brave enough and skilled enough to kill the ferocious beast. He' built a tower and according to the story, a young man had tied a bull to a chain and used it as bait to catch the dragon. The lindworm was killed and became the stuff of myth. And so there wasn't much surprise when the skull of a monstrous dragon was discovered in 1335. But of course, as we know now, the skull didn't actually belong to a dragon. In 1840, zoologologist France visited Clugenfort to inspect the famous skull. At that point, it hung from chains in the town hall archive, and it was clear to Anga it wasn't a dragon. It was the skull of a woolly rhinoceros.

[00:05:54]These giant shaggy beasts roamed northern Eurasia during the freezing plea scene until they went extinct about 10,000 years ago. And the town elders were allegedly so upset at their local monsters transformation into a rhino that they sent its skull to the Corinthian State Museum when it was established a few years later. You can still see it there today.

[00:06:15]Imagine what it would be like to find something strange or monstrous you don't understand. Indeed, when finding ancient fossils, it's rare to uncover an entire skeleton. When a discovery is first made, we are generally presented with just a single piece of the puzzle, and the rest of the creature must be extrapolated from there. Of course, today we're much better at extrapolating than in 1335. But that doesn't mean we've stopped finding fossils that shock us. And indeed, in the 20th century, monstrously shaped skulls were found that belonged not to mythical beasts, but to very real creatures.

[00:06:52]In 1938, South African school boy Ge Blanch had four of the rarest objects in the world in his pocket.

[00:07:02]Four strangely shaped rocks as big as the tip of an adult's thumb. Some had a slightly bluish tint, while others had the ochre stain of the soil where he had found them. Good was on the playground when he was called to the headm's office. He wiped his sweaty palms on his trousers and knocked on the door. A stranger was waiting for him and introduced himself as Robert Broom, a scientist who worked at a museum. Broom stood tall in the room, taking up space in his formal dark suit. He surveyed Ge through small round glasses. Broom pulled a piece of bone out of his pocket. It was a modeled jigsaw of black ochre and cream. Ge had seen this bone before. The boy had sold it to a quarry manager. Excited by its uniqueness, this manager, a Mr. Barlow, had shown it to Robert Broom, which had sent him looking for the boy.

[00:07:54]Broom was a medical doctor and paleontologist who'd been living in South Africa since 1897. He's perhaps best remembered as a fossil hunter and as one of the few early supporters of the idea that human ancestors had once lived in Africa. And in 1938, when Broom visited Ge Blanch's school, the hunt was on to find more of the remains of the strange ape men buried beneath the surface of southern Africa. By then, it had been more than a decade since the first human-like creature had been blasted out of the rock. In 1925, anthropologist Raymond Dart told the world he had found the missing link between humans and apes in Africa.

[00:08:32]However, almost no one believed him, but Broom was one of the few who did.

[00:08:40]He paid the boy a shilling per tooth on condition that he'd take him back to the exact place where he found them. After school finished, Ge took Broom to a hilltop on a farm called Cromry. CromDry means crooked turn in Africans. And there, Broom found even more bone fragments, and paleocientists have found yet more in the area over the years. The teeth were unusual, different from any Orolopycus teeth that had been found before. The preolars in particular were massive. Indeed, Broom described them as about half as large again as the Orolopycus teeth he had found before.

[00:09:15]And yet, he said the canines were remarkably small. This strange creature had a bony ridge that ran up the back of its skull, a bit like a fin. The juror and teeth that large must have attached to strong jaw muscles. And the ridge called the sagittal crest gave the jaw strength to crush food against those massive teeth. And indeed the teeth were absolutely giant, sometimes as much as four times the size of our chewing teeth. There was no doubt that this creature could chew better than any of the other hominins discovered so far.

[00:09:52]Fossilized teeth can tell us a good deal about the diet and lifestyle of their owner. A mouthful of canines cannot munch on grasses, while a jaw- packed with mullers cannot pierce and tear flesh. This creature's teeth meant that it clearly developed to eat grasses and plants, limiting its food options and its ability to consume the protein and fat-rich meat of other creatures. That's not to say it never ate meat, but it was primed for plants, berries, and nuts. It had evolved to be an expert chewer.

[00:10:22]Broom called the creature paranthropus robustus because he saw it as a side branch of humanity rather than on our direct ancestral line with the orolopithesines.

[00:10:32]Paranthropus means beside man while its skull, jaws, and teeth were robust compared to the other humanlike fossils that had been found so far. And indeed, when announcing the discovery, Broom was careful not to make the same mistake as Dart. He didn't go straight to scientific journals with his discovery.

[00:10:50]Instead, it was first published in the Illustrated London News with the headline, "Missing link no longer missing," causing some controversy.

[00:10:59]Multiple debates have surrounded Paranthropus throughout the time of its study. What exactly was it capable of?

[00:11:05]How close? And what type of relative to humans was it? And should it even be given its own genus? Some scientists disagree with broom and think the paranthropus robustus are just a slightly odd orolopythesine. And so they call paranthropus species oustropolipythecus robustus. But one thing they do agree on is that groom's homminin was more robust, more heavily built than other more grassile homminin species like us today or Raymond darts oropithesines.

[00:11:34]The term grassile doesn't actually have anything to do with how they moved. It's all about their teeth, jaws, and chewing muscles. South Africa's other southern apes such as Oralopycus Africanis and Oralopythecus transfences had jewels that were much more slender. And so whether we grant Paranthropus its own genus or not, Robert Broom had certainly discovered a new lineage of hominins, and the puzzle of this lineage was only just beginning.

[00:12:05]A clue came a decade later in 1948 as Broom and his colleagues found even more Paranthropus fossils, including a jaw.

[00:12:14]This time the fossils came from Swart Cran's cave, which is another site in the same fossilrich region nestled in the rolling savas of South Africa. Broom tried to argue that it was a new type of paranthropus. He even named it Paranthropus Craidens, but the creatures were later absorbed into Paranthropus robustus. At the time, scientists agreed that Paranthropus was rather strange looking, but they didn't know just how strange they could look. Indeed, they had only scraped the surface of what a robust homminin could look like.

[00:12:46]In 1959, American paleo anthropologist Mary Leaky found creatures with even larger jaws and teeth thousands of miles away from Crom Dry and Sword Crowns.

[00:12:57]Mary and her husband Louisis Leaky had been digging in the Old Vi Gorge in Tanzania since the 1930s. Today, the gorge cuts through grasslands. It's a steep ravine about 30 mi long. And the sides of the ravine are like a birthday cake of geology, split into red, cream, and ochre layers that each trap an epoch of time. And at Old Gorge, the Leakies had so far mainly found extinct mammals and a variety of stone tools, including handaxes. However, one morning, Mary went for a walk to one of the dig sites and noticed a bit of skull sticking out of the ground. After painstaking excavation, she found that there was more than just a fragment of skull. This was a new species of homminin. The find was nicknamed the nutcracker man because its skull and teeth looked like an old-fashioned nutcracker. Lewis named the strange creature Zinganthropus Boyceai. Zinge being the name medieval Muslim scholars gave Eastern Africa. and their sponsor was mining engineer Charles Boy, hence Boiseey. However, this find would eventually be absorbed into Paranthropus and became Paranthropus Boise. Even by Paranthropus standards, Paranthropus Boisee had giant teeth. Indeed, its cheek teeth are four times the size of modern humans. It also had the thickest tooth enamel of any known early human. Its wide, disshaped face made space for massive muscles to give its crunching jaw power. And scientists are still trying to figure out just how strong their bite was.

[00:14:26]They've created 3D models of their teeth and jaw and simulated how strong they would have to clench their jaws to crush food between those gigantic teeth. And through these efforts, we now know that they definitely had the strongest bite of any hominin. One set of these simulated muscles was able to bite down with a force of about 5,000 newtons, which is the same force that about six adults exert on the ground. But what made the Old Devi discovery so groundbreaking, aside from being the first paranthropus found outside of South Africa, was that it was found in a place littered with tools. Many tools were discovered in the same sediment layer as Paranthropus Boise. This creature looked like a nutcracker toy, a parody of a human ape. But could it have had the capability to use tools just like its grass cousins just like us?

[00:15:26]1 and a half million years ago, an ancient human treads the shoreline of Lake Takana, and he is being watched. He is a Homo erectus, standing tall as he walks over the muddy shore, his body moving much as ours would. In his hand is an issulan handax, a pear-shaped stone tool used earlier that morning to carve an ancient giraffe before digging for roots. But now something else nearby is digging. For amongst the reeds, a creature pauses its work and their eyes meet. This creature, however, is different to others that live near this lake. smaller in height than the Homo erectus and not exactly the same shape, much more similar in body type than the ancient antelopes and pigs that travel to the water's edge or indeed the crocodiles that lie within it. It is perhaps most similar to the giant baboons that roam the area, but something behind its eyes is altogether different to them. Perhaps not unlike the look an ancient human would get from the eyes of another human.

[00:16:34]We cannot be sure exactly how much of this the mind of a homo erectus would have been able to compute one and a half million years ago. But we can be reasonably sure these encounters did happen. Ancient humans had experiences that no one alive today could have that of meeting an entirely different species of homminin. In this case, paranthropus boisei.

[00:16:55]Fossilized footprints have been found near the eastern shore of Lake Turkana that belonged to two different homminin species. Analysis of them has proposed these species to be homoerectus and paranthropus boi and has found that the footprints were made within days or perhaps even hours of each other. This shows the coexistence and likely interaction between humans and paranthropus. But what exactly was the creature like that the homoerectus looked upon near the shore that day? How did it move? Did it remain hunched over its digging or could it stand? How did the fingers of its hands move through the reeds? Could the hands of this paranthropus have even held a stone tool?

[00:17:41]Making and using tools is not easy. For many years, scientists and philosophers categorized tool use as one of the things that made us human and importantly placed us above other animals and other apes. With tools, we can change the environment around us.

[00:17:57]Tools and our ability to harness them have ultimately allowed humans to take over the world. And so, ever since Mary Leaky discovered Paranthropus Boisei in Tanzania, Paleocientists have been debating whether these strange creatures could use tools. The tools at Oldi opened the question, but their connection to Paranthropus was quickly put in doubt by the discovery of another species within the same sediment layers, the human species Homohabilis. And so the answer would remain elusive for some time. In fact, it would be nearly 60 years until the debate took a giant leap forward.

[00:18:35]Green shrubs and long grasses cover the landscape of Nyanga, a site which hugs the northeast of Lake Victoria in Kenya.

[00:18:43]And below the grasses is a crucial piece of evidence in the paranthropus puzzle.

[00:18:48]Researcher Tom Plameumber from Queens College at City University of New York was excavating human-made stone tools from another Kenyan site, Canera, when Blastoyango from the National Museum of Kenya mentioned that evidence of similar tools had been found nearby. They visited this new site at Nyanga and saw some potential. We surveyed, said plumber, who saw some material on the surface. And a few years later in 2015, digging began at what would become one of the most important sites in human evolution. The team began excavating into the ochre soil and soon found a treasure trove of tools at what scientists now think was a butchery site. They unearthed 330 stone artifacts, which they believe were tools used to carve long deadad hippos and pound plants. But something else was very unique about the Nyanga site. At the previous site, plumber was excavating human fossils alongside the tools. But at Nianga, unlike both Kanga and Ulivi, there was no evidence of human fossils. There were, however, alongside these ancient stone tools, two Paranthropus teeth.

[00:20:02]And so, Nianka is crucial for precisely this reason. At last, we had Paranthropus and stone tools located together without any other contenders on the scene. And so, does this prove that they had the humanlike ability to use tools to butcher their food? Well, not entirely. It's certainly a key piece of evidence, but scientists also needed to show that the creature would have been able to hold, manipulate, and use the tools. Human hands are superbly well adapted for the use of tools. We have long opposable thumbs with broad tips that can grip and manipulate objects.

[00:20:37]Wrists that have a large range of motion and dozens of clever muscles that give us a precision grip with our fingers.

[00:20:43]The problem is proving that paranthropus could do anything approaching the same is tricky as it is rare to find fossilized hands or feet. They can detach from the bodies it decomposes or be eaten by hungry scavengers. The bones in the hands and feet are also small and fragile which makes them unlikely to survive. if the fossilization process.

[00:21:03]And yet, a few years after the Niyanga discovery, we would at long last get a good look at a paranthropus hand.

[00:21:17]At the Kooie Fora research project in Kenya, local community partners spend 7 to 8 months a year exploring, surveying, and excavating the earth. The site first established as a camp by the son of Louiswis and Mary Leaky Richard in the 1960s and now run by his daughter Louise has been a hotbed for homminin finds and in 2019 they found something special on the eastern shore of Lake Turkana. It was a partial skeleton that was then painstakingly excavated over the next 2 years. The fossils recovered from this skeleton of a paranthropus that lived around 1 and a half million years ago included teeth, skull fragments, and also an incredibly wellpreserved set of foot and handbones. The fossil handbones showed the Paranthropus's hand had a grip similar to ours, precise and nimble, but with the strength of a gorilla. It lacked our particularly mobile wrists. But crucially, the conclusion of a 2025 study on the fossils found that it would have been able to use tools. in their words, complicating the evolutionary history of hand and tool manipulation. And indeed, the footbones were just as revealing.

[00:22:24]They felt that the paranthropus feet were unquestionably adapted to walking upright on two legs. Like us, its big toes pointed in the same direction as the rest of its toes. Other ape's big toes stick out to the sides, which means they're able to better grasp branches with their feet and climb trees. And the joints in Paranthropus's foot also allowed it to literally have a spring in its step, something that enables modern humans to push off the ground when walking or running.

[00:22:55]The picture of Paranthropus that these finds give us is a stark contrast to what we may have imagined back in the 1930s or 50s as the first Panthropus fossils of their respective species found the light of day. Indeed, the more we discover about this homonyin, the more we develop a detailed picture of a complex mosaic of features. Some, like gorilla grip strength or a bite power similar to a hyena or grizzly, show us a creature that feels truly alien. But others, like the movement of the feet and the somewhat dextrous potential of the hands, paint an image of something eerily similar to us. And so this begs the question, what actually was Paranthropus to us? If it is a homminin and as such is more closely related to us than anything else left alive today, but where exactly in our family tree does it sit? Could we even consider it a human or a human ancestor?

[00:23:51]To locate Paranthropus' position on the homminin family tree, we need to push backwards in time as close as possible to where its branch diverged from the rest of the tree. We've seen so far that it existed alongside other homo species one and a half million years ago. But how much further back can we find species of paranthropus living on Earth?

[00:24:11]For much of the time paranthropus has been studied, precise dating of fossils has been difficult. Back in the days of Broom and the Leakys, fossil dating relied on geology rather than chemical analysis. Scientists made their estimations as to when an animal lived based on the layer of soil it was found in. Alv, for example, looks like a layered birthday cake. Each of those layers of sediment is linked to a specific time band. If archaeologists found a creature trapped in a specific layer, then they could tell that it lived at that time with an accuracy of around a few hundred,000 years. However, in the last 15 years, scientists have developed the technology to more confidently date paranthropus skeletons to a more precise degree. And as a result, we now know that paranthropus robustus began to walk the plains of southern Africa around 2.3 million years ago. Paranthropus boisei individuals found throughout eastern Africa from Tanzania to Ethiopia existed around the same time as their robustest brethren, albeit thousands of miles to the northeast. And so this evidence doesn't discount Paranthropus from having diverged from our human lineage. The homogeneous had emerged a few thousand years before this. So it would leave open the possibility of the paranthropus branch springing from ours shortly after that time. However, there is one extra thing to resolve. For Robustus and Boisei are not the only two species of Paranthropus.

[00:25:37]For in 1985, scientists made a discovery that was vital in locating Paranthropus' position in human evolution.

[00:25:50]British paleontologist Alan Walker was scouting the edge of Lake Tana. Tufty beige grass framed the bright blue green of the lakes's water. Walker and American anthropologist Pat Shipman had gone to the remote spot to follow up on reports of a hippo skull. Although no one actually recorded if they found the hippo as the pair became justifiably distracted. Walker went off on his own, only to come back a short while later with a sly grin. He had found something exciting. He told Pat in his classic understated fashion, "When you finished with that, I'll show you a homminid."

[00:26:25]And what Alan had found looked like no other homminid previously discovered.

[00:26:30]Indeed, even aside from their rather strange shape, the fossils were black.

[00:26:35]After the creature had died, its skeleton had lain in tuned in soil for millions of years, and that soil was rich in manganese, a brittle, shiny metal. Over the millennia, the mineral had leeched into the bones, turning them black as they transformed into rock. But even without the blackened otherworldly tint, the fossils would still have been a bit of a shock. The creature had a remarkable sagittal crest and large chewing teeth with thick enamel, hallmark Panthropus features. And yet, these fossils were estimated to be very old. More precisely, buried in a layer of rock that was around 2.5 million years old. And what was more, this discovery reminded the world of a homminin fossil that had been found almost two decades earlier in the Omo Valley in Ethiopia.

[00:27:23]In 1967, French paleontologists Camille Armbborg and Eve Coppins had found a single toothless jewel bone. They had named the species Paranthropus Ethiopicus and dated it to around 2.8 million years ago. This was much earlier than any other Paranthropus fossil, and no other fossils were found in the years that followed. The scientists argued that the Ethiopian find was some other form of orolopiththesine and not paranthropus at all. But when Walker found this strange black skull in 1985, it supported the older piece of jewel bone from Ethiopia and Paranthropus Ethiopicus came back from the cupboard of discarded species and was given its place as the oldest known form of Paranthropus.

[00:28:05]Later finds have continued to support this timeline. The Nianga tools discovered by Plumber and Onyango have been dated with modern methods to between 2.6 and 3 million years ago.

[00:28:15]Plumber also noted on their discovery, we think it's in the older end of that range. And though the species of Paranthropus the teeth belong to is unclear, it gives us definitive evidence for Paranthropus existing and perhaps even using tools as long ago as nearly 3 million years. This scuppers the possibility of Paranthropus emerging from the homo lineage and shows us they likely evolved from earlier more grassile oropithesine species. They are our cousins, but their robust branch emerged on our family tree even earlier than we once might have thought. This shows us just how ancient this robust homminin lineage was and also just how long it survived on the planet. The youngest paranthropus fossil nestled in the rock of Sword Grant's cave could have died as recently as 600,000 years ago, putting their tenure on the planet at over 2 million years. It is clear that they were highly successful on longived genus. And so where did they go? Our slim-faced, grassile branch of the homminin family endured while all hominins with powerful jaws and giant teeth would come to an end. Why did they go extinct?

[00:29:38]Megan Tyrion was built to kill.

[00:29:43]It was about the size of a modern jaguar but with a bigger neck. It had notably large shoulder blades supporting powerful shoulders and relatively short but incredibly powerful forlims. In fact, it was so heavily built that some experts dispute Megan could climb trees as well as modern jaguars. Yet, this powerful front section came with considerable advantages as well. For this feline was superbly well adapted for a quick, powerful pounce. Once in its grasp, its vicel-like forearms and forceful neck and shoulders could quickly expose the neck of its prey, and then its razor-sharp canines, so large they likely projected from its mouth at all times, would be put to use. Its saber teeth could perform a canine shear bite, penetrating the esophagus and major blood vessels of its victim. And sometimes the victims this ambush machine was preying upon were hominins.

[00:30:44]At Kooper's Cave system in South Africa, Paranthropus and Megan Tyrion appeared to have lived and died there together at the same time around 1 and a half million years ago. The big cats had been around in Africa for a lot longer, with the oldest example dating back at least 4 million years. And so it appears that as the many different species of paranthropus wandered through the grassy plains and wooded valleys of Africa, they were at risk from these killing machines and others like them. The juvenile paranthropus robuster skull SK54 shows two 6 millm puncture wounds consistent with the lower canines of an African leopard. And the evidence does not end there. In fact, it comes handinhand with more proof of paranthropy's upright nature. A fossilized hip, thigh, and shin in Swadran's layer member one was a huge find. Indeed, it was the first articulating hipbone, thigh bone, and shin bone of Paranthropus Robustas found. And it showed like the partial boy's eye skeleton from Kooie Fora that their South African relatives were also like modern humans, habitual upright walkers. This example, a female only 3'3 in tall and 60 lb in weight, also highlighted their dimminative size. And this size clearly came with vulnerability because these leg bones from Swadrans member one also displayed according to their discoverers tooth marks and other chewing damage identical to that made by leopards on the bones of their prey.

[00:32:17]And here yet again the more we form a full picture of paranthropus the more it becomes a patchwork of features. These creatures had huge teeth, powerful jaws, and grip strength equal to that of a gorilla. And yet, their overall stature left them vulnerable to leopards, hyenas, and highly specialized ancient ambush specialists like Megant Tyrion.

[00:32:38]And so, was this the reason for their extinction? Were they simply an easier meal than their taller, more grassile homminin cousins? After 2 million years of existence, was the Paranthropus genus eaten to extinction?

[00:32:53]No, because something else came for Baranthropus between 1 2 million years ago. Something that would also come from Megan Tyrion.

[00:33:08]In Slovenia, ghostly snake- like creatures lurk in underground pools.

[00:33:13]Their four little legs that pump against the water and long crocodilelike snouts that taste and scent the air. And this is necessary because inside these caves, the habitat of the European alm, there is no light at all. The rare pale cave salamanders therefore have very underdeveloped eyes. After all, what's the point of excellent vision when you're surrounded by darkness, but to make up for it, the creature is especially sensitive to smell, touch, movement, and even electricity, all of which help it track prey. However, more than a million years ago, their ancestors lived on the surface and could see. Researchers suspect that some individuals fell into the caves below.

[00:33:59]And with each successive generation, they adapted to their new environment, becoming highly specialized to this new biome. And of course, if they now return to the waters of the surface, they would stand little chance of surviving in this new world. Their fate is likely now bound to these depths.

[00:34:25]This may seem extreme, but this is happening all around us in the natural world on truly massive scales.

[00:34:33]Populations become dependent on certain niches within a biome and largecale changes to the planet can threaten those populations or sometimes entire species.

[00:34:45]Indeed, changing climates can be especially catastrophic. Most creatures on the planet have evolved to fit into a particular corner of an ecosystem. The temperature just right, enough food, not too many creatures trying to eat them.

[00:34:58]And so when the climate starts to change, this delicate balance is upended. Some animals move to similar habitats or change their behavior so that they are more comfortable. For example, mosquitoes have significantly expanded their niche as global temperatures rise today. There are even reports of caterpillar species in the northern hemisphere maturing earlier each year as springs become warmer. But of course, those that could not adapt quickly enough become extinct, just as Megan and Paranthropus did around the same time.

[00:35:33]Southern Africa, particularly the cradle of humankind, where Paranthropus was first discovered, was once a lush land of woodlands, lagoons, and wetlands.

[00:35:43]Plants were thickd, animals were plentiful, and competition was fierce.

[00:35:49]However, food was abundant and Paranthropus and other homminins could feast on nature's bounty. As well as this, scientists suspect that places where they find particularly high numbers of homminin fossils had the added attraction of fresh water, too.

[00:36:03]But eastern Africa, in contrast, was a much more challenging place. It was actually more dry than it is today.

[00:36:11]Rolling savas punctuated by the occasional thorny thicket or tree. But there was still water. Deep lakes appeared and disappeared over the years, some of them acting as transient hubs of life for animals and homins. And we can piece together these visions of the ancient earth by studying the teeth of those who lived there.

[00:36:36]All plants contain carbon, but there are different types of carbon.

[00:36:41]Paleocientists are interested in two particular kinds, carbon 12 and carbon 13, which are called isotopes of carbon.

[00:36:49]All carbon atoms have six protons, but they can have different numbers of neutrons. Carbon 12 has six neutrons and carbon 13 has seven. And the important thing about these isotopes for paleocientists is that they are radioactive and so they break down over time and we can use them to date organic matter. Fossils, for example, have less carbon 12 and carbon 13 in them than you would find in the atmosphere today. And so scientists split creatures diets into C3 and C4 foods. C3 and C4 are types of plants that have different ratios of carbon 12 and carbon 13. A C3 diet has lots of fruits and leaves, food which you'd be more likely, of course, to find in a place with lots of trees. A C4 diet, on the other hand, has lots of grasses, seeds, and tubers. And these are foods that you would be more likely to find in savas and grasslands. So, a C4 loving animal would have more carbon 13 in its tooth enamel. And this means that if a carnivore eats that animal, it would also have more carbon 13 in its tooth enamel. And it is analysis of these isotopes that help scientists figure out what animals ate millions of years ago.

[00:38:05]And 2 million years ago, Paranthropus was about to experience quite a shock.

[00:38:11]The climate and landscape it was used to was about to change. Around this time, there were quite a few connected shifts in the Earth's climate. There were changes in the Earth's orbit around the sun and the tilt on its axis, and this led to greater variability in climate.

[00:38:26]The Walker circulation began to shift. A massive global heat exchange system that operates in the atmosphere that is closely linked to El Nino and Leninia, climate patterns that influence rainfall. This meant the days got colder and drier and some types of vegetation died out whilst others flourished. And in South Africa in particular, the landscape got drier and woodlands gave way to grassy savas. Meanwhile, trees became more common in Eastern Africa and grasses were overwhelmed by woody brush.

[00:38:55]And this is where teeth and jaws can start to decide who lives and who dies.

[00:39:07]Paranthropus' big teeth constrained the types of foods they could eat. While they did adapt to eat the plants that were available to them, they lived in a narrow niche and couldn't pivot to new foods fast enough. This meant that when the climate changed, vegetation followed suit and competition for their preferred food increased, they were in trouble.

[00:39:27]Individuals died and entire communities died out and the populations began to fragment. Groups of Paranthropus would eventually get smaller and smaller until they ultimately disappeared. Indeed, Paranthropus' diets were so tailored to their environments that even the different species ate slightly different foods. Scientists have analyzed the scratches and marks on their teeth and they found that they inhabited different ecological niches. Panthropus boy's eye in Eastern Africa, for example, chewed on leaves and grasses for hours rather than cracking nuts between their teeth as suggested decades ago. Panthropus robusters, however, had a more varied diet, and their teeth reflect that with their pitted holes and worn tooth enamel. And this slightly more generalized nature perhaps influenced them lasting longer. The window often given for paranthropus boey extinction is between 1.4 and 1.2 million years ago with some individuals perhaps surviving until a million years ago. Robustus, however, is slightly later, 1.2 to 1 million years ago, with the last survivors making their way into the last million years. But sometime roughly 600,000 years ago, after over 2 million years of existence, the last Paranthropus closed its eyes on a world that had undergone remarkable changes throughout the lifetime of its genus.

[00:40:46]Though, of course, Paranthropus was far from the last homminin.

[00:40:51]Megantyion was survived by other saber-tooththed cats such as Hometherum, which stayed in existence until as late as 12,000 years ago. Homothetherum, unlike the generally solitary Megantyion, hunted in packs, which offered a variety of advantages, one of which being an increased ability to defend their kills from aggressive carcass stealing scavengers.

[00:41:12]Some of those scavengers came in the form of giant ancient hyenas, others walked on two legs. For Paranthropus was survived by the grassile hominins. And so what was it about this lineage that allowed them, our ancestors, to outlast their more robust cousins? And how does our own species, Homo sapiens, fit into the story?

[00:41:42]In the early half of the 20th century, rangers at Yusede National Park wouldn't discourage people from leaving rubbish for bears to eat. In fact, they went one step further. They made a show of it. In a large illuminated area surrounded by benches for spectators, rangers would dump huge amounts of leftovers, sometimes attracting up to 20 or 30 bears to compete for the food. Onlookers would cheer these garbage pitch shows.

[00:42:09]And the descendants of these bears still rummage through bins and landfills at any chance they get. Indeed, brown bears will eat almost anything. They have a variety of teeth that allow them to do everything from grip a wet salmon to grind through tree bark. Their diet includes, but it's not limited to leaves, moss, nuts, pine cones, roots, grasses, fruits, flowers, mushrooms, clams, crabs, eggs, mice, squirrels, deer thorns, and even ants or moths.

[00:42:37]Grizzlies in the Rocky Mountains will eat up to 40,000 army cutwa moths in a single day during the summer as they load up on calories before the winter.

[00:42:46]This ability to eat a vast range of food allows them to avoid the hassle of migrating to stay alongside food sources. Instead, using these calories to hibernate for the winter. And so, what begins with their teeth and broad diets has implications for the rest of their body and can even open the door to new capabilities and patterns of behavior.

[00:43:08]Whatever form an animal takes is essentially a bet, and there are many ways to play the game. Some animals are highly specialized, dependent on a single food source or habitat. Koalas, for example, are entirely reliant on eucalyptus leaves for food and habitat.

[00:43:24]The lack of energy in these leaves causes them to sleep for 18 to 20 hours a day. But they have survived doing this for more than quarter of a million years, possibly longer than our species has existed thus far. Whereas other animals are shown with a diet of brown bears rely on variety and versatility to survive. And so what bet had our ancestors made back in the time of Paranthropus? What form had we taken?

[00:43:49]What did we eat? And how did we live?

[00:43:59]Kenyan paleocientist Kamoya Kamehu was recognized as one of the world's greatest fossil hunters and single-handedly rewrote large tracks of the human story. He seemed to have an innate knack for spotting shards of bone nudging out of a rock's surface. And in 1984, he was scouting for fossils along the western shore of Lake Turkana. He spotted a section of skull on the shore of a dried up riverbed. And it revealed what was then the most complete hominin ever found. Takana boy, as they called the skeleton, would have been between 7 and 11 years old when he died. Despite his young age, he would have stood at about a meter and a half tall and if he had lived, could have reached the height of an adult man today. And this makes him very tall when lined up alongside other hominins that were around at the time. But he'd been trapped in the sediment for more than 1 and a half million years. His species was dubbed Homoagasta or the African homoerectus and looked much more like later humans than the homminins that had been discovered before. the ape-like orolopithesines, the robust paranthropus or the smallrained homohabilis.

[00:45:07]Indeed, Takana boy like other homoagasta and homoerectus individuals resembles us. He had long legs for walking and shorter, weaker arms that were less able to climb trees, and his teeth also resembled ours. The larger chunkier teeth of Oralopythecus and the massive teeth of Paranthropus begin to disappear from the fossil record in favor of smaller mers and preolars. And as the teeth got smaller, so did the jaw. It needed less power to chew and grind food. And in fact, scientists think that Tana Boy's teeth were what actually got him killed all those years ago. He had the fragments of a broken milk tooth in his mouth. And scientists think that he got an infection between that old tooth and a new erupting preolar. The mouth infection would have poisoned his blood and killed him.

[00:46:02]And so as homminid fossils get younger and closer to modern humans, their grassile traits continue while robust features disappear. Homo's teeth become smaller and their faces start to stick out less. Paranthropus' face jutted out more than ours or even Homoagasta and Homo erectus. Although later homminins still had strong jaws, they would never again be as powerful as giant tooththed paranthropus. And so just how crucial was our reduced tooth and jaw size to our eventual survival?

[00:46:34]The difficulty in examining the pattern of human origins is that we do not know exactly what was cause and what was effect. But grassile teeth and jaws appear to have offered later species an advantage. One benefit is that smaller, sharper teeth allow you to pierce objects with less force. Paranthropus mouths were highly specialized grinding machines, but rasile humans could eat a wider variety of foods than their robust cousins and could consequently survive a tumultuous climate and changing environments. And of course, this wider variety of food included the more regular consumption of meat.

[00:47:11]Paranthropus could and would eat meat.

[00:47:14]They, like us and our ancestors, were omnivores and would eat whatever they could get their hands on and teeth into.

[00:47:21]But experts believe that paranthropus meat consumption was more occasional and opportunistic, whereas grassile homminins took meat consumption to whole new levels. Although despite this, human teeth don't scream meate eater. When compared to carnivores like lions or even other meat heavy omnivores like badgers, raccoons or bears, they all have much more pronounced canines to tear at meat. Human teeth, on the other hand, are highly generalized. Our array of incizers, canines, and mers are capable of tearing, grinding, and cutting without specializing too heavily in any one aspect. This would have been useful when having to rely on new or changing food sources and also left us able to eat large quantities of meat when presented with the opportunity by our advanced tools enabled by our large brains.

[00:48:12]And so grassho humans may be defined and categorized as such by their teeth which has been a useful way to classify fines over the decades. But we do have other features that are vastly different to Paranthropus as well.

[00:48:25]Though Paranthropus could walk upright, the grassile homogeneous became masters of traveling long distances, allowing us to search far and wide for food and other resources. As well as this, our walking legs freed up our arms so that we could do other things while we were moving. And we took this much further than Paranthropus. This included multi-use handaxes like those developed by Homo Erectus and also the eventual use of the spear. And these types of tools allowed us to hunt, multiplying our food opportunities even further, eventually helping us fend off larger predators that might look to kill us, and even helping us compete with predators like Megan Tyrion for their kills. All of this brought calories, feeding brain size, and in turn allowing for more complex tools and strategies to be formed. And as our brains were getting bigger, our hands were getting nimler, thus more suitable for more precise work. And so we may share a common ancestor with Paranthropus deep in the heyday of the orolopythecines.

[00:49:24]But the longer our ancestors existed alongside Paranthropus, the more different from them they became. By the time of their extinction, we had become capable of many things well beyond their grasp. And we continued to break new boundaries after they were gone. And this journey is not over. Our species has created a great many new things, especially over the last 50,000 years.

[00:49:47]And interestingly, our teeth are continuing to evolve as well.

[00:49:55]As recently as 12,000 years ago, the human diet underwent a dramatic shift.

[00:50:00]When humans began farming, we shifted from the foods we foraged, which were coarse and hard to chew, to foods that we grew. Cereals and fruits became softer as we bred them for taste and ease of eating. And our teeth and jaws changed with our food. In Argentina, researchers have investigated the dental and jaw differences in two populations.

[00:50:23]One group in the Andes mountains that had turned to farming generations before and another group in the Andes that had maintained a huntergatherer lifestyle.

[00:50:31]They found that there was a notable difference in their jaws and teeth. When there is less stress on the jaw, it begins to shrink. And it doesn't necessarily take millennia for human jaws and teeth to adapt, with some research suggesting that it can happen within a generation. Some scientists think that this is even why crooked teeth are becoming more common. Jaws are getting smaller and weaker, but the number of teeth people develop has remained the same. This results in overcrowding in their mouths and teeth jostling for space and starting to overlap or go crooked. And as time goes on, it's likely that our teeth and jaws will continue to adapt to our environment and lifestyle, just as the rest of our bodies, our brains, and our mental capabilities will.

[00:51:20]The ability to adapt has always been humans greatest strength and has seen Homo sapiens emerge as the dominant animal on the planet. While Paranthropus' robust teeth and jaws made them perfect inhabitants of their southern and eastern African homes for millions of years when the world started to change, they were left stranded by these features. Unable to adapt fast enough, our grassile ancestors generalized teeth and jaws were just one of the weapons in their arsenal, giving them the flexibility to adapt and cope when times were hardest, helping them pass their genes from generation to generation until they were passed on to us.

[00:52:06]You've been watching the entire history of humankind. Don't forget to like and subscribe and leave us a comment to tell us what you think. Thanks for watching and we'll see you next time.