Hominin Fossils Found Deep in South African Cave | Secrets in the Jungle

30 miles northwest of Johannesburg, South Africa, in the Blue Bank River Valley lies the Rising Star Cave System. Hidden beneath the jungle canopy is a spectacular underground complex with more than a mile of tunnels, chambers, and subterranean rivers. This massive labyrinth has dozens of interconnected limestone caves and passages. People have been recreationally caving here since the 1960s. But parts of the system can be very dangerous and difficult to navigate. It's pitch black. And some of the passageways are so narrow that it's very difficult for a person to even fit through. This is not recommended for those who are claustrophobic or afraid of the dark. Deep within the complex, 100 feet below the Earth's surface, is the Denaleti Chamber. It's around 260 feet from the closest entry to the cave system and is extremely remote. To access the chamber, cavers have to navigate a series of challenging obstacles. The only way through is through a terrifyingly narrow passageway called the Superman's Crawl. It's only about 10 inches high. And most people only barely make it through by putting one arm above their head and having their other arm tight to their body, you know, like Superman. It is a 50-foot climb up a ridge called the Dragon's Back. Then a very tight squeeze down a frighteningly steep fracture lovingly called the Chute. In 2017, a team of international researchers exploring the chamber make a surprising discovery. Just 12 meters beyond the main passage, in a tiny crevice only a few inches wide, they find bones. The remains are brought to a lab where it's determined that they have found 28 skull fragments and six teeth. The bones are from a hominin, a group of primates that includes modern humans and our earlier human relatives. The bones are estimated to be about 250,000 years old. Finding a fossil like this is pretty cool. But in this part of the world, it's not that uncommon. The Rising Star Cave System is in an area of South Africa lyrically known as the Cradle of Humankind. Covering a region of around 180 square miles, spanning the Hauteng and Northwest Provinces, the Cradle of Humankind has been home to some of the most important archaeological discoveries of the last century. Since the 1930s, thousands of fossils, tools, and other evidence of ancient human activity have been found in this area. This is one of the most important areas on the planet as far as advancing and furthering our understanding of human evolution and our development as a species. There are 13 major fossil sites within the area, the most notable being a series of limestone caves known as Sterkfontein. In 1947, Dr. Robert Broom discovered a nearly complete skull that was named Mrs. Pless, short for Plesianthropus transvalensis, near man from transval. Mrs. Pless was a huge find. It's one of the most intact pre-human skulls ever discovered, and it's thought to be between 2.5 and 2.8 million years old. It was later reclassified as Australopithecus africanus, the genus that is probably the precursor to the genus Homo, to which humans belong. What's interesting is that Dr. Broom had to use dynamite and a pickaxe to excavate the fossils at Sterkfontein as they were embedded in the rock. But the bones found in the Dinaledi chamber were found tucked away, just lying on the surface. How did these bones end up in such a strange place? It's possible that this unfortunate individual was attacked by a predator, and then their body was dragged into a cave to prevent it from being stolen by other predators. African leopards are known to store carcasses deep in caves for safekeeping. Researchers wonder if this could be the work of some ancient relative of the modern leopard, or another big cat species. The team finds no evidence of teeth or claw marks or other examples of physical trauma on the bone fragments. Those would very likely have been present had these specimens been attacked and dragged in by a predator. Although it seems highly unlikely that an animal would be able to drag the body through these narrow passageways and over some of these obstacles. It's possible that the cave structure was different back then, and some areas may have been more accessible. Some caves can change over extended periods. Their entrances can fall apart, and new passages can open up over time. But analysis of the Rising Star Complex concludes that the structure of the Dinaledi subsystem has not changed much over the last several hundred thousand years. While there have been minor transformations due to rock falls and the accumulation of mineral deposits, the complex has remained relatively stable. So maybe it's not that they entered from the challenging terrain from below. Maybe instead, they dropped in from above. Death traps are special caves that are open to the surface and allow animals and even humans to fall in and give them no way out. But if this chamber had a death trap, you would expect these bones to be on the floor of the cave and not tucked away into some tiny crevice. The team establishes that the bones belong to a child, probably between four to six years old. They give it the nickname Ledi, short for the Setswana word Ledimela, meaning the lost one. To imagine a child down there by themselves in the pitch dark, it must have been terrifying. But maybe they weren't alone. This isn't the first time that bones were discovered in the Rising Star Cave system. In 2013, a group of amateur cavers exploring the chamber stumbled across bones that were just lying on the ground. After excavating the chamber, it turned out it was littered with bones, some 1,550 specimens belonging to approximately 15 individuals. They found everything, skulls, jaw bones, an almost completely intact foot, and even a hand with nearly all of the bones present. And we're talking about individuals of both sexes and of all ages, old, adults, juveniles, even an infant. The bones were dated to the Middle Pleistocene era, between 335,000 and 236,000 years ago, and given a new classification, Homo naledi. This is a previously unidentified hominin species, another missing link in our ancestral family tree. And what's even more shocking is that it seems to be a primitive species that lived in Africa at the same time as modern humans. Homo naledi has both Australopithecus and contemporary Homo traits. Strangely, the upper body is quite primitive, with flared pelvic bones, apish shoulders, but the lower parts of the body are remarkably human-like. They would have walked upright, with a similar stride to us, but their curved fingers also probably meant they spent a lot of time climbing trees. While Homo naledi brains were three times smaller than modern humans, they were surprisingly similar in structure and shape. It's a significant discovery because it calls into question everything that was previously believed about brain size, and evolution. Most evolutionary biologists will tell you that complexity in the hominin brain evolved alongside increases in size. But some experts now believe that despite having a brain the size of an orange, Homo naledi exhibited sophisticated behavior, including things like tool use. Looking at the size of the skull fragments from naledi, the researchers determined that this child was also very likely Homo naledi. But how did all of these individuals come to rest in this deep cave? Analysis reveals they don't all share the same degree of weathering from age, and some were found at different depths in the sediment of the cave floor. The bones must have accumulated in the cave over a long period of time, on the order of centuries. These individuals did not die all at once, and it seems like their bones were brought there on purpose. Some of the bones were articulated, meaning they were found arranged in the proper order, as they would be inside the body. This shows they were still attached by ligaments and flesh, and therefore, the bodies were brought in intact. The layers of sediment on top of some of these bones suggest that the cave was used to bury or deposit the dead. It's a pretty sophisticated behavior for such small-brained hominins. We always assumed that Homo sapiens and Neanderthals were the only ones to bury their dead. It may indicate a level of mental capacity we thought you could only find in us. It is believed that the child, Leti, was deliberately placed in the crevice upon their death. Perhaps there are other lost ones, like Leti hiding underground in the darkness, their ancient stories waiting to be told.