These are the oldest footprints ever found - the discovery that disturbs scientists

When we look at our closest living relatives, we are reminded. Of our particular. Place on the evolutionary tree. The chimps, gorillas, bonobos and orangutans all resemble us in many ways, in both body and behavior. Just like us. Orangutans are able to learn from each other, and they're often seen using tools. Chimps laugh when they are tickled, cultivate friendships and even go to war with neighboring. Groups Gorillas. Have been taught to use sign language and even use. It to lie. And bonobos are. Quick to share. Food and seem to be full of empathy. It's hard to. Gaze into the eyes of any of. The great apes. And not see a reflection of ourselves. However, as. Much as we may connect with our primate cousins, it's been about 6,000,000 years since the death of the last common ancestor. We shared with. Them, and since then, humans have become something quite distinct from the rest. Our brains have more than tripled in size during this time, and with our big brains we've become the most dominant species on the planet, capable of writing novels, building. Skyscrapers and. Exploring the cosmos, we are simply not the same as the. Other great apes in the past few. Million years, individuals belonging to the Homo genus experienced profound evolutionary developments that now serve as the foundation of the human race. These increasingly complex adaptations have allowed humans to fully dominate the globe, living in almost any habitat, controlling their very environments. But how exactly did we diverge so drastically? From the other primates is it? Just our big. Brains that make us. So different or. Something more. What were the? Defining steps in the history of our evolution that made us The Walking, talking, thinking, feeling, society building apes that we. Are what? Were the moments that made us human. For centuries. The very idea that there could. Have been an ancient species of human that existed before our own was inconceivable even though many animal fossils had been found. Through the years. No early human fossils had. The age of the earth was still. Very much disputed with most thinking that humans were created in their present form a few thousand years ago, even once. Darwin published On the Origin of Species in 1859. Few believed the. Concept of natural selection could apply to humanity. Darwin himself was surprisingly silent on the matter. But a pivotal discovery. Unearthed in 1856 during quarrying operations in the Neander Valley in Germany. Would shake. The scientific world pushing it closer to an understanding of the origin of humans. While. Expanding the mine, workers found. A partial skeleton. Of a male individual the likes of which had never been seen before. It was a. Specimen with an. Oval shaped skull with a low. Receding forehead, distinct brow ridges and thick, strong bones. The fossil was. From an individual. That would have had a big. Brain like us. But its other features were quite distinct. Although it certainly looked unique. At first. Even great minds like Darwin did not believe. The fossil could. Be an early human ancestor. But rather. Just an odd Homo sapiens specimen, but soon scientists. Realized. That what they found was not a human like us, but a different. Species altogether. By 1860. 4 the. Specimen became the. First, early. Human species ever named Homo neanderthalensis, The specimen was estimated to be. 40. 1000 years old. Several years after. Neanderthal. One was discovered. Scientists realized that. Prior fossil discoveries. In 1829 in Belgium and 1848 in Gibraltar were also Neanderthals, even though they weren't recognized at the time these two. Earlier discoveries were actually the first early. Human fossils ever found? These discoveries were just the start of our. Understanding of the immense evolutionary journey of humanity soon after, in 1891, another specimen was found in Indonesia this time a much. Older fossil. Eugene Dubois made it his life's mission to find the missing link between humanity and apes, wanting concrete proof. That Darwin's theory of. Evolution and the process of natural selection did indeed apply to mankind and his discovery. Which would later. Become called The Java Man would help to cement our evolutionary story. The Java Man's specimen had a pronounced brow Ridge, like the Neanderthals. An upright. Posture and a. Relatively big. Brain. However, its brain was smaller than the Neanderthals and Homo sapiens. This hominid would be named Homo erectus and lived around 1.5 million years. Ago at the. Turn of the 20th century, scientists began to draw the reasonable conclusion that the unifying feature between us, the Neanderthals and Homo. Erectus was our big. Brains that our intelligence and brain size defined the hominid lineage and set us and our human like cousins apart from the apes. The assumption was that large brain size was a. Precursor to bipedalism that we started. Walking upright to accommodate our big brains. But soon this assumption would be turned upside down. With the discovery of a skull of a. Small child in 1924. A school. So unprecedented. It would. Be called the most important anthropological fossil found in the 20th century. Tongue Child, as it would be named, was found during quarry operations in South Africa. Its brain was 1. 3rd the size. Of modern humans so small that at first, scientists. Thought it was. Just the remains of an ancient ape. But this was no ape. One important feature of the skull made this clear. The Foramen magnum is the void on all vertebrate. Skulls where the. Spinal cord. Attaches to the. Brain in four. Legged vertebrates who? Walk on all. Fours like dogs, cats. Or even chimps. This hole is located at the very back of the skull. In human skulls. This hole is. Distinctly in the middle. This allows the. Human body to be oriented vertically for walking upright. The same is true for the Neanderthals and for Homo erectus and the foramen magnum on the tongue. Child it too. Was located centrally, the placement more similar to Homo sapiens than to chimps. Or other apes. Tongue Child. Would later be classified as Australopithecus. Africanus, a type of hominid that predates the entire Homo genus Tongue Child, is estimated to have lived 2.8 million years ago. The fossil record. Seems to indicate. That Australopithecus is. Ancestral to the Homo genus, including modern humans specimens. Discovered in the. Following decades would help confirm the placement of the Foreman Magnum on this species among the most. Spectacular of these discoveries. Was a fossil nicknamed Lucy unearthed in 1974 in Ethiopia, Paleoanthropologist Donald Johnson and Tom Gray found several 100 bone fragments, which ended up representing 40% of a single hominin, the skeleton included. Parts of the pelvis, legs. And ankle and all of these bones. Proved that, Lucy. Had a body not only capable of walking upright, but a body made to do. So Lucy was classified as. Australopithecus afarensis and the rock in which she was found dated back to 3.18 million years. Lucy helped solidify the. Conclusion that human evolution began with the adoption of two legged walking while brains were still essentially ape like. It is bipedalism that defines the hominid lineage and was the first evolutionary breakthrough that began us on our journey to humanness. The first step. To true humanity was indeed. The first actual. Upright steps taken. But how far? Back Did bipedalism happen in our lineage? Some answers to this can be found not in a fossil, but in a few footprints. Mary Leakey and a team of paleoanthropologists discovered a remarkable number of footprints in 1976, preserved for millions. Of years by the ash of a. Volcanic eruption. There were tracks. From ancient giraffes, baboons, rhinoceroses, hippos, and about 70 footprints that looked surprisingly similar to those of modern humans. Not only did the heel touch the ground first in these. Bipedal walkers, but the feet. Clearly had an arch and a big toe aligned with the other toes. These adaptations are all essential to being able. To walk bipedally. An arch. Acts as a shock absorber. Since the. Foot is. Supporting so much of the. Body's weight. In chimps and other great apes. The big toe. Is more like an opposable thumb. But for. Bipedalism It shifts position to provide more stability and balance. It might seem like dating footprints would be even more challenging than dating fossils, but the Latoli prints were preserved in volcanic ash. Freshly erupted. Lava and ash contain a form of radioactive potassium. That has a very precise half life. It decays into argon and this half life is used by scientists to pinpoint the. Age of such fossils. With an accuracy of about 20,000 years using the potassium argon dating method, scientists stated the. Age of the. Footprints to somewhere between 3.75 and 3.59 million years ago. Given the clear. Evidence that our hominin ancestors were. Bipedal before they evolved to have larger. Brains. The next question becomes what behavioral and environmental? Pressures led to. Bipedalism there. Are a lot of theories. But no conclusive answers at this point. Early on, scientists. Proposed the. Savannah Hypothesis. Other evidence in the fossil. Record shows the. Climate in eastern Africa was becoming hotter and drier around 4,000,000 years ago. The new climate changed the landscape from Woodlands to more of a patchwork of trees and open grasslands. This might have been the push. That got our. Pre bipedal ancestors. Out of the. Trees and onto the ground where they could more easily travel on the open land and reach other. Sources of food like. Seeds from grasses. But in more recent years, scientists discovered an even older hominin, Artapithecus romidus, whose skeleton shows some evidence of bipedalism. Rd. dates. All the way back to four. .4 4,000,000 years ago in Ethiopia when the. Habitat was still very forested with. More frequent rainfall, the fossil seems to suggest. That. Bipedalism could have evolved when hominins were still climbing the. Trees as well, other researchers have suggested. That bipedalism might be tied to. Particular foraging strategies. From the ground, chimps stand on their hind legs to reach fruit in the trees, and this may have been such a. Successful strategy. For ancient hominins. That it slowly. Evolved into outright bipedalism. There's. Also a. Bioenergetic and thermal regulation hypothesis. First, humans walking upright expend 75% less energy than chimps who are walking quadrupedally. That means it would have been much easier for our ancestors to cover long distances than it is for more arboreal. Adapted Species. At the same time, walking upright reduces the amount of sunlight the body. Is directly exposed to, which was very. Important in a hot environment without much shade. The upright posture could have also had advantages for social status. Standing on 2 feet makes you look taller and possibly more capable of attracting a mate. One researcher suggests that the bipedal posture frees up. The hands for striking out. In other words, bipedalism allowed for more fist fighting, which might have been an element of males battling over. Mates, but perhaps? Most importantly, bipedalism freed up hands to carry things from children to food to tools and tool use was the next big step in the story of humanity. Although there are no. Tools directly associated. With Australopithecus afarensis, the oldest stone tools from Kenya date back to 3.3 million years. Ago which is. When the Australopithecines lived while we may not understand the. Precise factors that. Led to bipedalism. It's clear that this. Evolutionary adaptation was a watershed moment in human history, opening the gates for millions of. More years of. Profound and unique evolutionary changes. The Evolutionary. Story of humans is unlike anything else, and that's why we made. An entire series about it. About how one adaptation cleared the path for the next. Allowing us to become the upright hairless. Emotional, intelligent, and. World dominating apes. That we are today entire year.