The Evolution of Walking Upright - Essay Example

?Introduction Walking upright is one of the important characteristics or traits of humans which distinguishes it from other species. Over the period of timed, humans have developed the ability to walk upright and thus conserve their energy as compared to apes or other species which spend more energy while walking on their four. Though the initial thinking in anthropology was based upon the fact that hominids are different due to their big brains however, this thinking clearly changed as more historical research came to the light. The evolution of the walking upright and how humans learned to walk on two legs took place over the period of centuries. Early humans use to climb trees easily due to their ape like traits however; this was considered as necessary to allow humans to actually live in different habitats. The overall history of walking upright and how humans developed this ability therefore is almost 6 million years old. The earliest evidence of Sahelanthropus suggests that humans might have learned to walk on two legs approximately 6 million years ago. This evolution is again considered as important to actually allow humans to live in a diversified environment consisting of both the forests as well as grassland. With this evolution, human physiology also changed to allow humans to accommodate to work on two legs. (Nanda and Warms,36) This paper will discuss and explore as to how humans learned to walk upright on two legs and what physiological changes have actually allowed humans to actually walk on their two legs. Bipedalism Bipedalism is considered as a form of locomotion under which different species move by means of their two legs. The animals and all those species which move on their two legs are called bipedal. Humans are considered as one of the important species which evolved over the period of time to walk on their two legs. The debate and the overall hypothesis regarding the bipedal nature of humans are relatively long and require an extensive understanding as to how and when humans became bipedal in nature. It is believed that bipedalism evolved before the evolution of the large human brain or the stone tools used by the humans for hunting purposes. One of the key hypotheses was that the bipedalism was developed in order to free hands so that humans can actually hunt easily and move more efficiently. However, later scientific evidence clearly suggested that it may not be the case as evolution of walking upright has a history before the full human brain actually evolved. (Wheeler,62) It is critical to note that walking upright has not happened over the night and there were important physiological changes which occurred over the period of time. Available evidence suggests that there are important and critical differences between the physiology of the spines of apes and humans. It is this change especially in the physiology of spines of apes and humans which distinguishes them from each other. It was also this change which allowed humans to walk upright as compared to how apes walk. (Hunt) Physiology of Ape Scientific evidence suggests that early humans were either apes and evolved over the period of time to become humans or used some of the characteristics of apes. The early evidence that the humans actually used the ape like traits indicates that humans might have used four feet to actually move from one place to another. However, as the time passed by, humans developed the ability to walk upright suggesting a change or transition in the physiology of apes to suit to the human needs. Some of the early evidence do suggests that the apes were bipedal in nature too however, their ability to walk on four feet was limited in nature. Apes cannot walk for longer distances on their two legs thus making it relatively impossible for them to use two legs for covering greater distances. This ability therefore was restricted due to the overall physiology of their spines and how it differed from that of the humans as evolution took place. Though the apes can still walk on two legs however, to become fully bipedal in nature, important changes occurred in the skeleton of the apes. These changes occurred mostly in the skull, feet, knees and pelvis of the apes. A closer analysis of the physiology of the ape’s spine would suggest that it has a gentle curve whereas the spine of the humans has actually an S shaped curve. The gentle curve in the spine of the ape actually allowed it to carry the weight just above the hips while freeing other parts to allow apes to move easily over long distances. The spine generally enters the skull from the back which is considered as necessary because the spine of the apes is of parallel to the earth allowing them to actually carry weight on their hips while freeing front feet to easily move while carrying the weight. (Haviland,75) It is also critical to note that the spine of the apes is parallel to the earth whereas human spine is often upright and in vertical position. The overall pelvis of apes is also considered as different from that of the humans where the pelvis of apes is often flat and long thus forming a bony plate in the lower back where the spinal joints actually meet with the legs. Spinal length is other important parameters which differ from the humans because the spinal length of humans is relatively larger than the spine of the apes. This may be due to the curve in spines of apes. It is also important to understand that the neck of the apes is not supported by the spine and it is also because of this reason that the back of the apes is often having strong muscles to actually support it. The hip bone of the apes is relatively long too as compared to the humans which is essential bowl shape supporting its internal organs as well as balance the center of gravity within humans. Apes do not have such shape of their hips. Physiology of Human Spine The human spine is considered as the link between the human brain and the rest of the body as spine is being used to communicate between the brain and the rest of the body. The human spinal card looks like a long rope which runs from the base of the brain and goes down to the lower part of the back. It is also considered as one of the fragile parts of the body because the overall dependence of body to sustain itself and move largely depends upon the spinal card or the spine. The human spine is also called the backbone and the spinal cord of the body is actually supported by the backbone or the spine of the body. The human spine is basically a stack of 29 smaller bones which rest upon each other and these bones are called vertebrae. These vertebrae are cushioned when human spines bends down or move ahead to actually the efficient and painless movement of the spine and the body. (Kilgore, Trevathan and Ciochon,12) Human spine is actually joined with the head from the beneath as opposed to the apes as ape’s spine is joined with the head from the back side. The human movement occurs due to combination of certain anatomic features such as stretched knees, feet movement and the spine movement. These features also allow humans to walk upright on their two feet as opposed to the apes which walk on four legs due to their physiology. In order to allow humans to be fully efficient bipedal, the human skull practically resides on the spine as opposed to the apes. The pelvis of the humans is relatively bowl shaped in nature allowing humans to not only support their internal organs but to balance the gravity also in order to avoid falling down on the ground while walking on two feet. Further, the knees of the humans are in knocked nature which actually allows humans to kick forward as opposed to the apes who have relatively shorter knees which are often hard to bend thus not allowing apes to kick forward easily. The human legs also angle inwards to allow easy movement forward besides balancing the gravity on both sides supporting humans not to shift gravity on either side of the legs thus allowing easy and free movement. The fact that the spine is balanced over the pelvis of the body allows humans to maintain upright posture. It is also due to this reason that the minimum workload is placed on the muscles to actually maintain the upright posture thus allowing humans to walk over longer distances without actually straining their body or muscles with excessive stress and pain. It is also critical to note that the human spine is considered as important to protect the nervous system of the body. Spine works as a protective layer over the spinal cord of the body which serves as communication link between the human brain and rest of the body. The Evolution of Walking upright Though changes in physiology of spine of humans played an important part in ensuring that humans free their hands to hunt and gather food for themselves. The overall evolution of the humans and how they developed bipedalism therefore is based upon a diverse set of hypothesis as well as the evidence which outlines various reasons for this evolution. The Savannah based theory is one of the earliest attempts to define this evolution and how humans actually developed this tendency to walk on their two feet. According to this theory, while living in Savannah region, humans have to come down from trees and resultantly in order to gather food and other things; humans have to evolve the bipedalism to become well equipped to face the new challenges specially related with the food gathering and animal hunting. One important assumption under this theory is based upon the notion that due to global warming and cooling, humans have to come down from the trees and adapt to the new challenges of living on soil permanently because forests were rapidly shrinking down. What is also important to note that as this evolution was taking place and the humans learned to adapt to the walking upright, humans still had the ability to hang on trees and climb on them. As such, this suggests that at the time of evolution of walking uprights, humans have the capability to climb on trees and hold on to the tree branches. (Meldrum and Hilton,10) The Savannah Theory however, is not entirely correct in the sense that there is scientific evidence which clearly suggests that bipedalism started some 5 million years ago whereas hominids moved into Savannah some 3 million years ago. This clear gap therefore may suggest that the overall history of evolution of walking upright is approximately 5 million years ago. (Deacon,50) Another important theory regarding the evolution of walking upright is the knuckle-walking. It is now argued that the knuckle-walking may have been the start of the evolution towards bipedalism and walking upright as without knuckle-walking, it may not be possible for the humans to walk straight. It is suggested that walking upright consumes less energy as compared to the knuckle-walking therefore in order to consume less energy and travel large terrain humans may have to evolve a more efficient and less energy consuming method to walk long distances. By studying the biomechanics of both the chimpanzees and humans, anthropologists were able to suggest that taking shorter steps consume more energy or if there is more active muscle mass. As compared to humans, chimpanzees have the natural tendency to take shorter steps and thus consume more energy as compared to humans. Walking upright and on two feet therefore helped humans to actually run and walk briskly to chase their prey more efficiently because it offered them more energy to walk and run easily. (D'Aout and Vereecke,34) It is also important to note that this lesser consumption of energy by walking upright also helped developed another important tendency in humans to transfer heat out of the body. While chimpanzees have thick and large hair whereas humans have relatively thin and fine hair which can easily allow humans to actually lose heat at much faster rate. This quality along with the natural sweat glands therefore assisted humans to become more efficient at losing heat from their bodies as compared to other animals. The lack of fur on human body along with the less hair made humans more efficient at walking and thus in order to conserve the energy in the body and walk long distance, it became natural for humans to evolve a more efficient walking system which can allow it not only consume energy but also effectively navigate difficult terrains where humans lived initially during the early periods of living as bipedal. The role of terrain and overall area of navigation for humans is also considered as one of the reasons as to why humans actually started to walk-upright. The rough terrain in Africa and the later migration of humans to other areas of the globe may have been one of the reasons as to why humans were forced to adapt a different posture. This theory of navigating the rough terrain has come from archaeologists suggesting that the upright gait may have been the direct result of rough terrain which humans have to navigate in East and South Africa. The areas where early humans were living constantly changed due to volcanic eruptions and shifting of tectonic plates thus forcing humans to actually adapt to a different posture and gait. This theory further suggests that this terrain was difficult and as such offered security for humans due to the very nature of the terrain however; this difficult terrain offered an opportunity to humans to move across difficult terrain, balance themselves, climbing difficult rocks as well as scrambling and moving across broken ground. The difficult terrain therefore offered an added motivation to humans to actually improve their locomotive skills. (O'Carroll) This theory is relatively different from the above defined theory which suggested that humans started to walk upright because they lost the tree cover necessary for their safety. As discussed above that the humans have to come down from the trees not only because of thinning of the forests and climate change but also the food requirements. The recent theories however, suggest that it has more to do with the rough terrain rather than coming down from the trees. The rough terrain was not only safe for living purposes but it was also considered as ideal for trapping the preys thus was more suitable for hunting purposes. The above theory of evolution of walking upright also suggests that the rough terrain may have contributed to the development of the other skills of humans also. The development of cognitive skills as well as the communication skills may be attributed to the use of rough terrain. The developed cognitive skills may have further contributed to the development of walking upright as brain changes may have further supported this movement. Conclusion Walking upright is considered as the primary and fundamental difference between humans and other animals. This tendency to walk upright however, has evolved over the period of time as humans are believes to be belonging to the same species as that of chimpanzees and gorillas. It is important to note that humans developed this tendency due to the changes in the physiology of their spines as spine of humans is relatively different from that of the spine of other animals. The human spine is relatively upright and supports its natural organs while at the same time supporting humans to walk easily. Human spine is joined with the head from the back whereas the spine of apes is joined from the back. The curve in the spines of apes allows them to carry weight however, restrict their movement. One of the important theories of how humans developed the ability to walk upright is called Savannah theory. This theory suggests that humans developed this tendency because the climate change forced them to come down from trees. The global warming as well as cooling reduced the number of forests therefore humans have to come down the trees to survive. This theory however, has been challenged by recent evidence which suggests that walking upright on two feet was made possible because of the difficulty faced by the humans to navigate the difficult terrain of East and South Africa. Further, walking upright conserves the energy thus allowing humans to walk longer distances with relative ease and less energy. Works Cited D'Aout, Kristiaan and Evie E Vereecke. Primate Locomotion: Linking Field and Laboratory Research. London: Springer, 2011. Deacon, H. J. Human Beginnings in South Africa: Uncovering the Secrets of the Stone Age. Cape Town: New Africa Books, 1999. Haviland, William A. Cultural Anthropology: The Human Challenge. London: Cengage Learning, 2013. Hunt, K.D. "The Evolution of Human Bipedality." Journal of Human Evolution 26 (1994): 183-202. Kilgore, Lynn, Wenda Trevathan and Russell L. Ciochon. Introduction to Physical Anthropology. London: Cengage Learning,, 2011. Meldrum, D. Jeffrey and Charles E Hilton. From Biped to Strider: The Emergence of Modern Human Walking, Running and Resource Transport. London: Springer, 2004. Nanda, Serena and Richard L. Warms. Cultural Anthropology. London: Cengage Learning, 2009. O'Carroll, Eoin. Why did our ancestors start walking upright? Ancient terrain may hold clue. 24 May 2013. http://www.csmonitor.com/Science/2013/0524/Why-did-our-ancestors-start-walking-upright-Ancient-terrain-may-hold-clue. 22 November 2013. Wheeler, Peter. "Stand Tall and Stay Cool." New Scientist (1998): 62-65. 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