Walking upright on two legs is the unique characteristics that separate human beings from all other known primates. The unique attribute of the adaptation of skeleton to the bipedalism is utilized to recognize human hominid ancestors. However, due to the lack of the fossil record as evidences, the fragmentary of the remains of fossils as well as the challenges from inferring particular behaviour from such fossils, many vital questions have been remained unanswered which are related to the evolution of human bipedalism (Friedman,2006). Nonetheless, over the last few decades, various researches and studies are being conducted in order to enhance the knowledge regarding human locomotion mechanics to have deeper insights into the bipedalism of human beings. This paper is going to critically analyse and evaluate the history and background of human bipedalism. During the discussion the development of stone-tool technology will be considered in the paper. It is also focussed to discuss all the theoretical aspects of human bipedalism in brief.
Human bipedalism was driven by the principle of natural selection by Darwin. Hominines did not become bipedal for any specific reason but time allowed the evolution of bipedalism in humans as it was a favourable trait (Thorpe, McClymont & Crompton, 2014). It was beneficial for the efficient survival of both the units itself as well as its offspring. Out of all the great apes, hominines are the only species to have features of bipedalism. According to some modern anthropologists, the enlarged as well as complex brain structure of human being also contributes to the evolution of bipedalism among them. Paleoanthropologists, who study the evolution of human beings, provided a variety of ideas regarding the association between human evolution and the environmental factor. The environmental conditions stimulated many important developments of human origin. Human evolution coincided with multiple environmental factors that include environmental change such as cooling, drying, climate fluctuations and many others. Hominines experienced a large scale shifts in the temperature and precipitation that caused vast changes in the vegetation which shifted grasslands and shrub lands into woodlands and forests and as a consequence various changes in the climate had also been experienced (Foley & Gamble, 2009).
There is diversion as well as variation in the locomotive behaviours of primates. Apes, including chimpanzees, gorillas, gibbons and others show some particular loco motor habits arm swinging, fist walking, quadrumanous wlking and others (Schmitt, 2003). The most common mode of locomotion among the primates is the quadrupedalism. The walking gaits of primates widely differ from the other mammals. First of all, most of the primates use the diagonal sequence footfall pattern. Secondly, according to some researchers, primates have humerus which is relatively protracted at the forelimb touchdown. Thirdly, some other literatures indicated that most of the primates have relatively greater peak vertical forces on the hindlimd. Even, some studies by the researchers also revealed that quadrupedal primates used walking gaits that involved substantial increases in elbow flexion (Winder, King, Deves & Bailey, 2014). This kind of walking style has been documented in a wide range of primates which includes large-boiled quadrupedal apes. Various different features have been acquired naturally due to the human bipedalism. In this different and new mechanism of the body, the skull is balanced directly on the top of the spine. These features support the vertical trunk of the body and at the same time, it efficiently transfers the weight through the legs during standing, walking as well as running. Apart from that, various other features of human bipedalism have been achieved by the hominines. The closest living relatives of human being such as chimpanzees can spend very little time being bipedal due to the absence of such special features.
Many researches and studies have been conducted to find out the actual reason behind the transformation of human being into bipedalism traits, but no satisfactory result or evidences have been found in this regard (Winder, King, Deves & Bailey, 2014). Darwin linked this feature to tool use especially for defence as well as hunting. The theories of twentieth century proposed another range of factors that has driven the evolution of hominine bipedalism. Furthermore, as an environmental factor, scientists indicated that bipeds were regularly exposed to direct sunlight and standing upright would be benefited in many ways such as less body surface would be exposed to direct harmful sunlight and it would help them in finding relief in the cooler air.
Stone tools and its contribution towards evolution
Paralleling to biological evolution among the human beings, development of many new technologies and cultures allowed them to become successful and the main origin of evidence behind the success can be seen as the innovation and creation of stone tools and use of them for different survival purpose (Proffitt et al., 2016). According to some anthropological evidences, the first unquestionable stone tools were used by the human beings of East Africa almost 2.5 million years ago (Lewis & Harmand, 2016). They were named as Oldowan tools after the location and it consisted of different categories (Harcourt-Smith, 2010). The species of such stone tools have been found by the anthropologists at various sites in association with animal bones that displays the characteristics of those tools in the use of butchery or hunting any animals and this discovery of anthropologists provided indirect evidence of tool use. Even, some of the experts suspect that by 2.6 million years ago hominids had been making several kinds of stone tools for thousands of years and they were using it for different survival purpose (Diez-Martín et al., 2015). The origins of stone tools might have started more before according to some experts and it was considered as the first stage of human evolution (Harmand et al., 2015).
Origins of anatomically modern Homo sapiens
The fossils record, available to reconstruct the evolution of human being is relatively sparse and poorly dated. No informative fossils are there to clearly identify the actual early inhabitants (Stringer, 2016). Thus, the available records are highly biased and researchers still need to work to make the evidences stronger. Large number of human skeleton and dental materials has been recovered as an evidence of the origin of human being. Human pelvis also play a major role in many critical biological purposes and the fossil records reveals a profound story of the evolution of human pelvis. The pelvis of modern Homo sapiens is divided into upper and lower halves (Diogo, 2018). The upper half supports in changing the height and position and affects the ability to balance the body. Changes in the lower half of the pelvis ischium, sacrum and pubis, affects the anteroposterior as well as the transverse diameter of the birth canal. Even, the shape of the lower half of the pelvis always determines the shape of the birth canals which shows important differences between humans and the apes (Gruss & Schmitt, 2015).
Theoretical framework of human bipedalism
Some theories consider the efficiency of upright walking of human bipedalism feature. In the year 1980, some scientists stated that in response to the climate change, the hominids evolved to walk upright. Due to the environmental changes, the most efficient as well as energetic way to walk on the ground is bipedal walk and it as it was beneficial, it remained among the human origin. In the year 2007, a team of researchers conducted research on chimpanzees and founded that chimpanzees required 75% more energy while walking on treadmills when compared to two-legged humans. Due to all these reasons, bipedalism was welcomed and it also remained as an efficient feature among the human origins.
Heat theory
In his theory, Peter Wheeler first recognized the thermoregulatory advantage associated with the evolution of human bipedalism. According to the savanna based theory, the early humans were forced to adapt the method of bipedalism for their benefits. However, there are controversies and many other researchers argued that savanna grasslands were not the place of human bipedalism as some of them happened in the forested grasslands. Thermoregulatory change among the hominids took place, but there is no strong evidence to prove it as the reason behind the bipedalism (Lieberman, 2015).
Theory of energetic efficiency
The enhanced transportation efficiency can be considered as the reason behind human bipedalism according to this theory. Upright walking is effective and comfortable when compared to the walking of chimpanzees. However, the major challenge of this theory is that the first hominids did not possess the morphological changes which must exist in the theory (Gruss & Schmitt, 2015).
The vigilance theory
The theory was coined by Raymond Dart which states that in order see through the tall savanna grass, human acquired the position of standing upright and when they noticed it as advantageous they acquired it totally. In order to view the surroundings, some other creatures like squirrel, chimpanzees and others also can stand in an upright position for some time (Lieberman, 2015).
Conclusion
Theoretical evidences highlights the natural selection is aided to bipedalism and it has been hailed as one of the greatest evaluation of human beings. Many researchers and scientists have also gathered evidences in this regard. This paper clearly highlighted the origin of Homo sapiens along with its modern anatomical pelvis structure. It also discussed how creation and utilization of stone tools are associated with the human evolution. Finally it managed to jot down some theoretical aspects in this regard. Due to the new features, it is quite obvious that human beings are superior to other primates due to their ability of bipedalism as well as complex and elevated brain structure.
References
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