Evolution of Bipedality in Humans Essay

bipedism is a capacity, mostly associated to humans, to use two legs in motivity. Its origin has been given enormousness and distri just nowed as a topic of long debate among experts delinquent to the opening night that this form of loco bm gave elan for the development of modern human characteristics. Thus, a lot of theories were proposed and established in fellowship to result the logical rendering on its origin and development. The saddle of dealing with this classical issue lies on the fact that motivity is an activity that can not be fossilized.However, the genus Australopithecus af bensis fossils, the earliest hominid from Ethiopia and Tanzania, were found to live 3 cardinal eld after the appearance of hominid lineage around 6. 5 million geezerhood ago (Bipedalism, 2000). These fossils in a way may serve as evidence not save of bipedal travel plainly as well as hominid dental characteristics similar to apes. Bipedalism enabled humanoids to create tools appl y for the maintenance and defense of life and is also observed in premature(a) carnal species (Dhingra and Jablonski, 2004).This trait is commonly attributed as a product of evolution for it coincided with the physiological development of the human brains. As some(prenominal)(prenominal), bipedal locomotion has gone a very long and different history within physical demesne. Bipedal Locomotion Human locomotion is described as a savor slight flow of a series of actions including jounce and situation anatomys (Bipedalism, 2000). In the traverse phase, one leg shoves off done the toe then swings in slightly flexed position. As the foot creates contact on the ground through the heel, the leg becomes and remains extended to support the eubstance.Then, as the leg touchs in the swing phase, the body moves in the stance phase. On the other hand, chimpanzees are not capable of extending their knee-joints for a straight leg in the stance phase. They exert muscular power to sup port their bodies while their leg flexed tread denotes lack of toe off and heel strike in the swing phase. The human anatomical reference reference body structure is fully developed for terrestrial locomotion while chimpanzee anatomy is adapted for climbing and knuckle walkway (Bipedalism, 2000).Human anatomical adaptations include extensive and curved lower spine, a shorter and broader pelvis, a longer lower limbs and enlarged joint surface areas. In the swing phase, the heaviness of the body is delivered to the supporting leg while the symmetry is maintained at the unsupported side in the stance phase through contraction of gluteal abductor muscles in the hip. In chimpanzees, the gluteal abductors are not fully developed and their thigh bones do not slope inwards as in humans.Their feet are commonly a little bit apart and in walking, they tend to shift their upper bodies from side to side so as to transfer the weight on each leg. It is a fact then that chimpanzees and gibbon s can move through bipedal locomotion. Thus, as viewed by anthropologists, bipedalism is a hominid unequivocal adjustive capability (Bipedalism, 2000). Humanoids spend less energy through bipedalism than quadrupedalism because at a normal walking speed, the legs in a forward motion swing like pendulum then bringing back the forward neural impulse by slowing the swing foot before the fall (Hawks, 2005).Hence, this requires less muscular activity and energy than knuckle-walking. much all over, bipedalism raises the head which gives a sharp prune vision around the environment and making men available for carrying tools, solid aliment for thought items or other works. However, for early humanoids, bipedalism can offer disadvantages (Hawks, 2005). Without the ability to chain through feet makes them unsecured from their vultures. The loss of grasping foot made fractious for the early humanoids to climb through tress and escape predators, and for their young in clinging to thei r parents.Researches Findings Biologist and anthropologists have debated over bipedalism and proposed different hypotheses for possible account. However, these theories have their various(prenominal) strengths and weaknesses on the plausible understanding with bipedal locomotion. roughly of these theories correlated bipedalism to the animal species ventures on the savannah areas and was supported by the discovery of Lucy, a 3. 5 feet humanoid (Johanson, n. d. ). Standing up in savannah gives stunted humanoids a vigilant view on possible threat from their predators.Standing up in reaching out for foods is another possible explanation. In addition, an dependable posture may also help our antecedents in cooling their bodies against the animal(a) environment. In the postural feeding hypothesis of Hunt (1994), bipedalism has evolved from the early customary bipedal locomotion of humanoids due to woodsy food gathering. The conduct of chimpanzees and the anatomical structures of au stralopithecine conformed to this ecological moulding. Eighty percent of bipedal locomotion in chimpanzee was observed during feeding with arm-hanging stabilizing the posture.In addition, the upper body anatomical structures of australopithecines were ascribed to arboreal bipedal fruit gathering adaptation. The behavioural model of Lovejoy (1981), on the other hand, attributed bipedalism to the social, sexual and reproductive behaviours of early humanoids. Their sexual characteristics and anatomical structures were believed to be an implication of monogamous mating. This sexual attitude led to provisioning behaviour of the humanoid male species wherein their upper limbs were used in giving food stuffs to their mates.Even Charles Darwin constructed a model in providing a logical explanation for humanoid origin and bipedalism. He postulated that bipedalism impressioned from the terrestrial adaptation of quadrupedal species and the exigency for subsistence, required to giving freedo m for hands to accommodate other activities such as making tools for food hunting (Hawks, 2005). Aside from this, he also assumed that the habitat change from woodland to savannah paved the way for the less importance of climbing.Then, other researchers augmented Darwins assumptions by elaborating that upkeep in savannah made early humanoids to be vigilant over tall grasses and adapt in its sultry condition (Hawks, 2005). Thus, bipedalism provided them means for adjustments at these conditions by standing up leading to less sun video of the body. This model became the savannah model or killer-ape hypothesis. The aquatic supposition and the theory on the use of tools are deemed to offer unreliable explanation (Johanson, n. d. ). Most of the time, primates avoid water due to ferocious predators. On the other hand, stone tools only appear around 2.6 million years ago as contrasted with the 4. 2 million year-evidence of bipedal locomotion. According to Johanson (n. d. ), it is much b etter for the theorists to look not into the reason for the upright posture of our ancestors but rather on the advantages for the early humanoids that resulted to a behavioural change from quadrupedalism to bipedalism. Videan (2002) tested the different hypotheses for bipedalism (cited in Dhingra and Jablonski, 2004). The Carry Hypothesis described bipedalism as an adaptive means in the exploration of natural resources while carrying children, tools or foodstuffs.The food Hypothesis viewed it as a means towards the food gathering facilitation. Also, the conception that bipedalism gives animal species a sharp sense of sight in order to find good habitats prey or escape from a predator is called as Vigilance Hypothesis. vaunting Hypothesis on the other hand, explained bipedalism as a gesture of threat for animal species. Based on the result of this study, Videan (2002) successfully correlated Carry, Vigilance, and Forage Hypotheses towards environmental adaptation of animal species .Nevertheless, the Display Hypothesis gave explanation for the sexual attraction among animal species. Dhingra and Jablonski (2004) scrutinized the bipedalism in some(prenominal) animal species like lizards, birds, kangaroos, and dinosaurs. They concluded that bipedalism resulted from animals natural try out to adapt to their changing environment such as in escaping from predators or catching a prey, and in giving way to bodily part for other functions like the forelimbs in humanoids for feeding and wings of the birds for flying.According to Stanford (2006), arboreal bipedal gait is different from arboreal quadrupedal stance for he observed that while feeding in tree crowns, Bwindi chimpanzees changed smoothly from four-legged to three-legged and make up two-legged posture. This shift may have occurred in early humanoids. novel gorillas are terrestrially adapted but based on observations even adult male gorillas climb into tall trees for food. Thus, it is also possible for earl y humanoids to adapt a variety of bipedalism based on their ecological conditions.More than this, few evidences speak for terrestrial adaptation of modern chimpanzees considering the fact that they used to travel primarily on the ground and stay on trees only for sleeping or feeding purposes. These observations may denote the possibility of behavioral plasticity and arboreality in early humanoids. Based on the review conducted by Richmond, Begun, and Strait (2001), about the different studies on bipedalism, humans evolved from knuckle-walking and climbing ancestor as portrayed by evidences.These include terrestrial characteristics in the hands and feet, climbing skeletal structure, and knuckle-walking attributes in the wrist and hands. These features narrowed down the describe of theories concerning bipedalism. points from the paleobiology and paleoenvironments weakened the postulates based on monogamous social structure and open savanna-based bipedalism hypotheses. Rather, they s uggested giving more importance on hypotheses based on food acquisition and carriage and a deep anatomical exam on the extant anthropoid behaviors. ConclusionNo single mover may completely explain the origin of bipedalism. Perhaps the concoction of the factors considered in each theory that are deemed to be valid may provide much reliable reason for bipedal locomotion. The lack of complete fellowship on the anatomical structure of the early humanoids is a great burden in gaining a complete understanding on the origin of this locomotion (Hawks, 2005). Perhaps, a simple way of explaining bipedalism is that bipedal locomotion evolved as a result from the changes in the environment or social structure that is due to the availability of dietary resources to sustain life.It is hypothesized that in the late Miocene period, hominid food sources dispersed in some areas which forced hominids to travel, thus, led to the development of locomotion anatomical structures (Bipedalism, 2000).Refe rences Bipedalism.Human Evolution. Retrieved November 6, 2008, from http//www. stanford. edu/harryg/protected/chp15. htm Dhingra, P. and Jabslonski. (2004). Comparative Bipedalism how the rest of the animal kingdom walks on two legs. Retrieved November 6, 2008, from http//www. philosophistry. com/static/bipedalism. html Hawks, J. (2005). Why be bipedal?Retrieved November 6, 2008, from http//johnhawks. net/weblog/topics/bipedalism/why_be_bipedal. html Hunt, K. D. (1994). The Evolution of Human Bipedality. Journal of Human Evolution, 26, 183-202. Johanson, D. (n. d. ). What the Evidence Suggests. Retrieved November 6, 2008, from http//www. pbs. org/wgbh/nova/allfours/bipe-johanson. html Lovejoy, C. O. (1981). The Origins of Man. Science, 211, 341-348. Richmon, B. G. , Begun, D. R. , and Strait D. S. (2001). Origin of Human Bipedalism The Knuckle-Walking Hypothesis Revisited. Yearbook of sensible Anthropology, 44, 70-105.