Write an essay that identifies and discusses the many selective

Write an that identifies and discusses the many selective pressures leading to bipedalism in our ancestors and us - Essay Example While habitual bipedalism does not seem like the most effective and fastest form of walking and running, it portends various advantages for hominids over specific specialized quadrupedal forms. Although the reason why early hominins took a bipedal stance is not entirely clear, majority of these hypotheses propose the importance of selection pressures based on the environment in driving bipedal evolution (Sarmiento 62). As climatic conditions resulted in the recession of forests, hominins started to move out of the forests into the grassland savannas where it was essential to assume bipedalism to aid in survival. The postural feeding hypothesis seeks to assert the fact that a shared postural specialization and adaptation of apes, as well as the arboreal postures of food gathering involving vertical climbing and arm-hanging, are adequate enough to have been a selective pressure encouraging bipedalism in hominids (Sarmiento 63). The anatomy of both the australopithecine and the behavior of chimpanzees are the major points that inform this model of selective pressures towards bipedalism. For instance, at least 80% of the time that chimpanzees spend in a bipedal stance is when they are feeding, of which they use arm hanging to stabilize their posture at least 90% of the time in terminal branches of the trees, while 52% of arm-hanging occurs in the trees’ central parts (Sarmiento 63). For australopithecines, their torso form has adaptations to arm-hanging, which may infer that australopithecines adapted to selective pressures requiring arboreal fruit gathering. This specialized and early m ode of bipedalism evolved to become habitually bipedal much later. On the other hand, the behavioral model as an explanation for selection pressures resulting in hominid bipedalism concentrates on mechanisms of social behavior that influenced birthrate and survivorship. Human