Theories Of Bipedalism

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Essay outline – Theories of the origin of bipedalism. Introduction: There are dozens of theories that have been constructed to explain the evolution of the human upright posture and locomotion. It is unlikely that there was only one “specific reason why bipedalism was selected for” (Harcourt-Smith 2007), but it is clear that bipedalism provided a clear survival benefit. The theories to be discussed are arboreal bipedalism; the theory that our ancestors descended from the trees, allowing fluid locomotion. Freeing of the hands; the theory that the need for hands pushed us upwards and lastly, the aquatic ape theory; wading in water thrust us to walk upright. The negatives and positives of each theory will be examined to determine their likeliness or degree to which they would have affected the evolution of human locomotion. Theory One: Freeing of the hands The combination of tool use and the increasing need of “free” hands may have helped drive extreme lateralization in modern humans. a) Braccini (2010) researched the relationship between chimpanzee tool use and the ensuing effects on lateralization and posture. b) During tool use, chimpanzees would automatically become more lateralized, especially if the stance was supported (Braccini 2010). Therefore tool use may have pushed our nearest ancestors upright. a) What Braccini does not state is why chimpanzees and other great apes never evolved towards bipedalism since they all use tools (to an extent). b) Carsten (2010) discussed that the earliest of ancestors would have needed hands and arms for many reasons (self defense, food gathering, infant carrying), but was most likely “neither a trigger nor a promoter of walking upright”. Theory Two: Arboreal Bipedalism Instead of bipedalism stemming from an adaptation from knuckle-walking or other well-known theories, ancient ancestors

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