biosc writing origin of bipedalism

Bipedalism is one of many characteristics such as

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Bipedalism is one of many characteristics such as small canines, and large cranial size, which are unique to modern humans when in comparison with ape forerunners (White 2009). Using the structure of canine teeth and skulls is at times thought to be better for classifying ancestral species as being that of the Panini or the Hominini origin. For instance, due to the abundance of dentocranial fossils, it’s often this particular part of the remains that is considered essential to phylogenetic analysis (Crompton 2008). Yet, for phylogenetic analysis having a bipedal gait is a crucial element in the evolution of modern humans and bipedalism should be the foremost characteristic used when classifying fossils as hominin, or as non-human primates. The aim of this paper is to provide the differences of morphology between hominins and primates; to show through the recently discovered fossil evidence of Ardipithecus ramidus why bipedalism should be the definitive characteristic used in classifying past and future fossils as part of the human lineage. Lineage: All ape species fall into the mega-family of Hominoidea , which thus has two sub families, those being Hylobatidae and Hominidae . The Hominidae sub family is in itself comprised of three sub families which are Ponginae (orangutans), Gorillinae (gorillas), and lastly Homininae . The latter sub family then consists of two tribes, the Panini (chimps and bonobos) and Hominini (modern humans) (Crompton 2008). All the apes mentioned above share truncal morphology to one another, therefore, the importance and difficulty of classifying ancestral species in the outlined Hominoidea lineage should not be understated (Crompton 2008). This is also illustrated within Figure 1. Morphology: Bipedalism is the key defining feature between hominins and extant apes (Preuschoft 2004). There is a distinct divergence between panins, who employ knuckle-walking as their main method of transportation, and that of hominins, which evolved bipedalism as their system of movement (Crompton et al. 2010). Evidence of this can be seen in the occurrence of dissimilar anatomical features of panins and hominins to one another. The most crucial structures which indicate whether bipedalism will evolve in a species are the pelvis, femur, and vertebrae. In African apes craniocaudal differentiation has occurred
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O’Connor within the pelvis in which the lengthening of the iliac isthmus consequently causes the lower ilium to be extended cranially. This transformation of the decrease in the lumbar column and tightening of the sacral alae, within Pan, will confine and dorsally extend the lumbar to the iliac connection in the sagittal plane, eventually entrapping the caudal lumbar. The combination of decreased vertebral height with fewer (3-4) lumbar vertebrae will eradicate thoracopelvic mobility within panins (Lovejoy and McCollum 2010) (Figure 2). Subsequently, this allows extant apes to be impeccably adapted to vertical climbing and suspension, but for the ability of a bipedalistic gate to be unfeasible (Lovejoy 2009).
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  • Fall '12
  • Ernst
  • Hominidae, Hominina, Ardipithecus, bipedalism, C. Owen Lovejoy, Ar. ramidus

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