Natural Selection Argumentative Analysis

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One of the most important contributions made to the science of evolution by Charles Darwin is the concept of natural selection. The idea that members of a species compete with each other for resources and that individuals that are better adapted to their lifestyle have a better chance of surviving to reproduce revolutionized the field of evolution (Darwin, 1859), in addition The theory of natural selection is conditions of a habitat will 'naturally select ' individuals who are best adapted to that specific environment. Those individuals are more likely to grow to adulthood and reproduce. In short, sexual selection will vary according to environmental conditions. though it was not accepted until several decades after Darwin first proposed it…show more content…
All australopithecines possess anatomical characteristics of the pelvis, femur and spinal column that facilitate bipedal locomotion. Whether or not the australopithecines were fully adapted bipeds is still hotly debated in the literature. There are several important adaptations to bipedal locomotion that can be observed on skeletal material. First, the foramen magnum is shifted forward, underneath the skull. This positioning is indicative of the angle at which the spinal cord enters the skull (Tobias, 1998). The 's ' shape of the spine aids in balancing while walking on two legs (Johanson and Edgar, 2006). Adaptations more directly related to bipedal locomotion can be observed in the pelvis, the bones of the leg and the foot. The pelvis of a bipedal hominid is wide, with relatively short ilia that form a basin to support the internal organs. This arrangement facilitates the positioning of the hip muscles laterally with respect to the legs, enhancing balance while walking on two legs (Johanson and Edgar, 2006). The neck of the femur is lengthened in bipeds, adding leverage to the hip abductors and increasing the efficiency of bipedal locomotion (Boyd and Silk, 2003). Additionally, the articulation between the femur and the pelvis, and the arrangement of the knee ensure good distribution of weight while walking (Johanson and Edgar, 2006). The tibia also displays several features which indicate weight transfer from one leg to another: a relatively large proximal condyle and a near right angle between the proximal shaft and proximal articular
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