Quadrupedalism Research Paper

Quadrupedalism is the form of locomotion that uses all four limbs. Most, if not “all primates are, at least to some degree, quadrupedal, whether they’re entirely arboreal or spend some time on the ground” (Jurmain et. al. 2013: 130). Quadrupedal animals, also known as Quadrupeds, move with a pronograde posture. This is a posture in which the body is parallel to the ground.

Bipedalism is the form of locomotion in which the animal uses only two legs. Animals that use bipedal locomotion are called bipeds. Examples of bipedal locomotion include walking and running. Many quadrupedal primates are able to use bipedal locomotion but because of their anatomy, are unable to use bipedalism as their main source of locomotion. This is called facultative …show more content…
According to Lovejoy, chimpanzees and gorillas exhibit a bent-hip/bent knee (BHBK) gait, which is a direct consequence of an inability to position the center of mass of the head, arms, and trunk over the point of ground contact without simultaneously flexing both the hip and knee. (2005: 95). This is due to the fact that the great apes had very immobile lumbar spines in comparison to modern humans. They had much fewer lumbar vertebrae with the bottom vertebrae being immobile, causing them to have very stiff upper bodies with little to flexibility in their lumbar spines. That is why when it came to bipedal locomotion; the great apes had a very stiff and unbalanced gait which was also much more fatiguing in comparison to humans. As the need for bipedal locomotion increased, the need for balance also increased. The lumbar spine eventually lengthened, and became much more mobile than that of the great apes. The ilia and sacrum of the also became much wider and shorter. This was due to the fact that weight was dispersed differently through the pelvis in quadrupedal and bipedal locomotion. As a result of the widening of the sacrum the sacroiliac joint, which connects to the sacrum, caused a forward curving of the lower spine, called a lumbar curve. This curve along with the backward thoracic curve in the upper spine helped keep the weight centered and …show more content…
To accommodate for the increase of pressure as the hip joints spread, the femoral head adapted and grew in size to counteract and absorb the pressure. As the gluteal muscles became the main propulsive force that pushes the leg for locomotion, the femoral neck also grew in length to give the gluteal muscles an advantage. The femur was then angled inwards in order to keep the legs more directly under the body (Jurmain et al. 2013:203). This causes the knee joint to be closer to the center of the body than the hips. This angle is referred to as the bicondylar angle, with the knee joint referred to as the valgus knee (Kappelman 2007). By having the knees closer to the center than the hips, the feet become situated right below the center of

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