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Bipedal Pelvis

When I think of bipedalism and its effects on the skeleton my thoughts always go to the pelvis. I guess since the pelvis is one of my favorite parts of the body because of the unique design evolved for our bipedal locomotion and some fun other stuff. Overtime in our different species ancestors there are changes within the pelvis that allow us to walk upright without discomfort, and (tying back to my previous blog post) why our pelvis is much different than our cousins the chimps. We evolved our narrow anatomic modern pelvis with a more circular birth canal about 200,000 years ago (Gruss, Schmitt 2015), but it did not happen all at once. This took millions of years of our changing of different species ancestors who used different locomotion or in later times similar locomotion to get were our pelvis are now. according to Gruss and Schmitt our pelvis are shorter than that of apes which lowers our center of gravity allowing lumbar lordosis to occur (inward curve in our lower back). This allows us to walk full time as bipeds and not have any trouble with it. While we walk our pelvis allows for us to be supported by one leg and the pelvis tipping to the other side in order to balance. Our iliac blades are also curved outward in a bowl shape while non-human primates are more tall, flat plates allowing them to easily move on all four. When walking upright they tend to lean their trunks toward the supporting side and outstretch the arms, while their side to side weight shifts use more energy. There's also the birth canal aspect of the pelvis, but that would be another blog post in itself. 

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  1. Marc KisselJune 10, 2020 at 7:49 AM

    great research here, Sara. You get to the main point here which is trying to conserve energy. chimps can walk bipedally but they aren't as efficient. of course, we might want to wonder how less efficient an early biped was versus a modern human. One problem we have is we don't really know why we became bipedal! I wonder if different theories would imply different things about the morphology of early hominins. nice job and good research

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