Bipedalism

    Bipedalism is defined as the condition in which having two feet or using two feet for locomoive purposes. Humans are the only organisms that are capable of standing and walking on two feet as well as in an upward position. Apes are able to walk on two feet, but are not able to stand as straight as humans. They also use their arms differently when walking, but can also use them like humans to extend their hands to grab an item of interest. While there are multiple features of bipedalism, I chose to focus on the pelvis area and the difference or similarities between them. 

    For humans, the only difference you will see in the pelvis is between males and females. The pelvic area for a women is most of the time larger as well as wider. This is because women's pelvic areas are meant to widen during childbirth. Male pelvic areas appear to be smaller in comparison to women's for that reason. The purpose of our pelvis is for the balance of our upper body as well as keep us from falling over. Our bodies have a curvature located in our lower back which supports the balance of the upper body. For humans, are iliac blades located on the upper half of the pelvis and differ from apes in size, shape, as well as orientation. Human iliac blades appear shorter which lowers our centre of mass and avoids rubbing of the lumbar vertebra and the iliac blades. For non-human primates, the iliac blades are tall, flat plates that run posteriorly over the hip. 

     When we are bipedal walking, the body is supported by a single leg when you are taking steps.The pelvis will tend to dip towards the leg that is unsupported. Humans also have strong gluteal muscles that help balance the pelvis more efficiently by pulling back the unsupported side of the pelvis. When apes walk bipedally, they tend to lean their pelvis towards the supported leg or by stretching out their arms to support themselves. 

    There are multiple differences between human and non-human primates pelvic areas. What I found to be the most interesting is that female apes pelvis are designed similarly to female humans. This is because they give birth similar to humans. Of course all mammals give birth , but the pelvic region is similar to our towards the lower region of the pelvis. Our sacrum allows for our babies to come out anteriorly while baby apes come out posteriorly. 

    I feel the bipedalism transition of the pelvis is important because like the spine, the pelvis supports the upper body and the ability for human and non-human primates to walk properly. The pelvis must be able to support the weight of the upper body while allowing for us to keep or balance of our lower half as well. I also love how for women, the pelvis is designed specifically for the creation of life.  

https://royalsocietypublishing.org/doi/10.1098/rstb.2014.0063