User:Aripastore/sandbox

Male versus Female
Examination of the pelvis is the most useful method for identifying biological sex through the skeleton. Distinguishing features between the human male and female pelvis stem from the selective pressures of childbearing and birth. Females must be able to carry out the process of childbirth but also be able to move bipedally. The human female pelvis has evolved to be as wide as possible while still being able to allow bipedal locomotion. The compromise between these two necessary functions of the female pelvis can be especially seen through the comparative skeletal anatomy between males and females. thumb|A male pelvis (left) compared to a female pelvis (right) from a posterolateral view. Differences in the sciatic notch and overall shape of the ilium can be observed. The human pelvis is made up of three sections: the hip bones (ilium, ischium and pubis), the sacrum, and the coccyx. How these three segments articulate and what their dimensions are is key for differentiation between males and females. Females acquired the characteristic of the overall pelvic bone being thinner and denser than the pelvic bones of males. The female pelvis has also evolved to be much wider and allow for greater room for a safer delivery of an unborn child. After sexual maturation, it can be observed that the pubic arch seen in females in generally an obtuse angle (between 90 and 100 degrees) while males tend to have more of an acute angle (approximately 70 degrees). This difference in angles can be attributed to the fact that the overall pelvis for a female is preferred to be wider and more open than a male pelvis. Another key difference can be seen in the sciatic notch. The sciatic notch in females tend to be wider than the sciatic notches of males. The pelvic inlet is also a key difference. The pelvic inlet in females be observed as oval-shaped in females and more of a heart-shape in males. The difference in inlet shape is related to the distance between the ischium bones of the pelvis. To allow for a wider and more oval-shaped inlet, female ischium bones are further apart from one another than the ischium bones of a male. Differences in the sacrum between males and females can also be attributed to the needs of child birth. The female sacrum is wider than the male sacrum. The female sacrum can also be observed as being shorter than the sacrum of a male. The difference in width can be explained by the overall wider shape of the female pelvis. The female sacrum is also more curved posteriorly. This could be explained by the need for as much space as possible for a birthing canal. The articulating coccyx in females is also generally observed as being straighter and more flexible than the coccyx of a male for the same reason. Because of the female pelvic bones in general being further apart from one another than those of the male pelvis, the acetabula in a female are positioned more medially and further apart from one another. It is this orientation that allows for the stereotypical swinging motion of a female’s hips while walking. One of the last key differences can be seen in the auricular surface of the pelvic bones. The auricular surface seen in females generally has a rougher surface compared to the surfaces seen in males. This difference in the texture of this articulating surface may be credited to the differences in shape of the sacrum between males and females. These key differences can be examined and used to determine biological sex between two different sets of pelvic bones; all due to the need for bipedal locomotion while having the need for childbearing and childbirth in females.