It seems to be normal for the birthing process to be painful for human females, but it was not always. As I stated in my blog describing the difference between the male and female skeletal structure (http://anthropologicalconcepts.weebly.com/blog/male-or-female), the shape and position of the human female pelvis is what makes birthing painful. The human birthing process is “weird” by other animal's standards. The average time a human female spends in labour is a good nine or more hours, while all other primates give birth within two hours. Another evolutionary problem that makes birth painful is the size of the skull. The reason this is also evolution's fault is because bigger brains means bigger skulls. This is also why, when human babies are born, they are helpless because they have not completely...formed in a way. If they were to stay long enough to be more cognitive, like let us say a baby chimpanzee, the head would be too big to get through the birth canal and will most likely kill the mother. “we need a wide pelvis to bear big-brained babies but a narrow one to walk or run efficiently.”
There is something only humans can do because of our bipedalism, but with this something it causes stress but can cause pain later in life. What I am talking about is lifting heavy objects. You may have heard the phrase “lift with your knees not with your back.” While that is optimum, the knees are not very happy about it. After a while with lifting or just running the cartilage and joint fluid (lubricant) that is between the femur and tibia can wear down, and when it does that leads to knee pain because the bones will now be rubbing directly against each other. This in turn cases arthritis. Even if your knees get the focus when lifting heavy things, just walking, not even running, can affect the lumbar (lower back) region. Reason for this is when walking the curve of the lumbar region (image below) absorbs the shock. This is a good thing because without the shock absorbing lumbar it would be incredibly painful to walk. The entire back would hurt if it were straight; that or we would still be quadrupedal. There are also cases of slipped discs (“a vertebral disc that is displaced or partly protruding, pressing on nearby nerves and causing back pain or sciatica.”), but that mainly happens because of injury or weakness; also these can happen anywhere in the vertebrae, not just the lumbar region.
Please feel free to comment on what you thought of the blog, or other physical anthropological subjects you would like me to cover.