User:Stammen.44/sandbox

Topic: Human skeletal changes due to bipedalism

1. Ruff, Christopher. "Ontogenetic adaptation to bipedalism: age changes in femoral to humeral length and strength proportions in humans, with a comparison to baboons." Journal of human evolution 45.4 (2003): 317-349.

This article does studies to show the adaptations to the lower/upper limb bone length and strength due to bipedalism while comparing it to baboons.

2. Richmond, Brian G., David R. Begun, and David S. Strait. "Origin of human bipedalism: the knuckle‐walking hypothesis revisited." American journal of physical anthropology 116.S33 (2001): 70-105.

This goes back to the origin of bipedalism and how it first started to evolve and why. It goes into further depth of the characteristics of the shoulder, arm, wrist and hand shared by African apes and humans.

3. Wittman, Anna Blackburn, and L. Lewis Wall. "The evolutionary origins of obstructed labor: bipedalism, encephalization, and the human obstetric dilemma." Obstetrical & gynecological survey 62.11 (2007): 739-748.

This article discusses changes to the pelvic architecture due to the upright, bipedal posture and how it can cause complications during childbirth. compared to other primates, these problems are mostly in humans.

4. Gatesy, S. M., and A. A. Biewener. "Bipedal locomotion: effects of speed, size and limb posture in birds and humans." Journal of Zoology 224.1 (1991): 127-147.

This article studies the difference between biped locomotion in birds and humans. The kinematic variation is due to differences in posture and limb segment lengths.

5. 5. Ryan, Timothy M., and Gail E. Krovitz. "Trabecular bone ontogeny in the human proximal femur." Journal of human evolution 51.6 (2006): 591-602.

This article discusses the developmental changes in the human femur associated with the acquirement of bipedal locomotion.

https://en.wikipedia.org/wiki/Human_skeletal_changes_due_to_bipedalism

Some suggestions to add to article:

1. Maybe add some problems due to these human changes. Found an article that discusses problems during labor due to changes in the human birth canal and larger human brains, ergo, larger human skulls.

2. The same article mentioned above also points out some differences in morphology between the male and female pelvis bones as well, I found this quite interesting and thought maybe it could also be added.

3. There is a lot more detail that can be added to the 'Hip' section. There are further in-depth details in the above mentioned article that I believe would be appropriate to add.

My Edit:

The ilium changed from a long and narrow shape to a short and broad one and the walls of the pelvis modernized to face laterally, both of these changes combined allows for an increase in area for the gluteus muscles to attach which helps stabilize the torso while standing on one leg.

FINAL DRAFT STARTS HERE

The sacrum has also become more broad which increases the diameter of the birth canal so that it is wider and makes birthing easier for females. In order to provide more surface for ligaments to attach to help support the abdominal viscera during erect posture, the Ischia spines became more prominent and shifted towards the middle of the body.

Increasing brain size has also been significant in human evolution. It began to increase around 2.4 million years ago but modern levels of brain size were not attained until after 500,000 years ago. Zoological analyses have shown that the size of human brains is significantly larger than what you would expect for our size. The human brain is in fact three to four times larger than its closest relative - the chimpanzee.

The gluteus maximum became a major role in walking and is one of the largest muscles in humans. This muscle is much smaller in chimps, which shows that it has an important role in bipedalism. When humans run, our upright posture tends to flex forward as each foot strikes the ground creating momentum forward. The gluteus muscle helps to prevent the upper trunk of the body from "pitching forward" or falling over.

Human feet have evolved enlarged heels in order to bear the amount of weight that has also been increased.

Human walking is about 75% less costly than both quadrupedal and bipedal walking in chimpanzees. Some hypotheses have been supported that bipedalism increased the energetic efficiency of travel and that this was an important factor in the origin of bipedal locomotion. Humans save more energy than quadrupeds when walking but not when running. Human running is 75% less efficient than human walking. A study helped to prove that walking of living hominin bipeds is noticeably more efficient than walking of living hominin quadrupeds, but the  costs of quadruped and bipedal travel are the same.

https://en.wikipedia.org/wiki/Human_skeletal_changes_due_to_bipedalism