Assignment:
Giovanni
1.) According to evidence in the fossil record, when did bipedalism emerge?
Evidence of bipedalism dates back to 6-7 million years ago.(Proctor 14) This evidence was found by a researcher and published in Nature's journal in 2002. (Proctor 14) This evidence, named "Toumi" was found in Chad, Africa and belongs to the species: Sahelanthropus tchadensis.(Proctor 14) While researching evidence of bipedalism is nascent relative to the age of science, Anthropologist continue searching the corners of the earth for more ancestral evolutionary evidence. It is fascinating to see how adaptations dating back millions of years have accumulated to shape our contemporary life.
2.) Name the genus and species that is believed to be the first bipedal hominin.
Sahelanthropus tchadensis is claimed the first hominin to be bipedal.(BBC) This hominin is known to be bipedal because of the way its spinal cord exits the skull.(BBC) The spinal cord exits straight downward parallel to knees which is used to support the argument of feet at that time being planted flat on to the ground. (BBC) With these observation, researchers propose this species, "Toumi" to be bipedal.(BBC) It is interesting how researchers come to these conclusions because of subtle differences among hominin remnants. This proves Anthropology as a meticulous discipline.
3.) Discuss at least five skeletal changes that occurred to allow for effective bipedal locomotion.
There are many subtle differences among hominin skeletal changes. Firstly, the angle the spinal cord exists the cranium is a skeletal change to adapt to bipedalism.(BBC) Secondly, the shape of the ankle joint changed to resemble a square also allows for walking by allowing a foot to plant fully on the ground, underneath the knees.(BBC) Thirdly, wider, bowl-shaped pelvic girdle is another skeletal change to support our bipedal adaptation.(Proctor 4) Fourthly, longer femur bones is a change that coincides with bipedalism.(Proctor
4) Lastly, a "s-shaped curvature to spinal column, and non-opposable hallux" are further physical evidence for changes that facilitate effective bipedal locomotion. (Proctor 4)
4.) Discuss at least two advantages and disadvantages of bipedal locomotion.
Despite bipedalism being advantageous for modern humans' lifestyle, there are plenty disadvantages for this adaptation. For example, the lumbus spine has a tendency to have problems.(BBC) One of these problems are vertebrae pressing on spinal nerves because of dislocation or misalignment.(BBC) This causes pain and discomfort in the back.(BBC) Another disadvantage of bipedalism is it makes the reproduction process for women more dangerous.(Proctor 8) Conversely, an advantage of bipedalism is the ability to travel farther distances for food and resources.(BBC) Another advantage is it allows for greater horizon views.(Proctor 8) Altogether, there are trade-offs to bipedalism, but if you were to ask me - I prefer to be on two feet.
5.) Discuss at least three theories on the origins of bipedal locomotion (these theories can be from your textbook, academic journal articles, films, etc.) Please don't forget to properly cite your sources. Please also discuss which theory you think is the most likely explanation for the transition to bipedalism.
Peter Rodman and Henry McHenry's propose a theory known as Patchy Forest Hypothesis which say bipedality may be an adaptation due to changing hominin habitats.(Larsen 299) Specifically, as forests thinned and savannahs began to increase, primates began walking on two feet.(Proctor 6) This theory agrees with Darwins' theory of natural selection because an adaptation for bipedalism prevailed in a changing environment. Rodman and McHenry support this idea by estimating, "Apes' quadrupedalism... is not energy-efficient in Africa's patchy forests".(Larsen 300) Thus hominins that walked on two feet were more likely to survive and reproduce than those that walked on four limbs. It should be understood bipedalism is a complex adaptation and singular events cannot be asserted for the sole reason; however, it is reasonable to say the patchy forest hyptoheiss is a significant driving forces for bipedalism.
Another peculiar theory is Darwin's hunting hypothesis which considers these four facts: intelliegence, bipedalism, tool use, and canine size.(Larsen 297) Based on these four criteria Darwin proposes humans adapted for bipedality.(Larsen 297) While this theory is reasonable, evidence does not strongly support Darwin's claims. For example, the first tool remanent is dated to 2.6 million years ago.(Larsen 298) On the contrary, bipedality dates back to 6 - 7 milllion years ago.(Proctor 14) There are more factual evidence that do not coincide with Darwin's claims; nonetheless, this theory is reasonable.
Lastly, Owen Lovejoy's theory proposes monagomy and altruism as reasons for bipedality.(Larsen 300) He notes hominins most likely to survive were bipedal.(Proctor 7) This was because males in monagomous relationships helped their partner and offspring survive.(Larsen 300) While this theory is interesting because it suggests a large act of monagomy and altruism dating back 6 - 7 million years ago, it seems like a farfetched theory.(Proctor 14) It is unlikely for the reasons of modern humans do not stricly practice monagomy. Especially in our society, it is apparent a substantial amount of people have a tendency to have multiple partners throughout their life. This is seen through cultural tools we made and use like Tinder and other various dating web applications. This behavior has accumulated over time and is seen commonly throughout history. Therefore, it is more believable for Lovejoy's theory to be a significant driving force if we practiced monagomy and altruism more often. In all, McHenry's and Rodman's theory is most plausible as a significant driving force for bipedality.
Derek
According to the evidence, bipedalism was present approximately 6-7 million years ago. ("The Real Reasons We Walk on Two Legs, and Not Four" , 2016) Additionally, "The Origins of Us - Bones" provides an example that bipedalism may have been present as long as 8 million years ago.
The first bipedal hominin was believed to be the Sahelanthropus tchadensis. This hominin was believed to be bipedal based upon the base of the skull and neck being tucked below it, in a vertical position. This differed from that of an ape or chimpanzee, as their necks are horizontal. ("The Real Reasons We Walk on Two Legs, and Not Four" 2016)
In order for bipedalism locomotion to occur, multiple skeletal changes must have occurred. First, the spine had to form an S-Shape, which allows the body's center of gravity to be above the pelvis. The human pelvis has a short ilium, which promotes stability. Legs on bipedal humans were longer, which improved efficiency of each stride. The foramen magnum is positioned underneath the skull, which demonstrates that the head sits on top of the body. The foot possesses an arch, which provides increased leverage as the body pushes forward and acts as a shock absorber when the foot makes contact. (Larsen, 313)
Two advantages of bipedalism include the body's ability to free up the arms, allowing the human to carry items such as weapons or food. Also, bipedalism allowed our ancestors to reach higher branches, where food was more prevalent. ("The Origins of Us - Bones" 2013) Two disadvantages of bipedalism include problems with the lower back. This occurs based upon the S-curve of the spine. All of the upper body weight is placed on the lumbar section of the spine, which can cause many different problems. ("The Origins of Us - Bones" 2013)
Charles Darwin explained that bipedalism allowed the freeing of the hands to carry weapons. Once tools and weapons were able to be carried, Darwin explained that large canines were no longer needed for protection and hunting. Rodman and McHenry's explained that bipedalism were related to the efficiency bipedalism provided. They explain that in areas where the forest became fragmented and food dispersed, bipedalism allowed hominis to be more energy efficient when scouring for food. Lovejoy's hypothesis was similar to Darwin's, but Lovejoy believed that the freeing of the hands allowed for more food to be provided to mothers and children. (Larsen, 320-322) I believe that bipedalism occurred as a result of forest fragmentation and food dispersion. This theory more likely explains the evolution of bipedalism and provides the most logical reasoning that would explain why this change would have occurred.