bipedalism

While humans and primates are related in many ways, there are distinct characteristics for hominids. The most unique characteristic difference that separates hominids and non-human primates is bipedalism. While hominids walk on two feet, non-human primates are quadrupedal, using all fours to get around. Multiple experiments were conducted to identify between the advantages and disadvantages of being bipedal. The first experiment involved observing human and non-human primates and their difference in methods of locomotion. All of the people observed used two feet to get around. At the same time they all made use of their hands whether it was the biker steering his bicycle or the multiple people on holding their cell phones. On the other hand, the video of the gorilla demonstrated quadrupedalism. While the gorilla was able to go from walking slowly to running on all fours, it was unable to use its hands for other tasks. The gorilla demonstrated knuckle walking because they have many wrist and forearm features that allow them to do so (Hirji, 2009). Through observations in the video as well as at the zoo, it was easy to see that non-human primates do not have a skeletal structure that is specialized in bipedal locomotion. All in all bipedalism is necessary in order to carry objects and complete other tasks while moving. Therefore, the human body was able to evolve to compensate for bipedal locomotion. The next station involved putting the observations from station one into practice. Each group member walked normally and walked while holding two grapefruits in order to depict human bipedal locomotion. Each time was recorded to compare to the times of humans walking on all fours. Next each group member walked on all fours and then walked on all fours carrying the grapefruits in order to replicate quadrupedal locomotion. Based on the time differences it was able to be determined that bipedalism is a more beneficial and efficient mode of locomotion compared to quadrupedalism. The two bipedal trials were completed in a faster time than the two quadrupedal trials. On average, trial one was completed in 4.7 seconds and trial two was completed in 4.6 seconds. On the other hand, the quadrupedal trials were completed, on average, in 5.3 seconds and 6.9 seconds. It was much harder to walk on all fours carrying objects than it was walking on two feet. Based on this evidence, bipedalism is a much more efficient method of locomotion and allows hominids to walk with ease while carrying objects. Station three attempted to recreated the effects of the suns exposure on bipedal and quadrupedal primates. Since their statures differ, the sun will have different effects on each. It was evident that the bipedal person was hit with the suns rays mainly on the top of the head, while the quadrupedal person was mostly exposed on its back. Hominids have a smaller surface area of skin exposed directly to the sun’s rays. On the other hand, quadrupedal primates have a larger surface area exposed. “Experiments show that when the sun is high, bombarding the earth 's surface with intense radiation (because the rays pass through less atmosphere), far less body surface is exposed on a biped than on a quadruped” (Wheeeler, 2008). Since quadrupedal primates have more skin exposure, them may be able to absorb more Vitamin D, which is obtained from the sun’s rays. Overall, this station demonstrated how bipedalism is advantageous because there is less sun exposure, which leads to a decrease in body temperature. The last station compared human footprints with those of other hominids and non-human primates. After the human footprints were traced and compared to the pictures, it was easy to see that human footprints most resembled examples E and D because of their similar shape. Even though the human and primate footprints were similar, there are some distinct differences. To identify a hominid footprint from a non-human primate footprint, the big toe can be studied. Unlike non-human primates, the big toe of a human is not opposable. Also, humans tend to have longer, thinner footprints compared to wider, shorter footprints of non-human primates. Additionally, non-human primates have bones equipped for life in trees so their hand and foot bones tend to be rounder and curved. Another method to determine hominid from non-human primate footprints is the distance between heelstrikes. Humans usually have a longer distance between each heelstrike. A group member’s heelstrike distance was measured by walking on paper with wet feet. Using the average heelstrike distance versus the group member’s height, the stature of a hominid was estimated. This proved that bipedal locomotion leads to longer heelstrikes, which means taller hominids. Furthermore, the longer heelstrikes showed improved efficiency while walking and the ability to be hands free.

References:

Hirji, Zahra. "It 's All in the Wrist." Earth Magazine. N.p., 1 Oct. 2009. Web. 24 Nov. 2012. .

Wheeler, Pete. "Human Ancestors Walked Tall, Stayed Cool." Thoughts on the Origins of Bipedality. Mesa Community College, 2008. Web. 24 Nov. 2012. .

References: Hirji, Zahra. "It 's All in the Wrist." Earth Magazine. N.p., 1 Oct. 2009. Web. 24 Nov. 2012. . Wheeler, Pete. "Human Ancestors Walked Tall, Stayed Cool." Thoughts on the Origins of Bipedality. Mesa Community College, 2008. Web. 24 Nov. 2012. .