Physioanatomical Analysis of Australopithecus Afarensis
The first Australopithecus afarensis was found in 1974 by Don Johanson at Hadar in Ethiopia, Africa, and dates from about 3.9 to 3 million years ago. The very complete fossil is thought to be a female skeleton and it is called “Lucy” after a Beatles song. Because the skeleton is 40 percent complete, it facilitates a more accurate analysis in a broader sense. When comparing A. afarensis to a chimpanzee, a species with many traits that for hominins are considered primitive, and a modern human, it is concluded that the subject is very primitive, because it shows few developed ...view middle of the document...
Many important derived traits are seen in the construction of a human skull. First of all, the foramen magnum is located more to the center of the bottom of the skull, because of the humans’ more developed bipedalism. On the contrary, chimpanzees’ and A. afarensis’ foramen magnum is closer to the back edge of the bottom of the skull, which indicates less developed bipedalism. Another derived trait is that the human skull’s broader part is in the upper part of the skull and it is very rounded, while chimpanzees’ and A. afarensis skulls are broader in the bottom part of the skull and have a backward horizontally elongated skull, which suggests thicker muscles on the neck to hold a less centered head caused by a less developed bipedalism. One more human characteristic is a larger forehead and small brow ridges, but chimpanzees and A. afarensis have no foreheads and even though chimpanzees have thicker brow ridges, A. afarensis’ brow ridges are very thick also. Also, humans have a very flat postorbital constriction and even though A. afarensis has a flatter constriction than chimpanzees, their mandibles are still very far out. In addition, humans use tools and have a smoother diet, so they have a small zygomatic because they don’t need thick muscles for their mandibles. On the contrary, chimpanzees and A. afarensis have bigger zygomatics than humans because of their diet. Also, chimpanzees and A. afarensis have a bigger ascending ramus of mandible than humans.
The diet an organism follows influences its anatomy. Even though humans, the A. afarensis, and the chimpanzees share the same dental formula (2-1-2-3), their teeth are very different. A. afarensis molars are bigger and thicker than chimpanzees and humans, while humans have smaller teeth than the other two species. Also, both chimpanzees and A. afarensis have a larger and pointed canine. In conclusion, A. afarensis and chimpanzees have sharper and bigger teeth than humans, because their diet is tougher.
The main characteristic of hominins is their ability to walk on two feet. However, this was a long process of evolutionary change throughout a long period of time, so many earlier hominins had a less efficient posture and structure than more modern hominins. The human pelvis is narrow, short, circular, and is constructed in a basin shape while all of the pelvis’ bones are well balanced for a standing position. In contrast, the chimpanzee has a long, narrow, and flat pelvis, which is very unstable for bipedalism. Moreover, the A. afarensis has a somewhat circular pelvis, more narrow but bigger in anterior-posterior breadth. A. afarensis Pelvis is much more like humans than chimpanzees.
Another important sign of evolved bipedalism is the shape and size of the extremities. Human femurs are longer than the tibia but not much; also, they are attached closer together on the pelvis to increase stability. Human upper extremities are shorter than lower extremities, our fingers and toes...